Sailplanes International Axle build/rebuild

[Doc J]

This assuming I can repair the wing to some form of functionality. The adhesive used to bond the skins to the core has proven to not stand the test of time. I've found two other areas of delamination. Although small it is an indication that the wings are not durable and may not be suitable for flight.

And as mentioned the fuselage isn't worth the effort to re-wing. So while I'm willing to try to build the model as supplied. I'm not going to try to make a silk purse out of this sow's ear. Some designs are fundamentally flawed and aren't worth the effort to try to rehabilitate. This is one of those such designs: its only merits is in trying to relive ones youth.

Axle wings:

Skin adhesion on these models was always a problem and it was always solved in much the same way:

Fill any obvious dents or depressions with lightweight spackle - even on a brand new kit this was sometimes a problem. Those were the days!
Then wing bag the wings with 2oz cloth all over and maybe a bit more at the roots and LE's. This forces the resin into the voids and pretty much takes care of the delamination problem. If done right, there is vast strength increase and very little weight penalty. If you want to be super cool with a glasslike finish, then wax up a couple of mylar film layers and tape them at the LE or TE (TE is best) into an "open book"and bung the glass onto them first before bagging the entire caboosh.

In any case, as I remember the wing was only about 7% thick so they need a bit of help - but I could be wrong on that after 50 years or so.

Axle Fuse:

For the fuselage, there needs to be reinforcement around the wing "axle' whatever you do. We used to start with a couple of nice 3mm layered/chamfered to 6mm birch ply plates epoxied along the wing/axle area. Now we have industrial adhesives that can take care of the polyester/epoxy bonding with a little surface prep, but then it was sawdust mixed with epoxy.
After that lay in glass wherever you can get it. Again, now that can be done with industrial adhesives, and with a high probability of sucess, though you might have to warm the mix up a little to get it wet enough.

The bonding strength of these newer industrial glues is phenomenal.

After that, a bit of sandpaper, some elbow grease and a couple of rattle cans plus a few cool stickers will see the flying speed increase phenomenally - as these things do.

Doc.

 

[Red]

The Zagi is by far the most dangerous airplane. Usually flown by roving gangs wearing backwards hats with razor blades on the wings.

 

[Konrad]

That backwards hat is a dead give a way. But I guess that is to protect their red necks.

 

[Konrad]

Axle wings:

Skin adhesion on these models was always a problem and it was always solved in much the same way:

Fill any obvious dents or depressions with lightweight spackle - even on a brand new kit this was sometimes a problem. Those were the days!
Then wing bag the wings with 2oz cloth all over and maybe a bit more at the roots and LE's. This forces the resin into the voids and pretty much takes care of the delamination problem. If done right, there is vast strength increase and very little weight penalty. If you want to be super cool with a glasslike finish, then wax up a couple of mylar film layers and tape them at the LE or TE (TE is best) into an "open book"and bung the glass onto them first before bagging the entire caboosh.

In any case, as I remember the wing was only about 7% thick so they need a bit of help - but I could be wrong on that after 50 years or so.

Axle Fuse:

For the fuselage, there needs to be reinforcement around the wing "axle' whatever you do. We used to start with a couple of nice 3mm layered/chamfered to 6mm birch ply plates epoxied along the wing/axle area. Now we have industrial adhesives that can take care of the polyester/epoxy bonding with a little surface prep, but then it was sawdust mixed with epoxy.
After that lay in glass wherever you can get it. Again, now that can be done with industrial adhesives, and with a high probability of sucess, though you might have to warm the mix up a little to get it wet enough.

The bonding strength of these newer industrial glues is phenomenal.

After that, a bit of sandpaper, some elbow grease and a couple of rattle cans plus a few cool stickers will see the flying speed increase phenomenally - as these things do.

Doc.

That was all covered earier in the thread. But migration of any adhesive that doesn't desolve the core through the skin and the old adhesive is a problematic process at best. I know I've tried it many times.

Again, there really is no point in trying to make a silk purse out of this sow's ear!

 

[Doc J]

The Zagi is by far the most dangerous airplane. Usually flown by roving gangs wearing backwards hats with razor blades on the wings.

Dayum - is that the FAI Nose police?

Doc - who never wears a hat bckwards.

 

[Doc J]

That was all covered earier in the thread. But migration of any adhesive that doesn't desolve the core through the skin and the old adhesive is a problematic process at best. I know I've tried it many times.

Again, there really is no point in trying to make a silk purse out of this sow's ear!

Prick it.

Doc

 

[Konrad]

At what spacing, the devil is in the details. Again it doesn't really work as the old adhesive acts like a peel ply.

 

[Doc J]

At what spacing, the devil is in the details. Again it doesn't really work as the old adhesive acts like a peal ply.

Make a pricker roller and prick it all over. The nails go through the veneer and the adhesive. The resin goes into everything.

You mean "Peel" ply?

Doc.

 

[Konrad]

Yes thank you.

As the old failed OEM adhesive usually is still attached to one surface (veneer) it does not allow the epoxy to bond to the veneer to core directly. The prick “repair” has a bond that is foam core to old adhesive. With some epoxy rivets going through the old adhesive layer and veneer. But the failing old adhesive to veneer bond is still there. With a solvent this adhesive might to reactivated. Unfortunately all the solvents I know of that might reactivate old adhesive will dissolve the foam core.

I’ve had better results with steam and heat. But like with solvent based repairs one needs to watch for damage to the foam core.

Still don’t know the hole spacing of your repair.

The proper way is to reskin.

 

[Doc J]

Yes thank you.

As the old failed OEM adhesive usually is still attached to one surface (veneer) it does not allow the epoxy to bond the the veneer. The prick “repair” has a bond that is foam core to old adhesive. With some epoxy rivets going through the old adhesive layer and veneer. But the failing old adhesive to veneer bond is still there. With a solvent this adhesive might to reactivated. Unfortunately all the solvents I know of that might reactivate old adhesive will dissolve the foam core.

I’ve had better results with steam and heat. But like with solvent based repairs one needs to watch for damage to the foam core.

Still don’t know the hole spacing of your repair.

The proper way is to reskin.

I made a roller with about 20 rows of sharp tacks and about 50 on each circumference. That would be about 1,000 pricks per roll so I guess it would be around that many per 6" x 2" strip.

Might be better just to make a quick bagged set of new wings though its rather negates the Repair and refurbish objective I suppose.

Doc.

 

[Konrad]

I made a roller with about 20 rows of sharp tacks and about 50 on each circumference. That would be about 1,000 pricks per roll so I guess it would be around that many per 6" x 2" strip.

Might be better just to make a quick bagged set of new wings though its rather negates the Repair and refurbish objective I suppose.

Doc.

So 83 stabs per square inch.

We need to define what we are repairing. I'm trying to repair/rebuild the Axle sailplane.

 

[Doc J]

So 83 stabs per square inch.

We need to define what we are repairing. I'm trying to repair/rebuild the Axle sailplane.

I made the pricker roller to experiment with foam cores that had through-holes for resin 'pillars'.

It worked, maybe 20 to 30% more rigid, but with some labour and weight penalty. The intention was to make it automatic, and therfore controllable but due to the circumstances at the time, that never happened.

I did use it to repair a tailplane for a friend's scale job in the manner I have decribed, a long time ago - and it worked very well - hence the reference.

Doc.

 

[Konrad]

One pro and one con position on that style of repair. That’s what I like about these forums.

 

[Doc J]

One pro and one con position on that style of repair. That’s what I like about these forums.

Really its just a simple decision: Is the work needed to refurbish the model justified to the owner?

Yes = do it. No = flog it on to benefit someone who has enough, or the right level of nostagia to undertake the work.

Doc

 

[Konrad]

Really its just a simple decision: Is the work needed to refurbish the model justified to the owner?

Yes = do it. No = flog it on to benefit someone who has enough, or the right level of nostagia to undertake the work.

Doc

I just have an issue with selling sub-standard items. I have to sleep with myself and my conscience: it's a heavy burden!

 

[Doc J]

I just have an issue with selling sub-standard items. I have to sleep with myself and my conscience: it's a heavy burden!

Sell sell sell...

 

[Konrad]

Sounds like my broker!

 

[Doc J]

Sounds like my broker!

I'm quite sure that someone - espcially someone old and fishlike (like me) in the UK woud snap it up. Also the box is not too large so it would not need limb amputational - hey I invented a word! - shipping costs.

Flog it!

Doc.

 

[Konrad]

You want it? PM me and we can discuss condition and terms.

 

[Doc J]

You want it? PM me and we can discuss condition and terms.

I had mine in the 70's. Good thing is that now I can fly my own stuff.

But there are a lot of people who Im sure wou be glad to take it off your hands.

Cheers,

Doc.