Glueing butt joint?

[kayakn]

so around the beginning of april i will be glueing the bottom panels and side panels of my tug-along together...so i was wondering how i should go about this. i bought 2 gallons of jgreer epoxy (red system for glueing applications) i also bought 1 pound of silica (isn't this the stuff for bonding?) i need to know how to glue the panels together?? the bottom panels are 5/8" doug-fir marine ply and sides are 3/8" df m. ply and they are connected by butt joint with an 8" wide butt block.

----should i coat the surface with mixed epoxy and no filler so i don't get a dry joint and then apply the mixed epoxy with filler over that?

----should i just apply the mixed epoxy with filler right to the joint without applying non-filled epoxy?

** I am using silicon bronze screws in addition to the epoxy and to aid in the clamping/keeping together.


Thanks,Blake

[DuncanvdH]

I normally do it like this. Apply unthickened epoxy on both gluing surfaces. Let dry to the point where it is still sticky, but on touching (with your GLOVECOVERED knuckle) no epoxy mixture comes off. Now apply thickened epoxy and put joint together. If you do not use the preapplication youre joint will be very weak as all epoxy is absorbed by the surfaces. I have experienced this myself.

Take great care handling silica powder. Use a suitable dust mask to protect yourself.

[RodB]

Standard procedure here..... apply unthickened epoxy to both surfaces... let sit for 20 minutes...then apply thickened epoxy with silica (cabosil) liberally to one side (or lesser amount to both surfaces) and clamp together... works great.... (be sure you have some squeeze out for a good glue joint).

Get a system III manual or the book "The Gougeon Brothers on Boat Construction"... they are both very worthwhile as references...

Good luck,

RodB

[Thorne]

You can also use weights (toolboxes, bricks, etc) on the blocks to add additional pressure to the joint, although with proper pilot holes the screws should do the job. Don't over-clamp or squeeze out too much epoxy or the joint will be weakened.

[switters]

don't forget the wax paper

[Tom Robb]

Choose door number one.
Thorne said, don't starve the joint with too much clamping pressure and as switers suggested, don't glue it to the workbench.

[Cuyahoga Chuck]

One of the reasons I stick with slow hardener is I have enough time to paint straight epoxy mix on to the intended surfaces, than add thickener to the remainder and complete the glue joint.
Whenever I intend to do epoxy glue-ups I do a dry run first. I talk myself thru' the process to make sure I have all my untensils. Cup, mixing sticks,brush, spatula, gloves, rags etc. The resin and hardener and thickener are close at hand, etc. Once things start going wrong they don't usually get better.

[kayakn]

very helpfull!! thanks, i have to glue 2 15' long pieces of 5/8" plywood together so it will be tricky doing that much in a limited time..one last question..

-can i glue the butt block to one piece and let that harden some what then lap that half over the other half... similar to this

step 1: _- glue butt block to one piece of ply
step 2: _-_ glue the ply with butt block onto other piece of ply

or should i just go for it and try and put it all together at one time?


Thanks a lot,
Blake

[AstoriaDave]

-can i glue the butt block to one piece and let that harden some what then lap that half over the other half... similar to this
step 1: _- glue butt block to one piece of ply
step 2: _-_ glue the ply with butt block onto other piece of ply
or should i just go for it and try and put it all together at one time?Just go for it. It is easier than it sounds. Make sure the surface you are working on (I like the "A" side of a piece of AC plywood) is clean and flat. Cover the area where you will be working with wax paper, taped down at the corners. Lay out one of the pieces, and butt the second one exactly as you want things to turn out. Run a couple small nails into each piece outside where the butt block will be and set the one you will leave down firmly in place (run the nails so their heads pin this piece in place).

Brush the ply pieces with mixed resin (hardener and the other component (A), properly mixed). Enough will run into the joint. Mix up some more resin, at a rate of about 0.1 cc part A per square inch of bonding area (see below for example calculations), and stir in some of that silica until it is syrupy and not runny any more. Spread that stuff uniformly on the butt block area and put the block in place. Secure it with more small nails so it does not move. Set heavy stuff on top: lead weights, concrete blocks, your mother in law, etc.

If the temp is anywhere near 60-70 F, and you used medium or fast hardener, it will be done the next day.

That 0.1 cc of part A per square inch: suppose your buttblock area is 10 inches by 6 inches. that is 10 x 6 = 60 square inches. You only need about 0.1 cc/sq inch x 60 sq inches = 6 ccs of Part A. Pull that much out of the part A bottle and put it into a small cup. Likewise, with a different syringe, pull the required amount of hardener out of its bottle and squirt it into the mixing cup. Mix these for a minute or two and then add about a level teaspoon of silica to it. Stir until uniform. Is it syrupy and not runny? then you are there. Use the mixing stick and a plastic squeegee (came with the resin kit, I bet) to spread the stuff uniformly over the butt block contact area.

Note: you can use the graduations in the cup to measure resin, also, but it is harder to get the measurements right, and you will have to mix larger batches -- which wastes resin.

[kayakn]

I did it! and it wasn't hard at all. i was nervous starting to put the first pieces together but once i did that it was easy!! i glued the sides of my tug together to make the long pieces and i glued each half of the bottom together and in 2 days i am going to finish gluing bottom together:D:D:D seems like i am moving fairly quickly now. i will post pics on my thread when i load them..

Thanks, Blake