[wollins]

I've always used WBPU for my glassing and have never heard of folks using the oil version for glassing. Any particular reason why? I have used the oil based to seal my wood first before glassing with WBPU so I was thinking why not just use the Oil based for the whole process since I use it to seal the wood anyway?

Also ... any better product to seal the wood? Sanding sealer, dope etc etc. Suggestions?

Colin

[cessna180]

I seal balsa with a mixture of dope (does not matter butyrate or nitrate; remember butyrate goes over nitrate but nitrate does not go over butyrate) talcum powder and some aluminum paste. Mix with some thinner so the consistence so the mixture flows out. If it is to thick dope will tend to rope. Use lots of talc and sanding is very easy. About 3 coats should be ok. The use of aluminum paste highlights any imperfections in the balsa structure. I have used WBP but when it dries it is dry but with dope application of another coat blends into the other coat because it melts itself together. I use dope to apply fabric or silkspan and you can release it with thinner and re-apply but with WBP you can not. Also WBP dries clear but oil base dries yellowish. For glassing I like a product called EZE-KOTE. It is water based resin, fast drying and easy to sand.

[wollins]

Originally Posted by cessna180

For glassing I like a product called EZE-KOTE. It is water based resin, fast drying and easy to sand.

I've heard of EZE - KOTE ... not tried it myself yet. Would one have to seal first if using this?

[cessna180]

I would say yes. Sealing the balsa first fills in the ( I call them pores) in the wood and makes a smooth finish. Before glassing structure must be smooth. Just like a paint job. Paint will not hide imperfections. To get a good paint job the under structure must be as perfect as possible.

[Mike Sebastien]

If you are Fiberglassing a surface with finishing epoxy and fiberglass cloth you do not need to seal the wood.

[michaely]

Originally Posted by cessna180

I would say yes. Sealing the balsa first fills in the ( I call them pores) in the wood and makes a smooth finish. Before glassing structure must be smooth. Just like a paint job. Paint will not hide imperfections. To get a good paint job the under structure must be as perfect as possible.

Have to disagree.... if you are using any plastic (eg. Monokote), fabric (Koverall, fiberglass cloth) or paper (silkspan) covering there is zero need to "seal the wood" or fill the pores in the wood and doing so just adds weight. The covering is the smooth base for any further finishing such as paint.

This is different from applying an liquid product - dope, Balsarite, etc. - to act as an adhesive for a paper, plastic or fabric that does not come with its own adhesive backing. And in the case of open balsa wing structures, typically this adhesive is only applied to the perimeter of the panel to be covering - and the covering on that panel then tightens a bit through drying or heat - before the whole covered component is further filled and finished in with dope, etc.

When I have 'fiberglassed' a fuselage or sheeted wing, I just sand the balsa reasonably smooth and do not apply a pre-coating of any kind before sticking the glass cloth to the balsa with resin, etc.

I suppose you can make a case for dope and some other clear coatings strengthening particularly weak balsa sheeting but usually this strengthening is sought in the film/fabric covering.

I could wrong but I think the only time filling in the wood pores/sealing the wood with sanding sealer/clear dope was used was with some old time control line 'knock out beautiful' models where NO covering was used and the dope colors needed a smooth/pore filled balsa surface.

just my recollection,

[Trumpetman]

Deluxe Materials has a good video on how to use Eze-cote:
http://m.youtube.com/watch?v=yP05qv3...ature=youtu.be

I really like the stuff! Great results, no epoxy mess and water clean-up.

[Dangaras]

I have done the glass over, both balsa and foam. Ive used the ezkote & the minwax water based varathane over both.

There is no reason for pre-sealing with oil based or epoxy liquids. It was an old method with glow to stop the fuel from soaking into the wood and making it turn to a sponge consistencey, you can imagine what the last flight looked like.

The trick with the glassing over any surface is a smooth finish. Foam or wood. With the minwax Ken Manuel (FFX Fighters) taught me to dilute it 50% to save weight and he knows what he is talking about when building with foam.

Process -> Apply, let dry, light sanding, apply, let dry, light sanding, apply, let dry, light sanding. The more you apply the less of the weave you see. Sanding after each coat is essential. Perfect finish every time!

The EzKote is $24 and is expensive minwax in my experience. Got a bottle free, will never buy it.

If you want a glass like finish, 20 minute epoxy diluted 25% with alcohol (you want a very runny consistency) and applied with a brush will self level and will form a smooth glassy finish. Ive done that as a last coat just to see how it would turn out and it looked amazing. Did not need sanding but took 24 hours to dry. You can do that after the first minwax application, let dry & light sanding, cycle.

This is assuming you fly electrics only....

[Thunder Chicken]

For those who've glassed with the polyc and fibreglass, is there a weight difference to get that nice glass like finish?

[Dangaras]

Originally Posted by Thunder Chicken

For those who've glassed with the polyc and fibreglass, is there a weight difference to get that nice glass like finish?

With thinned poly (50% water) you apply and lightly sand, apply and lightly sand with fine sand sandpaper until the weave disappears, then you will have that smooth finish.

To get the same I've found 20 minute epoxy thinned 30% with 99% rubbing alcohol will give a smooth finish however it always weighs more and is a pita to sand.