rtfm
Well-Known Member
Hi. Having sold my Fleabike project, I've started again with a clean CAD screen, designing the next one. The TCF will be built using the cedar strip canoe method. Cedar strips over formers, glassed inside and out with 6oz cloth.
That is the basic concept. However, I'll be using balsa for the strips, with Paulownia bulkheads and hard points. I've used DevFus CAM for the former design and exported them into Shapr3d where I've been tweaking them. The hard points are CNC cut out of Paulownia so that they mate perfectly with the inside fuse surface. Then bonded in place and glassed. I'll add five bulkheads to take the loads of the wings and the landing gear.
I'll build the bottom half of the fuselage EXACTLY like a canoe, bonding the strips in place and fairing the strips when everything is in place. I'll also include Paulownia gunnels (on the inside - I think they are called inwales?) - to add rigidity. The strength of the structure is in the glassfibre, not the wood, which mainly serves to keep the two glassed sides apart, so the balsa will be very suitable. I could use foam strips, but that wouldn't look anywhere near as impressive.
Weight: The basic fuselage is surprisingly light - about 15kg glassed inside and out. That's a pretty handy weight to begin with before adding the inwale, bulkheads and engine mount reinforcements.
Strip planking the wings is an interesting challenge. Traditionally one would bond ribs to the spar and cover everything in fabric or ply or some other material. However, in order to get the (3mm) planking for the wing surface following the airfoil contour, it is necessary to use ribs which run along the length of the wing, not across the chord. I won't need many - after all the front and rear spars act as lateral ribs - so maybe one or two more. I'll construct a Paulownia "frame" for the wing, with leading edge shaped on the CNC. Trailing edge would also be CNC cut, so that each strip lays securely on the lateral ribs and can be bonded to the more hardy Paulownia frame. I'll make the wings in sections (like all Fleas) with hinges allowing the wings to fold. But I'll also make each section in top and bottom halves, so that I can more easily mount them on the formers, and then glass the insides before joining the halves together.
No pictures to show really - just some ideas on my computer screen. But here are the basic profile and plan views. Length: 2.7m, wings: front: 5m, rear: 4m both with 1000mm chord (ie 9m^2 or 96ft^2). Power: I'm thinking of the Aeromarine v-twin (60hp, 800cc 4-stroke, fuel injected, electronic ignition - 52kg) or the slightly less flash v-twin from Hummel (83lbs/32kg)
That is the basic concept. However, I'll be using balsa for the strips, with Paulownia bulkheads and hard points. I've used DevFus CAM for the former design and exported them into Shapr3d where I've been tweaking them. The hard points are CNC cut out of Paulownia so that they mate perfectly with the inside fuse surface. Then bonded in place and glassed. I'll add five bulkheads to take the loads of the wings and the landing gear.
I'll build the bottom half of the fuselage EXACTLY like a canoe, bonding the strips in place and fairing the strips when everything is in place. I'll also include Paulownia gunnels (on the inside - I think they are called inwales?) - to add rigidity. The strength of the structure is in the glassfibre, not the wood, which mainly serves to keep the two glassed sides apart, so the balsa will be very suitable. I could use foam strips, but that wouldn't look anywhere near as impressive.
Weight: The basic fuselage is surprisingly light - about 15kg glassed inside and out. That's a pretty handy weight to begin with before adding the inwale, bulkheads and engine mount reinforcements.
Strip planking the wings is an interesting challenge. Traditionally one would bond ribs to the spar and cover everything in fabric or ply or some other material. However, in order to get the (3mm) planking for the wing surface following the airfoil contour, it is necessary to use ribs which run along the length of the wing, not across the chord. I won't need many - after all the front and rear spars act as lateral ribs - so maybe one or two more. I'll construct a Paulownia "frame" for the wing, with leading edge shaped on the CNC. Trailing edge would also be CNC cut, so that each strip lays securely on the lateral ribs and can be bonded to the more hardy Paulownia frame. I'll make the wings in sections (like all Fleas) with hinges allowing the wings to fold. But I'll also make each section in top and bottom halves, so that I can more easily mount them on the formers, and then glass the insides before joining the halves together.
No pictures to show really - just some ideas on my computer screen. But here are the basic profile and plan views. Length: 2.7m, wings: front: 5m, rear: 4m both with 1000mm chord (ie 9m^2 or 96ft^2). Power: I'm thinking of the Aeromarine v-twin (60hp, 800cc 4-stroke, fuel injected, electronic ignition - 52kg) or the slightly less flash v-twin from Hummel (83lbs/32kg)
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