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About those fiberglass butt joints. . .

PuddlePirate

Member
Jun 3, 2007
8
0
Maine
oldsparkey said:
I don't use the epoxy and wood flour mix ... just epoxy.

Chuck.
thanks Chuck, that makes sense. :D

Being that this is my first build, I think that I'll stay away from the scarf joint for now.
 

seedtick

Well-Known Member
Jul 22, 2006
1,160
7
Denham Springs, LA
I've hesitated to jump into the fray here on butt vs. scarf, but there is a couple of things ya'll need to consider

One is that you don't need to scarf a whole panel of plywood. Yes I agree that a 4' scarf is difficult. But for the sides, what's length of the scarf you need? 10"? 12"? Even if your scarf for the bottom is right in the middle, then that's a 2' scarf. Orders of magnitude easier than a 4' scarf.

A belt sander makes quick work of scarfing, just don't apply much pressure and watch the glue lines. I've never scarfed 1/8 " ply, but 1/4 is a breeze.

The scarf doesn't have to be perfect - check out the photos on the "marsh pirogue" thread. That scarf on the sides took maybe 15 min. the scarf on the bottom was less than 30. Glue it up by saturating the wood edges with epoxy, then add a little wood dust to get ketchup consistency and glue up the scarf. Wax paper on top, wax paper on bottom and you don't have to worry about whether or not the glass is saturated or if it stayed in place . Just keep the pieces lined up.

Cheapest thing in the world (just about) is scraps of 1/4" plywood. Practice. Make a 2" long scarf, then move up to 4 or 6", then another step to the 10" sides. Biggest thing is to keep the panels from moving while you cut them down.

If the boards are lined up correctly, you can't resin starve a scarf joint. Think about it, the most you can compress a 1/4" thick piece of plywood is 1/4". If I lay a 2X4 or 2X6 over a 2" scarf joint then the wieght will only press down to the thickness of the plywood. If the wood is aligned, then the scarf is 1/4" thick, no matter how much pressure you put on top 50lb or 100 lb. Kind of like the glue between the edges of the butt joint, you squeeze it to the thickness of the plywood, BUT too much pressure on the butt joint will starve the glass on the outside.

Keith and I test our scarf joint by breaking the trimmed pieces from the edges, if the edges don't fail in the joint then you've made a good scarf.

sorry for the rant

rant over
 

FlaMike

Well-Known Member
Jun 20, 2007
624
2
Spring Hill, FL
www.ptponds.com
That is not a rant. That is information we all can use and we didn't have to pay a thing for it.
Roger, that!

Don't get me wrong, I don't fear doing a scarf joint, I've made them before on other projects, with both ply and solid wood planking. But from what I've read lately about the different methods of joining two sheets of plywood, it seemed to me like the glass cloth butt joint looked to be faster and easier to do, and should come out looking pretty good.

If it works, then good. If not, then I'll get another sheet of ply and go with a scarf joint. After all, I'm building the Pirogue as practice for my next build, the Jon boat. Now that one is one that I could go with the butt joint with the plywood back-plate. With the seats and casting deck, I'm pretty sure I could easily keep that backing plate out of sight. That's something I can't do too easily on the Pirogue. Maybe I'm making too much of that, but that's just me.

David,

Lots of good info in your comments on a "Flats" Jon boat! I did ask Uncle John, the designer about raising the sides, he didn't seem to like the idea. After looking at the plans again, I can see where, due to it's construction, this would call for some re-design work that I don't think I'd want to attempt.

The areas I will be fishing are fairly well protected waters for the most part. Often, they will be surrounded by mangroves which provide a wind break. Many are quite calm and flat when the water outside these areas are too choppy to be safe.

The problem comes sometimes, when you have to go through the unprotected waters to get to the flats, or to get back home. On those days, I think I'd rather either stay home, or go bass fishing on an inland lake or river. I always keep an eye on the weather when on the water. With a little speed, I can usually get back before it gets rough, or at least find a protected area to scoot into and wait it out.

I'll be taking up almost half the boat with a forward casting deck, plenty of storage underneath. With a tiller steered outboard motor, it would be kind of hard to fit a rear casting platform. But I have no problem casting from the poling platform, myself. Besides, I doubt I'll ever have more than one other person with me on the boat, most of the time I go solo, anyway.

Mike S.
Spring Hill, FL
 

keith

Well-Known Member
there is no perfect boat, thats why me and mick, sparky and others have more than one boat. a flat boat for flat water and a V-btm for rough water.and if I use this kind of glue or wood, someone else can always find a reason to use another. there is more than one way to build a boat and I'm not in a contest with who can throw a anvil the furtherest. most people were saying butt, butt, butt and there are people out here that say scarf. and i use more than one kind of glue, I have used weldwood for over 40 years and I buy titebond III by the gallon and west epoxy (rant 2).have a nice day, later Keith
 

FlaMike

Well-Known Member
Jun 20, 2007
624
2
Spring Hill, FL
www.ptponds.com
I will be using a scarf joint when I make the rub rails. I've read what you and others have said about keeping that joint away from the center of the rail, where the wood is under the most stress. I'll keep the joints more towards the ends.

and i use more than one kind of glue, I have used weldwood for over 40 years and I buy titebond III by the gallon and west epoxy (rant 2).have a nice day, later Keith
I was going to ask you a series of questions about those glues, but I just found out I can pull up all of your post, at once. Rather than pester you with questions you've probably already answered, I'll read those post, tonight.

Don't want you to get the idea I don't like traditionally built boats! In fact, I LOVE them! The boat I'm building now, and the next one, are being built for a specific purpose, and I'd like to have them in the water, as soon as possible. But once that's out of the way, I'd like nothing better than to talk to you about building a more traditional Pirogue, using traditional methods and materials.

Many don't know that Florida has a rich history of cypress boat building. There's actually a couple of small boat yards building cypress plank-on-frame boats, not too far from where I live, down in Tarpon Springs.

This would be a boat that I'd want to build, just for the fun of it. Something that I'd not have any reason to rush through, building it because that's what I want to do. But I'm not so sure the local cypress mills turn out wood that would be suitable for this sort of thing. When I get to this project, I'd like to discuss that, and other things with you.

Mike S.
Spring Hill, FL
 

hairymick

Well-Known Member
Dec 8, 2005
2,107
2
Queensland, Australia
G'day Mike,

I forgot to mention that I use scarf jounts on my gunwhales and shear clamps. Lots of them.

To cut hem, I have made a jig that fits my 12 inch bench top disc sander. I can cut identiccal scarfs time after time using this method and only use cheap slash pine off-cuts for the gunwhales and cedar off-cuts for the shear clamps.

I use the ratio of 1 to 12 for the angle and a quality PVA (AV190) glue for the joints. It is very strong and sets up in about half an hour.

Robins P5 required some serious edge bend in the gunwhale strips and the glue held fine. I have just never been able to do a wide scarf in ply using a hand sander that I have been completey happy with. I have been unable to keep the feathered edges completely straight. To me, a scarf joint is like a mitre joint, Nothing looks worse to me than an imperfectly fitting mitre joint.
 

FlaMike

Well-Known Member
Jun 20, 2007
624
2
Spring Hill, FL
www.ptponds.com
Keith,

Would that be due to your boats being of historically true designs and built with traditional materials and methods? (I just visited your web site, HOLY CARP! Very impressive work!)

I'm under the impression that the boats built with variations of the "stitch & glue" method, or "tape & glue, is a stressed or "tortured" plywood construction, where the different panel's torque play against each other to define the shape of the hull.

I am wrong in thinking that boats of this particular type, such as Uncle John's designs, have the greatest stress near the center of the side panels, making the center NOT the best place for a scarfed joint in a rub rail?

Or is the curve of the rub rail such that the bending stress is about the same, all along it's length?

Guess this is one of those "Inquiring minds want to know" kind of questions.

Mike S.
Spring Hill, FL
 

oldsparkey

Well-Known Member
Aug 25, 2003
10,261
90
77
Central , Florida
www.southernpaddler.com
keith said:
there is no perfect boat, thats why me and mick, sparky and others have more than one boat. a flat boat for flat water and a V-btm for rough water.
I have used weldwood for over 40 years and I buy titebond III by the gallon and west epoxy (rant 2).have a nice day, later Keith
Keith
You are correct , besides a person can never have to many boats, just don't ask my wife she thinks I have to many. :lol:

When I made the stripper I used the titebond to hold the strips before I epoxyed them , that is some good glue.

All of my boats have the joint in the middle so it lines up with the rest of the joints when assembled. I did build one where the joint was at the ends but that was because I stretched it out to 18 feet. I added the extra 2 feet to a 16 foot strip for the railing.

Chuck.
 

keith

Well-Known Member
my boats will have a long smooth curve in the center and a tight twisting on the ends and of course my sides are not flat. depending on the style, most of the time, my breasthook will max out my plywood. styles will vary, but on a 14 foot marsh pirogue, I come back from the stem about 18 inches and open the sides to 18 inches and make the breasthook to fit. so my stress is on the ends. if your sides are flat with one long curve, you have no stress. most of mine are compound. Later Keith
 
Hi Everyone,

I had captured much of what Dave Carnell had figured out over the years, including Plywood Butt Joints as referenced earlier here.

Dave was an amazing guy, a DuPont chemist who built many boats and did extensive experiments with wood, fiberglass and epoxy. I enjoyed talking with him occasionally on boatbuilding forums and occasional email. He is gone now but some of his knowledge and information remains for us that Make Stuff. I have tried to grab all of Dave's writings over the years; what I have is HERE: https://arduinoinfo.mywikis.net/wiki/Boat_Building That's a WIKI I write for Other Stuff but one of my many Grandchildren has said he will keep it alive 'indefinitely'...

We recently got a small piece of land on the Withlacoochee river a little north of Blue Springs State Park. We will camp there pretty often. We have kayaked quite a bit of the Suwannee in that area and love it. Meanwhile I am building a 12' UncleJohn ( UncleJon? ) boat here in the snow on Vermont in the basement of our log cabin.

Just finished the Fiberglass Butt Joints.
 
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Kayak Jack

Well-Known Member
Aug 26, 2003
13,800
136
83
Okemos / East Lansing Michigan
Welcome aboard, Terry. The only name I recognized out of those you cited was Suwanee. I paddled a bit of the Suwanee, say, 10-14 years ago with Bill Logan, and some of his marvelous buddies. Bill’s gone now, but his old man river is still rolling along.
 
Hi Jack and thanks for the welcome! After all the crazyness and unhappiness in so many kinds of media it's a relief to just get with people who Do Stuff. Like:
  • Figure Stuff Out
  • TRY stuff out
    • Learn from failures, still smiling!
  • Make stuff work
  • Help other people to Make Stuff Work
That's always been my favorite STUFF!

I'll be 81 about the day I launch on the Withlacoochee. We'll see what stuff works...
 
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Kayak Jack

Well-Known Member
Aug 26, 2003
13,800
136
83
Okemos / East Lansing Michigan
Aha! A fellow Olde Farte! I’m 83, recovering from a total knee replacement. Planning spring trips on bike and in canoe. A few of my stories are in Trip Reports, Tales From The Log of The Ruptured Duck.

Go forth, young man, and explore! Wear yourself out!
 

PeteStaehling

Well-Known Member
Aug 23, 2020
144
2
69
Tallahassee Florida
I haven't built a boat in years, but have done a variety of methods of joining sheets. I found that butt joining and using glass worked just fine and was easy to do. Planing scarfs was harder to do but also worked fine. I recently tried masking a fixture for an old circular saw for cutting them and it seems to work great. I plan to use it on the build I am currently working on. So far I have only done a few tests on scrap, but it went well and was super easy.

The fixture is a crude thing that I threw together as a proof of concept, expecting to make something nicer, but it works well enough that I may not bother. Maybe if I remember to take picture when I scarf some plywood I'll post some. Here is the ugly fixture:
1548
 

Kayak Jack

Well-Known Member
Aug 26, 2003
13,800
136
83
Okemos / East Lansing Michigan
Like you, Pete, I eschewed the scarf joints, and did butt joints. I reiforced mine with a 2” wide piece of 4mm okoume with beveled edges. About 1 ounce in weight of overkill that has withstood my hamfisted misuse of the boats.

A couple of times, in going over beaver dams, the boat was bridged with me in the boat, both ends supported and the center in mid air. While I can’t recommend the technique, it did work. All the cracking and creaking wasn’t from my boat - it was sticks breaking in the dam.