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Best glue for older rubber hull?

Posted: Sat Apr 12, 2014 8:14 pm
by DLee
I discovered that the end pieces on my T9 were coming off when I tried to set the boat up today. I broke out the repair bag and found the neoprene cement the Mark at Long Haul sold me a couple years ago. I cleaned the hull with white gas, not toluene, as this is what I had and it was an alternate in the instructions on the neoprene cement can. I sanded the rubber a little, cleaned it again and applied the glue per instructions in two coats.

One section seems to have stuck fairly well but another didn't stick at all. At first I though it was the glue now I'm thinking maybe I needed to sand the surface more… not sure. It's outside now, re-glued with a board and weight sitting on it - I'll check it again in the morning.

My gut feeling is that the neoprene glue isn't right for the old rubber application. I'm pretty sure Mark sold it to me for use not he AII hypalon hull. In the section where it didn't stick I could literally pull the recently applied glue off in small sheets and roll it into balls to clean the area. Any suggestions? Could improper sanding have this affect?

The neoprene glue seems a lot easier to work with than some of the other (two part) glues that have been mentioned here.

I'll report on what the overnight curing brings…


Re: Best glue for older rubber hull?

Posted: Sun Apr 13, 2014 3:15 am
by idc
When I used long hypalon strips to patch my old rubber-skinned T9 I used hypalon two part cement--I forget the brand. I sanded both surfaces fairly vigorously and cleaned with toluene, if I remember correctly. I basically followed the instructions. After letting it all cure for a day or two, I then ran a bead of aquasure (aquaseal?) around the edge of the strips to make sure there was no lifting there and filled in the odd nick in the skin at the same time. The rubbing strips have stayed on for several years now and don't look to have suffered at all.

I remember gluing down bits of the rubber bumpers at the same time, though I've forgotten how extensive that problem was. However, like you, I've recently noticed that bits of the rubber bumpers are lifting, so I should be doing something about glueing them down again. I've been putting it off as I've bad memories about how toxic the whole process was, given the solvents involved. (And I've been horribly busy with other stuff.)

I'm not sure what neoprene cement is. Is it the same as aquasure/aquaseal? I tried using a big tube of that to stick a patch on an old rubber-skinned Tyne Prefect (an English brand, single-seater). Unfortunately I think the rubber material on that boat is totally shot as, while it floated for the whole journey, when I got it out the water, on further huge areas of the hull the outer layer of rubber was basically 'bubbling' off. The patch had nothing solid to stick to. My plan is to try completely reskinning this boat with pvc (possibly retaining the canvas topdeck).

All the best,

Re: Best glue for older rubber hull?

Posted: Sun Apr 13, 2014 9:46 am
by DLee
Well I just went out and checked my neoprene glue job and it seems to have worked. I'm guessing that temperature was down into the low 40's last night so I'm going to let this cure a little bit more before I try sliding the hull in. This cured outside overnight with a 2x4 on top of it for flattening and a 20~25lb rock for weight.

The section at the back of the bumper is where the glue stuck perfectly the first time. The spot that has a lot of excess around it on the lower forward section is where I glued it twice. The second time that I glued it I didn't put the second coating of glue on per instructions, as the second coat seemed to pull up the first coating of glue. Since this did stick I'm thinking the problem may have been not enough sanding or cleaning of the rubber surface beforehand. Mainly sanding is what I'm thinking.

This was definitely the worst section with the bumper coming off. Enough that I could have worked my fingers underneath it to the other side of the boat if I had tried. I'm wondering now if this might have been some of the cause for my crazy steering with this boat. These flaps may have been catching a lot of water as I paddled.

I'd like to clean the excess glue up but I'm worried the white gas will soften the good parts. That's what seemed to be happening when I cleaned it originally.

If it warms up today I'll glue the other side down and try fitting the frame after that cures.

The nice thing about this neoprene glue is that it really didn't smell that much when using it outside in the light breeze I had yesterday. I applied it with my finger inside a vinyl glove.



Re: Best glue for older rubber hull?

Posted: Mon Apr 14, 2014 8:04 pm
by ChrisO

A few thoughts on gluing the old rubber hulls. Yes it can be tough to get a good bond. A good sanding is essential. Toluene will bite better into the rubber than white gas. Higher temps will activate the glued surfaces better, a sunny day or a hair dryer/heat gun help. You might have to wait a bit longer between coats of glue.
Any (silver) wax on the hull could interfere with the glue, so will any gumminess or hardening of the rubber. Maybe a fresh tube or can of glue will be better too, more aggressive solvents!
No, I don't know of any better glues for this! Aquaseal is a Urethane glue.

Re. removing excess glue, try a small block of latex as an eraser (available at art supply stores). The glue might stick to this better then to your hull and come off without solvents.


Re: Best glue for older rubber hull?

Posted: Sat Jul 26, 2014 10:43 am
by DLee
Follow up:

The work I did on my T9 with neoprene cement seems to be holding up pretty well. Mark Eckhart at LongHaul recommended this cement for the older Klepper rubber. The boat has pretty much been together since I made these repairs and I was a little worried when I packer her up a short while ago. My frame always sticks inside of the hull and I usually have to wrap a line around the bow and stern, tie the other end of the line to a tree and then work and gentleman the frame loose. I have been perfecting the use of old AEII deck pieces (bow and stern) between the frame and hull of the T9 to keep it from sticking. This last frame removal went comparatively easy compared to some of the other sweat wrenching and jerking battles I've had. I mention all this because it puts a lot of stress on the section stern piece that I recently glued. So the bottom line is the neoprene glue held nicely - where it was applied properly.

One of the problems I had working with it was actually prepping the surface and Mark confirmed that this is probably the biggest issue working with any repair on the old rubber. Whatever solvent you use to clean the old rubber off, it just wants to just keep eating away at the areas that are still holding solid. So that pretty soon the small repair area has become quite large. So judicious use of the cleaner is in order. I also didn't use a rough enough sandpaper. I think I prepped with something around 150 grit and Mark recently sent me a new can of neoprene cement (for applying some D ring patches to the outer hull of the T9) and included some sandpaper that looks like 50 grit!

I also noticed that Mark seems to do his gluing either on the boat frame itself or a mold. I did my gluing with the skin loose and I think I will have it on the frame next time.

All the areas that I did glue properly have been holding up nicely and don't seem to want to peel off. I was re-gluing the fitted stern piece onto the boat and I missed a couple spots on the outer edge. These spots are weak and it's plainly obvious that a little pull on them will open up huge gaps in the glued area. Where the seam is glued really well all the way out to the edge the bond seems fantastic. I asked Mark about this and he confirmed the the edges are the most vulnerable areas for after gluing. He said to be sure and get a solid coat of glue out to the edge and beyond; he may have even suggested making a masking tape border so the cement can be applied liberally beyond the edge. Mark also suggested filling any cracks in the edges and just covering the edge overall with AquaSeal after the neoprene cement has dried.

The neoprene cement does dry an amber color and can look kinda sloppy if you don't clean it up nicely during the application so I think applying a thin bead of AquaSeal around the seam will be my approach the next time around.

As far as my T9 D-ring patches go... they were going to be for attaching the exterior Harmony sponsons I have for sailing. The T9 is currently out of commission for aluminum clip replacement... so I am going to experiment with attaching the D ring patches to the exterior of my black hypalon hull of the AEII with heavy duty velcro. This would be a great solution for the T9 as well if it works. The Harmony sponsons have to make re-entering the swamped T9 much easier. I recommend these sponsons for any sponson-less folding boat as a great safety measure.