Transom overhaul aluminum to wood -glue or sealant ?

[orlandoclippertim]

Have orlando clipper aluminum hull. Have my transom insert about ready to go back in. The aluminum where the old wood was polyestered in was heavily pitted from water pockets in the interface. I prepped the aluminum by sandblasting all corrosion away. Cleaned with acid and alodyned it. Then 2 coats (thick) of 2 part epoxy primer.
I want to put something between the new wood and the epoxy primed aluminum to keep out any water. Something which is slightly flexible. I dont think I want something really rigid (polyester?) that when the wood is under a strain the glue just pulls the epoxy primer off the aluminum allowing water up against the bare aluminum. I am thinking a little flexibility and elastisity will prevent this. Maybe something thats NOT PRIMARILY a glue. There are quite a few through bolts in this situation ( aluminum - wood wood - aluminum ) so i am thinking of something less adhesive than the T-88 that I used to glue the 2 sheets of the wood together with.
I guess whatever sealant will have to be anerobic since no air can get between the wood and aluminum when I squish it together. I am guessing this means a 2 part (A+B) type material ?????? Is there a 2 part marine sealant ?
There is a 2 part one for aircraft windshields but it's MONSTER STRONG and maybe too visgus for this situation since my clamping force will probably be fairly limited. i also want something I can get loose if I have any problems down the road. Dont want to hve to distroy the aluminum in the hull to get the wood out ! (or maybe the next owner) I am thinking a 2 part silicone might be too hard to remove later....

What to use ? ( please no-one suggest gorilla glue ........)

Tim in Orlando

 

[62 ROYAL SCOTT]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Post a pic.

 

[stalker14]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Here is what I did, Only I did not paint the aluminum first. I wanted the epoxy to bond to it and to keep water out. Paint first means the epoxy bonds to the paint. I can't say if that is better or not.
http://forums.iboats.com/showthread.php?t=528313

 

[ezmobee]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Your excellent prep and painting of the aluminum should be more than sufficient to prevent any further corrosion. I would not glue the new transom wood in place. (that's just my vote)

 

[kfa4303]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Ditto. It sounds like you did a great job prepping the aluminum. A well sealed transom, properly bolted in place should last for ages. You could seal around the perimeter of it with some 3M 5200 just to be safe, but otherwise you should be good to go. Plus, I like the idea of being able to remove the transom in the future should the need arise, rather than gluing/fastening it in place forever.

 

[ezmobee]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Also, if the transom wood drops into a "tray" of sorts at the bottom, and that tray doesn't have any drainage, drilling a couple holes in it may help any water that may find it's way in there to drop out instead of laying.

 

[stalker14]

Re: Transom overhaul aluminum to wood -glue or sealant ?

Yea but my transom metal was so full of holes from the corrosion the next step was to cut out the metal and weld in a new piece. This way I sealed the holes and prevent water from getting in between at the same time. I think what I have done will outlast the boat, but that is what I think.

 

[kfa4303]

Re: Transom overhaul aluminum to wood -glue or sealant ?

I'm sure it will. It sounds like you prepped it very well. As long as there are not dissimilar metals touching you won't get the electrolysis that caused the pitting initially. The water won't hurt the aluminum one way, or the other. Be sure you coat any and all of your stainless steel, fasteners with 3M 5200 to seal them up nice and tight. It's great stuff that dries strong, but flexible and has very strong adhesive properties too. You can even get it at Lowes/HD for about $7 for a tooth paste size tube. It is a little goopy, but cleans up pretty well with a bit of Acetone.

 

[Woodonglass]

Re: Transom overhaul aluminum to wood -glue or sealant ?

I am NOT a Tin Boat guy, but my research has led me to believe and agree with the others that the Wood transom insert on an aluminum boat should not be "Glued" to the Aluminum outer skin of the boat. Your excellent prep of the surface leads me to believe the standard/normal methods of installation is all that's required for it to last several more decades. If, big If, you decide you really want to then I'd look into PL Premium Construction Adhesive. It is a polyurethane product that remains totally flexible when cured and is super strong. Used here on iBoats a lot in the restoration of boats. You did not mention what your fabrication methods were in making your new wood transom insert. If you sealed it properly with Epoxy and continue to seal any/all holes and mechanical attachements to it you should have no issues for decades to come.

 

[orlandoclippertim]

Re: Transom overhaul aluminum to wood -glue or sealant ?

I think I agree that I would rather use some type of compound which is not primairily an adhesive - so as not to glue it TOO strongly. I haveused the PL type and it seems like a cousin to liquid nails. Way too tenacious for my purpose here.
and it wont harden without air.

I have used a 2 part polyurethane rubber for making rubber molds. You can get it in different hardnesses - and it isnt very adhesive. If I smeared it on both sies and then assyembled it (maybe with the bow hoisted up verticle so the transom is horizonal) I would think it would form a prefectly form fitting "gasket" conforming to both sides but without sticking really hard. Seems like I could even pop it appart and reassyemble it without even hurting it maybe. I might have to use some silicone mold release on one side to help that if I wanted it to do that.

I plan to seal the wood insert ( 2 pieces of 3/4 marine ply glued with T-88 epoxy) with either epoxy varnish or polyester resin brushed on. The oregional one had glass cloth and resin sealing it over. not sure if the cloth is really doing anything.
There are lots of through holes in the transom for various sized bolts (knee braces and others) so i am planning to make these holes in the wood a bit oversize so I can coat th inside of the through holes and still have clearance for the bolts not to dragonce there is epoxy or resin on the walls of the holes. I think through holes are a weak spot on transom wood. No good to seal all over just to drill holes and have the water go straight into the middle of the wood sandwitch.

Tim

 

[stalker14]

Re: Transom overhaul aluminum to wood -glue or sealant ?

I wouldn't use polyester resin without glass, it will just flake off, been there done that. I would spend the extra coin on epoxy for sealing the wood, my 2 cents. It sounds to me that you are gluing the transom in, like said above if you are happy with the aluminum skin and you prepared and painted it then sealing up the wood with a quality epoxy should do the job. Be sure to seal any holes you drill as well. That is a bit of a pain but if you can pre-drill the holes it is easier to seal them up before you install the wood for good. Also as stated above use 5200 or 4200 for any bolts or whatever you install.

 

[ezmobee]

Re: Transom overhaul aluminum to wood -glue or sealant ?

What he said ^^^^ Poly is useless without glass. Go with epoxy.