JEM Watercraft

Hi -

Here's another update on the World's Slowest Build(tm). I've started the butt joints Here's a couple of snaps for your viewing pleasure:
In this one I've aligned the two pieces to the string and the marks on the floor, made the ketchup-consistency epoxy/wood flour goop, filled in the gap and added a bit of weight (Dad was in the Navy; the weight is a 3 inch 50 shell casing)


I let that set up over night and then taped the seam. I used 6" 6oz tape because that's what I bought. I then read the how-to in the tutorial section where Matt says to use 10" across the joint. I rationalized for a while and then decided that since I'm going to glass the whole boat inside and out, that 6" on the joint would probably work out OK.


So far I've finished making one of the bottom planks and am taping the second one right now. The second plank is sitting on top of the first (with a trash bag in between) so that I could line them up exactly and not have to hassle with the string. Hank's Advice For First Time Builders: don't do the butt joints all at once. At most do one side of the boat, then you can do the other side by doing what I've done with my bottom planks. When you're done each plank will exactly match its mirror image on the other side of the boat. This probably won't eliminate every problem you have with your build, but it will remove one bit randomness from the process.

While freely admitting that Raka's prices are most excellent, living as I do about as far from them as I can get without leaving the Continental US, I've continued my search for local suppliers. To that end I've found a marine supply store about a half mile from where I work (West Marine in South San Francisco for those of you building boats on the Peninsula) that sells West System Epoxy. I got their regular hardener, but I've just read where H. Mick says that the special hardener doesn't amine blush, and I wonder if I can safely switch to that hardener for the main glassing of the boat and not have a problem with the butt joints (and the fileting as well).

- Hank

G'day Hank.

Looking real good so far,

I haven't used the regular hardener, but I have used other cheaper resins on the fillets.

I would keep the regular stuff for fillets and get the special hardener for the glassing. It really is magnificent stuff to use and even seems to wet out the glass mat better. I have heard the two hardeners are compatible but I would recommend you contact West Systems to make sure. They aree good people and will help you if they can.

I have left my boats about a week after the top coat of resin went on and had absolutely no issues with ammine blush.

You can mix and match the Part B's of System 3 Expoxy as long as both Part A and any of the System 3 Part B's are designed for 2:1 mixing. You can use any exoxy system on the boat as long as one system or brand has cured before applying the other.

After talking with Dave Carnell, the expert on expoxies as well as System 3, you can actually mix expoxies so long long as you have the right ratio of A to B from one system totally blended in one cup and the other system blended in another cup before combining the two. Seems risky, but I've done this with some 2:1 and 4:1. MK

In your particular situation, I'd say long as you're not mixing the different hardeners in the same cup, you should be ok.

Thanks for the replies. My current plan is to get the planks butted together, and filet the seams with the regular hardener. When it comes time to glass I'll get the Special Hardener and use it. So rather than mixing them in the cup I just want to put one over the top of the other and have everything stick together. The consensus seems to be that I'll be fine doing that.

- Hank

For the What's it Worth Department ....

Down here in the land of heat and humidity commonly called Florida I get the epoxy from Raka and when I do I have Larry send me the slow and the fast , they are mixed in a container ( I have dispersing pumps on) and used as needed which gives me a medium hardener.

I have found by mixing them I have some epoxy that I can work with in the heat without is setting up really quick but quick enough to do what I want it to.
When I built the one kayak the epoxy with it was Systems Three and later when it started getting low I ordered some from Raka , combined the two of them and could not tell any difference with the mix over individual epoxys. They both were two to one mix and have made a lot of boats.

Chuck.

MATT - entered in error. PLEASE delete this message? Thanks.

(First mistake I've made since 1952 when, once, I thought I was wrong - I wasn't.)

On glassed, butt joints, I have been thinking. (Admittedly, the only time I have tried one of these, it CRACKED when I tried to turn it over. I immediately reverted to using a piece of plywood which I KNOW works. It spreads the load very nicely.)

I can't see why 8" or 10" wide tape (or cloth) would be needed. Has anyone done destruction tests on these joints? By the time you get an inch away from the joint, you're back to parent material, and no longer on a joint. Just thinking of aircraft-type experience here.

I think that a much more effective - and efficient - use of glass would be to double the layers. Thickness would seem much more important than width. To that end, if a builder used, say 3" tape in double layers, I would offset it. First layer with, say, 1" to the left of the joint and 2" to the right. Second layer with 2" to the left and 1" to the right.

I always glass my boats inside and out, so all butt joints would have three layers inside and out. That seems pretty stout, ehh? Thoughts?

I thought about doing a couple inch overlap to get me out to 10", but for one reason or another, I didn't. If I end up swimming in between two halves of a canoe I'll let you know.

- Hank

Hank,

Unless you misuse your boats like I do mine, you'll likely be OK. My boats are a tool, not a toy. While I don't seek out rocky landings, neither do I avoid them if that's where I want to go. Beaver dams are travelled fully loaded. Boats are picked up fully loaded. The boat serves me, not the other way around.

This gives me a few hours of pleasurable work in the winters.