breasthook oddities and setbacks

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breasthook oddities and setbacks

Postby DanaDCole on Mon Mar 30, 2015 9:11 am

I'm wondering if this has happened to anyone else: When installing the lower breasthook (yes I go it right--the lower is straight across and the upper has a decorative curve), I had to force the sides out quit a bit to get it in place. No problem I thought, the breasthook is CNC-cut so it has to be correct, right? Well now I'm not so sure.

When it came time to install the deck I found that I had quite a wide gap out to the sides, up to 3/4" or more in some areas. There was even a gap between the deck edge and the edge of the breasthook itself, as much as 1/2" on each side as I recall. This seemed very odd to me--the breasthook and deck should match exactly, even if the shape of the hull itself is not exactly right. Well there was not much I could do about it at that point and I had no way of knowing which part was wrong, the breasthook or the deck, so I forged ahead. I did not want to try to fill in such large gaps with thickened epoxy as stated in the manual, so instead I fashioned cleats out of laminated strips of 3/8" thick material--three thicknesses to make sure I had plenty of gluing area for the deck. By using 3/8" laminated cleats I did not distort the hull shape much if at all. This at least eliminated the almost impossible job of having to fillet the deck-to-hull joint from inside the front locker--a job I was dreading and wondering how to accomplish without a huge mess.

Anyway, all seemed fine until it came time to install the upper breasthook. At the two "horns" I had as much as an inch-and-a-half gap on each side! I tried building an elaborate Rube Goldberg clamping scheme to pull the sides in but this seriously distorted the hull shape. So I gave up on that idea and am in process of fabricating a new upper breasthook to fit the hull as it is now. Maybe it will be off some, but I think it will still float. :-) It does not seem to me that a change in the shape that high up will have much effect on the shape below the waterline, where it counts.

The only theory I can come up with is that the lower breasthook is misshapen because the upper breasthook and deck are a fairly good match (breasthook a little smaller than deck because the topsides tilt inward a bit). Has anyone else had this problem or do I have something completely out of whack? I know there will be things that have to be adjusted here and there because wood does not bend the same on every boat, but why would the deck not match the lower breasthook? They are sandwiched together for Pete's sake.
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Re: breasthook oddities and setbacks

Postby craig on Mon Mar 30, 2015 1:27 pm

I believe the parts were correct as-is. I had the same issue with my build but I believe the upper topsides panel is suppose to fit directly on top of the bottom panel, i.e. there is supposed to be a gap from the outside of the hull to your anchor deck panel. I also assembled my anchor deck by scarfing two pieces together, and assumed that any error in size was due to my mistakes there. In the picture you can see a little light through the joint.

So now that you installed shims, is your top panel bulging outward at that seam?


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Titania, launched January 2015
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Re: breasthook oddities and setbacks

Postby DanaDCole on Mon Mar 30, 2015 3:19 pm

Thanks Craig. I did not install shims, I installed cleats where the deck was over 1 1/2 inches from the panel. I see you are building from plans. I am building a kit and it seems to me that the angle of the breasthook should be exactly the same as the angle of the deck, which sits directly on top of it. They are offset by the parallel lines of the cleats edges, so the angle should be the same. The breasthook's angle is much wider, spreading the hull out much too wide for the deck and subsequently the upper breasthook.

As you know, there are cleats from the stem to BH1, but not from BH1 to BH2. I simply extended the cleats from 1 to 2 to give the deck something to rest on.

Does this make more sense now? I am not home right now. I may try making some pictures and drawings to clarify. Not having access to the manual right now I am wondering if the lower breasthook was supposed to go below the cleats instead of flush with them, but I don't think that's it.
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Re: breasthook oddities and setbacks

Postby John in CC on Mon Mar 30, 2015 7:41 pm

Dana,
I had exactly the same problem.

A lot of times at night I lay in bed thinking about this boat and this is one part I have thought about a lot!

The solution I used was pretty much the same as what you did, as I understand it. The upper breasthook didn't fit at all and I made a new one that would fit.

What I think I did wrong on the lower hook was that it needed to be beveled on its lower edge. With the edge left square it hits on the bottom edge first in the bow. The shape is cut perfectly at the top and will fit snug against the bow if it is beveled. Without the bevel it kicks out the shape a bit making the top breasthook not fit. Everything is together now and I pretty much had forgotten about it until now. It looks fine and could not effect the performance.

I hope I wrote that so it made some kind of sense. I should draw a picture : )
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Re: breasthook oddities and setbacks

Postby John in CC on Mon Mar 30, 2015 8:02 pm

Image

This is not beveled, basically increasing the size of the hook.

Image

Hope the crude drawing make more sense that my crude writing : )
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Re: breasthook oddities and setbacks

Postby DanaDCole on Mon Mar 30, 2015 10:15 pm

Thanks for your input. As I recall, the tops of the upper panels were vertical enough that I didn't feel there was any beveling necessary, and it was not suggested in the manual. At any rate the amount it pushed the sides outward (about 1 1/2" on each side) was much more than a bevel would have prevented.

When I looked at the deck lying on the lower breasthook, it was similar to this drawing made quickly with cheap software and somewhat exaggerated:
Image
The drawing is a little confusing. E.g., I don't know enough about the software yet to make the lines dashed where they go under another part, but I think you can figure it out--the deck is above the breasthook and cleats.
What I am trying to show here is that the lower breasthook is much wider than the deck at the edge of the breasthook. I did not attempt (it's late) to draw the upper breasthook, but it matches the deck very well--a little smaller because the topsides panels lean inward near the stem. So what happened was that the lower breasthook forced the upper panels out quite a bit--a total of almost 3 inches at the widest point. This left huge gaps around the deck, which I filled in with cleats below the deck. There is no way to make the topsides panels fit the upper breasthook without seriously distorting them, so I am making a new one.

The point of these posts is to find out if others have had the problem, why the breasthook was cut that way on a CNC machine, and if it is correctly cut then what was my mistake? It seems to me that when the deck is laid directly on top of the lower breasthook they should closely match, so that's why I think there is a mistake in the way it was cut. Obviously I am wrong though if no one else is having this problem. (John, I just re-read your post and saw where you said you had the same problem--sorry I missed it before. I still believe that a bevel in the lower breasthook would not help that much--it would only bring the sides in 1/2 inch or so and the total discrepancy is around 3 inches. Also it looks as though you may be talking about beveling the front tip only. If that is correct, that would move the breasthook forward, causing the sides to flare out closer to the stem--worse problem.)
Last edited by DanaDCole on Tue Mar 31, 2015 2:00 am, edited 1 time in total.
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Re: breasthook oddities and setbacks

Postby craig on Mon Mar 30, 2015 11:23 pm

Dana: I understand your post completely now that I have read it more slowly (shame on me for reading this blog at work haha). I mistook cleat for shim. I guess to answer your question, then my deck was slightly off between bulkhead 1 and 2 (where there isn't a cleat), but not enough to worry about and easily filled with thickened epoxy. I would say that everything fit properly. I indeed probably should have beveled the breasthook like John mentioned but that would only account for a bit of space. I remember that the lower breasthook was a BEAST to install. I really had to work hard to push out the panels and get everything in alignment because the epoxy glue made everything very slippery. Since I am building from plans, I'll be happy to measure the part from the full-size cutout if you want to compare with your part (assuming you can approximate the measurements under the deck). I find it odd that yours was off-size. I don't understand how a CNC machine could cut a part too large uniformly; rather, making a mistake on one side seems more likely.

Also, how did placement of the lower breasthook affect the shape of the hull aft of bulkhead 1? If I remember correctly, bulkhead 1 is already glued in place and should have locked the hull in the correct shape aft of that to bulkhead 2. Placing the lower breasthook in place should have stretched out the hull from the bow to bulkhead 1 only, if I am remembering correctly.
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Re: breasthook oddities and setbacks

Postby DanaDCole on Tue Mar 31, 2015 2:23 am

Craig, you are absolutely right. The lower breasthook was indeed very hard to force in as you say, but there is no way it could have stretched the hull out at BH1 and aft. DUH! The only things that make any sense now are either that the deck and upper breasthook are both too narrow or that I have made some stupid mistake that I still can't figure out. But why is the deck too narrow at BH1, and why is it narrower than the lower breasthook? And, if the deck and upper breasthook were cut too narrow, why are John and I the only ones having this problem?

At this point I will stop fretting about it though. I solved the problem with the deck by adding cleats and I am fashioning a new breasthook. The hull shape is off at the top but I don't see how that can affect the shape at the waterline and below, where it counts. And as I said an advantage of adding cleats between bulkheads 1 and 2 is that I didn't have to crawl into the locker and try to fillet the underside of the deck. The deck is glued securely to the cleats and of course there is a substantial fillet on top.

A somewhat related question: Did you install 3/4" x 1" cleats on the topsides panels and if so how did you manage to bend them as the approached the stem? I finally gave up and resorted to 3/8" cleats doubled and glued together. I tried bending the 3/4" cleats using a heat gun, but on a bend that long I couldn't get the heat evenly distributed all along the length of the curve.

Anyway, thanks very much to you and John for your input. It has helped a lot, especially the part about BH1. (I guess my brain is ceasing to function properly.)
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Re: breasthook oddities and setbacks

Postby craig on Tue Mar 31, 2015 9:02 am

Presentation2.jpg
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I did install the cleats on the top, and have a horrible memory of CRACK on the port side. Sigh! I suspended a weight from the middle and let it slowly bend over several days and then tried it. You could also soak a towel and wrap it around the wood overnight.

I stand by what I said about bulkhead 1/2 and how I don't understand how pushing out the hull forward of bulkhead 1 would affect aft of bulkhead 1. HOWEVER, I overlaid the breasthook and anchor deck from the parts layout page in the manual, and they overlay perfectly. Admittedly that is an imprecise way to check but if your breasthook was truly larger then that must be a mistake.

But, like you said, it has absolutely nothing to do with sailing performance. As long as the curves look good you are A-OK!

- Craig
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Re: breasthook oddities and setbacks

Postby DanaDCole on Tue Mar 31, 2015 11:17 am

Thanks Craig and I agree 100%, except the anchor deck and upper breasthook are smaller, not larger--they did not quite reach the hull on either side. (They are actually about 1" to 1 1/2" too narrow total, not the 3" I was saying earlier.) The proof of the pudding is that the deck is too narrow where it rests on bulkhead 1. That has to mean that either the deck and upper breasthook are too narrow or bulkhead 1 is too wide. I do not think it is the latter, i.e., I'm positive the deck and breasthook are too narrow,

Anyway, I got the new breasthook fabricated and installed this morning. I'll send some pictures after it is cured and sanded. The cleats look a little rough because of all the attempts I made to install the "factory" breasthook and then ripping it out after the glue was mostly cured. So I have done a lot of filleting to fix that. Thankfully that area will be painted so once I get it smoothed out and painted it will look fine. Here's a shot of the breasthook clamped and curing:
Image
Pretty rough, but not that bad considering I guess. The only thing now is that on the port side the cleat and hull curve in a little just aft of the breasthook thanks to all the brute force work I did on it. It's not too noticeable unless you are looking for it, but I wish I had thought of making a new breasthook to begin with. Well I gave up trying for perfection a long time ago.
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