advice wing tube issues

[richard armstrong]

on my chipmunk the cardboard keeps coming out i glued it several times and the tube is starting to come apart

wondering what the best method would be?

an off cut of philonic tube? if i can find the right size

make a fibreglass tube with a paper over the metal tube i have 1 and 2oz cloth

at this point i am open to ideas

tube OD 31.9mm

Cardboard tube
ID 32.1mm
OD 34.5mm
wall thickness -1.1mm
length - 142mm.

tube.jpg (108.88 KiB) Viewed 11933 times

[Rob Buckley]

Richard, we need a bit more information. What's the metal tube for, what's the cardboard for? I hope it's not structural cardboard.

[stewart clifford]

Speak to Richard at Falcon, he normally has a good selection of tubey stuff

[richard armstrong]

cardboard tube acts as a guide for metal tube as part of the wing joining through the centre of the fuse on the chipmunk, is more of a guide than structural

[richard armstrong]

thanks stu spoken to him at a show i will try Falcon again

[Alan Cantwell 1131]

Without this cardboard tube, would the wing wobble? If the answers yes, it's structural,

[richard armstrong]

Without this cardboard tube, would the wing wobble? If the answers yes, it's structural,

thanks for the correction, alan, the wing would wobbe but they are held with locking bolts as well in the wing and inside fuse

[Rob Buckley]

Putting the wing root bending loads through cardboard into 'metal' is structurally interesting!

What's the span of the model? If it's not particularly big, make some ply rings to closely fit the metal tube and just glue the wing halves together and the tube to the ribs.

[richard armstrong]

it's the black horse mk1version chipmunk the mrk2 version is better design http://weymuller.free.fr/notice/notice_035z5863.pdf

wings are in 2 slides to fuse and lock by bolts in the wing and in the fuse


Wingspan : 2,170 mm 85.43 in.
Length : 1,740 mm 68.50 in.
Weight : 6.6 kg 14.52 Lbs.
Radio : 06 channels.
Engine : O.S GT 33CC - 45CC Gas

[Rob Buckley]

Is the tube through the fuselage a bit of bog roll too?

If so, a far better solution would be to replace the whole lot with a slightly bigger aluminium tube & phenolic outer combination in the wings & the fuz.

Another solution would be good fitting disks on the fuz sides and ribs of decent pywood. That would make assembly slightly more fiddly, but the structure would be better.

You could lay up glass on the metal tube to make a new wing sleeve, but that would be a complete swine to get off again.

[Dave Collis 2296]

Is the tube through the fuselage a bit of bog roll too?



You could lay up glass on the metal tube to make a new wing sleeve, but that would be a complete swine to get off again.

If you cover the metal tube with a layer of plastic covering film, ultracote, monocote etc, 3 or 4 good coats of wax, some mould release and spiral wrap the tube with 2 layers of 6 oz. fiberglass tape about 4" wide, you can get the f/glass sleeve off.
It does take a bit of doing, though soaking in hot water will help dissolve the mould release agent.

Cheers,
Dave.

[richard armstrong]

Is the tube through the fuselage a bit of bog roll too?

yes the bog roll effect is what it came with

If so, a far better solution would be to replace the whole lot with a slightly bigger aluminium tube & phenolic outer combination in the wings & the fuz.

that a massive undertaking as the wing tube are cardboard as well and they are in good nick and i take the advice what's not bust don't fix

Another solution would be good fitting disks on the fuz sides and ribs of decent plywood. That would make assembly slightly more fiddly, but the structure would be better.

i like this idea make a disc or 2 each side for better glue holds for the tube to fit in the Fuz

You could lay up glass on the metal tube to make a new wing sleeve, but that would be a complete swine to get off again.

[richard armstrong]

If you cover the metal tube with a layer of plastic covering film, ultracote, monocote etc, 3 or 4 good coats of wax, some mould release and spiral wrap the tube with 2 layers of 6 oz. fibreglass tape about 4" wide, you can get the f/glass sleeve off.
It does take a bit of doing, though soaking in hot water will help dissolve the mould release agent.

Cheers,
Dave.

i think i going to have a go of making a tube

clean the existing tube rap a fine bit of paper to give me a .25 gap, cling-film rap that once, 6oz cloth was suggest, but i only have 4oz and 2 oz in stock, which i cut down into strips, but i can purchase 6oz tape

once complete i will take on robs suggestion of making glue rings inside fuz for support and hold

i have some discretion on hole size on the fuz so can go slightly bigger if needed

[Dave Collis 2296]

I don't know if I would use just paper.
I used the plastic wing covering as it has a shiney finish that wont absorb any resin that gets on it. Paper being slightly porous will soak up any resin that might get on it. You will now have a solid metal/fiberglass tube assy.
Make sure to wax very thoroughly and use a mould release (PVA) made for use with fiberglass.

[richard armstrong]

I don't know if I would use just paper.
I used the plastic wing covering as it has a shiney finish that wont absorb any resin that gets on it. Paper being slightly porous will soak up any resin that might get on it. You will now have a solid metal/fiberglass tube assy.
Make sure to wax very thoroughly and use a mould release (PVA) made for use with fiberglass.

i did think of using parcel table as it repels epoxy

using paper the clingfilm over that would that work ? your thorghts?

[Phil Clark]

Some epoxy laminating resins stick to cling film (been there, done that)........covering film or parcel tape + wax is the best solution.

Cardboard outer sockets in this application are utterly useless......unlike phenolic, cardboard can and will compress under constant load so the fit will become loose & sloppy. Phenolic or GRP sockets are the best solution. Bonding a new GRP socket into the existing cardboard socket in the wing won't really solve the issue........the card can still compress between the new GRP socket & the ribs + if the new GRP socket isn't bonded fully end to end into the cardboard, the new socket can start to move in the old..........best solution, get rid of the lot & replace with a quality phenolic/aluminium assembly.

Phil

[richard armstrong]

Some epoxy laminating resins stick to cling film (been there, done that)........covering film or parcel tape + wax is the best solution.

Cardboard outer sockets in this application are utterly useless......unlike phenolic, cardboard can and will compress under constant load so the fit will become loose & sloppy. Phenolic or GRP sockets are the best solution. Bonding a new GRP socket into the existing cardboard socket in the wing won't really solve the issue........the card can still compress between the new GRP socket & the ribs + if the new GRP socket isn't bonded fully end to end into the cardboard, the new socket can start to move in the old..........best solution, get rid of the lot & replace with a quality phenolic/aluminium assembly.

Phil

thanks phil for the advice

i will take it on board, i would go the whole hog but its a lot of work, and cost, for now i will have a go at making a 12" FG tube to cut and fit fuz part, and at a later date, when i am better cash wise i will strip out the old tubes in the wing and remake them in FG, but for now i will make do for the short term

[richard armstrong]

6oz x 4" tape ordered

i have deluxe eze kote would that be OK to make the tube or go full epoxy?

https://www.deluxematerials.co.uk/gb/rc ... 00746.html

i use this on several applications before to good effect, mainly wings and fuz with 1-2oz cloth for painting? finsh is as good as epoxy

i have a G2 pond sealer coming as well

[richard armstrong]

which mould wax do i need and release agent ?

PVA blue? i one i spotted

[Phil Clark]

Meguiars Mirror Glaze #8.........6-8 coats of it