Large Model Association Forum

Dear all. I have rather rashly decided to build myself a 1/4 scale Mitsubishi A5M4 Claude over the winter and hopefully get it flying before the end of next summer (fat chance). I have been thinking about producing a 2 part fuse with the separation line a little aft of the main wing.
I am thinking about using 4 wing tubes and sockets of around 10mm diameter spaced equidistantly around the periphary of the fuse formers. Do you think they would be better spaced at 12,3,6 and 9 o'clock or at 1.30, 4.30, 7.30 and 10.30. The later will probably work better as it will interfere less with the wing saddle. Phil sells 10mm ally tube + phenolic socket in 500mm length which could give upto 250mm in each fuse half with the socket passing through 4 formers in each half if their spacing is 80-odd mm. Alternatively I could buy some carbon tube and lay up my own tubes from glass cloth. Does this sound feasable, bonkers, overkill?

Many thanks, Rob


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Rob,
4 tubes sounds simple in theory, but have you tried assembling a wing with only 2 tubes, they have a frustrating habit of binding after about 1" of tube has been inserted - I fear 4 would be a nightmare.
Why not have just one large tube that would take all the load and have a smaller stub tube that mates just before the main one is home, although even that one would be redundant once the bolts are aligned.
The alternative is to dispense with tubes altogether and build substantial flanges that mate face to face with 4 (or if you feel unhappy with that) 6 bolts, equidistant around the periphery.
Attached is a picture of our Comet which has no tubes in the fuselage, just relies on flange to flange joints. What you can't see in the picture is that the rear faces of the flanges are fibreglassed to the fuselage sides. The fuselage is 16ft long, so a 1/4 scale A5M4 should be fine.

Interlocking st/st fish plates is another option. These are built into the main side, upper & lower fuselage longerons so all loads are transfered to a main load bearing structure. The inner plate has a nut silver soldered to it's inner face to accept the fixing bolts. In this application, I used M5. The plates are boned & screwed to the main longerons (Cyparis in this case, with a doubler in the plate locations).

This method was used on the 2 part fuz on Ali's 30% Skyraider I built 4-5 years back.........easy to build & easy to assemble.

Phil