Looking to increase the thickness of the thigh braces on 2 boats. The boats are plastic (polyethelyne), but would be adding these to the thigh braces which I think are a different (harder) plastic on one but not the other. What is the adhesive of choice? Marine goop?
Possibly also gluing two layers of minicell together to make a thicker layer, so the adhesive should be able to do that also.
Peter, I can’t speak on whatever plastic your boat is, but I have successfully adhered minicell braces to plastic on a typical rotomold kayak, as well as to a S&G’s epoxy coating under the coaming, and to a couple of NDK/SKUK glass boats made with whatever resin they use. The glue was Barge rubber/shoe cement, available in pretty much any hardware store or big box homebuilder store.
Minicell to minicell also sticks well with Barge.
The trick is to paint on a THIN layer to BOTH sides that will mate, then allow a few minutes for it to get slightly tacky—not TOO tacky, because you might want to slightly adjust the fit. Then press together firmly and hold. If possible, juryrig a light-pressure clamp to keep the pieces together for at least a few hours. The stuff fully cures in about 24 hrs. For best strength, don’t use the boat till that has happened.
For holding the pieces together after the first few minutes, I put something like a strip of corrugated cardboard between the clamps and the foam. This kept the glued foam on without putting divots in it.
I think a shop once used AquaSeal adhesive for the same purpose.
Used Marine Goop to build up the thigh braces on my Prana last fall. Think I used 1/2" foam, gluing it to the existing braces.
I recall holding each brace in place for about 10 minutes where the brace curves , then used duct tape along the edges. Let it sit for a couple of days before getting in the cockpit to check. All good.
Marine Goop is great stuff. I also use it to patch tiny holes in my household rubber gloves.
You can also use Weld Dap contact cement for minicell to minicell, or minicell to plastic. It works faster (on contact when both surfaces have been cleaned and brushed with a coat of cement) than with goop and/or 3M marine adhesive sealants. With the latter, the drying time is longer so you have to keep the pieces pressed together either with tape or clamps to get good uniform adhesion. With the contact cement, once the coats on both pieces are semi-dry, you line up and press the pieces together for pretty much the permanent bond. If you screw up in lining the pieces up, you will pretty much have to destroy the foam trying to separate it.
Only time I prefer to use goop or similar is when I am trying to fill some voids between pieces (especially plastic on plastic) such as installing an aftermarket hatch cover kit.
sing
Whitewater open boaters have been using minicell to construct pedestals and knee pads/cups for quite a few decades. Pedestal construction typically requires laying up multiple layers of minicell plank glued to each other. Over 90% use DAP Weldwood contact cement, the flammable variety, which comes in a red and black can and can be purchased inexpensively at nearly any Walmart or hardware store. As sing said, it results in an immediate contact bond, so use some indexing marks to ensure proper alignment.
I use inexpensive, metal-handled “acid” brushes to apply the contact cement. I recommend roughing up the foam surface a bit with something like 100 grit sandpaper, and make sure you use at least two, if not three applications of cement to the foam as it can be rather thirsty.
There are a lot of other things you can use, most of which will be more expensive and leave a residue that is much harder to remove if that ever becomes necessary. The only other adhesive I would personally consider is 3M spray adhesive if you don’t want to take the time to brush on contact cement.
@sing said:
If you screw up in lining the pieces up, you will pretty much have to destroy the foam trying to separate it.
Yup. That’s precisely why I used Marine Goop. Wiggle room is good when it’s hard to see what you’re doing.
I always used the DAP red label.
put a coat on each surface, let dry, repeat and install.
Don’t screw up…
It isn’t too hard to align thigh brace pads in kayaks. You are generally not using material that is so thick that you cannot easily bend it into a convex shape. Make a few indexing marks on the foam extending onto the boat along one side of where the pad should meet the hull. Align the bent pad along that edge using the marks, and roll it into place so as to avoid any air gaps. It is really quite easy.
It is good to use a small roller to approximate the pad to the hull after placing the pad.
I’ve used both.
I prefer contact cement. No worry about it moving while drying.
I’ve always preferred contact cement, specifically DAP Weldwood Contact Cement GEL. While the liquid contact cements work great, the gel stays in place better and doesn’t drip when you’re transferring it from the can to the parts to be glued. It spreads easily, too.
When gluing Minicel foam, I always apply two coats to each part, because the first coat will be mostly absorbed by the foam. A second coat insures that you get a lot of glue area and results in a stronger bond. On hard surfaces like boat hulls and decks, a single coat is fine, with two on the foam parts to be attached.
With contact cement, modifications and repairs take a matter of minutes. Goop products work well, but take much longer to cure (overnight at least for a good bond). If you choose to use Goop, it doesn’t matter which one of their products you use (Marine, Plumber’s, Automotive, Household, Shoo-Goo, etc.). The only difference between them - other than the label - is that Marine Goop contains UV inhibitors, which is only important if the bond is going to be exposed to sunlight regularly. Inside a kayak, that’s not an issue.
I always use DAP Weldwood red label; has worked well for me on the 10 or more boats I’ve outfitted.
If I am gluing 2 layers of minicell together I always put on a fairly thick coat of Weldwood on both pieces; then let that coat completely dry.
Then I put on a second coat on both pieces, and line them up as best as I can, before attaching the 2 pieces together.
I always place weight on top of the pieces that are being bonded together to assure there are no gaps between the 2 pieces.
If the temp is low I heat up the Weldwood, and the pieces of minicell “before” I apply each coating of Weldwood.
My wife doesn’t like it much; but I use her hair dryer as heat source…
Example of usage of water bottle weight is shown in photo of a Mad River Flashback I restored, and re outfitted.
pblanc is pictured test paddling another Flashback I reoutfitted.
I value his judgement regarding outfitting, boat restorations/repairs, and paddling in general
BOB
@bnystrom said:
I’ve always preferred contact cement, specifically DAP Weldwood Contact Cement GEL. While the liquid contact cements work great, the gel stays in place better and doesn’t drip when you’re transferring it from the can to the parts to be glued. It spreads easily, too.
I agree with Brian on the use of DAP Weldwood Gel.