OB15 Panel Butt Splice

futuravision · Post by **futuravision** » Wed Sep 24, 2003 11:58 am

Morning All.

I'm still reviewing my plans before I start my building process. Two things have jumped out at me from the plans. The first is that on my drawings, it seems like the third layer on the transom (where the mounting plate is) does not extend all the way to the bottom of the boat. It appears to stop at the motor well floor.

Second, the butt splice dimensions are not shown on my plans. It shows the width as 254mm in the nesting drawing, but doesn't talk about lengths.

Once again, any help would be appreciated.

Post by **jacquesmm** » Wed Sep 24, 2003 4:55 pm

A butt block should cover the whole seam . . . the length is the length of the seam.

All hull panels are full length. They are not the same length when unrolled but will fit.

clearwater · Post by **clearwater** » Wed Sep 24, 2003 8:37 pm

jacquesmm wrote:All hull panels are full length. They are not the same length when unrolled but will fit.

Hunh?

I got the butt block splicing part. I didn't understand the part quoted above. I noticed the same thing with the "third layer on the transom" in my OB15 plans, and I thought I new what the answer would be, but was waiting to see. Sorry Jacques, but the last line does not compute. Could you (or anybody else that knows) say again please?

RonnieE · Post by **RonnieE** » Wed Sep 24, 2003 10:24 pm

The dimensions for the butt blocks are on the drawing with the nesting of the side and bottom panels. Sorry I don't know the exact drawing number because my plans got wet on the corner and can't be read. My plans are not metric but do specify: width = 10' The length is equal to the length of the seam between the two panels that are being glued together.

Yes, the transom is three sheets thick from the top of the cut out in the transom to the bottom of the motor well. Cut the transom for the size motor you will be using(either 15" or 20" shaft), install the motor well and then measure that distance and cut the third layer of plywood. You could also do the math. The well intersects the transom 8" from the keel(Top drawing on D107_2). If you have a 15" shaft motor then the third ply is 7" tall. Hope this makes sense and helps.

futuravision · Post by **futuravision** » Thu Sep 25, 2003 9:29 am

Jacques, that is what I thought. My concern is that the butt blocks will line up with each other and will also overlap at the chine when put together. This will mean that there will be a spot on the seam where the chine will be raised by 6mm. Surely not a big thing, I was just curious to see if that was meant to be there or not. I had thought that maybe i could router out a notch at the chine so that the two panels won't have a "bulge".

Clearwater, I am kind of unsure of the unrolled part myself.

RonnieE, I saw the same things on myplans. The ten inch basically matches a metric of 254mm.(Now I see how that Mars craft went down with the discrepencies over metric and feet/inch.) Seeing as this is my first boat, is 7" a big enough mounting plate? Probably a moot point anyways because the motor I'm gunning for is the Honda four stroke 40 and I believe that it comes with a 20"shaft length.

MikeS · Post by **MikeS** » Thu Sep 25, 2003 3:59 pm

Don't worry about the transom! Jacques designs to the standards required of all boat manufacturers. Build the boat one step at a time and all will work out in the wash. I'm pretty sure Jacques has taken the butt block location into account although I haven't built this boat. But I can assure you that the larger boats work out exactly as advertised so just keep on trucking! I can't recall anyone posting about a butt block problem for the OB15.

MikeS

FLYonWALL9 · Post by **FLYonWALL9** » Thu Sep 25, 2003 7:06 pm

at the seams where your butt blocks meet just take a saw and cut an angle while they are stitched is how i did it so they will fluch out. don't worry about any gaps it happens. they are good live and love them. just where the blocks meet at the chine run your jigsaw or skill down that edge. it will turn out fine. also you may want to think about not having your chine run the length of the bow. try to stop it about 3 or so feet from the bow. depending on if you used 1/4 ply. its a pain to get the chine straight when fairing such a small joint. this was done by several builders unlike myself but i sure wish I had. I would have ended up with a much nicer line.

clearwater · Post by **clearwater** » Sat Sep 27, 2003 10:41 am

Fly, that is a great tip on the chine... Thanks.

Also, I suspected that I would be beveling the butt blocks slightly to help smooth where they meet, but I planned on looking at it when the hull was stiched together. Because of the way the sides lay against the bottom to create the chine, I was not sure if any scarfing would be necessary. The two peices (bottom and side) would meet at such an angle that I was hoping I would not need to touch the butt blocks for the bottom peices. I am not as confident about the sides, though. I was considering terminating the side butt blocks at the chine line to prevent possible bulging, then filling with fillet any excess gap created. Remember, some gap is good, and this axiom is going to be my saving grace.

I suspected

that the transom was three layers on the top and two on the bottom. I think the transom is supposed to be a total of 3/4" (18mm)thick. This could be done with a single peice of ply, but I guess most builders use 2 @ 3/8" (2 @ 9mm) epoxy laminated to accomplish this. This would mean the third layer; on the inside of the top of the transom, is added to increase strength and support for the moter (I guess).

On a final note, like any of you reading this thread for its original content care, I've finally scrounged enough cash to order the materials for my first OB15 without making the Chief Financial Officer at home angry. Just need to finish a couple small projects at home, rearrange the garage, and I'll be ready to go. (how do you spell WHOO-HOO!)

FLYonWALL9 · Post by **FLYonWALL9** » Sat Sep 27, 2003 12:01 pm

clearwater,
The transom I used two layers of 3/4 for the whole thing. So the end result was a total of 1 1/2 thick throughout the whole thing. I did have to do a strange joint you cant do it with one sheet without having a joint on the outside and one on the inside at opp ends. So on the outside my joint is about a foot from the end and opp end on the inside is the same. I buttered the ends with epoxy and wood flower. I know this is hard to explain but it worked really well. It kept me from having to do two layers here and three layers there. So I have the same thickness throughout.

With the butt blocks, I wouldn't worry much about the keel although I did angle cut those as well as the chine. You will see how it comes together when you lace it all up. Then you can make your cuts and make it fit however you wish. I WOULD REALLY do away with the chine at the bow as stated above. Just start it like 3 or so feet from the bow. Again you can see this when you get it laced up. I think it would make for a much cleaner line at the bow. Mine has some waver to it. No big deal from a fishing stand point. Don't get me wrong I am rather pleased with what I have done to this point and hope to have pictures up soon with it on the trailer.

I am now waiting on more epoxy so that I can do my inside glassing. I have my stringers in and filleted. So at this point its really going tons faster than the outside.

Hope all this helps.

clearwater · Post by **clearwater** » Sat Sep 27, 2003 12:50 pm

I understand what you are saying about one sheet of ply for the layer(s) on the transom. I'm confused on why you used 2 layers of 3/4 though. Is that per spec and I just missed that part? Or do you have an "experimental craft :twisted: " you want to run a larger moter on?

At what point did you run out of epoxy

Did you start with 7.5 gallons? I expect I will end up ordering more at some time since I don't think the console is included in the BOM, but I have been wondering how much I can expect to get done in the first 7.5 gallons.

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