Mixing aluminum and fiberglass on a bass boat?

[northrivergeek]

I'm curious about the use of aluminum with polyester resin and glass.
I have some areas of my boat I'm wanting to glass in Aluminum I beams to the floor and create a frame for extension of my bass boat deck, so that I don't have to have any screws penetrating the new floor I'm about to glass in.

Are there any issues that I need to consider before I glass these down to the floor ? And will it even work ?

Will epoxy resin be better to do this with ? Stick better ? or will the Poly work as well ?

Thank you in advance
Sean

[marshmat]

Hi Sean,

Bonding to aluminum is extremely difficult. The polyester won't do it, and even with a good epoxy it's tricky at best.

There are a few adhesives that do work for aluminum bonding. They are rather expensive (try $100+ a litre) and require very careful surface preparation and application procedures. Look up "Hysol structual adhesives" for an idea of what's available and how complicated it is to select them.

Perhaps there's some way to get your new deck in place without resorting to gluing things to the hull. Could you offer any pictures or drawings of what you're hoping to do with this boat?

[rasorinc]

Try 3 M. They have a marine dept. who has answered my questions. Also I know they are bonding aluminum and steel thin plate to plywood now for box utility trailers that allows for movementdue to heat and cold.

[ondarvr]

Like marsh said, we need a little more info. Do you actually want to bond to the aluminum, or just use it as a support under the deck? If it's a support and encased in glass, then the bond isn't as critical, but if you plan on actually bonding to the aluminum, polyesters not the right product.

[northrivergeek]

Obviously no bass boat users replied lol .. ok let be spell it out a little more clearly and I'll include pictures too.

I have a bass boat a 1986 Hydra-Sport that I replacing all the wood in, new transom, stringers , floors etc .. after all that is complete and the top cap is reinstalled, I am going to extend the casting deck and add more storage compartments.
I have some light weight aluminum I-Beams, that I am going to make structural supports for the deck extension. These will rest on the lower level of the cockpit area on the new floor that will have fiberglass covering the new plywood floor, I just want to secure them in place so the don't rub and shift and rub any holes into the glass covering the wood, also did not want to use screws to secure the aluminum frame down, and the aluminum is lighter trying to keep the weight down so doesn't affect weigh of boat any more than necessary . less holes less places moisture can penetrate the new glass and wood below the new glass.

The pic with the areas with yellow arrows, are the gluing on glassing surface, of coarse these pic were both taken 1st day I started tearing all down to redo the boat, and yes I know a cant glass or glue in on top of the carpet etc

I hope this is clearer for all who are trying to help
Thanx

http://i29.photobucket.com/albums/c296/northrivergeek/P1010013a.jpg

http://i29.photobucket.com/albums/c296/northrivergeek/Hydrasport%20restore/P1010012-1.jpg

[ondarvr]

I have a box somewhat similar to yours, made from aluminum and it sits on the F/G deck (sole) in my boat. I just glued rubber to the bottom of the aluminum in a few places and set it in place, so far it hasn't moved in 7 years. When I clean out the boat it can be moved if needed, if you want it to stay in place permanently then just glue it to the floor.

[LMB]

I think a polyurethane bonding/sealant would work fine. 3M 4200 would be sufficient and could be removed later if necessary. 5200 would be more permanent, but both allow for some movement, while retaining excellent bonds. ondarvr suggestions sounds good to me as well.

[Deeman]

Why not just velcro the box in place. It just has to hold itself down and not shift, rattle, etc. Then you can always remove it if you need to get under it.

[Rick Willoughby]

Sean
There is another thread that discusses this in detail. There are some good glues bur as Matt points out surface prep is mandatory.

One of the guys who posted on the other thread bonds aluminium for a living and he said epoxy will do a good job. There is one really important thing to understand. Aluminium has low corrosion because it has a very hard oxidised layer and it oxidises very quickly. You need to bond to the aluminium to get a bond that will survive not to the oxidised layer. The method to do this is to place the epoxy on the surface and use it as a cleaning paste to seal out the oxygen while mechanically cleaning.

I have used a Loctite glue with setting agent that performed very well but have never tested the cleaning under epoxy. Suggest you make a test piece and try it out. It will be much easier if you only have to handle one glue. I do know that epoxy is not real good if you do not clean the surface.

If you do make a test piece I would be interested in the comparison with mechanical clean in air and with no cleaning.

Aluminium and fibreglass work quite well in combination because they have similar elastic modulus.

Rick W