Guess I'd be "Buttin' in" if I suggested that all you butt joint folks try to learn to scarf. It's a whole lot less trouble.
Glue problem
- Thread starter JAYCEESFOLLY
- Start date
Be more than happy to give you or anyone else a quick class on scarfing. Come on down.
You GAR ON TEE that your sides are identical by clamping them together and sanding or planing them down to match before moving forward. We do this even on plank pirogues that have one board per side. Just cutting to a pattern doesn't always assure two matching panels
You GAR ON TEE that your sides are identical by clamping them together and sanding or planing them down to match before moving forward. We do this even on plank pirogues that have one board per side. Just cutting to a pattern doesn't always assure two matching panels
What I'm trying to say is.....If I want a 16' boat, I do a butt joint and I know I have a 16' boat. (Just like the last two) For unexperienced builders doing a scarf, I may end up with one side panel 15'-4"......the other 15'-11". Now I have to shorten the long panel to match the shorter one.....and I don't have a 16' boat.
Seedtick......Your on my short list of places to visit and people to see! :wink:
Seedtick......Your on my short list of places to visit and people to see! :wink:
I've not built a boat, but let me make a wild guess. You make the scarf joint before you cut the panels to the exact length. Is that the answer to O.Y,'s question?
Bob
Bob
no. seed cut the sides first as in ; http://www.neilbank.com/phpBB2/viewtopic.php?t=3681
later keith
later keith
See if I got it now Keith. You know what the scarf ratio is so you cut each peice that much longer. All the peices get the scarf ramp cut at the same time so they are all the same and when glued everything is the proper length. Do I get a gold star now or a head thumping?
Bob
Bob
O.Y.
I will build one when I get my garage cleaned out. The other day I tried to get a hole started in it with a Bobcat. Ran into the mess as fast as I could and bounced off. So now I don't know. Sorry Capt. Merryweather.
Bob
I will build one when I get my garage cleaned out. The other day I tried to get a hole started in it with a Bobcat. Ran into the mess as fast as I could and bounced off. So now I don't know. Sorry Capt. Merryweather.
Bob
Scratches & pitting on the plexy, lots of epoxy and too much weight, combined with the heat from the curing process could have all added up to this problem.
Just a little more theory.
If it were me, I think I'd either try to locate some more plywood and try again, or enough plywood to make an additional butt joint to get the original length back, long before I'd "settle" for making a boat smaller than I wanted to build in the first place.
I imagine you had a reason for selecting the size you started to build, unless those reasons have changed, you won't be building the boat you wanted to.
Mike S.
Spring Hill, FL
Just a little more theory.
If it were me, I think I'd either try to locate some more plywood and try again, or enough plywood to make an additional butt joint to get the original length back, long before I'd "settle" for making a boat smaller than I wanted to build in the first place.
I imagine you had a reason for selecting the size you started to build, unless those reasons have changed, you won't be building the boat you wanted to.
Mike S.
Spring Hill, FL
Mike and others:
Thanks for the suggestions and ideas. I decided to cut the end of each side panel off and re-glued them this morning. I had to cut 3" off each piece. The overall length of each finished (glued) panel went from 15' 8" to 15' 2". I also used waxed paper this time as well as the plastic sheets.
I also glued & glassed both sides at the same time(after reading Chuck's post). We will see how this comes out later today.
Mike: I really didn't have a specific length in mind when I started this project. I was going to just let the length come out to whatever the 4 x 8 sheets of ply gave me. I know I am going to build another one later this fall. (I hope the other half doesn't read this!!! She will increase the length of my honey-do list.) This piro is just going to be my experimental unit. I am going to see what sort of performance I can get out of this thing and how well it meets my needs and expectations.
Thanks for the suggestions and ideas. I decided to cut the end of each side panel off and re-glued them this morning. I had to cut 3" off each piece. The overall length of each finished (glued) panel went from 15' 8" to 15' 2". I also used waxed paper this time as well as the plastic sheets.
I also glued & glassed both sides at the same time(after reading Chuck's post). We will see how this comes out later today.
Mike: I really didn't have a specific length in mind when I started this project. I was going to just let the length come out to whatever the 4 x 8 sheets of ply gave me. I know I am going to build another one later this fall. (I hope the other half doesn't read this!!! She will increase the length of my honey-do list.) This piro is just going to be my experimental unit. I am going to see what sort of performance I can get out of this thing and how well it meets my needs and expectations.
Dang,
Looks like ya'll settled everything after I left this morning. Yes allow a couple of inches for the scarf overlap. For 1/4" plywood an 8:1 scarf uses 2" while a 12:1 scarf uses 3".
Practice making your scarfs on scrap plywood pieces, so you'll have confidence when you scarf your sides and won't end up with a 14' boat if you started with 16' sides.
In reality, I don't think many folks can tell the difference between a 16' boat and a 15' 10" one
Looks like ya'll settled everything after I left this morning. Yes allow a couple of inches for the scarf overlap. For 1/4" plywood an 8:1 scarf uses 2" while a 12:1 scarf uses 3".
Practice making your scarfs on scrap plywood pieces, so you'll have confidence when you scarf your sides and won't end up with a 14' boat if you started with 16' sides.
In reality, I don't think many folks can tell the difference between a 16' boat and a 15' 10" one
Somehow I was thinking the loss of length was more than that, so I can certainly see just going on with it. As for me, just about everything I do is "experimental." 
seedtick,
You always give good advice! But I think he's talking about a butt joint here, not a scarf. So, no loss of panel length from the joint itself, just from the earlier problem.
Mike S.
Spring Hill, FL
seedtick,
You always give good advice! But I think he's talking about a butt joint here, not a scarf. So, no loss of panel length from the joint itself, just from the earlier problem.
Mike S.
Spring Hill, FL
Seedtick, When you hinted that had he used scarf joints he wouldn't have had that problem, I guess I don't understand. On scarf joints, don't you still have to use a release agent (wax paper, Plexiglas, etc.) and press the joint together until the glue sets? Sounds the same to me.
Edjumakate me here, ehh?
Edjumakate me here, ehh?
IMHO.
An advantage of the scarf joint is that the epoxy that squeezes out of the joint is only a thin line, not the 2" or 4" or whatever width tape you use on the butt joint. So yes you still use the wax paper but you don't have a couple dozen of square inches of epoxy touching it (giving more opportunity for sticking).
Another advantage of the scarf joint is that, if you align it correctly, you cannot squeeze out the epoxy between the scarfed edges. With the butt joint, too much pressure will starve the glass tape of resin. You may have trouble believing that you cannot starve a properly aligned scarf joint. BUt if you think about it in the macro sense - think about gluing up 1/4" scarfed pieces and keep the two pieces of plywood (the scarf joint) an inch apart. Butter up both sides and add weights. As you press down, the weight will stop when it rests on the 1/4" thickness of the unscarfed part of the plywood. In this scenario, you cannot squeeze glue out of the joint without compressing the plywood -which is difficult. If you keep this picture in mind, then move the scarfed joints together until they're 1 mm apart. You still can't press all the glue out. If you're still with me, you have a joint that's 2 or 3" wide, well epoxied and a lot stronger that what you have when you join the sides of your pirogue to the bottom. That's probably not the best explanation but if I lost you let me know and i'll try again.
To me the time spent feathering in the edges of the tape around a butt joint is more than the time required to make a scarf.
guess i'm just a diehard fan of scarfs
An advantage of the scarf joint is that the epoxy that squeezes out of the joint is only a thin line, not the 2" or 4" or whatever width tape you use on the butt joint. So yes you still use the wax paper but you don't have a couple dozen of square inches of epoxy touching it (giving more opportunity for sticking).
Another advantage of the scarf joint is that, if you align it correctly, you cannot squeeze out the epoxy between the scarfed edges. With the butt joint, too much pressure will starve the glass tape of resin. You may have trouble believing that you cannot starve a properly aligned scarf joint. BUt if you think about it in the macro sense - think about gluing up 1/4" scarfed pieces and keep the two pieces of plywood (the scarf joint) an inch apart. Butter up both sides and add weights. As you press down, the weight will stop when it rests on the 1/4" thickness of the unscarfed part of the plywood. In this scenario, you cannot squeeze glue out of the joint without compressing the plywood -which is difficult. If you keep this picture in mind, then move the scarfed joints together until they're 1 mm apart. You still can't press all the glue out. If you're still with me, you have a joint that's 2 or 3" wide, well epoxied and a lot stronger that what you have when you join the sides of your pirogue to the bottom. That's probably not the best explanation but if I lost you let me know and i'll try again.
To me the time spent feathering in the edges of the tape around a butt joint is more than the time required to make a scarf.
guess i'm just a diehard fan of scarfs
Seedtick:
Good explanation. It makes sense to me. I am a rookie in this boat building business, so I did not attempt a scarf joint. I didn't have a lot of confidence with working with 3/16" plywood. I am planning on trying it on my next boat.
I checked on the side pieces that I re-glued this and can report that it was a success. The joints look great and glassing both sides at the same time was a timesaver. Thanks for the idea, Chuck. Tomorrow morning I am going to dry fit(using screws) the two stem pieces and see if the side panels will bend OK.
I have a couple of questions:
Do I put the outer gunwale on before or after I attach the sides to the stems? It seems to me that it would be easier to attach the pieces before they are bent and attached to the stems.
Same question for the inside chine. I am putting a 3/4 x 3/4 chine in to help support my weight. I think attaching both when the sides are flat on the table top are the easiest way. The instructions that came with the UJ plans say to bend the sides and attach the stems before putting the gunwale on, but it seems easier the other way. I am adding gussets to the frames to compensate for the removal of material for the chine.
I am leaving for a trip to Atlanta GA tomorrow at Noon, so I may not get to answer any of your replies until at least Thursday. I should be back by Sat or Sun.
I am very pleased with the way the new butt splice came out!! The plastic sheets make a very smooth surface with very little sanding required.
JC
Good explanation. It makes sense to me. I am a rookie in this boat building business, so I did not attempt a scarf joint. I didn't have a lot of confidence with working with 3/16" plywood. I am planning on trying it on my next boat.
I checked on the side pieces that I re-glued this and can report that it was a success. The joints look great and glassing both sides at the same time was a timesaver. Thanks for the idea, Chuck. Tomorrow morning I am going to dry fit(using screws) the two stem pieces and see if the side panels will bend OK.
I have a couple of questions:
Do I put the outer gunwale on before or after I attach the sides to the stems? It seems to me that it would be easier to attach the pieces before they are bent and attached to the stems.
Same question for the inside chine. I am putting a 3/4 x 3/4 chine in to help support my weight. I think attaching both when the sides are flat on the table top are the easiest way. The instructions that came with the UJ plans say to bend the sides and attach the stems before putting the gunwale on, but it seems easier the other way. I am adding gussets to the frames to compensate for the removal of material for the chine.
I am leaving for a trip to Atlanta GA tomorrow at Noon, so I may not get to answer any of your replies until at least Thursday. I should be back by Sat or Sun.
I am very pleased with the way the new butt splice came out!! The plastic sheets make a very smooth surface with very little sanding required.
JC