Bending meranti for the rubbing strake

[kilderkin]

I wanted mahogany for the rubbing strake, transom skirt trim and toe rails, planning to keep it varnished for contrast. I found an 18' length of meranti (phillipine mahogany) at a good price, and bought it. I have cut the first level for the rubbing strake, offered it to the boat, but am really concerned at the difficulty of bending it, especially the forward 6' of the hull. The wood would be under serious stress to pull away from the hull all its life. Two possibilities:

a) Build a 20' long steam box, and at least get the approximate bend set in the wood. Might be fun!

b) Cut vertical saw slots part-way through the inner surface of each piece, ensuring that the slots are filled with epoxy as it's glued up. (There's probably a name for this approach)

I would appreciate comments and experiences with either approach, and any other approaches that might work. Two other thoughts are to make up a stainless steel bracket to go around the forward end, or to put a 1/4" SS bolt through all sic pieces and the bow to take the strain.

Thanks

Steve Walker
Kilderkin II

[JonLee]

That bend forward is tough indeed. As I was makingthe bend (during dry fitting), I was getting the feeling that something was about to give....particularly on the first layer. I used a bit of a cheater method to get it to work. Keeping the piece screw in aft, I bent the forward end as much as I dared. Using a long bar clamp, I clamped it in this position (the other end of the clamp was hanging on to a small block screwed into the opposite side of the bow). Then, I poured a good bit of boiling water all over the rubrail. I then laid a bunch of shop towels over the area that I figured had the highest stress concentration, and poured more boiling water. I let everything dry overnight. The combination of the heat and the moisture sufficiently relieved the stress in the wood fibers that I was able to make the rest of the bend without fear of catastrophe.

[chaertl]

Hi Steve,

I used red oak for mine and started at the front so I had the full leverage of the rail to bend it around that front curve. I used wet towels and gradual bending to get them to go. Whatever you do, don't skip putting them on. Just read my last post.


Chris

[kilderkin]

An update:

Thanks for the replies, they helped me understand the issue better - nice to know I'm not the only one to face this.

I was at the Mystic Wooden Boat show today, as was Geoff Kerr (who built Pocketship #1 - she was also at the show). Here are some of his comments:

a) Meranti is a good wood for this.
b) Steaming is a good idea (PVC pipe screwed to a 2x4).
c) Hot water and towels also works.
d) Even just throwing the wood in the river (tie it to something first) for 24 hours is a great help.
e) And my favorite economy steamer - put down black plastic sheeting, wood goes on top. Wet thoroughly, then wrap the whole bundle up and leave it in the sun.

As it's supposed to be in the 80's in the next few days, I might try e) on my last offcut.

While at the show, they demonstrated a steamer. It was 40'x2'x2'. When they opened it, they took out a 3"x18" piece of oak, about 25' long. They then took it in and fitted to the boat - maybe 20+ volunteers, and 8 or so crew. It bent as they needed. It had been in the steamer for 3 hours, under the one hour per inch rule.

SteveW
Kilderkin II

[mtsailor]

Instead of steam, I've used thin strips (1/8 - 1/4") which will make the curve without splitting out. Fix them to the hull with resin and brads, one on top of the last to the required thickness. Shape/sand and you have a fine looking strake ready for glass & clear finish. Good luck. Jer mtsailor http://gallery.me.com/jermcmanus

[kilderkin]

So, I went with the steamer, and yes, it was fun. Two 10' sewer pipes (new, never used), the burner from the turkey fryer, an old gas can as a kettle, and a few 2x4's to support the plastic pipes. Dowels every 6", which swelled and became solid supports. Add to the mix some rather nice single malt, my son, and 6 pre-cut strips of meranti. About three hours later we had all 6 strips clamped to the boat, and left to take a set. Right now, there are the first two strips each side comfortably on Kilderkin II, and waiting for sanding.

Another experience to add the the whole process!

Thanks for all the advice and comments!

SteveW
Kilderkin II