JEM Watercraft

Jack
I am with you on this my boats have to stand up to what I dish out are they are not worth a plug nickle to me I haven't built a cart yet so I drag mine some land where I want rocks gravel logs whatever.
On the splices a wide one next to the wood the step in a inch on both ends so it spreads the load and braces more tward the center where the splice is just like a building truss
I don't like the looks of the blocks for a splice ( Personal Preference) so I screw a block to my splices when I make them until after I turn them and get glass on both sides then they should be stouter than the wood
Ron

G'day guys,

I have tested these fibreglass splices to destruction and the splice will break on the edge of the woodflour every time.

I believe the fibreglass splices are significantly less strong than a butt joint.

Having said all that, it is important to remember that no panel in a kayak or canoe exists on its own. Each panel is joined on its edge, at an angle to at least one other panel and so on.

I would call this form strength in that the angle each panel is at in relation to the panel it is joined to more than doubles the structural strength of those two panels on their own, combined.

In total, the fibreglass splices in the 4,5,6, or more panels in a S&G canoe or kayak make for a very strong boat indeed. adding the butt block will make for a stronger joint but this added strength is not necessary IMHO.

A butt block or series of them will also make for heavier and less elegant joints.

If someone is going to test their completed boat sufficiently to require the stength of butt blocks, the rest of their boat will be in a world of trouble and perhaps they should reconsider the type of boat they are using.

If plans for S&G boats had the butt joints staggered, I'd feel a helluva lot more comfortable. I never have liked the looks - from an engineering point of view - of an uninterrupted seam wrapping all the way around a boat. Has always looked to me like a disaster waiting to happen.

THAT'S why I believe in a plywood backing plate for butt joints. Heavier, yes. Must add 5, maybe 7, ounces to my boat. But hull integrity is very important to me.

Just me. I like a strong hull with no moving parts. If I'm going to trust my Life to it, I want it Simple as an anvil, serious as a shotgun.

A certain kayak kit manufacture use to use the backing plates but discontinued them and recommends using a piece of fiberglass to cover the joints.

The glass will keep the joint from breaking and then later when you glass the outside of the boat and the inside you have a double amount of glass over the joint. IE. 4 layers and that will not break , the rest of the boat might but that joint won't.

A backing plate is OK if you are into having some discomfort while sitting and paddling since the backing plate is usually where you sit. It also has to be covered with fiberglass so why not just use the fiberglass.

I have built numerous wood boats this way and none of they have come apart at the center or any where else. They have been used off shore (salt water) Swamps and even down a river full of rapids and are still in one piece. If you are foolish and do take a boat made from 1/8th inch wood down a rapid filled river at flood stage. I don't recommend it but I have done that for a 5 day trip , Never said I was smart , just have a lot of faith in the boats I make.

Most laminated canoes , that you purchase already made ,have a center thickness if about 1/8th of an inch to 3/16ths of fiberglass. That helps to keep the manufactures cost down so he can make more profit. They put the extra glass in the bow and stern because that is where most beginners at paddling misuse's the boats , running into trees , other boaters , stumps , sand bars , rocks , swimmers , docks , boat ramps and anything else.

Our wood ones are thicker and a darn site better looking , with epoxy saturated wood ( it increases the strength of the wood up to 4 X's) Then they are skinned , coated , protected ( your choice of terms) with fiberglass inside and outside with fiberglass.

My guess is that it is why one kit manufacture use to show one of his wood boats that flew off a vehicle going 60 MPH down the road and only had some scratches while a store bought boat that had the same misfortune was in splinters.
It is NOT who designed the boat ... It all boils down to who made the boat ( No matter which one or style) we can make them the way we want them , the choice is ours and ours alone.
Our boats are not just one part or piece or one thing , they are a total of all the parts (everything) working in harmony.

As someone we know , would say ... That is my rant for the day , two uppercuts , self inflicted , and off sitting in the corner for several hours to heal.

Chuck.

G'day Jack,

If the butt blocks make you feel more comfortable and secure in your build then use them. it is your boat, build it to suit your desires, there is nothing at all wrong with over-engeneering a build.

Like Chuck, I have absolute faith in the integrety of the boats I build and their design. We all trust our lives to our boats.

Like you, I am hard on my boats. My wooden ones have stood up to my forms of use and abuse magnificently. Way better then my factory fibreglass jobs. The worst thing to happen to them so far is a few scratches and gouges that have been easily fixed. Remember, so far, I have only been using the very cheapest of ply available. C and D grade veneers on the outside that are probably less than 1/64" thick and some sort of filler in between. My total ply thickness is only 3mm or less than 1/8". The ply is utter rubbish and I will not be using it again.

No boat of mine has failed structurally or in any other way. They are lighter and stronger than similar all fibreglass boats - panel splice included.

This is not because I consider myself a particularly good builder, but more, a reflection on the quality of the design. have faith in Matts build instructions mate. They are spot on and won't let you down.

Wow. I better do some more on the boat quick. This thread is in danger of turning into a philosophy discussion

I'm hoping to get one of the middle (and maybe on of the top as well) planks butted together tonight.

G'day Hank, sorry about the thread-jack mate.

Many of us are geezers and we wander sometimes. only trying to help.

Morning -

Actually I like the thread-jacking. I look at my build log as one by a complete novice aimed at other complete novices. So, a digression into the theory and practice of butt joints (if these threads are findable by the Google web-crawlers the search strings coming into this site must be pretty funny), can only help the newbies in the crowd.

- Hank

PS - I did get one of the middle planks put together last night.

G'day Hank,

Thanks mate. Its all good fun.

The fibre glass butt splices work well enough for me. If you follow Matts build instructions, you won't go far wrong. There are plenty of Matts boats out there that have been built using this method. I haven't heard any mention of them failing.

Well I keep plodding along. I've completed the two middle planks and started the first of the top planks. And I've found yet another excuse for my one-piece-at-a-time build pace. I have ideas about how to make the process go better and since I didn't do all the planks in one go, I can try out the idea on the next plank.

Here's one of the middle planks, post gluing, pre taping (sorry for the poor focus). The point of the picture is that I have made a huge mess of the job. There's fillet goop all over the place.


I've been reading the various build logs and one of the handier tips is to run masking tape along each side of a seam before filleting as a way of keeping the mess to a minimum (remembering, of course to pull up the tape before it becomes part of the boat). It seemed to me that a butt joint is just a really short seam. So I tried the tape method on my first top plank:


That's pretty snazzy, if I do say so myself.

- Hank