Belhaven bottom bevel

[zumwaltd]

I have a question regarding the bevelling of the bottom of my Belhaven I am constructing.  I know I need to

bevel the inside edge of the 3/8th inch plywood where the two bottom pieces join but where the bottom transitions into 1/4 inch at the bow do I bevel that as well?

 

Thanks for the help.

 

Dave Z.

[maligno]

I didn't bevel the 1/4" panels but after opening up the "butterfly" I used a few dowels inside at some stitches to keep the joint centered. 

 

What was curious when I opened the panels was the bottom at the transition joints dished inward; I had to push them down with a pole to make them pop outward.

 

Also I found out that you need to cradle the bottom very well to keep the keel and the chines fair because there are no longitudinal stiffeners at the early stages of the build.

 

Rolando

[zumwaltd]

Rolando, thank you very much for your input.  It helps me visualize what is going to happen when I begin joining the bottom panels.

 

Dave

[Designer]

Rolando makes good points. You do not need much bevel but more a softening of the inside corners of the bottom. This is more necessary where there is a lot of compression like the forefoot where both sides of the bottom are pushing hard against each other. Without the bevel the inboard edges are landing on a peak and would rather slide by it's opposite partner than stay in line.

 

Rolando's point about the bottom support is important. You need to make sure that the cradle reaches the chine so that it does not dish the flimsy (at this time) bottom.

[Lynn Watson]

So a good cradle would be there to hold the hull panels straight when the hull is light and floppy, then support it evenly later, when it gets heavy, right? What's the best spacing for the supports for, say, a Belhaven? I like the carts that were discussed earlier, but they look a bit sparse...

 

And while I'm asking, could someone explain the 3/8" -- 1/4" bottom panel setup? I'm a little confused about that.

 

Thanks,

Lynn

[maligno]

Lynn,

I started out with four supports: at the transom, at bulkhead no. 3, at the temporary frame and at bulkhead no. 1, using the dimensions of the frames. When I stitched the panels, only the transom support fitted exactly; the rest needed a little tweaking. If I were to do it again I'd put an additional support between each of these points. The current set up has blocks under the keel and chines between the bulkhead locations.

I made sure that the diagonals measured from the bow tip to the beams of the bulkheads/frames were equal, that the chines were level and that the centerline is where it should be. The forward end was off by 3 cm to port so I evened it with wires and turnbuckles which I kept in place until after I framed the V-berth.

I haven't turned over the hull yet and I'm hoping there won't be any major surprises when I do.

Re the 3/8" - 1/4" bottom panel setup:

The bottom panels are made of 3/8" plywood except for the forward end which is 1/4". The thinner plywood sheet is flexible enough to shape the front end without the need for strip planking. Joining the unequal panels takes a little thought. I did mine by scarfing the inner side of the 1/4"; the outer side of the 3/8" was scarfed up to 1/4".

Rolando

[Lynn Watson]

Okay, that sounds like plenty of support to hold everything straight and fair, got it. Squaring up the bulkheads with diagonals is essential!

 

Thinner ply for easier bending makes sense, but -- so many rocks and dead snags around here. I suppose there are things people do to beef up the bottom in front; I'll do a search in the archives about that.

 

Thanks for your advice, Rolando

 

Lynn

[zumwaltd]

Rolando, do you have a picture or two of your cradle you could post? 

 

Thanks,

 

Dave Z

[maligno]

Lyn,

 

Graham said the stringers attached inside on the 1/4" as per plans make the front end strong enough.  

 

I used a double layer of biax instead but only because I want that part of the bottom easy to clean without the stringers getting in the way.

 

 

 

Here's how the wire tensioners looked.  I had to check the alignment of all the sections at least once a week to make sure nothing went out of kilter while I was working inside.

 

 

 

Dave,

 

The cradle can be seen when I hoisted up the front end to remove the keel stitches:

 

 

 

Some of the blocks at the keel and chines:

 

[zumwaltd]

thanks, this helps a lot

Dave Z

[Lynn Watson]

Yes, thanks a lot, Rolando; great pictures.

 

I like the biaxial cloth, too!

 

Lynn