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Old 09-12-2011, 12:46   #1
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Cabin Roof Beams - Built in Place

My cabin's really just a cuddy added on to a daysailor. For the roof bracing, he used about 5/8 x 5/4" strips lengthwise, along the axis of the boat, with a 1/4 ply top. Looks like the braces are from exterior ply. There are I think 3 across the top. They help the shape just fine. But, they sure don't feel beefy to stand on. With the mast just in front of the cabin, I know my weight will be on it a few times at least.

So, I'm thinking a couple cross braces inside, laminated into place, epoxied, blocked at the ends, a few screws. The entire cabin's only about 5' long, and 2-1/2 to 3' wide. I think a couple braces maybe 1" wide x 1-1/2" tall would be good.

What wood should I use, and in what thickness, so that I could simply bend the layer to shape, clamp it, and add another layer? I'd rather not have to steam bend these...
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Old 09-12-2011, 13:33   #2
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Re: Cabin Roof Beams - Built in Place

I would use 1- 2" wide 1/4 " plywood. 3 or 4 should do. Laminate in place and brace up with some more of the same to keep the tension while curing. Like a spring holding them up. Just cover the ends of the braces with 3 mill poly tarp pieces.

The thicker, the stronger but you will end up with a divit in you Knogin if too thick!
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Old 09-12-2011, 13:35   #3
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Re: Cabin Roof Beams - Built in Place

Thats 3 or 4 pieces for each beam making it about 1 inch thick.
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Old 09-12-2011, 16:22   #4
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Re: Cabin Roof Beams - Built in Place

Depends on the camber of the cabin top. For pieces that short I'd start with 3/8" solid stock. If it has a really pronounced camber you might have to down to 1/4", if it's pretty flat you might be able to do 1/2". I would not use ply for this, as half the plies will have the grain facing the wrong way for this application and so will be half as strong for a given thickness. Ply for structural beams is just wrong. I would use a nice sticker dried local timber, not kiln dried garbage from the local hardware store. Don't know what kind of boat this is, but based on post's of the OP's I have seen I'd guess it's a woody. Even more reason to use decent timber. If it will be finished bright you can do fun things like alternating layers of light and dark timber when laminating the beams, or finishing with a final layer of birds eye or burl or whatever you like that's only 1/4". I' prefer something light but strong for deck beams and house beams. Spruce, alaskan yellow, port orford, nice VG fir which has been carefully selected and sticker dried, etc. In an application like this you could have fun and go with Alder or Cypress or whatever you think will look good with the present interior. Here's some laminated deck beams in my last boat-
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Old 09-12-2011, 16:34   #5
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Re: Cabin Roof Beams - Built in Place

Yes Minaret, You are absolutly correct. Not to mention it would look great. I mentioned plywood only because it is easy. The laminated cross section gives it enough (Not the greatest) strength and I assumed it would be painted over as it was an said to be an add on cuddy, My bad because I know how to spell assume and shouold not have.
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Old 09-12-2011, 16:37   #6
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Re: Cabin Roof Beams - Built in Place

Quote:
Originally Posted by S/V Antares View Post
Yes Minaret, You are absolutly correct. Not to mention it would look great. I mentioned plywood only because it is easy. The laminated cross section gives it enough (Not the greatest) strength and I assumed it would be painted over as it was an said to be an add on cuddy, My bad because I know how to spell assume and shouold not have.

No worries, we all have different approaches. Maybe acquiring decent timber is impossible for the OP and the ply fix would be a good option for him. He might think I'm crazy and you're a genius for suggesting ply...
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Old 09-12-2011, 17:58   #7
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Re: Cabin Roof Beams - Built in Place

Here are a few shots from inside. I measured stuff to make sure. The roof beams are actually 3/4" x 1", white oak, on 10" centers. The width is 41"overall outside, the length is 61" overall outside. The back bulkhead is 1/2" BCX, as is the ledge the roof beams sit on. The sides and top are 1/4" BCX. That's 1" x 3/4" between the sides and roof, 1" x 1" at the bottom of the sides, and about 1/2" x 2" BCX just in front of the portals. My idea was to ass a similar vertical brace behind the portals, so about a 16" C-C distance, and then laminate cross beams between them. The cross beams would be tight up into the existing fore-aft roof beams.

Also, this gives a pretty good view from outside. There is significant crown.

I was thinking of ripping something like a doug fir 2x4 into 1/8 or 3/16" slats.

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Old 09-12-2011, 18:00   #8
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Re: Cabin Roof Beams - Built in Place

Oh, and it's not pretty inside. It will probably get 3 coats of primer, and live life like that. This is not a Bristol boat. If it looks great from 10' away, I'll have done myself very proud.
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Old 09-12-2011, 18:26   #9
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Re: Cabin Roof Beams - Built in Place

Looks like a stitch-and-glue Bolger build. If the exterior of the house is glassed I'd consider adding a few layers to stiffen up the cabin top instead of more framing, it could give you the same result with a lot less weight and work. Also if you aren't using very expensive timber and are happy with regular kiln dried VG fir, which seems perfectly appropriate here to me, you might consider a sawn beam in an application this small. Wastage wouldn't be too severe, and the material is cheap, though the end result is not quite as strong. That camber is severe, you might need to go all the way back to 3/16" for the aft end of the house. Thats a lot of lams and will take time, though it's no big deal. Fasteners will be a pain on the first few lams since you are attaching to 1/4" ply and wont be able to use fasteners, just braces. This means you need to wait for cure times for each lam until you have enough meat to use a t-nailer or stapler for succesive lams, then you can stack them all on at once, using braces again to apply pressure for the final lam to cover up any fasteners. Looks like fun!
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Old 09-12-2011, 18:30   #10
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Re: Cabin Roof Beams - Built in Place

Great pictures! Given the logitutal "stringers" (Odd!) and looking at the camber I would consider spiling a 1x6 to the camber, then doubling it . Follow the camber athwart notching out the logitudals. , Fasteners from the top, Then paint. Then a clear, bright 1/4 X 1 1/2 strip/batton for an easy fashion statement.

The "Add on" cuddy looks like it was original... nice.
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Old 09-12-2011, 19:16   #11
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Re: Cabin Roof Beams - Built in Place

Thanks gents.
It's a Culler Sharptown Barge. Similar to sharpies by Bolger, Atkins, Chapelle, Parker, more Culler, etc.
I bought her from an estate midway through restoration and a few improvements. There are things I would have done differently. Alas, it's in my garage now.

I switch ideas often, between laminated and sawn. Neither look fun. It's cramped in there. From the glass work I've done, seems it would be an even bigger bear to attempt that.

I like the trim strip idea, SVA. May need to consider that. If I went sawn, 1" white oak would probably be sturdy enough (judging from the dozens of plans I've studied), especially for such a short beam.
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Old 09-12-2011, 20:42   #12
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Re: Cabin Roof Beams - Built in Place

Also, here's a link to my photobucket page, where you can get a good overall look at the progress. I've done a lot for the leeboard mounts in the last few months, but not updated the thread...

boats pictures by karlwms - Photobucket
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Old 03-06-2013, 21:40   #13
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Re: Cabin Roof Beams - Built in Place

Okay, I am taking a break from the leeboard pivots because I need to finish the cabin stuff first.

So, attached are some pics to show what I've done with the above.
First, I'm adding Wiley style windows, also shown in the Gudgeon Brothers handbook. Drop-open plexiglass that gets a small frame around it to wedge them shut. So, to start, blocks on either side of the windows for these window frame brackets. Also, above them, blocks to help support the grab rails that come through there, and are the ends of my cross beams:





Next, a test-fit for cross braces about 3/4 x 1-3/4, custom fitted. You can see there's a gap where it needs a spacer for the center stringer. These took many hours and templates and the sides don't match and... And I routered the edges round for hand-holds and a place to tie things.



You can see how they fit into the blocks and across the top they'll support the bottoms of all 3 stringers. Glue and screw, nothing's going any where.

These are the braces alone:



Last pic's the glue-up of the spacer blocks for the center stringer. Once done, they'll get the round-over treatment as well, screws removed, then West 6-10 and screws from the bottom-up at each end and in each stringer.



It may be a little over designed, but it will support my lard jumping up there in an emergency, allows for the operational window frames, provides solid mounting so that the grab rails won't give way from me using them, and in addition, provides a few nice hand-holds and tie-downs inside.

By the way, the inside of this thing isn't much more than a pup tent, or a good place to store gear on a wet day sail. So the minor loss of headroom may be offset by the pull-up bars.
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