garch 22

My Feedback: (7)

Fellows,

I am about to start glassing some foam floats purchased from Seaplane Supply, and would like to try either Minwax oil based polyurethane or their water based polycrylic instead of
West Systems Epoxy resins. I plan to first apply a coat of light spackle to fill the pores, sand smooth, and then use 2 oz. glass cloth on the tops of the floats, and a couple layers of
2 oz. to the bottoms. I talked to Mark @ Seaplane Supply about doing this, and he was not familiar with these products and was hesitant to give a recommendation, wondering if there
might be problems with adhesion to the foam. I have read that the Minwax products are only about 60-70% as strong and hard as epoxy resin, but think it may be adequate for my
project, which involves mounting a single 36 inch float under a Great Planes Viper 500 with foam floats on the wingtips. Am trying to keep the AUW under 5 pounds. I have used the
water based polycryllic on balsa sheeted wings successfully, and know that the Minwax products go on much lighter than the Epoxy, but would like to get more input before committing
to this method.

Has any one used either of these products for glassing foam floats? If so could you comment on the following:

- Which product did you use and how did it adhere to the foam ?
- What kind of strength and hardness does it produce as compared to the 2 part epoxy resins ?
- Will the bottoms stand up to the usual rigors and abuse of float flying without first sheeting them with a plywood veneer?
- Am I using a proper weight of glass cloth for the tops and bottoms ?

Thanks for any advice.

JimCasey

My Feedback: (1)

Don't use the oil-based version if you want foam to be there afterward. The solvents will attack the foam.

I have used WBPU successfully. It may not be stronger than epoxy, but it's stronger than balsa. That's all that counts.
Also it doesn't stink. It's not toxic. It cleans up with nonstinking nontoxic solvents (water) .
It's thin enough to brush on easily.
2 ounce cloth sounds like overkill. I use the 3/4 oz sig cloth available from the hobby shop and even it is hard to keep bonded to corners sometimes. Multiple layers of 3//4 oz are better than one layer of 2 oz.

I like to use a 3" section of ply on the bottom just in front of the step. That's the point that takes all the beating and where it sits in transit.

arobatx

I've had the same experience as Jim...I use thinner cloth with the WBPU, and lots of coats. I usually apply a generous coat of the PU directly on the surface, let cure and sand. It appeared to give a better grip for the cloth than applying it all at once....at least for balsa sheeted items. Since the PU dries pretty quickly, I'd recommend playing with some scrap, and seeing how well the adhesion is with your application style, and run with what works!

goirish

I use the WBPU on all of my seaplanes. Never a problem and I fly alot off the snow in this great state of Michigan. I use the lite weight fibreglass cloth.

goirish

I guess for clarification I use the Min-Wax water based polycrylic.

garch 22

My Feedback: (7)

Thanks for the responses guys, very helpful

It looks like the Minwax Polycrylic is the way to go. Still debating about wether to sheet the bottom surfaces.
Are most of you using plywood or balsa, or just glassing over the foam?

Blue Skies, Clear Water

arobatx

I typically sheet the foam with balsa on top and on the sides....the bottom ahead of the step gets 1/16 ply, behind the step is balsa. All is then prepped and glassed with 1/2-3/4oz glass, using Minwax Polycrylic.

JimCasey

My Feedback: (1)

I agree with Chad. Sheet the float, and use ply where it'll take abuse. I have omitted sheeting the bottom behind the step, and just glassed that.
I also like to epoxy a strip of carbon fiber lengthwise along the sides just above the step for about 3 inches fore and aft. The step is a notch and that's where the float will break. The CF beefs 'er up a bunch at about a nanogram weight penalty.

garch 22

My Feedback: (7)

Excellent suggestions Jim , think I'll take your advice and sheet the bottoms and reinforce above the step with some carbon strips.

Some of you mentioned that it's difficult to make 2 oz. glass cloth stay down at the edges, and prefer to go with 3/4 oz. for that reason. Are you saying that you are lapping the glass over
the edges onto the adjacent surface? It would make a lot of sense to try and protect the edges as much as possible. I have not had much luck trying to wrap 2 oz. glass around a tight
bend, but maybe the lighter stuff will be more willing.

Blue Skies, Clear Water

JimCasey

My Feedback: (1)

>>Are you saying that you are lapping the glass over the edges onto the adjacent surface? <<

If you don't do that, you're just building pre-fractured floats that just don't look broken yet.

Most of the strength you get from glass is from wrapping the cloth onto adjacent surfaces.

Square Nozzle

My Feedback: (1)

Also, orient the weave of the glass cloth 45 degrees to any corner that you want the glass to go around. It will conform to the corner better, where if you lay the weave 90 degrees to the corner it will tend to lift at the bend.

garch 22

My Feedback: (7)

All this makes sense, so here goes some glassing at 45 degrees. Will post some pictures of the finished project on this thread if anyone is interested.

Blue Skies, Clear Water

42etus

My Feedback: (2)

Please, post some photos when you're done.

Mike Ferretti

My Feedback: (1)

How Fuel / Nitro resistant is Water based PolyUrethane??? I use high nitro fuels. I've started using Klasskote Epoxy paint. If W.B.P.U.V. is not fuel resistant, can it be top painted with epoxy paints???
M.F.

JimCasey

My Feedback: (1)

Once it's dry, it's pretty well inert to everything.