About those fiberglass butt joints. . .

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About those fiberglass butt joints. . .

Postby FlaMike » Sun Jun 24, 2007 5:03 pm

I've been studying everything I can find on this Forum about joining two pieces of plywood to make one long piece and understand that most seem to favor the wood-backed butt joint. At least, I think that is the general consensus. But I would like to try building one without that plywood butt plate showing up in the middle of my boat.

Since I'll be starting work on my Uncle John's Pirogue on Monday, to be used as a learning build for my next boat, UJ's Jon boat modified to be a fly fishing flats boat, I want to get most of my "experimenting" done on the Pirogue.

But I'm not so sure that building the Pirogue will really tell me how a joining method will work out on the Jon boat, since the bottom panel of the Pirogue is so much narrower than the bottom of the Jon.

Of course, the Jon boat has three full-length runners on the bottom that will run across the butt joint, and I think that would help the situation quite a bit. Anyone think that notion has any merit?

Also, the type of joint I'd really like to try is the fiber glass only butt joint. I found an excellent article by Dave Carnell on this subject. He seems to know what he's talking about and drops a couple of Big Names in his article that looks to back up what he says. The article is HERE.

Anyone do it that way? I sounds pretty good to me, but things often do and then turn out to be not quite what I thought.

If you haven't read that article, you might want to give it a look. I could really use the Forum's expertise on this one!

Mike S.
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Postby hairymick » Sun Jun 24, 2007 5:19 pm

G'day Mike,

I use he fibreglass splice or butt joint as recommended in Jemwatercraft.

It is easy to do and works well for me.

If I remember correctly, Uncle John reccommends a scarf joint for his pirogue and many use that method. There are tutorials and tricks both here and on the Jem site on how to do them as well.

I have done the scarf joint thing on a UJ pirogue. while it works well, I found it more difficult to do - well and don't think the end result is worth all the extra effort.

Once a fibreglass splice is completed, it should be just about as strong as the original ply. Perhaps a little more brittle is all. When combined with the side panels, rubrails,keel and so on, it is plenty strong enough for anything you will want to do with your boat. the panels require a little bit of care when handling during the stitching stage. This would probably apply equally to a ply backed butt joint or even a scarf joint too.
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Postby oldsparkey » Sun Jun 24, 2007 5:24 pm

I epoxy saturate the wood at the joints , let that cure over night. Now cut some glass so it will extend out about 3 inches on each side of the joint.

1....Put down some plastic then the boards to be joined in the position you want them.
2....Lay down the glass and apply a coat of epoxy to wet it in. when it is transparent then cover it with some more plastic material and a thin board to cover the whole area , apply a light weight to hold the board in place and let it cure.
When that is done , remove the weight , board , plastic and turn the boards over and repeat the process on the other side.

This will make a strong union between the boards at the butt joint...... build the boat and then fiberglass it inside and outside .... this protects the wood making a sandwich of it with the wood in the middle and the glass on the outside. It also adds another layer of glass and epoxy over the butt joint.

So far none of mine have come undone and the one canoe (1/8th inch wood , done that way ) made it down a river full of rapids on a 4 night 5 day camping trip. I hit one rock ( it jumped right out in front of me in that one rapid ) and had a loud .... KRACK . After getting home and checking the canoe all I could find was one little scratch and no damage.

I did check it really good , even sanded the graphite off the bottom to make sure , then put on three new coats.

Chuck.
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Postby Kayak Jack » Sun Jun 24, 2007 6:11 pm

oldsparkey wrote:... 1....Put down some plastic then the boards to be joined in the position you want them.
Mike,

There are some areas of Chuckie's tome that may require clarification or explanation to you.

By "plastic" Chuck means a thin sheet of plexiglass. It won't stick to the epoxy, and it leaves a glass-smooth surface.

By "position you want them", he means proper alignment. This is a bit difficult to explain without graphics, but is extremely important. When joining two pieces of long, thin panels, you HAVE to have the joint at exactly the correct angle. That should be, but may not be, with the two edges even up against each other.

A far more accurate way is to know the offset or curvature needed for the final panel. I think that Matt Langenfeld (JEM Watercraft) has some assistance for you on this.

Another area to beware of is when turning the once-joined panels over to glass the second side. This panel, now very long and thin, is very susceptible to breaking the half of a joint just completed. Use two people, and great care when turning over the long panel the first time.

I've used the 6" wide piece of plywood as a butt block because it adds strength to a joint. Joinery is a fine art. Joints, when compared to the parent material, will have one of three characteristics: weaker, heavier, or both.
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Postby hairymick » Sun Jun 24, 2007 6:28 pm

Mike,

While everything Jack said is correct and very important, especially on something more complicated than a UJ pirogue.

There are some differences, specific to a UJ pirogue.

1. The bottoms of your side panels are flat and straight. When you do your joint, all you need to do to ensure accuracy of panel alignment is to ensure that the bottoms of the panels when joined make a straight line. :D

2. With the bottom of the boat. the UJ way is to join the two sheets together and then lay it on the assemped sides and THEN mark round the hull to get the correct bottom shape.

About the only thing you need to align is the join in the bottom sheets with the join in the sides. Even this is not critical. It just makes it look better.
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Postby Kayak Jack » Sun Jun 24, 2007 6:40 pm

Yep, Mick's right. I was talking about joining two panels that would make one, say 15' long and 4"-6" wide. Alignment is much easier if the joint is a few feet across. Thanks, Mick.
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Postby oldsparkey » Sun Jun 24, 2007 7:55 pm

Jack corrected a couple of items I was not that clear on when explaining them. So let me correct what Jack said on a few items.... Since I have made 5 of the pirogues....... One was out of Red Wood Strips ( 144 of those strips ) the rest plywood.

1... If the side panels are matched evenly then you will not have a problem , you are only making one board out of two of them. Actually you will be taking 6 boards and making three from them. Two side boards and one bottom.

2....There is no need of an offset or any form of curvature when making the pirogue. The curvature comes later when you assemble the pirogue. The end pieces and ribs determine the curvature of the sides and the rocker in the bottom. Everything is straight up to that point.

3.... I have never had a problem with the panel breaking when I turn it over , just be careful with it , place a hand on each side and just roll it over.
A butt joint the way I do it has never broken , scarf joints have. I really do not like the scarf joint , lots of work for something inferior. I need to say they my boats were made from 1/8th inch wood , this is why they weight between 32 to 40 pounds for a 16 footer and doing a scarf joint is next door to useless on wood that thin. All they do is break on me when moving them.

4.... You could use a piece of the plywood to do the butt joint in place of the fiberglass and if you do then angle the bottom of each inside one and the one across the bottom of the boat or you will be cussing a blue streak. plus using 1/4 inch wood you would have a 1/4 gap ( hole for better words) right in the middle of the boat.

When Jack built his Coho by Pygmy boats that was the way John Lockwood (Pygmy Kayaks) said to do it.
Later when I built my Coho the suggested way of doing it was with the fiberglass. That keeps the hump out of the inside center of the boat which the paddler would be sitting on part of it. :roll:

5.... I tried (on some scrap wood ) to break a butt joint with the glass and guess what , the wood outside of the joint broke , the glassed and epoxy saturated portion remained intact.

6.... Epoxy saturating the wood will/can increase the strength of the wood up to 4 times its original strength , then adding glass to it just kicks it up a few more notches.

It is your boat , do it the way you want and are comfortable with , my ideas are only suggestions , nothing more , nothing less.

Chuck.
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Postby FlaMike » Sun Jun 24, 2007 9:10 pm

It is your boat , do it the way you want and are comfortable with , my ideas are only suggestions , nothing more , nothing less.

To a certainty! Although I ask for advise and opinions, whatever I finally do, I alone am responsible for what I do. That's the way it should be, and is.

From the questions I asked, I got a lot of very vaulable and useful information! A few days ago, someone made a post asking if there were any classes available on building these boats. I don't think he realized that he was sitting in the very classroom he was looking for.

Out of curiosity, did anyone try the link I posted in this thread. Just wanted to make sure I did that right, and to see what was thought about the info in the article.

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Postby nobucks » Mon Jun 25, 2007 12:36 am

I used the glass butt joint on my 14 foot catboat and I like it. It's easy and strong. I used two layers of 9 oz glass on each side, if memory serves.

Here's a pic of said butt-joint, i.e., the Payson Joint, courtesy of http://www.duckworksmagazine.com

Image
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Postby FlaMike » Mon Jun 25, 2007 12:58 am

nobucks,

The method you posted is exactly as described on the page I posted. I like the way they are applying the glass tape on both sides at once, so there's no risk in turning it over to do the other side.

Well, since no one has raised any serious objections to this method, I am going to give it a try on my build.

I still have some time to further study the Forums, it is my intent to steal as many good ideas as I can! :D

I should be starting a Pirogue build thread sometime Monday evening, with pics.

Thanks all!

Mike S.
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Postby Kayak Jack » Mon Jun 25, 2007 11:15 am

No need to fret, stew, and feel any guilt over stealing ideas here. They're freely given. Each of us has a different experience base, expertise bank, and knowledge set. Each of us will put forth ideas that seems to us to be the-best-so-far-that-I've-tried.

Each paddler is paddling in different environments. No single way of doing things will work in all cases, and no single way will work best in but a few environments.



Except, of course, the stuff that I say.
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Postby FlaMike » Tue Jun 26, 2007 8:35 am

KY,

I wasn't so much confessing about stealing all the good ideas as I was bragging about it. :lol:

I'm working under the assumption that if a modification, a method, or idea is posted on the Forum, that it's being offered up into the public domain. Unless, of course, the poster makes a statement to the contrary.

My first post in a "build" thread will be made in a few minutes. I'm starting my Pirogue this morning. I'll be taking lots of pictures to post and I promised Uncle John I'd send him a set for his web site, too.

Who knows? Maybe I'll post something that someone will consider "worth stealing," too! 8)

Mike S.
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Postby PuddlePirate » Tue Jun 26, 2007 3:46 pm

nobucks wrote:
Image


now I'm all confused. If you use this method do you still use the wood flour/epoxy mix between or just epoxy saturation
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Postby PuddlePirate » Tue Jun 26, 2007 3:53 pm

FlaMike wrote: ...Who knows? Maybe I'll post something that someone will consider "worth stealing," too! 8)


FlaMike
Don't worry. I'm going to be following your post very closely and gleaning everything I can when you start your UJ Jon boat. :D
I've decided thats going to be my first build. Don't have much use for the Pirogue with 3 boys, though it does look like a fun little boat.
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Postby FlaMike » Tue Jun 26, 2007 6:17 pm

I can see where you'd be able to maintain a little more "command and control" in that Jon boat, considering your crew. I won't be starting that one until I finish the Pirogue and I started on it, today.

Of course, if you are looking at the size Jon boat that requires 4 sheets of plywood, you could make TWO of the large-size Pirogues! :D

Get your building skills down on those, then build the Jon, you'd have your own Navy.

Mike S.
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