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View Full Version : steambending chines??? (my first boat)



Tom Wilkinson
07-21-2001, 09:17 PM
I am building a 15 foot runabout. (rascal by Ken Bassett) and I am ready to install the chines. They are douglas fir 13/16 X 2. I am concerned about the joint where they meet the stem. They are let into the stem but ther is a considerable amount of twist by the time they get back to station one. I am able to clamp everything into place but it seems to be under a lot of stress and I am afraid the joint will break when i remove the clamps. Would steaming the chine and clamping it in place for a couple of days take a lot of the stress out of it or is this a normal thing that I should not be worried about? Thanks in advance, Tom

Thad
07-22-2001, 09:51 AM
You can effectively steam D. Fir, at least if it is not kiln dried. My experience with fir is that if you think the stresses are likely to break the piece it is likely to break. Unlike oak or cedar which generally will be fine if they make the bend initially, fir often breaks a day or more later. Just when you think you are fine, bang!

RGM
07-22-2001, 07:26 PM
Tom, as Thad suggests, steam the chine pieces and roll them into position. You'll get less heartache by doing this and some good practice at steaming. Rolling the chines in cold might work for you until you start driving fasteners into them, that's when they tend to start letting go. You don't have to steam the whole thing, just the twisty part so if you're not set up with a long steam box yet no big deal, build a small one for now. Besides the usual wood boat books that discuss steaming there's an article in the June 2001 issue of Fine Wood Working that may be of interest. If your fir is not kiln dried steam it for about an hour/inch of thickness. If your material is kiln dried then use it as kindling for your fireplace and make new chines from air dried stock. Don't even bother to put kiln dried fir in your boat. Good luck.

jeff pierce
07-23-2001, 05:28 PM
I have some thoughts prompted by RGM's response, where he said "you don't have to steam the whole thing". First however, a couple of caveats:

1. I suspect RGM is an experienced boatbuilder, I am not. I am just a bit further ahead on my first boat than Tom.

2. I don't know the details of the "rascal" plan

Anyway, my boat plans specify dry bending of shears and chines. There is significant bend and twist in these members. There are few transverse frames in the design, thus the shape of the shear and chine lines is controlled by these members taking a smooth, "natural" bend. I would think that steaming only part of the length of these members would locally change the stiffness and might cause it to take a different shape than the designer intended.

Its just a thought to ponder. And yes, I did break both a chine and one shear lamination. My problem was poor material selection, though. I traced both pieces back to the same piece of 1 x 4 stock, which had some fatal flaws.

Whatever you choose to do, Tom, good luck and post pictures.

Tom Wilkinson
07-23-2001, 07:03 PM
The material I am using is clear vertical grain douglas fir but it is kiln dried. I have read several articles on steam bending and some indicated that kiln dried lumber would work fine. The chines are currently clamped in place and breaking the would didn't seem to be a problem. The thing I was mainly concerned with was the glue joint at the stem. I am using west system epoxy with a filler.

Doug-a-lug
07-23-2001, 07:45 PM
Tom,

My brother and I built a Rascal about 3 years ago. We used spruce for the framing and chines. If memory serves, we had no trouble laying in the chines; I Ken Bassett calls for laying in the chine pieces begining at the stem and working aft with a piece of 2x2. We left the chine "fat" past station 2 (or was it 3?), then faired the 2x2 down with a hand plane.

Our Rascal is for sale, but my brother is out of town for another 3 weeks. E-mail me, and I'll send you his e-mail address...he'll remember the details more than I did. Also, Ken Bassett is always helpful on the phone; we called him 2 or 3 times for advice.

ps: plan for seat belts! She is a fast one!!

Doug

RGM
07-24-2001, 02:41 AM
The primary reason that you don't want kiln dried fir in your boat is that it is prone to rapid decay and it's cellular structure has been compromised by the rapid drying associated with kiln drying. But it's your boat so build it out of whatever you want and whatever is available to you. Don't be concerned about causing "local changes to stiffness" by only steaming part of the stick, it's not an issue. You are building your boat with your own eyes and hands, how it turns out is entirely up to you not the designer. He's not there to help you roll those chines in is he? Good luck.

Art Read
07-24-2001, 05:09 AM
For what it's worth, I inadvertantly bought some kiln dried CVG fir to re-do some shear clamps that I felt weren't "beefy" enough. I'd tried to get the originals out of some nice, air dried "boat timber" that I'd made my bilge stringers with and paid top dollar for, but lost more meat to the saw kerfs and planer than I'd hoped. The replacements were beautiful... right up 'till the moment they broke. The "skimpier" originals, (which I'd thankfully saved) bent in fine and took their fasteners with no problems at all.

jeff pierce
07-24-2001, 01:33 PM
RGM is right, of course. Funny how I realize sometimes too late that I don't know what I'm talking about and should listen to those who do. Oh well, ya live and learn.

Tom Wilkinson
08-16-2001, 08:12 PM
Well, I ended up steaming the chines. I used the kiln dried fir against some of the posts here but it is what I had. Steamed them for about two hours and layed them in and left the clamped for a week and a half while on vacation. Removed the clamps and the held their shape very well. We will see how well they hold up to fastening but no problems so far. I am on to the plank battens for the bottom and plan to use a similiar process to fit them.

jeff pierce
08-16-2001, 10:27 PM
Glad to hear its going well. Now where's them pictures, eh?