pacoflyer

My Feedback: (23)

Alberto,
I've only used the aerosol with propellant.

paul

kenh3497

I've read many times about sealing the balsa before laying down the polycrylic to prevent absorption.

I'm thinking out loud here as I've never used poly and fabric. HEY, no smart remarks from the peanut gallery

How about spraying a mist coat of the polycrylic on first to seal the wood? It could go on pretty dry if you just "dust" it on. On the other hand if you put the poly directly on, most of it will evaporate.... right???? so not much weight to be gained anyway????? I have also read some will "seal" the wood before using epoxy. It seams a bit counter productive to seal the surface instead of letting the bonding agent (epoxy or poly) not soak in a bit for the best bond.

So with he above said.... If you chose to seal the wood to prevent absorption, I would find a way to use the same product to seal, as what will be used to bond the fabric of choice to the wood. I think you will solve any issues from dissimilar materials bonding (or not) to each other.

IMO, you have only one chance to bond the fabric to the wood as securely as possible to gain the most strength and that is the first coat of what ever product that touches the wood and cloth at the same time with nothing between them.


OK... My flame suit is on

Ken

ululi1970

Ken,
I have read about people suggesting the same thing (using the poly as a sealer). I am concerned about the water soaking into the wood and causing warping issues. I think that is the reason it is recommended to use a non water based sealer as a first layer. Of course, I could use a lacquer based polyurethane, which would not require a sealer, but I'd like to avoid dealing with fumes, plus I like
being able to clean up stuff with water. I got a can of hairspray and will experiment with that. BTW, there were several types to choose from, most of them listed water as the first ingredient, so I stayed away from them. I picked one that has alcohol as first ingredient and no water at all. I will build another panel and experiment with hairspray+water based poly and report back the results.
Alberto

pacoflyer

My Feedback: (23)

Alberto,
I too would be hesitant to use anything water base on bare wood for fear of raising the grain. That's why I have used the hairspray first with good success. If you can't find a lacquer based hairspray, juts go get a can of Deft sanding sealer and use that instead. I'm doing a plane now that I used the Deft product first, then used the Polycrylic water base product right over it to apply my 3/4oz cloth. I have yet to have an issue with delamination. All that dissimilar material/ adhesion discussion is exactly that.... Discussion. I'm sure there's a chemistry lesson in here somewhere but I can tell you using the two products together won't fail you. I have used the Deft product throughout the glassing process too, but using the Polycrylic sure cuts down on the fumes and eases clean up. You won't have any problems with delamination as long as the Deft sealer is fully cured.

Hope this helps,
paul

ululi1970

Paul,
It is not just discussion. As I mentioned in post 22 above,
using deft under poly resulted in blisters forming when heated to 150F.
You may argue that 150F is extreme, but it is not unheard of in a car
in direct sunlight. Once I left a heli canopy in the car. It basically melted down...
Alberto

pacoflyer

My Feedback: (23)

Alberto,
I'll keep the 150 degree issue in mind. Usually though, I try not to keep anything of value in 150 degree heat. Here in Buffalo, New York, that's something I would never worry about as hell might freeze over before that happens. I know of several Top Gun builders in south Florida however who routinely use the method I have described. Additionally, I've had sun/heat damage done to Monocoated,"Solartexed" and fiberglassed models before in heat, a lot less oppressive that 150 degrees. I'm gonna continue to use these two products together as it's easy,it works and produce beautiful durable results for my planes. To each his own I guess

Good flying,
paul

bacon104

What about removing monokote from an arf and glassing? What problems would you run into doing this?

Avaiojet

None,

Just remove the stuff then glass. I'm doing that now!

Charles

kenh3497

I've used the light weight spackle quite a few times as a "leveler" on balsa. I thinned it with water to make a light slurry and painted it on. I've never had a warping issue. It dries fairly fast, like a WBPU does. I guess my only concern, using a wood sealer, is not having the first coat of product soak into the wood providing the best bond possible with the glass cloth.

I guess it comes down to what ever works for you.

carry on

Ken

ululi1970

I did some experiments with alcohol based hairspray. 2 coats of hairspray, 6 coats of WBPU + fiberglass cloth. Baked at 150F for 1/2 hour, no bubbles/blisters.
I did noticed though some warping at the end. Not sure when it started. It may have been there from the beginning, though I noticed only after a couple of coats of WBPU.
So now I am doing a final experiment
with just a sheet of 1/6'' balsa (no frame). So far the first coat of hairspray went on without warping. The second is drying right now. Will then do the usual
WBPU. I reckon that if warping occurs, a plain sheet of balsa should show it. Will check after each coat.

My only gripe is that the only hairspray I could find that is alcohol based is scented. What happened to the old cheap hairspray?

Alberto

ululi1970

Ok,
it seems that if I do not apply the hairspray liberally the warping occurs after applying the WBPU, while if I apply the hairspray liberally warping occurs right away. Either way, no good. Probably the harispray is not the right one.
Pacoflyer suggested a lacquer based one. Will look into it.
At this point, if I can't find it I am inclined to go with the DEFT sealer and make sure I do not leave the ship in a hot car...

Alberto

jaka

Hi!
No hairspray is necessary!!!!!!!!

j.duncker

My Feedback: (2)

I agree, I never used any pre treatment, just epoxy onto bare balsa or veneer.