martin collins 1 Posted February 5, 2023 Share Posted February 5, 2023 Always loved Gee Bee`s but i prefer the Sportster models, D, E and Y to the more familiar barrel shaped R1, R2 and Z models. Late last year i bought a D model Sportster which was fitted with a small glow engine which had soaked several tankfulls of glow fuel into it`s structure over it`s long life which was now clearly over by the state of the oily covering and loose tail structure. I love the shape and the cheap price (next to nothing once the engine was sold) persuaded me to buy it to use as a template for a foamboard replica which will probably come out at half the weight of this porker. I`m thinking of making a start on it this week and it will be my first foamboard model with undercarriage, what are the best ways of making the structure undercarriage safe, looking for advice from those that have done it, the sprung wire will need to be wing mounted not bolted onto the fuselage. Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted February 5, 2023 Share Posted February 5, 2023 Great subject Martin. We were discussing GeeBees today and wondering what a fatty GeeBee racer would look like... Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted February 12, 2023 Author Share Posted February 12, 2023 GeeBee Model D build is now under way, i de-constructed the tail/fin area of the oil soaked balsa model, the airframe weighed 1lb 12ozs so it will be interesting to see how much lighter this new build comes out at. A good start is that the new foam board fin/rudder, tailplane/elevator has come out at exactly half the weight of the original balsa parts. 😁 Tomorrow i will be starting on the fuselage, still pondering on the undercarriage mounting, i have some ideas but if anyone else has some thoughts please let me know. Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted February 13, 2023 Share Posted February 13, 2023 Hi Martin, Great subject. Undercarriage mounting in foamboard is one of the big challenges! I think the key is always to keep the weight down so there is less energy to dissipate, and so avoid the requirement to over reinforce, adding weight and perpetuating the cycle. The way I have done this is to use a 1/16" ply centre rib and use this to locate ply plates where the end of the undercarriage leg can locate. I then added a couple of liteply half ribs to support an undercarriage plate and mounted the legs similarly to your picture. The ends of the legs are solidly located in the wing and rearward shock is absorbed by twisting the legs. At less than 2lbs, you could use 10 gauge. The further trick is to have a solid plate to attach the leading edge of the wing! I use a minimum of heavy materials, but focus on a core 'crutch' where the firewall, leading edge and undercarriage mounts are all firmly attached. That way flying and landing loads are distributed. In the case of my current project (a Pitts, believe it or not!), I'm using a central keel in the fuselage which extends upwards to include cabane struts, and downwards to include an undercarriage block. From the motor mount back to the lower wing leading edge, it is doubled either side in 1/32" ply. That way the soft foamboard has a solid gluing face where the strength is needed. Graham 1 Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted February 22, 2023 Author Share Posted February 22, 2023 Fuselage progress, all the fuz parts weigh 4 ozs compared to the 9oz of the original balsa fuselage, tailplane/fin are half the weight of the balsa ones so should fly well hopefully. Tailplane/fin are just resting on it for a `glory shot`! I have a used un numbered 3s motor which runs a 10x7 prop which has been looking for a home so that is going in the GeeBee, i have had it mounted already and it will be going back on tomorrow to run it up and make sure it is all good and i can get some power readings before i finish the front of the fuselage. Tomorrow evening i will start on the wings, next update will probably be Sunday. 2 Quote Link to comment Share on other sites More sharing options...
J D 8 Posted February 23, 2023 Share Posted February 23, 2023 On 05/02/2023 at 21:32, Graham Davies 3 said: Great subject Martin. We were discussing GeeBees today and wondering what a fatty GeeBee racer would look like... Pretty much the same as standard I recon. Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted July 13, 2023 Author Share Posted July 13, 2023 Been out of the building loop for 6 months due to completing a Classic car rebuild which is now done and dusted so hoping to restart the GeeBee build later on next week, just got the wings to put together, aiming to have this one finished sometime next month. Will update once the wing is on the building board. 1 Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted July 14, 2023 Share Posted July 14, 2023 Look forward to that Martin. We need another injection of foamboard ingenuity! Working on a Mk2 version of a Pitts Special at the moment. I never got to the bottom of the problems with the Mk1, but suspect airframe flex wasn't helping. Mk2 is a bit bigger at 45" and uses some carbon rods to stiffen up the wings. Lots of slight tweaks to our arsenal of techniques, but more on that if they prove successful! It's going to be covered with brown paper/ PVA and painted with emulsion before a coat of gloss water based varnish. I've trialled this already and it seems to offer a good tough semi gloss finish. I'll keep you posted, but vacate your thread for now! Graham 3 Quote Link to comment Share on other sites More sharing options...
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