Bending brass a little

[matthewsx]

A picture of the boat might help but you probably don't need to worry about bending it at all. Assuming you're screwing it down to the rail this thin of a piece of brass should conform nicely to whatever arc you need. Just drill holes where you need them and start in the center. Bedding in the screws is more of an issue but you already know how to do that.

Cheers,

John Matthews
Masse - San Juan 7.7 @ GTYC

 

[spike7638]

A picture of the boat might help but you probably don't need to worry about bending it at all. Assuming you're screwing it down to the rail this thin of a piece of brass should conform nicely to whatever arc you need. Just drill holes where you need them and start in the center. Bedding in the screws is more of an issue but you already know how to do that.

If it were a 6-foot piece, I'd agree. At 12", with screws only at the ends (to avoid chafe at any screwholes in the middle!) that's just not feasible. Love the San Juan by the way,,,

 

[matthewsx]

Assuming you have the material already and only have just enough for the part in question. Jamestown only lists thickness for 3/8" material at .375" so yours is ~.625 "? You should be able to anneal the part with a torch before forming and then create a buck as others have suggested to get the exact curve you're looking for.

Cheers,

John

 

[P. Waller]

Not kidding at all...putting a couple of coats of varnish on a few square inches of teak is such a tiny fraction of each year's prep work that it's something I've barely noticed. I mostly want to do the bends for aesthetic reasons.

The first job that I had after HS was at the Lippincott Boatworks, building 30" cruising sail boats, one of the options was a 3/4" wide X 3/8" thick 1/2 round stainless rub rail nearly the entire length of the hull.
We simply screwed them on, no prebending, no forms or other machine work, the material that you describe may be easily bent by hand.

Drill it, countersink it and screw it down as it will easily follow a 72"+ radius.

I built 95 of these boats

https://www.spinsheet.com/boat-reviews/lippincott-30-used-boat-review

 

[WalterC]

I run such pieces through the ring roller to get an even arc. If you need an almost perfect looking arc, perhaps you know someone who has one?

Oops! Forgot it is not round but oval shaped. My advice won't work.

 

[RJSakowski]

If I understood the OP, the arc is in the plane of the flat side. This is much more difficult to bend as the work will try to twist. Capturing the piece between two forms, one concave and one convex, that are fastened to a backing plate The forms should the thickness of the brass or slightly more and a cover plate fastened through one form and the backing plate will keep the brass from twisting. A pair of clamps can be used to draw the two forms together.
It will help to anneal the brass before bending. There will be a small amount of spring back. That can be compensated for by decreasing the radii of the forms.
The following drawing illustrates the idea. The curvature has been exaggerated
.

 

[spike7638]

End result: RJ's method worked pretty well. The middle pieces -- with the arcs cut out -- needed to be thicker than shown, so clamping things to hold the half-round flat on the bottom piece while clamping required a little jiggering. To make the bend, I used a couple of pipe-clamps to provide the pressure, and had to really crank on them. Both the pink and the green pieces in RJ's picture ended up with considerable grooves in them -- like 3/32" deep -- but because I'd cut them with excess curvature in anticipation of spring-back, it all worked out.

I did, with a scrap, try the "just screw it down and bend it" approach. In an initial test, screwing it down to a test piece in about the position it would be on the real piece (i.e., near the edge), bending the other end inwards ended up splitting the wood (3/4 teak!). Secured better, in a beefier piece, the bending process deformed the half-round at the second screw-hole, where all the load was, and the rest of the half-round remained more or less straight. No doubt I misunderstood the instructions.

--John