Butt Block placement for OB 15

[mac4]

I think I may have installed the butt blocks for the bottom panels incorrectly. ( this sounds like a joke doesn't it ! )
I glued them to where there is a 4" gap between the blocks at the keel line. My thinking was that since this space is exactly 4" this must be correct as the first interior layer of tape is 4". It made perfect sense until I saw a picture of a build with the blocks butted together in the hull. Hull is spot welded upside down on frame ready for fiberglassing.

Could anyone tell me if this is wrong ? I'm running out of pepto-bismol......



i'm not even gonna give my name on this one

[AussieBoater]

I've got a gap in mine too... same thinking. I don't think it really matters, they are only there to add strength to the join.
We'll see I guess

[mac4]

Thanks Paul for your response. Nice to know someone else had the same train of thought.
Maybe it's nothing to worry about. Good luck with your boat.


John

[Cracker Larry]

this must be correct as the first interior layer of tape is 4".

This puzzles me Every Bateau boat I've built called for 6" biax tape on all the structural joints, and most planing hulls require 2 or 3 layers of it on the inside of the keel, with the layers offset. This means the minimum footprint of the tape would be 7", not 4.

Also, you are going to have 1 or 2 layers of tape running down the chines. Did you extend the butt blocks to the chines or leave a gap for tape there too? And after all the taping is finished, won't the entire inside bottom get covered in a layer of 12 ounce cloth, overlapping 6" down the keel line?

[mac4]

Yes Larry, you are correct, the outside keel and chine get taped once with 6" then the entire outside hull gets fiberglassed. The inside keel and chine get the 4" tape then 6" tape then the entire inside hull also gets the big fiberglass.

The keel line on the hull panel is more or less straight, but the side of the hull panel (where the hull panel meets the side panel ) is more curved. The hull butt blocks mimic this pattern. They (the blocks) are straight on one side, more curved on the other. If you leave a gap at the keel line and butt the blocks against the side panel, it creates a nice 4' gap which I think is for first layer of tape for the inside keel. However, where the bottom and side panel blocks meet inside at the chine line they are butted against each other, no gap. Sheew, I hope that made since, kinda hard to explain.

The plans do not mention exact placement. I opted to have a continuos double FG taping at the inside keel instead of the the inside chine line.

Not sure what you mean by 7" foot print. 6" on top of 4" leaves a 6" foot print, right ? The second layer of 6" tape when passing through this gap ( on top of the 4") is going to have to ride up a little over these bottom butt blocks.

What do you think ? Sound right to you ?

John

[Cracker Larry]

The inside keel and chine get the 4" tape then 6" tape then the entire inside hull also gets the big fiberglass.

I've never heard of a lamination schedule like that, but I haven't built that boat either. Are you sure that's right? All I've seen use 6" only for the keel.

Not sure what you mean by 7" foot print. 6" on top of 4" leaves a 6" foot print, right

That would be right if you use 6 and 4. Like I said, most boats use overlapping layers of 6", which will leave a 7-8" footprint. This is my FS18 for instance. You can also see that I use fiberglass splices instead of butt blocks.



I would verify the lamination schedule with Jacques.

[jacquesmm]

We specify almost exclusively 6" biaxial tape in that type of boat. When you have 2 layers or more, you offset the edges.
For the OB15, the plans clearly say 2 layers of biaxial tape 6".
One layer of 4" (probably woven) followed by one layer of biaxial is not as strong however, the boat is very strongly build and if you did it that way, it will work.

[Cracker Larry]

Thanks Jacques, just as I suspected.

[mac4]

Larry your work looks outstanding ! Very nice. Thanks for the pic.

I am ashamed that I have misunderstood the plans at such a basic starting point. Thank goodness I have just really started. The plans say ;
" Keel lamination, inside: 2 layers biaxial tape, on putty fillet.
Outside, 1 layer biaxial tape plus bottom fiberglass all overlaps staggered at least 1"."

For the inside chine, plans say;
"2 layers biaxial on 1/2" radius epoxy putty fillet. Stagger layers."

These statements are on the Construction and Lamination "blueprint". It naturally has arrows pointing to the concerned area on a cut away of the boat. This cut away shows what looks to me to be two different size tapes . Looking at them again, I don't see how they could be construed as anything but two different size tapes. I ordered the fiberglass kit from Bateau, it came with , among other things, 4" and 6" tape. Both biaxial. There is much more 6", never gave it much thought as plans call for more usage. I thought I was following the plans. (wow). Jacques, nowhere that I can find, does it specify "two layers of biaxial tape 6"." I'm not picking nits here just trying to explain how I got from there to here.

I have no desire to deviate from the plans and thank you both for your help. Your comments at this early stage in my build have corrected what would have been an entire boat built with the wrong lamination schedule. Although still sound, just plain wrong. ( double wow ) Awesome to have such backup.

John

[Cracker Larry]

No problem, it's an easy fix at this point. Glad we caught it