Electronic Second Wind 91-1
Second Wind 91-1
THE MOTHER OF ALL NEWSLETTERS!
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New Prefab SABER Spar Option!
As an option, we are now offering totally prefabricated spars for the Saber. This makes the Saber wing among the fastest and easiest multichannel glider wings to construct. Many feel that the Saber wing, with the prefabricated spar, is an easier wing to build than even the expensive, pre-sheeted wings of the competitors. The prefabricated spar is manufactured totally from space age materials. The core is a high density Rohacell, while the top and bottom caps are a special tapered carbon fiber laminate. The thickness of the tapered top laminate is a little thicker than is the bottom, to yield an extra margin of safety during positive maneuvers such as during winch-box-lifting launches. To insure that the carbon fiber and the Rohacell never part company, the entire spar is wrapped with glass fiber and special reinforcement is used in the root area.
These optional spars are at least as strong as the historically robust built-up wood and carbon fiber spars normally supplied with the kit. Each of the prefabricated spars is about 1/2 an oz. lighter in weight than is the stock spar so you are paying no penalty for going with the optional spar. The cost of a set of prefabricated spars, when purchased along a Saber is $65.00. When purchased separately, a set of the spars is $79.00 plus shipping. Many will find that these prefabricated spars are a most worthwhile investment . . . particularly if you are short on building time or if you just want to be sure that this critical step is done right. ________________________________________________________________________________
The Saber and the Red Tailed Hawk
by Richard Farrar - WA
For Steve Cameron it was a beautiful day. No blue sky or sun, after all, he was in Seattle. Steve was thermaling out high above the ridge at the east side of Sixty Acres. His sleek Saber, a new open class glider from Dodgson Designs, flew in sinuous, long circles as it climbed ever upward toward the clouds.
Smooth as a feather the big red tailed hawk slipped into the bottom of the lift. Steve quickly spotted the bird. The aggressive shoulder notch on the leading edge of its wings sent the slightest icy chill down his spine. But the bird was 500 feet below the Saber, not to worry. Besides, Steve was there first. It was his thermal!
The ten foot glider continued its long, graceful sweeps upward. Red Tail was coming up fast on the inside and it became impossible for Steve to maintain the proper distance between the hawk and the plane. It was hard to believe the bird could rise so rapidly.
One could almost hear the Cameron Missile Control Officer, "Range 330 feet and closing . . . range 109 feet and closing!" Steve activated his HEAP (Hawk Evasive Action Plan). "Range 70 feet!" The voice was almost hysterical now, for there was no mistaking this raptor's intent. He was rushing in for the kill!
At the last second, with barely 34 feet of sizzling air between hawk and plane, Cool Hand Cameron put HEAP #5 into action. With a flick of his finger - Full Down Elevator! The big plane responded instantly to the expert touch. Down it went, plummeting just inches past the outstretched, razor-sharp talons. The plane's speed was too much for Red Tail, and after one quick regretful look he gave up the chase. The hawk climbed back into the thermal, doing lazy circles in the sky. He was feeling good. After all, now it was his thermal. As the Saber streaked away across the fields, Cool Hand Cameron began to get hot. "Hey, I was there first. Just who does that big bird think he is anyhow?" His decision was made. In a graceful but determined arc the Saber crossed the field again and reentered the thermal near the bottom. Red Tail was way up there. Plenty of room this time. No question about it. The famous Cameron Concentration switched on as he focused on the wind, the temperature changes, the movement of the grass, the rising current and all of the factors which made him the Swordsman of the Sky. Up the Saber went as Steve worked the plane though the column of air. Steve had that certain look he gets when he is in a thermal. He appears transported. He seems to be in the plane itself. It is a wonderful harmony of glider, man and the elements. The focus is complete. The screech was silently deafening. Red Tail launched a kamikaze attack. With wings hunched up like a F4U, he dove down out of the heavens. The hawk resented the serenity of the larger bird that seemed able to challenge his domain and to actually fly like a hawk. It was intruding in his air space. This thermal just wasn't big enough for both of them! Crack! The hawk hit the Saber with a brutal blow to the body. "Oh," came Steve's anguished cry, "he hit me in my empennage." The vicious slashing attack was over as fast as it started. The rudder hung by a bare control wire and the hinges were torn out. There was a long gaping hole in the fuselage where the vertical fin curves up. Claw marks were on the stab. The Saber took it well. Incredibly, in spite of all the damage, Steve brought the plane in without further bloodshed. Steve says that it is not true. It is not true that he is putting a radio controlled dart gun into the nose of the Saber. But he still gets a defiant look when he talks about it. "But, hey, after all, it really was my thermal." ________________________________________________________________________________
The Slash of the Saber!
by Bob Dodgson
The Saber is off to a great start. In my 19 years in the business, I have never had a kit that has met with such an immediately enthusiastic response from owners. No matter what glider they have been flying before, they like the Saber better. People are trying to unload their Magics, Falcons, Legends, etc. Even Lovesong flyers are fast becoming Saber addicts. To my surprise, its relative real world performance is considerably above even the computer projections. The computer shows the Saber falling slightly behind the Epoch Lovesong in minimum sinking speed. This is not the case in practice. The consensus of opinion is that the Saber can work even lighter lift and climb faster than the Lovesong. There is nothing like it! [This might have been a bit over-enthusiastic! Time has not shown the Saber to outperform the Windsong/Lovesong in light air.] Those, who have bought into the tips up = better handling myth/fad, have not flown a Saber! The experts agree that it is one of the best handling gliders they have ever flown. What is more, it lands better than any of the other competition designs (except for maybe the Lovesong). It has the needed flap/aileron ratio so that when the flaps are deployed they really work to slow the ship down. The other current designs have flaps that are too short to do the job. Without a doubt, the SD7037 airfoil is some kind of magic! It will probably be the airfoil of the decade. When we selected the SD7037, we gave serious study to the SD8000 which also shows good performance. The 7037 has slightly better projected performance in minimum sinking speed, about the same maximum L/D and slightly poorer performance at the high speed end. With 3 degree reflex, we believe that the 7037 can match the high speed performance of the 8000. Therefore, the 7037 appears to have a slight overall performance advantage for a thermal/multitask competition glider. What is more, the 7037 is a thicker section so it is a more practical airfoil to structure for those winch-box lifting zoom launches! Walt Volhard reminded me that for those who have a problem soldering the wing servo leads to the Deans plugs, you can simply pull the pins out of the Deans plug and secure a pin in a vise while you solder on the wires. Reinsert the pin into the plug after the soldering is complete. Walt also has used Dap Fast and Final spackling compound as mentioned by Frank Weston in Byron Blakeslee's March 91 Soaring column in Model Aviation. Walt says that the Fast and Final is super light weight and easy to sand for filling any ridges in the foam wing cores before applying the obechi skin. Since the obechi is so thin, any imperfections may show through. Fast and Final can take care of them quickly and with negligible weight gain. We have been more than pleased with the obechi skin on the Saber. It is actually lighter in weight than a 1/16 balsa skin would be! We plan to eventually phase most of our kits over to obechi. We expect our competitors to soon follow suit. At any rate, the Sabers are the ones to beat! ________________________________________________________________________________
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Titillating Tips
Your Favorite Model Could Use Some Silicone in a Couple of Places!
from Dick La Barre - CA
Dick La Barre uses a silicon gasket around the wing root to provide an air seal at the wing-to-fuselage juncture of his Saber. I assume that Dick uses the same system on his other Dodgson Designs kits (do not use this method on the Pivot). Go ahead and apply the covering to the wing and paint the fuselage. Stretch and tape saran wrap type plastic over the side of the fuselage in the area of the wing juncture. Apply a bead of colored (to match wing color) or clear silicon around the perimeter (keep the bead within 1/32 of an inch from the edge) of the root rib. Make the bead as even as possible and about 3/32 in diameter. Immediately slide the wing onto the fuselage, attaching a rubber band, at the screw-eye, to hold the wing tightly against the side of the fuselage. Initially use hand pressure to force the wing against the fuselage side to augment the rubber band pressure. Silicon should squeeze out all along the root rib's perimeter. After the silicon has cured, slide the wing and Saran Wrap off the fuselage. Carefully peal off the Saran Wrap. With a razor blade or scissor, cut the excess silicon off that squeezed out beyond the perimeter of the root rib. Now, as you might envision, when the wings are assembled onto the fuselage, the flattened silicon bead will provide a perfect air seal.
Emergency Rubber Revisited
from Dick Roddy - TX & Mike Dooley - WA
This suggestion first appeared in Second Wind 89-2 from Dick Roddy. Mike Dooley found this wing tensioner particularly useful with the Saber. On our other kits, their is an access hatch that allows you to wrap the wing tensioning rubber band as many times as necessary between the two wing screw-eyes. Since the Saber has no hatch, it is necessary to get plenty of tension on the rubber before pulling it through the fuselage. One great way to get just the perfect tension, is to fabricate the rubber by cutting donuts of rubber off the end of a hi-start. The tension can be adjusted by how wide you cut the donuts. In general, the heavy-duty hi-starts with larger diameter tubing seem to work better than the rubber from smaller diameter tubing. A related tip to keep in mind with the Saber, is to insure that there is as much room as possible between the wing screw-eyes when the plane is assembled. Do this by screwing the screw-eyes into the root rib as far as possible, even in past the point where the threads end.
Stab Grab
from Roger A. Crabtree - SC
Rather than using a slight bend or a little beeswax on the stab pivot wire to keep the stab halves from working apart in flight, Roger says: "Substitute 1/8" O.D. x 3/32 I.D. nylon pressure tubing in place of the brass tubing for the forward stab pin (the stab alignment pin). This tubing grips the wire so that it doesn't slip apart. It is available from hydraulic supply houses at 10 cents per foot. The stab wire must be in the tube when it is epoxied in place to keep it straight.
Tunnel Humming
with Al Doig - CA
The Saber fuselage has the wing plug behind the location of the wing tensioning rubber band. This is a great location from all standpoints except for one. If you have not carefully guided the wiring harness so the wires run down before going forward to the receiver, you can hook a wire with your rubber band hook when assembling the glider. Our musical spelunker, Al Doig, passed along an easy solution to the problem. What you do is to make the hole through the fuselage for the rubber band a 17/32 diameter circle. Be sure that the hole is located so that no part of it will be exposed when the wings are installed onto the fuselage. Glue, CA or Epoxy a section of the cardboard ballast tube into the hole to form a protected tunnel for the rubber band and rubber band hook.
Ruffles Have Ridges . . . But Solid Core Wings Shouldn't
from Mike Dooley - WA
It appears that Mike may have solved one of the few problems that can be an annoyance when applying the balsa wing sheeting to the foam cores, using the transfer tape method. It would probably work just as well if you had to splice obechi sheeting for the Saber (Normally, you do not need to splice the obechi, when building a Saber, except if and where it has a split). It seems that no matter how carefully you splice the wing sheeting or what adhesive you use for splicing, ridges can appear from nowhere along the glue joint after the wings are covered. This seam lifting is usually minor in nature and it does not impair the structural integrity of the wing but it can mar the perceived perfection of the wing surface. Mike's cure is simple and has totally solved the problem on his gliders. It is necessary to sand the glue joints on the inside of the balsa sheeting as well as the seam along the exposed surface of the sheeting. As usual, make sure that you remove all balsa dust from the sheeting using a vacuum and then a tac cloth. After applying the sheeting tape to the foam core but before you put the prespliced sheeting onto the core, lay a strip of the transfer tape centered on each splice seam on the inside of the sheeting. Before removing the backing tape from the tape applied over the seams, press the tape down very hard against the balsa sheeting. Since you are only pressing the tape against the balsa sheeting on your building board, you can press much harder than you can once the sheeting is on the foam wing core. Now, when you pull the backing paper off the sheeting tape along the inside seams of the sheeting and over the surface of the foam core and apply the sheeting to core, the seams will be forced into a "bond for life" with the core. Best of all, these seams will not lift as the wing ages.
But Weight!
from Brian Molloy - MO
For Brian, the prescribed ballast slugs and wood spacers were too bulky for easy transport in his field box. He opted to fill one end of an 8 long x 1/2 O.D. brass tube with lead so that the entire tube and lead weighed 5 oz. He then filled a brass tube, the next size smaller, with lead. This smaller diameter slug is cut to the length needed so that when it is inserted into the empty end of the original 8 long brass tube until it contacts the lead filled portion, the outer end of it is flush with the end of the 8 long brass tube. Note: you must drill a 1/8 diameter hole through the wall of the of the 8 brass tube at the edge of the lead filled portion and angled toward and exiting the lead into the empty interior of the tube. This small hole lets the air flow when the removable slug is inserted and removed. You can also insert a wire or small screw driver into the hole to help push out the removable slug. With this system you can install only the 8 long tube in each wing and have 5 oz. of ballast per wing or you can insert the removable slug that weighs about 5 oz. into the 8 tube before inserting the 8 tube into the wing, yielding 10 oz. of ballast per wing. Either way, no wood spacers are needed and the entire ballast system can be stored in the 2 8 long brass tubes in the field box. ________________________________________________________________________________
Letter Rip
Vee a Butt
November 15,1990
Dear Bob, I have a Titillating Tip for you. When joining sheeting it always seems that there are gaps no matter how careful you are. If you're using epoxy for attaching the skins, the epoxy seeps through. If you're covering with film, the gaps and hard ridges show through. What I do is this. With a metal straightedge and a sharp Xacto blade, trim the edge with the knife angled back toward the straight edge one or two degrees. Now, when you butt two angle-cut sheets together there is a V-shape at the joint. Don't make the angle too extreme, just one or two degrees per side. Now, flip the two sheets over and run a length of masking tape completely down the joint, butting the two sheets tightly. Press the tape down firmly. Flip the sheets back over and run a bead of medium CA glue down the joint. Immediately sand down the joint with a flat sanding block with two hundred grit sandpaper. Sand lightly, the object being to fill the V with balsa dust. After a few seconds, the glue should be hard and the joint filled and smooth. If it is not smooth, it doesn't matter because the V side is the inside. Flip the sheeting over, remove the tape and you'll be amazed at the nearly invisible seam you've made. If you think this joint is weaker that a normal butt joint, make one and try to break it. With a completely filled seam, glue can't flow through and there are no hard ridges which are impossible to sand flat. --Terry Lissansky - Wilmington, DE
Saber . . . the Long and the Short of it.
October 23, 1990
Dear Robert, Sabers were two for a quarter back in 1960 and I could only get them in the men's room at the local Standard station. When I heard Dodgson Designs was selling them for about $300, I wondered what kind of s__t-for-Brains would pay that kind of money. Then I heard the new Sabers were 121 inches . . . Finally, a Saber that fits. P.S. I'm enclosing two stamps and a self-addressed envelope in this missive because I didn't know if you wanted stamps on an SASE or stamps not on an envelope or you can call me Ray or you can call me Jay, or you . . . .
Old Gasbaggers Never Die . . . They Just Go Tips Up!
December 5, 1990
Dear Bob, I am enclosing $2.00 for a year's subscription to your Second Wind Newsletter, and two stamps for your new catalog. It looks as though the aileron sailplane revolution for which you are in very large part responsible is really taking root, with fully half of the East Coast competition sailplanes now sporting ailerons. Even I am succumbing, after twelve years with polyhedral gasbags, although I hedged my bet last year with a Falcon 880. --Green Air, Gordon Stratton - Kew Gardens, NY
Electrified Camano
December 12, 1990
Bob, enclosed are a few pictures of my electrified Camano. Specifications are as follows: Flying Wt - 90 oz, . . . Wing Loading - 15.3 oz per sq ft . . . Motor - AFI Direct Drive Cobalt 40 . . . Motor Batteries - 22 Sanyo AR 450 installed 11 per wing . . . Prop - K&W folding 9x6 . . . Motor Switch - Hy Sky . . . Radio - Airtronics Vision . . . Receiver Battery - SR 300 "square".
I modified the airframe behind the standard flap linkage to accept two Futaba S133 servos for the stab and rudder. The flap servo is an Airtronics 631. Aileron servos are Futaba S133s in the wing.
As configured, the motor will pull for about 45 seconds. The climb angle is not radical but will get you up to winch height or above. Makes an excellent practice ship when the fields are wet!
Soaring the Camano 'E' is not really that different than a lighter airframe. It lands at a noticeably faster airspeed. You have to set it up for a longer approach. The key, as it is with every plane, is to fly it smoothly. I will continue experimenting with the Camano 'E'. I am thinking of replacing the 45 AR batteries with 20 900 SCRs. This would put the weight around 100 ozs (16.9 oz per sq ft wing loading). This would enable me to use an AFI 40 FAI armature (750W vs. 450W) to enhance its LMR competition potential.
Video Venting
Sept. 15, 1990 (this letter was written in response to a letter from MCV expressing interest in doing a construction video on the Saber)
Denny Darnell, Model Construction Videos
Thank you for your letter and for the tape "An Evening with Selig and Donovan". I enjoyed watching the tape and am returning it to you under separate cover. As you may know, we have been providing videos on our kits since 1983. They have covered the gambit from promotion to construction.
Unlike some of the kits available, our plans are highly detailed and professionally drawn (by myself) in Autocad. I have a degree in Architecture and so know how to provide well thought-out and documented working drawings. A recent rarity in the industry, we also provide extensive and comprehensive building instructions to guide the builder through the construction sequences. We will probably be providing a video tape on the Saber ourselves and have already shot some of the footage. Now that I have made major progress in beating my stuttering problem, I can make videos with about a tenth as much editing as was necessary before. If your company makes a video on the construction of the Saber, I would hope that you build it according to plans and specifications. I have heard from many of my regretful customers in the past who have screwed up their planes by following the advice to make "improvements to the design" by some soaring columnist or other "expert" in the field. Any deviation that you may make from plan is your responsibility as are the consequences from those who follow your tape. Enclosed is our catalog with our prices included. I do not know if you have seen our most recent (released in 1987) promotional video. With the Saber out, I have to get my butt in gear and make a new one. In case you have not seen it, I am sending you a copy, along with plans and building instructions on the Saber. We have been shipping saber kits for a month now. The problem is that we are selling them faster than we can get the fuselages made. Availability varies from week to week. So far, the longest wait for a kit has been about 3 weeks. I must say that I was amazed when I heard that your tape on the Falcon 880 was based on the version with the pre-sheeted wings. I would have thought that it would have been much more helpful if you had covered the entire construction of the Falcon including sheeting the wings. Falcons up here have been folding wings, largely because there were no building instructions and very little detail on the plans, so the builder simply did not know how to epoxy up the carbon fiber and sheeting properly. Evidently, your video leaves the people out in the cold who opt to sheet their own wings. While I feel that a construction video is of more use on a kit that is not properly documented to start with, I know from my own experience that there is a market for video tapes. I have sold many hundreds in the last seven years. When I first started making videos, my kits were the only kits available with the present-day multichannel control system, including crow etc. People needed the tapes to understand what was happening. Naturally, the advanced control system made my kits more complex to rig than were the standard polyhedral ships that were the accepted state of the art. The video was a great tool in the education process. I plan to continue to use it as time allows. Thank you for your interest in the Saber. Good luck with your video business. September 25, 1990 Dear Bob, I could have predicted the contents of your letter. You see, I've read your newsletters and I've always felt you to be a bit opinionated. Like, if you didn't invent it, it's no good! But I had talked to a few people who said "Bob really isn't like he sounds - a egocentric who thinks he knows everything!" Well I don't know! Your reply to my letter would tend to indicate the opposite. Why don't you lighten up? I really don't want to bandy credentials with you but for your information, a degree in architecture does not qualify you or anyone else to write technical documentation, nor to design models I'm just getting into the video business and plan to learn as I do. AND, I am probably just as opinionated as you are. But I'm not writing back to you to offer opinions as that doesn't feed the bulldog. (Some other time maybe?) I just thought that since we (MCV) plan to do kit videos you might be interested. You see Bob, you're not IN the video business, even if you've sold tapes (I've seen em.) I just feel that maybe people ought to do what they do best, and maybe they ought to have an open mind while they're doing. The thing is that it kind of pisses me off that you state that our tape leaves the viewer with no information on sheeting. In reality, the tape shows not only the method used to epoxy the sheeting, but recommends a brand of epoxy and shows how to mix it. The tape also shows how to vacuum bag the sheeting to the core. (The sheeting used on the Tape is not balsa, but Rho cell). We also show how to glass bag the whole thing. (This is optional, of course, as balsa could have been used in place of the cell). The results are that the builder gets information on how to do either. The principle is the same for balsa, cell-sheeted wings, or blue foam. The tape is wing-construction intensive. You obviously haven't seen the tape nor talked to anyone who has. Furthermore, you imply that we might be blamed if someone folds a wing. What bulls__t! While I haven't seen any Falcon wings fold, I've witnessed a few Windsong ailerons buzzing at moderate speeds. (They probably didn't follow directions, huh?) If you've read this far, I'd like you to know that I feel a lot better now having stated my piece. So with that, I'll close and wish you also good luck.
Musings from the mile-high maven of multitask
February 6, 1991
Dear Bob, many thanks for Second Wind 90-2, as always an interesting and provocative read! I really enjoy it and think it is an excellent service to Dodgson kit builders. Hope everything continues well with DD. I've been intending to write to better explain what I mean by sky covering ability, but seem to be more busy since I retired than when I was working! There probably is oxygen deprivation here at the 6,200 ft. elevation where I live, so I'm content to leave the nuts and bolts of modern RC sailplane design to the experts. I very much enjoy building and flying glider kits and like to sample as many as I can. The contest winners advise sticking to one design, however I just can't seem to do it! I will stick my neck out and offer two propositions to Second Wind readers: The first proposition drives from observing the bast array of gliders that people enjoy flying. Also, from seeing that no one design will work best in all conditions. Personal preference is the largest part of the decision on which glider to fly. Regarding the second proposition, new glider fliers quickly learn that RC Soaring is a simple game: just fly around in up air and avoid down air. Actually, the game can be thought of in three parts: searching for lift; getting out of down air as quickly as possible; and once found, flying in lift as much as possible. This implies that soaring is three dimensional. Gliding may sometimes appear two dimensional, especially when searching, but lift and sink add the third dimension - up and down. Striving for maximum L/D in theoretical still air is no doubt a worthwhile design exercise. However, I submit that real world contest flying is rarely done in still air flying in a straight line. Often the ability to scoot though sink and arrive at lift quickest is more important. For our local contest flying conditions I have found that giving up a little L/D, and/or minimum sink rate, for a little better penetration (faster cruising speed at best L/D) pays off more times than not. This is just my own preference, and what I mean when I say I like a glider with ground covering ability. I'm not saying that people all over the country will come to the same conclusion. Although I do see a definite trend toward faster high performance ships. The second point also considers the glider's launching ability, handling characteristics in identified lift as well as in difficult conditions, and in general, its flying fun quotient. This last item is important because a glider that is enjoyable to fly will get more practice time - and thereby produce improved contest results. Please understand that I'm not advocating any particular design as optimum for everybody, nor depreciating the Windsong/Lovesong. It's a fine glider, and in many conditions almost unbeatable in thermal duration. Personally, I'm excited to try a Saber because, as I read the computer polars, it has a higher speed at best L/D that a Lovesong, although the max L/D is a little lower. As mentioned above, this is exactly the trade-off I've found useful for our contest conditions. I'd order one now except for the fact that I've got a bit of bench backlog, including the Pivot I bought last winter and haven't started yet! --Best regards, Byron Blakeslee - Sedalia, CO (Byron is the highly respected soaring editor of Model Aviation.)
It takes a warped mind to get straight balsa!
December 28, 1990
Dear Bob, I thought I'd write to you to say that I am getting close to finishing my Lovesong. I sure am looking forward to flying it in competition in 1991, especially against my friend who has a Falcon 880. Thank you for all the helpful hints over the phone. You certainly stand behind your kits! I thought I might mention some building tips that have helped me along with my Lovesong. As an alternative to using polyester resin to bond the wood pieces to the fuselage, I recommend CA glue. I feel that it creates a better bond and speeds up the building process. Another thing I did was use Goldberg's Magic Filler to fill in small gaps between the spar and the foam core on the bottom of the wing. This insures that when the sheeting is applies, there will be a smooth transition between foam and the spar. The filler was easy to apply diluted with water. It is super light and Sands easily. It also is sold under the Red Devil label as Onetime spackling compound. The last tip is for the correction of warped wood. When I received my Lovesong kit, all the wood was straight and true. However, after the wood sat around my basement for several months, the 1/16 balsa sheeting became severely warped. This I assume was caused by humidity. At first I thought of just replacing the wood, but my local hobby shop did not have high quality wood like that found in the kit. Instead, I soaked all my sheeting in a bath tub full of hot water for ten minutes. This relaxed all the warps. I then placed each piece of wood on my building table, and I covered them with waxed paper. Books were placed on top to keep the wood flat until it dried. In a few days the wood was dry and the sheeting was perfectly flat and straight. For less severe warps, I have used steam from a kettle to straighten both balsa and spruce. To get out warps using this method, just hold the wood over the steam and bend the wood in the opposite direction to the warp. When it cools it should be straight. Repeat the process if it is not. Well, that's all the tips I have for now. By the way, I read a favorable report about the SABER in last month's Models Builder. The author felt that the SABER would out fly the Falcon 880, and the author owns a Falcon! Keep up the good work! October 10,1990 Dear Bob, I know you have more than enough testimonials as to the performance of your sailplanes but I'd love to tell you my story. I built a Lovesong last winter and entered my first contest with it this August. I got the most points of anyone in all classes in the whole contest Since this contest, the Lovesong has won 4th place and 1st place in 2 other contests. I also fly the Pixy and won 2 3rd places with it this year. My friend, Chris, also built a Lovesong last winter and in one of the ESL contests this summer, he took 1st place. The Lovesong proved itself to us dramatically this summer. In sport flying, I've had many good long thermal flights, one over an hour. I enjoy the Lovesong and Pixy so much I'm ordering a Camano! Your sailplanes are a pleasure to build and fly.
Letters from the Sanded Gentry of Soaring Serving in Saudi Arabia
(I guess they would rather be Thermal Jumping than Camel H--ping!)
November 27, 1990
Dear Mr. Dodgson, enclosed are two stamps for your brochure and hopefully, any additional information on your new Saber. I just finished reading the exciting introduction by you in Model Aviation. I put the magazine down and now am asking for your brochure. The review says very detailed instructions. I have built several planes but only one glider, the Prodigy. None are foam. You, of course, don't know my abilities, but is it probable that I, the first time at wing sheeting and working with a fiberglass fuselage, would have good building success with your Saber? The wings and stab come off for transport, right? I currently have my Prodigy here in Saudi Arabia but time and soaring locations have been very limited so far. I keep it in a plywood case I built that holds the glider, my radio, radio tray, and solar panel for battery charging. Thank you for your time and the information. Sincerely Don R. Moore - Desert Shield, Saudi Arabia February 22, 1991 Dear Sir, I am a soldier in the United States Army and have been deployed in Saudi Arabia since August. We were one of the first units to become active. I am also a member of the Tidewater Model Soaring Society of Hampton, VA, and the Academy of Aeronautics. Recently I started receiving my copies of Model Aviation Magazine from AMA and I realized how much I miss the hobby and how long it has been since I have been able to fly my glider. I have been flying for a couple of years and have become very active. My unit is the first leg in the Logistical System and although we were the first here, we will also be the last out. As time goes on, I find myself searching for things to fill my very limited free time and I would like to stay active and current in the hobby. The area that we are located in is well removed from the front and the lift is amazing. This adds to my strong desire to get back into flying. My problem is that my time and funds are extremely limited. While I was reading Model Aviation, I saw your ad and became interested in your models. I have several friends that have also become interested and would love to see your catalog. I would greatly appreciate any assistance that you can lend in helping me to get re-involved in the sport. Sincerely, Dale O. Caroe. 7th Trans 6p, 24th Trans Bn, 567th Trans Co. APO NY 09770. My deepest gratitude to all who served so well on behalf of our nation and the UN coalition
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A New Spin on the Mating Process
from Pat McCleave - KS
This winter, Pat McCleave was flying his Camano on the slope with his "good flying buddy" Carl Williams who was flying a Coyote. During the course of their daring aerial ballet, the Coyote (on top) and the Camano (on bottom) came together for a moment of ecstasy. Unfortunately, the attachment became more that just a brief encounter and the gliders would not come apart. Pat applied full flaps to the Camano in order to put the brakes on so that the Coyote's inertia would force it to slip off the front of the Camano. It worked great and as soon as the Coyote had uncoupled, Pat neutralized the flaps on his Camano and sped away. Alas, the speed of the flapped Camano was slower than the stall speed of the Coyote so when it slipped off of the back of the Camano, to start flying on its own . . . it didn't. Instead it spun helplessly into the slope. Fortunately, it escaped undamaged in spit of the unceremonious landing. I guess that the moral of the story is: "Never put your flaps down in a mating situation.
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Good News!
Rumors abound that the JR 347 transmitter will get an update, including a camber changing switch, so you will no longer have to change the camber with the rotary knob! This feature will make it a more practical radio for competition sailplane flying.
Dave Johnson - OR, says that the new Futaba radio ($319.00 Tower price) can be used on the Saber if you Y the flaps and can settle for the imprecise rotary camber change as per the JR. It looks like the new Airtronics Infinity will be a super low/mid cost Saber radio! ________________________________________________________________________________
Buy/Sell
Gliders
Jerry Jarvis of Al's Hobbies, 54 Chestnut Hill Road, Norwalk, CT 06851 (203)846-9090 says: We have a used Todi with two complete (i.e. long and short) wings in good flying condition - $150.
Jake Watkins Has the Windsong, that he flew in our Promotional video, for sale for $300.00 (including shipping anywhere in the US - this Windsong is a proven contest winner.) He also has a Lovesong kit with fuselage built and fiberglassed - $250. (Jake has gotten Saberized bigtime!) Call Jake during the day at (206) 483-0110. Jake also has an Ace Channel 50 Silver Seven Tx and Rx for $100 total.
Ballast etc.
1/2 inch Lead filled brass tubes. With wood spacers. Sets are based on 8 Inch wing tubes, as specified in Dodgson's kits. Price $20.00 Per set. Bill Hanson, 5518 172nd Street SW, Lynnwood, WA 98037 (206) 742-4150
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SABER MK II, III, etc.
by Al Doig I Have flown Dodgson Designs sailplanes for years. When the SABER was introduced, I bought one. The Saber is a super sailplane to fly. It thermals extremely well, is a good light-air airplane, and has an impressive speed range! I believe it will outdo the Lovesong - except in landing. With 90 degree flaps, the Lovesong comes to a halt and comes down like a parachute. The Saber slows down, but still keeps coming, rather fast. The wings of my Saber came out with almost no dihedral. Also, during a rather spirited launch, I experienced aileron flutter. It has not happened before, nor since, but did concern me. I also keep my wing bags on the wings to hide the ungarnished and plain wing tips. I sneak sideward glances at all the swoopy, swept embellishments of other high tech competitors. I have never been one to keep my hands off a Dodgson Design. So, I set off to explore some areas I thought might be done better. Other things were done out of curiosity. My first Saber was a very early kit. Dodgson discovered he had sent a set of cores with the spar offset by 1/8. Whilst this would have made little difference either in construction or flying, the Saber was being built for a Product review. Bob sent another set of foam cores, leaving me with an extra set. With my usual engineering acumen I built a new set of wings incorporating all the changes simultaneously. This way, no one could point to any one as the source of failure. It also would keep Bob Dodgson busy trying to decide which modification to assail. The dihedral problem was attacked first. The reason it is hard to get much dihedral is a fairly thin wing section and a 3/8 wing rod. The lower surface of the top spar is covered with a carbon fiber strip. This prevents the brass tubing from resting against the bottom of the top spar. This carbon fiber should be sanded at an angle to permit the tubing to touch the spar at the inboard end. The top inboard end and the lower outboard end of the brass tubing can be filed just a tad, to allow a bit more angle. Finally, if a lighter thread is used to wrap the inboard end of the spar, the spars can be a smidgen further apart. However, do not allow the spar to protrude above the foam surface. With obechi sheeting, any lump will show and it is so thin that irregularities cannot be sanded out. With all this grunting I was only able to get a total of nearly three degrees. I decided that the place for the aileron servo was not at the inboard end of the ailerons, as shown on the plans. I located my servos at the ends of the wing spars. At the time, this was about at the aerodynamic center of the aileron. The purpose was to raise the flutter frequency of the aileron. This shrewd selection was negated by a later change which reduced the length of the aileron. However, in any event the aileron is driven much nearer its center. A sudden burst of ingenuity caused a decision to reduce the length of the ailerons and increase the length of the flaps by three inches each. I reckoned I needed all the flap I could muster and ailerons are usually oversized anyway. This decision now caused both the flap and aileron to be driven off center a bit, but not enough to cause problems, I rationalized. The last modification was to add winglets. I did not scarf the tip as shown on the plan, but sanded it perfectly square with the trailing edge and epoxied a 1/8 ply rib on the end. I then constructed two 6 long, constant-chord, built-up winglets, tipped up at 15 degrees and swept back 15 degrees [Oh no! Not the Kasner Cresent, Al!]. I construct all my wings with a ¸" wide .007 carbon fiber sandwich between the top and bottom trailing edge sheets. This not only keeps the trailing edge uncommonly straight, but permits it to be sanded to a knife edge. This sandwich was continued on through the tip. The winglets were sheeted with obechi.
Flap wing tip extensions, swept 15 degrees.
The foam flat tip cores showing the end ribs. The left-hand top has been sanded to shape.
After a hand chuck, over tall dirt, we put her up on the winch. I had copied the Saber program over to another alternate on my Airtronics Vision radio so changes could be made without altering the basic program. A bit of up-trim was required to compensate for the slightly aft shift of the center of lift due to the back sweep of the winglets. I also found the ship to be very sluggish in roll. Even increased aileron throw and a decrease in differential did not give really satisfactory control. It was difficult to find any change in the flight performance. If there was a change in thermal turning, it was barely detectable.
Friend Dick LaBarre also flies a Saber. On one test day, we each flew around for ten minutes to get a good feel for our aircraft. We then switched transmitters and flew the other's Saber. We stayed close to evaluate relative performance. Neither could truthfully say there was any difference. I thought mine had slightly better L/D, but quantitative data is difficult. The slight sluggishness in roll of my Saber may have skewed our feelings somewhat.
The wing-tips are up 15 degrees and swept 15 degrees.
Next, I took the winglets off and flew the Saber with just the squared-off tips. It flew like a saber, but the roll rate was still unsatisfactory, even with the winglets off. This told me that Dodgson knew what he was doing when he calculated the aileron area required. It would be possible to make the ailerons 3 longer, as well as the flaps. This would move the end of the aileron 3 closer to the wing tip and may adversely affect tip efficiency.
Next step was to put the winglets back on the tips, without the 15 degree upsweep. The problem here is that without the upsweep, the inboard end of the tip is thinner than the outboard end of the wing. This caused a step-down on the underside of the tip. I flew this configuration for several sessions and had the vague feeling that the overall performance was up. It also felt better in thermal turns. So, I decided to do it right and build a proper tip extension.
I used a hand carved foam core for the new tips. The foam came from old wing cradles. I traced the tip outline onto 1/8 ply and made 4 copies. The stack of 4 ribs were sanded down 1/16 all around to allow for 1/16 balsa sheeting. The balsa was used so it could be sanded down to fair with the wing panel.Two were set aside for the root ribs and the remaining two outboard ribs were further sanded down 1/16 all around, to provide proper taper. The foam was cut to shape, tapering from 6¸" to 6. The tip foam was 6¸" long. Sweep-back was 15 degrees. The ribs were glued to the ends of the foam with UFO. Then, the tips were shaped with a sanding block, using the ribs as end templates. Of course, with hot wire equipment, a quicker job can be done. The leading edge was sanded flat and a 3/32 balsa sub leading edge glued in place (same as Saber wing). 1/6 balsa sheeting was applied with transfer tape. The trailing edges were tapered to receive the .007 carbon fiber sandwich, which was epoxied in place. A 1/8 x 3/8 spruce leading edge and a 1/2 square balsa tip were glued in place. The assembly was sanded to shape. The trailing edge is sanded to a knife edge and the leading edge sanded to a very blunt contour. The tip was epoxied to the wing outer panel and reinforced with a 2 strip of fiberglass. Excess epoxy is removed from the fiberglass with toilet paper. To solve the roll rate problem without enlarging the ailerons, I took a lesson from friend Keith Finkenbiner. Keith flies a Falcon 880 and has uses the Airtronics Vision to mix flap into aileron. This provides full span ailerons and is smooth as glass in operation. I mix only 50% or so of flap, so it doesn't move as far as aileron. Those with separate flap servos and a Vision radio should try this. How does the Saber now perform? Difference in performance was now noticeable! Light air performance is superb. The stall characteristics are as good as you would want. Speed range has not been degraded at all. Why better performance? There are three things working here. First, the all-up weight went from 75 oz to 77 oz and the wing loading dropped from 10.5 to a tad under 10 oz/sq ft. The wingspan increased to 136 (increasing the aspect ratio). The effect of the swept-back tips is pure conjecture. Whether this whole thing was a real increase in performance or an increase in self-confidence - I don't really know. Though I really love contest flying, us old guys are not all that good at it. In the first contest for the new Saber, I was 2nd out of 24. Every flight was a max. After the first flight I knew I could find lift on the rest. On a light-lift day, when one area died, I felt comfortable scooting around to find another. That is the real plus of the Saber and Falcon, etc. If you need to get out of a dying area, just put the nose down and GO!
Is this the end of the story? - Not quite.
The next week was a larger contest of 73 entries. I determined to do a reasonable job on this one. I scorched the first launch. In the middle of the upward zoom, I had wing flutter that caught the attention of all hands. As the Saber continued to fly normally, I set off to find lift. I had no trouble maxing and came in with a reasonable number of landing points. One look at the wing told the story. Both wings were broken at a 45 degree angle indicating a flutter break as opposed to an overload-type break. Both breaks were at the same angle and exactly the same place. Both were at the end of the spar and through the aileron push-rod slot.
The lesson to be learned here is that we must pay attention to the system. Initially, I had not intended to add non-standard tips. So, I did not consider the move of the aileron servos to the end of the spars particularly important. I also made the mistake of not fiberglassing around the aileron push-rod exit slot. That was before I added 7 inches to each wing tip. Most important I did not fully consider the effect of a swept-back tip on an outer panel that was not designed to resist unusual high torsional loads (flutter).
So what shall we do now? - Quit? - no, I'll press on a bit. The wing break is a severe crack in the upper obechi sheeting of right wing and a somewhat lesser crack in the left one. Both wing ends yield to upward pressure, but everything is still in alignment and the lower sheeting seems intact. I intend to smooth down the cracks and work UFO in. Then I'll apply a staggered double layer of fiberglass over the break. Then I intend to apply light fiberglass from inboard of the break to the tip, top and bottom.
I had considered a spar extension, but think now that the fiberglass will not only provide needed torsional rigidity, but sufficient bending strength for that length of wing tip. Anyway - we'll give it a go again. I was sufficiently encouraged by the initial results to take this one more step and give it another test. I'm bound to carry this to some sort of conclusion. Would I advise others to undertake a similar program? No, I don't think so. After the broken wing flight, I received the Contest Director's permission to install the standard wings. I maxed the next flight with no problems and I couldn't detect any difference in thermaling ability. Now if I could only make three good landings on the same day -. I think there is a kind of tipmania going around. Studies do show that swept tips decrease tip drag. In fact a late study says that a sweep of 60 degrees is optimum! However, I'm not sure that most flyers would detect the difference. As my old daddy used to tell me during story time "THE THUMB IS GREATER THAN THE TIP"
The problem with making modifications to the Saber, or the Falcon, or any high performance ship is trying to evaluate the effects of those changes. You can't even change wings between flights and make real sense out of the results. The only thing you have is a gut-feel for the results. All you can do is fly the thing for a year and see how you do. Then, I suspect any improvements is because you have really gotten in tune with the ship, which is what you should have done in the first place, instead of trying all those darned-fool ideas.
Anyway - I am building another Saber. It will have the 3 longer flaps, 3 shorter ailerons (with ail/flap transmitter coupling), aileron servo in center of ailerons (with more care), but no special tips. I'm also going to try epoxy and vacuum bagging the obechi. There's no end, is there?
HOWZAT! ________________________________________________________________________________
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This page was created by Bob Dodgson of:
Dodgson Designs
21230 Damson Road Bothell, WA 98021
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