Panic bipe, wing reinforcement

[Don Fry]

Sorry to interrupt the CAA consultation debate, but I am knocking up a Panic bipe, from the current J Perkins kit with built up wings. I need a small hack to stop my current small hack crisis (all broken or worn out). For some bizarre reason they have chosen to reinforce the centre section with a glass bandage, rather than internal structures. This bandage takes the flight loads. I intend to abuse it in flight.

Now I have no memory of how to do this neatly. I have found some nice glass cloth. And I have epoxy lay up resin, and finishing resin, and I have isopropyyl alcohol. And brushes, and rollers.

How do I apply this so the edges are neat, and its looks generally neat, and the fraying edges are kept under control.. It's a 120mm strip, applied all round the wing.

[JOHN MOSLEY 2]

I am using the thinness of ply 1/64" and I stick on with contact adhesive. Hate using those bandages that need filling and get the resin wrong and does not go off leaving a sticky mess.

[Don Fry]

John, what model. I have the same thoughts, but I can imagine some stresses in the wings if looped in its own length.

[Former Member]

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[Dwain Dibley.]

I use an old credit card for smoothing out the resin, after it has gone off a little.

But, a second on Percys' Aliphatic idea as well.

D.D.

[Nigel R]

Yup, aliphatic or just plain old pva.

If you can, purchase a square metre of glass tissue or very thin glass cloth, and do it in two or three layers (first one wide last one narrow) as that needs no finishing at all.

[Former Member]

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[Don Fry]

When you say fine, do you mean the 25 gsm stuff I use for skinning airframes.

[Don Fry]

As it's a bipe, and if you can't do new tricks on hack, what can you do new tricks on. And test the result.

I've done the lower wing as John Mosley suggested. I used .2 mm proskin, a epoxy/ glass sheet material from Mick Reeves models, decreased and abraded. Don't use contact adhesive much nowadays. Stinks. Applied and put down with a roller. Easy to do, usual get it right first time tension, very neat. There is a straight, .2 mm step at its edge, a flat surface overall. After a couple of hours I loaded it up to 15 kilos, positive and negative, which on a bipe is over 12 g stress. And no sign of failure. So I am happy the lower wing won't fail. Thank you John

Ive dug out my bag of skinning cloth, 25 gsm stuff, and zero cost, this gets done with offcuts. And the benchtop aliphatic glue. I've got the first layer on, using a roller. Same as skinning. I think I will use 3?, or 4? stepped layers.

Any suggestions, 3 or 4. But the weight bag awaits the result. Better broken on the ground, and have confidence when you opt to take off.

Might be a couple of days as some rotten piece of pondlife pushed my boat trailer off the quayside into the river last night. It weighs 300 kilos. Tomorrow afternoon, me and my neibours will get it out. That will cost me whiskey, so no model building.

[Engine Doctor]

Hi Don . So as not to get a ridge where the glass mat ends try this. Join the wings then apply the glass mat and resin. Now apply another coat of resin over the first coat while it's still tacky and out from the edge of the mat about an inch onto the balsa. Now wrap it with cling film. Try to apply the cling film as smoothly as possible avoiding trapping to many air bubbles. Smooth it out and leave to fully cure. When cured the cling film will come off easily and the resin should have feathered out onto the balsa so that no ridge is left. Any air bubbles can now be filled and the whole lot sanded lightly to remove the gloss so that covering will grip . I have done this on a few models now and once covered is virtually invisible. It's also very strong as the tapering resin has some flex rather than a stiff edge across the wing .

[Brian Hammond]

I,'ve used glass reinforced sticky tape and had no problems so far

[Nigel R]

Don yes the 25gsm is the stuff. I've used 2 layers on monoplanes up to around 7lb with no trouble.

After the seconds layer is on and dry fill the weave with another round of aliphatic or pva. Apply with the usual old credit card.

[Don Fry]

Anyway, having got the boat trailer out, cast of thousands. And done all my tax returns.

The wing has been finished, 4 stepped layers of 25 gsm, and aliphatic glue. And it did the 12 g stress test.

So thank you everyone, as I have now got 2 ways to sort this problem out.

Mind, the kit has two sets of holes in the wing ribs. If I did another, I think I would use a pair of short carbon tubes, with some liteply washers to load spread into the ribs.

[Nigel R]

4 layers was very enthusiastic! Mind you my current one, being a 60 size sort of thing, will probably receive 3 layers, in widths 1", 6" and 12".

My dad has used plain old PVA and cotton medical bandages for many moons. All very low tech. Seems to work though.