Thread: GIS beginners build in Concord, NH

Alright!

There is no distortion, she is fair fair fair all the way through, no gaps around any of the BH's (except my oversize chinelog notches and the upper side arms of BH3-- did this in the dry fit too-- but that'll all fill really nice). She is one beautiful lady, and her crosscheck measurements are all within 5mm.

And even if it did need correcting, a hacksaw blade between the bulkhead and the ply can undo the glue anyway. It's not as difficult as you think. You'd just need a temporary spreader to take the load while you make the cuts.

But all seems to be well, congratulations

Gots me some bedamnable gaps between the bottom of the BH's and the now-flat planed bottoms of the chinelogs. I'm thinking of filling them with a strip of thin wood glued onto the bottom of the BH's. Any issues with that, anybody? Any other suggestions? About 5mm or so gap, so I don't necessarily want to totally fill it with epoxy.

Thanks!

(I tried to be very careful so this wouldn't happen, but apparently I boofed it up good)

Originally Posted by callsign222

Gots me some bedamnable gaps between the bottom of the BH's and the now-flat planed bottoms of the chinelogs. I'm thinking of filling them with a strip of thin wood glued onto the bottom of the BH's. Any issues with that, anybody? Any other suggestions? About 5mm or so gap, so I don't necessarily want to totally fill it with epoxy.

Thanks!

(I tried to be very careful so this wouldn't happen, but apparently I boofed it up good)

I think you'll find that very suggestion is in the plans somewhere. Regardless of that, it's what I'd do.

Richard

Originally Posted by Daddles

Now THAT's an explanation you usually don't see, usually all you get is a blanket 'don't overtighten' with no explanation of how you know. Thanks. Would be a good one to include in your plans sets Mik.

Richard

If I can add to MIK's comment on how you know that you've overtightened, I'd add that if you know you have a tight joint and you've put enough epoxy in there, but not too much, I always tighten the glue joint slowly with a hand driver or very slowly with the drill and watch for the glue to just start to squeeze out...when that happens I give it a few seconds because it takes time for the glue to move...especially if it is thick like peanut butter, I then give it a slight extra turn of the screw and stop...so once some glue has started to come out, you can stop...the glue is in there and it will be a strong joint...a little extra turn of the screw (quarter or half turn) to get a tad more squeeze out is OK, but. This is fine for tight joints that you haven't loaded with extra glue, and it comes with practice. The other way you can tall is by watching the fairness of the plank...if you have begun to bend something out of fair, then you've overtightened and you need extra glue in there to fill the gap or you need a shim.

I'd love to share with the people of this great forum the best (and most secret) key to strong glue-joints in the world. This is especially good for people who can't help but make their glue joints really tight but then have to worry about squeezing all the glue out. This is a great one for any glue surface. I learned it while at Boat school, but not from the school but rather from the best book on boatbuilding by my friend John Brooks called "Plywood Glued Lapstrake Boatbuilding".

The secret is backing out the joint. You make the bevel (which is what we are usually doing for a glue joint) and you make it concave, that is you back out the joint such that it is hollow. This way if you tighten up the joint there will always be a 1mm or so of space for the epoxy to reside. It won't all squeeze out when you clamp down and/or fasten.

On the boat we built at boat school, I had just read about this technique, and about how failures can occur if you have the opposite, a concave glue joint. You can imagine that if one planed the chines flat but left a crown and you glued down the bottom tight to this, you'd create a pressure point in the middle squeezing out much of the glue and reducing the faying surface area by a lot. I saw this going on on the sheer clamps or perhaps the chine logs of the 30-footer we were building and I thought...that can't be good. We were planing down big laminated pieces of timber, all Doug Fir, and so many places we had not gotten the faying surface flat or concave. I brought it up to my teammates they shook it off as no big deal. Two years later, I found out that the glue joint had let go along a section of sheer clamp...and I would put down a 100 bucks that it was a place that had not been planed all the way flat.

I have a number of tools I use to back out a joint. I'll use a paring chisel and slice wood off, paring across the grain. It takes no time to get a hair bit of concavity. I also have block planes that I've ground curves into the iron. So when the planes goes across the surface -- like planing the chines -- it automatically cuts a shallow concave surface.

Good night.

Originally Posted by Daddles

I think you'll find that very suggestion is in the plans somewhere. Regardless of that, it's what I'd do.

Richard

Good one Richard.

No probs as a solution and almost eliminates the risk of overtightening the joint. It is also a nice bit of detail design.

However if the temporary fastening has been done right then the extra protection probably is not needed.

MIK

Originally Posted by Compass Project

The secret is backing out the joint. You make the bevel (which is what we are usually doing for a glue joint) and you make it concave, that is you back out the joint such that it is hollow. This way if you tighten up the joint there will always be a 1mm or so of space for the epoxy to reside. It won't all squeeze out when you clamp down and/or fasten.Good night.

That technique is a good one Richard. Thanks for sharing.

Another simple and quick one I used in a past life making cricket bats (joining the handle to the blade) is to draw a rasp in the direction of the grain of one face of the joint. (hold the rasp at 90deg to the grain). For a stronger joint, draw the rasp across both faces of the joint. This cuts a series of V grooves which increases the surface area that the glue binds to and ensures the joint is never dry, no matter how tight it's clamped.

Damn! You guys are three days too late! Awesome suggestions... Why didn't I think of that!

I feel smarter for when I build #2 of my soon-to-be-designed STS! Right, Mik, right?

Edit: (I can't find the strip of wood suggestion in my plans... maybe I'm blind...? ...I looked?-- using it anyway, best idea.)

Callsign....sounds like you are learning a lot and that is what matters....plus your boat will come out great because you are careful, follow the plans, and put a lot of effort in. Every boat is a learning opportunity so don't think pros just throw boats together without any learning either! More boats under our belts just mean we have more ways and reliable ways to fix our screw ups! (...like the uncured epoxy coat on my expensive, labor intensive carbon fiber oar blades that the customer wants like in a few days!)

Cheers

Hi Callsign,
Your build is looking really nice! I hope I'll be as far along on mine by the end of this winter. Had a quick question about the foils though. Mine are shaped nicely to the templates and i have them trimmed to length. Yesterday I also trimmed the lower trailing corners as per the plan. I just wanted to double check that these angled cuts on the lower trailing edges do NOT get rounded over, but the bottoms of the foils DO? I want to get them sealed up this weekend and start on my birdsmouth mast after the U.S. Thanksgiving holiday. Keep up the good work! maybe one day when we both have completed boats I can come up to NH to go sailing.
Cheers,
Albert

Howdy,

I think I have a weak point in the documentation. The trailing edge of the foil needs to finish about 2 to 4mm wide after using the template and that width needs to be applied from top to bottom.

So you need to cut the outline of the blank first (straight leading, top and bottom edges and curved trailing edge) and then use the template for the foil shaping so the trailing edge is a consistent width.

I will have to have a look and see why sometimes the curve is cut after the template is used on the trailing edge meaning that face gets wider toward the bottom of hte board.

Best wishes
Michael

Originally Posted by Boatmik

Howdy,

I think I have a weak point in the documentation. The trailing edge of the foil needs to finish about 2 to 4mm wide after using the template and that width needs to be applied from top to bottom.

So you need to cut the outline of the blank first (straight leading, top and bottom edges and curved trailing edge) and then use the template for the foil shaping so the trailing edge is a consistent width.

I will have to have a look and see why sometimes the curve is cut after the template is used on the trailing edge meaning that face gets wider toward the bottom of hte board.

Best wishes
Michael

Mick, the instructions also appear to make it optional to cut the taper in the trailing edge. Are there any issues if that taper is not made?

Originally Posted by woodeneye

Mick, the instructions also appear to make it optional to cut the taper in the trailing edge. Are there any issues if that taper is not made?

Too right. If you don't do that, she'll turn around and head back to the dock everytime a pretty girl walks by. That's fine for some of you but married men deserve to be warned

Richard

Originally Posted by Daddles

Too right. If you don't do that, she'll turn around and head back to the dock everytime a pretty girl walks by. That's fine for some of you but married men deserve to be warned

Richard

Daddles, how much RED have you consumed this evening?