AeroTech Pitts Python 50cc

Having decided that getting the fuselage down stairs and into the drive so i can fit wings and check CG may be more challenging than I thought. However, my better half has graciously allowed me to assemble it in the guest bedroom where there is more space. Then "panic mode" cut in whilst assembling. The interplane struts don't follow the wing contours. Scratching head and thinking I have bought a "Dummy". Looked at the "manual", a picture book in reality. No idea. As I was just about to find a large hammer and axe and end it all, I had one thought. Are the struts different lengths, they don't look it. Pulled out the tank again and removed centre wing section. Now pulled out struts........................... Bloody hell! There is a slight difference. Right then I will swap them round, nothing to lose. Refit centre wing, slide top wings on to tubes and place struts in their supposed positions. They now fit! :woohoo:

So Brian, your not the only one that gets sudden out of the blue issues.:lol: .

Phil
I see the pilot is lying under the wing looking puzzled!

Simon O wrote: Phil
I see the pilot is lying under the wing looking puzzled!

:lol: Yes, that is Mutley. I rescued him from Dastardly Dick as he had not had a medal as promised. Even he was baffled by the strut issue. Heh! Heh! Heh!

All the strut brackets have had flange nuts fitted. As these type of nuts have a wider body it gives more surface area for the epoxy to bond to. Once the epoxy has virtually set I then placed the brackets in an oven at 150 C for 20 mins. This cures and bakes the epoxy rock hard. Whether this idea will stand up to RC flying I don't know but I used to bond industrial diamonds into steel spindles for CNC milling of precision screw threads and they did not come off.

Thanks to Mike's link the fasteners turned up the very next day, Saturday. I ordered some Rivnuts 4mm x 10mm and some Threaded Inserts also at 4mm x 10mm. This gives some options on which is best to use.

The Pitts makers say use a wood screw into the pre-drilled holes to secure the wing tubes in the centre section and wings. :huh: That maybe okay for the Americans with their big SUVs because they don't have to keep unscrewing the damn things. After while the screw holes are going to get loose for those of us who have to dismantle every time. I will modify the attachment of the wings.

Built into the wing centre section are some thick ply blocks pre-drilled for the screws. Also in the wings too. After some thought I decided to go with the Inserts. These require drilling a 6mm hole then using an Allen Key wind them in. My theory is that when the 4mm bolt I am going to use is wound in and engages with a hole in the wing tube it is really only torqueing down on the head of the Insert. If in the future I cross thread the aluminium inserts I only have to wind them out and replace. The centre section is done.

Now I have a bit of quandary that I hope someone can assist with. I could do the same method with the wings but in practice I am thinking that any slight change in dimensions due to temperature or humidity might make engaging the bolt difficult. If I make the wing tube hole slightly larger then the wing may not sit closely up to the centre wing leaving a small gap. My other thought was and if I heard correctly from Pete Chilver and his RockStar Bipe that his Flying wires keep his top wings in place. Therefore I will hang fire on this part of the job for now.

You shouldn't have a problem lining up the bolts Phil. The inserts have a hex"socket" which is slightly larger than the tapped hole,this helps steer the bolt into the thread. I use these inserts too, usually with nylon screws but when using steel screws, I lube the screw with a spot of WD40,

Thanks Brian, in image 2 you may notice that the inserts are already done and the button head screws engage into a 4mm hole I made in the ally tube. The bolt must go into the hole correctly, if it distorts the tube it may be a sod to slide out again and again. If the designers had used a one piece tube then all that would be needed is securing the wings. Like my Beast Bipe has.

However what I am asking is 1: do I used same method on wings or 2: could I just use flying wires to pull the wings back neatly up to the centre section.

Whilst twiddling my thumbs this afternoon waiting for the glue to set on my custom battery tray, I think I may use the insert method. On the locating screw I will grind it to a point so as the screw moves inward it will line itself up taking up any slight differences in expansion/contraction of tube and wood. The latter issue I have struggled sometimes with the Beast due to temperatures/humidity, mostly during the warmer months.

Battery Tray installed. It's as far forward as I can get it and I estimate after the temporary fit of wings previously that it will need about 400 gms of lead on top of engine box.

After some consideration I decided on not going slope soaring so spent some time on the Pitts. The top wings are now modified and now all that is required to secure them is a 4mm machine screw, an Allen key. Turtle deck now has 3mm T-nuts installed to locate it on the fuselage. Engine bolts "blued" and torqued up.

Looks like an ugly YAK don't it?.......:lol:

Virtually ready for it first fire up but once I fuel it, it will have to stay downstairs and outside (she says) and that's the problem at the moment with limited space in hangar. Time for a tidy up (again)

No.