furn1593

when building balsa floats is it necessary to polyurathane the inside of the floats as well as the outside, I plan to cover with monocote.
recommended glue, polyurathane (gorilla glue), titebond II, or ca?
need to keep the weight as low as possible, ie. dont want to glass them.

Walt Thyng

My Feedback: (9)

Water WILL find a way inside your floats. The answer is Yes, at least one coat.

Actually, the best waterproof glue for balsa floats is good, old-fashioned Ambroid. CA would also work and I understand there is a water-resistant Titebond. If you poly the exterior it won't be a real big issue.
Walt

JimCasey

My Feedback: (1)

Walt's advice is good.
Once water finds its way into the floats it feeds fungi and bacteria. Balsa rots quickly. I have had leaks in my monokote over the sheeting of foam floats and 2 weeks later the balsa under it is black and squishy.

So yes, seal the balsa from the inside.

It has been so long since I used ambroid that I forgot about it, but it WOULD be fine. When the solvent goes away it becomes something close to the same chemical used for screwdriver handles (Cellulose acetate) . Epoxy and polyurethane are also waterproof. CA turns into plexiglass (polymethylmethacrylate) when it cures, so there's another waterproof option. The waterproof version of titebond is polyurethane. The other versions are water soluble-might as well forget about them.

Balsarite or fuel-proof dope both do a nice job of sealing the outside and monokote sticks well to them.
before you cover with monokote, lay a strip along the edges and the keel if v-bottom. This gives you a double thickness where abrasion is likely to damage the coating.

Laird SS

What about placing a strip of fiberglass along the center of the vee on a v-bottom float for abrasion resistance? That would be more durable than a double layer of monokote.

JimCasey

My Feedback: (1)

What about placing a strip of fiberglass ........
The 2 layers of monokote are so that you have a little extra before the bottom erodes completely thru. Glass cloth would help but it's not very erosion resistant. It IS strong, and that counts, too.
Probably the best thing would be cutting a wide rubber band and stretching it along the bottom and supergluing it to the keel of the float.

furn1593

choosing polyurathane - semi or gloss - what does monocote stick better to?
also the only water based was minwax polycrilic - still looking for h2o poly.

Walt Thyng

My Feedback: (9)

H2O poly = Minwax Polycrylic available in small size (4-6 oz?). Monocoat doesn't go on easily. It's like putting it over a fibreglass or ABS cowl regardless of sheen. Ultracoat does a better job, but still isn't easy -requires a lot of patience.
Walt

tbgiambruno

I sealed all my joints and then used spray primer to prime my floats, I then covered them with Monokote. Some paint transfered onto the Monokote because of the iron, but I was able to use some paint thinner to clean it off the Monokote.

My question is: Is Monokote sufficient enough to keep the water out or should I remove it and glass the floats instead. Any advice is greatly appreciated.

Walt Thyng

My Feedback: (9)

If you've lapped your seams and they are tight you should be fine. I covered a set in Polyspan and never had a problem.
Walt

tbgiambruno

Thanks, i will just go with the monokote and hope i did it right.