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How to glass a Horner wing tip

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Old 12-08-2013, 06:11 AM
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Snoopy
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Default How to glass a Horner wing tip

Hi needs some help and advice.
Sorry if this is a little long winded just trying to explain the help needed. Built one wing tip, for a wing with a cord of 26 inches and thickness of 4 inches. The wing tip design is “Horner” wing tip. Please note that this wing tip does not have a single straight surface. Made the first one from foam, wire cut it, shaped it and covered it with 1/8 balsa. This was difficult and very time consuming. Worked out well and looks great but do not want to do it again. Would like to build the second one from foam, shape it correctly then vacuum bag it in fiberglass.
The big question. Would like to set the tip down on a flat piece of glass, fiberglass the Horner-tip and then vacuum bag it. Please note I have never done this before.
1. Place the tip on the glass
2. Cover the tip with 2 layers of 2 oz/sq-yd cloth.
3. Due to the shape and folds in the material that will happen do not know what peel to use.
4. Breather cloth layer which one do I use.
5. What bagging material do I use to conform to the shape and not pull on the tip in the wrong directions deforming it?
6. Will seal the bag to the glass as required to get a vacuum.
Thanks for the help.
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Old 12-08-2013, 11:40 AM
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BMatthews
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Why does it need to be vac bagged? It's only a wing tip after all. You laid out all the possible problems with attempting to vac bag a nasty part of this sort. Short and nasty compound curves you are trying to cover with films that don't want to bend that way. I would suggest it's just simply easier to do the glassing without the vac bagging.

Shape it in foam then cover it with thin fiberglass and a minimal amount of resin.

I would start by taking the rough formed "block" of foam cut to the side and top profile and layout the outer edge. Then cut a slight groove about the size suitable to take some butcher's string or builder's chalk line string. Into that groove lay up some epoxy resin and a bundle of coarser glass fiber you get by pulling out a few strands from some 8oz or heavier cloth. This cord will give the edge some hardness and strength. It will also serve well as a hard edge to lay up the cloth and later on for cutting back the excess and supporting the foam during the final sanding of the skins. After this hard edge cures shape the foam to suit.

At that point I'd just lay on some cloth and brush it down with a minimal amount of resin to wet it out but not flood the cloth. When cured to a softer "green" state cut away the excess around the edges and let cure hard. Then brush on a second light coat of resin as a PARTIAL filler coat. Again do not try to flood the surface with resin. You want to more smear on a thin coat and be a final seal to the cloth weave. When this second coat has cured hard after a couple of days lightly wet sand and then it's ready for a high build automotive sanding primer. Apply a couple of coats, let dry well and then wet sand to a slick and smooth finish.

If it's a lacquer base primer like many used to be you will have to mask off any exposed foam. Or if you use two layers of something like 4 oz cloth you could get away with melting out the foam for hollow tips. Your choice. Oh, the other option is to use a balsa face rib attached to the foam. When glassed over this face rib will be secured and act as a glueable surface to mount the tip to the wing.
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Old 12-09-2013, 05:26 AM
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thankyou for taking the time to ansere my question. i will try to do some vacuum bagiing on some small pieces if works great. if it does not i will follow your instructions. waiting for some materials from CST to try the bagging method.
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Old 12-15-2013, 08:18 PM
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If its white foam you used, your'll just crush it if you vac. bag it
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Old 12-16-2013, 04:23 AM
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If it is 1 or 2 lb. density white styrofoam you can vacuum bag it but you will need to regulate the hg down to 4.5-5 inches MAX. just like we do on skinning our wings that use 1 to 2 lb. density foam with balsa skins or it will certainly crush as already stated.

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