Kevin T's BB3...

K

Kevin T

Active member
Been sitting on plans and material for a Black Brant 3 for about a year now. Other priorities intervened and have kept us from moving the project forward, but we finally got started this weekend.

Ordered meranti plywood (1088) from the folks at Cedar Tree - great people. Prices were a little steeper than what I could find online, but I could forgo shipping costs which balanced it out. Also decided to go with MAS epoxy. I have experience with West Systems and liked the product, but was convinced by others more knowledgeable than I to go with MAS. So far, so good.

The plan is to build a standard BB3 with one exception - I will not be including the standard "cutout" for the motor in between two sponsons. I plan on deleting the cutout and going with a more conventional, self baling motor well. I raised this issue about a year ago on the site and got all kinds of feedback, both positive and negative. After talking with the Devlin folks and others on the site I decided to go this way. This isn't a new innovation - a gentleman in Florida tried it with his BB2 displacement hull (and didn't like the results) but I think the benefits of this plan will outweigh the costs.

I have a 30hp Mariner (Yamaha manufacture) that should push the boat along just fine. Now to the project...

Built the cradle - it might be a little high but it's great for working on the scarf and lofting the panels. We'll chop it down once its time to stitch the panels.
View attachment Scarf Setup.jpg

We decided to sand the scarf. It wasn't too difficult, but I'm not sure I would choose this method again...results appeared acceptable - we'll find out once the joint has dried.
View attachment Scarf Sanding.jpg

Decided to clamp the scarf using drywall screws (per Devlin's book). Used a snapline on the garage floor as a reference line.
View attachment Scarf Joint.jpg


That's it for this weekend. I've enjoyed watching others build their boats, so I'll try to return the favor by posting pictures along the way of our build.
 
Looks like ya got a good start to your build! I do like the way your shop is set-up, but I didn't see a butt block mounted anywhere. I found a butt block very usefull when I built my mallard last year.
Dennis
 
Looks great! You have one of the coolest (and quickest) parts of the build coming up cutting and stiching the hull - enjoy it!

Have you thought about what custom mods you are going to add? Not much sense building a custom boat without some nice custom touches.

One thing I'd change to do it over is that I put the standard size plug in and that is a pain trying to wash the leaves, grass, grit, snails, etc.... out. I'd find some sort of 2-3" diameter plug to put in so I could more easily wash that stuff out.
 
Way to go, Kevin.

You have some fun times ahead while this build comes together. As questions come up there are plenty of us to help out.

My personal opinion is that the motor cutout is an advantage in the BB3 but then again I don't think we have seen anyone build a BB3 without one. Good luck with it. If it were me I would make the sponsons per plan and just not cut out the motor well, build a second transom, etc. as you want to do. That way if it turns out that you don't have the performance you are looking for you can just cut out the motor well with minimum extra work. Just a thought.
 
Way to go, Kevin.

You have some fun times ahead while this build comes together. As questions come up there are plenty of us to help out.

My personal opinion is that the motor cutout is an advantage in the BB3 but then again I don't think we have seen anyone build a BB3 without one. Good luck with it. If it were me I would make the sponsons per plan and just not cut out the motor well, build a second transom, etc. as you want to do. That way if it turns out that you don't have the performance you are looking for you can just cut out the motor well with minimum extra work. Just a thought.
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Pete's advice is sound. I think you will get good performance with the BBIII as you plan to build, though. Have you looked at the other plans with conventional transom to see how devlin builds them? I have a snowgoose with the conventional transom and I really like it.
 
Thanks, Guys.

Tod:

I've kept careful track of all the mods that I like on this site - even put 'em on a spreadsheet. Just added the "oversized drain plug" that you mentioned. Great idea.

Also, I'm basically planning on building the motor well as Devlin and others on the site have. If, in the event of a performance disaster, I need to revert to the original design I can just get out the chain saw and have at it. I doubt I'll need to though.

I'm really looking forward to this build. After watching Charlie's come together so nicely and seeing Brian's in person at the midwest gathering in Wisconsin it's time to get going.

Tod, you mentioned using peel and stick fiberglass tape in one of your posts, but I haven't been able to find a source. Any ideas? Thanks.
 
Thanks, Guys.

Tod:

I've kept careful track of all the mods that I like on this site - even put 'em on a spreadsheet. Just added the "oversized drain plug" that you mentioned. Great idea.

Also, I'm basically planning on building the motor well as Devlin and others on the site have. If, in the event of a performance disaster, I need to revert to the original design I can just get out the chain saw and have at it. I doubt I'll need to though.

I'm really looking forward to this build. After watching Charlie's come together so nicely and seeing Brian's in person at the midwest gathering in Wisconsin it's time to get going.

Tod, you mentioned using peel and stick fiberglass tape in one of your posts, but I haven't been able to find a source. Any ideas? Thanks.
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"Peel Ply" is what you are talking about, I think. Not enough guys use it, it is great when laminating glass on fillets. Devlin talks about it in his book and I got mine from RAKA, but everyone should have it. After you lay down your laminate, you put it on top and squeegee all the extra epoxy out so you have a high glass to resin ratio (insures the strongest and lightest laminate adn that your glass does not float in the expoxy lifting it from the wood, which weakens the bond) and peel ply fills the voids in the surface of the glass so you dont' have to fill them with fairing compound to smooth (or grind the top of the weave off your glass to get the glass smooth).

It is wonderful stuff, you put it on when you make the laminate and tear it off the next day with a loud RIIIIIIPPPP! What I did was to cut mine to shape and lightly iron to remove the creases than lay it on as you get a fillet done. If you get good at it you can be literally done withthe fillet adn fairing without doing any and trust me, I'm picky as to how the finished product needs to look. You can't get 100% of the fillet, like the corners, I had silver dollar size areas that I don't peel ply where the hull meets the side (where the two pieces of peel ply come together. I cut the peel ply wo eb 4 inches, or so, wider than teh laminate (two inches wider on each side).

T
 
Kevin,
Dave built one when He was still on the cape without the well cut out. It had a motor mount similar to what you are describing. I will look for the photos of it on my backup disc of some of the old pictures. That boat flew with the 25 on it.

Looks very good so far. Todd is very right about the peel ply. Awesome time saver.
 
Guys:

I "successfully" scarfed my plywood last weekend - it cured and everything looks good. But today when I lofted and cut the panels out I decided to test the scarf on my scraps. Granted, they were very thin - about 3 inches wide so there wasn't a lot of wood, but I was surprised at how weak they were. A little bit of stress and snap!

The scraps broke along the scarf line, but it was wood that snapped and not the epoxy. I do not believe the epoxy failed. I used a sander to make the scarf so it wasn't perfectly flat, but it was very close. I had a 1 in 8 inch slope, used thick epoxy and clamped it up good with screws. Any suggestions? Am I being an old woman here or should I burn it and start over?

I plan on reinforcing with fiberglass tape, but guess I could also epoxy a backer board of plywood on the inside of the hull as well. Any thoughts? Thanks.
 
...also, if I reinforce the scarf with a backer board, should I do it now before stitching and gluing or after the boat is in it's final form? Thanks.
 
Guys:

I "successfully" scarfed my plywood last weekend - it cured and everything looks good. But today when I lofted and cut the panels out I decided to test the scarf on my scraps. Granted, they were very thin - about 3 inches wide so there wasn't a lot of wood, but I was surprised at how weak they were. A little bit of stress and snap!

The scraps broke along the scarf line, but it was wood that snapped and not the epoxy. I do not believe the epoxy failed. I used a sander to make the scarf so it wasn't perfectly flat, but it was very close. I had a 1 in 8 inch slope, used thick epoxy and clamped it up good with screws. Any suggestions? Am I being an old woman here or should I burn it and start over?

I plan on reinforcing with fiberglass tape, but guess I could also epoxy a backer board of plywood on the inside of the hull as well. Any thoughts? Thanks.
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I hate to tell you, but something is fucked up - sorry. Don't burn it, but redo somehow. The joint should be as strong or stronger than the wood. I broke all 6 of my left over strips as a test and they all broke other than at the scarf.

It sounds like maybe you had a dry joint. To properly scarf, you need to paint the joint with unthickened epoxy and then the thickened. The thickened shoudln't be all that thick either - ketchup, rather than peanut butter. Did you do that or just put thickened?

T
 
...also, if I reinforce the scarf with a backer board, should I do it now before stitching and gluing or after the boat is in it's final form? Thanks.
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The backerboard is going to get in the way of the joints and because the stitch and glue doesn't use frames/forms to shape the hull it depends on a uniform bend in teh plywood to give a smooth bend. A backerbaord may/will give you a flat spot.

T
 
Kevin,
I picture is worth... well you know the rest.

Can you take a picture of the break and post it. I think I am picturing it right but its hard to be sure.
 
Kevin,
I'd like to see a picture of the break. How thick is the ply that you are working with. You said the epoxy did not break. But the wood did... Where and how?

If you busted the wood away from the epoxy holding it I would say you have a bond issue. But if the ply failed and the joint held then you have just seen what the panel strength is for a very small section.

Are you glassing the hull inside or just covering with epoxy only for the finished product?

A repair is possible and can be done with glass and epoxy but may require some grinding.

But you may not need to depending on how the scrap broke.
 
If it broke along the scarf, but not at the epoxy, I would agree with Tod that it sounds like the joint was not saturated with straight epoxy first. If it was a little too thick and some of the scarf received no epoxy, well this area would be pretty thin and I could see it snapping rather easy.

Looks like I might be alone on this, but I would probably set this aside for the deck and start with two new panels. I could envision grinding that joint down and building it back up with epoxy and reinforcing with glass tape, but I just wouldn't want that as the hull.

If you have a pic that would be great. Good luck.

Ryan
 
Thanks for the feedback guys.

This morning I decided to test the strength of the panel scarfs just to be sure they were strong enough. My son and I stressed the panel against a fulcrum to see if the scarf would fail - I put quite a bit of pressure on the panel - enough that I'm happy with their strength and will keep them as is. I was fully prepared to stress to the point of failure and redo the joints if necessary, but I don't think a redo is needed.

I've done fiberglass and epoxy work in the past, but never had to do a scarf joint. I followed Devlin's directions to the letter but was surprised when the test scraps broke so close to the scarf. Reading your comments about dry joints and epoxy that might be too thick actually helped put my mind at ease, as I think these steps were done correctly.

I will reinforce the joints with fiberglass tape as insurance and keep you posted on progress. Thanks again for your help - it's great that we can benefit from others' experience and opinions on this site.
 
Thanks for the feedback guys.

This morning I decided to test the strength of the panel scarfs just to be sure they were strong enough. My son and I stressed the panel against a fulcrum to see if the scarf would fail - I put quite a bit of pressure on the panel - enough that I'm happy with their strength and will keep them as is. I was fully prepared to stress to the point of failure and redo the joints if necessary, but I don't think a redo is needed.

I've done fiberglass and epoxy work in the past, but never had to do a scarf joint. I followed Devlin's directions to the letter but was surprised when the test scraps broke so close to the scarf. Reading your comments about dry joints and epoxy that might be too thick actually helped put my mind at ease, as I think these steps were done correctly.

I will reinforce the joints with fiberglass tape as insurance and keep you posted on progress. Thanks again for your help - it's great that we can benefit from others' experience and opinions on this site.
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That is good that you are comfortable now. I can't reconcile the description of a 3/8" x 3" plywood snapping under a little bit of pressure, though. Did you test break all 6 of your skinny strips, how did they do? a 3/8" x 3" piece of okoume should take a whole lot of force to brake, scarf or not.

T
 
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