Andrew, I'm not sure if I'm understanding your "mixing water". What you should be doing for best results in misting foam wing cores with a spray bottle. I hold the bottle about 24" from the surface so just a fine mist falls on the wing cores. If you are actually mixing water with the ProBond that's probably why you are not satisfied with the results. Ed ----- Original Message ----- From: "Andrew E. Mileski" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, September 09, 2002 4:58 PM Subject: [RCSE] Fun with Probond
> I've used Probond to sheet a foam wing before, but never on anything else. > I'd thought I'd experiment with it and see what it can do, as I had a wood > bonding job in mind for it that needed gap filling ability, and a large > amount of Probond still in the bottle. > > For those that aren't familiar with it, Probond is a polyurethane glue > from Elmer's. It's claim to fame is that it expands to fill voids in > the joined surfaces, and is easy to sand. It is triggered by water. > > With no added water, Probond about doubled its volume with the mositure > in the (slightly humid) air. The resuting bond was filled with quite > large bubbles, resulting in large voids (weakness). It took a long time > (about a day) to harden. It is also rather heavy; might as well as use > epoxy which would be stronger. > > With a maximum amount of water added (more than Probond wou1d mix > with), Probond roughly expanded by at least a factor of 10. The > resulting bond was filled with pinhole size bubbles. The excess water > didn't seem to have any effect, other than to create voids where it > was contained. The excess water would eventually drain and evaporate > out of the porus bond, but it can be poured off in the mixing stage. > It took almost 2 hours for it to harden. > > I'd recommend about 2-4 drops of water per teaspoon of Probond, mixing, > then applying immediately to a moistened surface and clamping/vacuum > bagging. The more water, the less time you have to work with it, as > it will start expanding. Adding some extra water seems to be a must. > > Note: after it's initial expansion, Probond shrinks a bit while it > hardens. > > I tried splicing 1/16 Balsa sheeting with pure Probond (no added water). > I didn't care for the results. It had the same bad side effect as > using CA to splice, namely it deeply penetrates and stains the surface > of the wood. This makes for a noticable joint when painting, covering, > or staining the sheeting. Again, it took a very long time to harden, > which probably added to the penetration problem. > > I didn't try splicing with a Probond/water mixture. It is just too slow > for my desire (and I like slow glues). > > Summary: Probond (polyurethane) glue is great for sheeting foam wings > (mix in some water for best results), but not for general wood > construction, IMHO. It has very low tack, and takes too long to set. > I'm sticking to yellow carpenter's glue and medium/thick CA for general > construction. > > -- > Andrew E. Mileski > Ottawa, Canada > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
