I'm looking for others ideas for taking templates for new oak ribs

C

cygnusv

Well-Known Member
Joined
12 Feb 2013
Messages
287
Location
Yorkshire, UK
www.best-camping-stoves.com
Further to an earlier post I've now received the oak for sistering 6 ribs that need doing. I'm sistering because our marina is changing hands and not currently lifting boats, the nearest place who can do it is at least 5 hours away. I'm simply adding strength until everything returns to normal and we can have a few weeks on the hard.

The air dried oak I'm using has been profiled already and is currently sat on the bottom of the (fresh water) marina under several feet of water where I intend to leave it for the next 2 weeks or so. Hopefully this will make the oak easier to steam. Just for interests sake, the ribs are 32mm wide and 25mm thick.

I'm hoping to make a template to preform the shape of the ribs so that they will slip between the existing stringers, hopefully making a snug fit without stressing the original ribs and hull planking.

So, any ideas for producing an accurate set of hull shaped templates? Also (because I've not done this before) Is it normally necessary to allow for 'spring back' of the bent shapes if the timbers are thoroughly steamed through.

Thoughts and ideas very much appreciated. Stu
 
Certainly I would go for the laminated option but I would not use oak as it is not so easy to glue. I am not sure about soaking the oak but if you steam it well then it should form to any decent mould as long as you have enough clamps. There will inevitably be some springback and also the wood will want to change shape as it dries depending on the grain. They are not huge ribs so I would not expect this to be overly problematic.

There are loads of ways of making templates. Some people just cut cardboard up until it fits. You can take a scrap of ply and use the intersecting arcs method. Cut a bit of ply to roughly the shape of the hull, it doesn't have to be accurate. Take a compass and with the ply held in place next to the hull simply butt the point of the compass against the hull and draw an arc on the ply. Do this at regular intervals. Now when you remove the ply and set it on a board on which you wish to mark your profile all you need to do is put the point of the compass on the furthest points apart on one of the curves and draw two curves on your board which will intersect. This intersection point will accurately reflect the point your compass was against the hull. If you do this to all the curves then you will have a dot to dot of all the places you took a 'reading' off the hull. Then take a nice bendy batton and make a fair curve joining them up which will be the same as the hull. I hope that explains it.
 
Thanks everyone. I think I'm going to try the laminating method first. To actually fit the ribs I'm going to have to shift a load of plumbing. I can though, get thin ply strips into place without disturbing anything. This and the fact that I laminated some 'bent on edge' oak trims, so I know that I can do it without a lot of grief.
 
Don't bother about "steaming" the ribs. Although tradition always says you have to steam them, the easiest and most effective way is to "boil" them. During my boatbuilding career (I am now retired) we used a pipe sealed at one end, placed at a 20 degree angle, filled with water and a fire at the lower end. When the water was boiling, we would put the 1 1/2" x 1 1/4" x 30ft rock elm or danta ribs into the water for about 20 minutes. We could then feed them over the top of the keel and bend up both sides of the boat where they would be temporarily clamped and tacked into place before planking.
The "boiling" method is far quicker than steaming and meant that we could bend the ribs around a 48ft motoryacht at 7" intervals in half a day. If the wood is left in the boiling water for too long you can boil the goodness out of the timber but the trick is to pull the ribs out occasionally and check their flexibility.
 
itchenseadog said:
Don't bother about "steaming" the ribs. Although tradition always says you have to steam them, the easiest and most effective way is to "boil" them. During my boatbuilding career (I am now retired) we used a pipe sealed at one end, placed at a 20 degree angle, filled with water and a fire at the lower end. When the water was boiling, we would put the 1 1/2" x 1 1/4" x 30ft rock elm or danta ribs into the water for about 20 minutes. We could then feed them over the top of the keel and bend up both sides of the boat where they would be temporarily clamped and tacked into place before planking.
The "boiling" method is far quicker than steaming and meant that we could bend the ribs around a 48ft motoryacht at 7" intervals in half a day. If the wood is left in the boiling water for too long you can boil the goodness out of the timber but the trick is to pull the ribs out occasionally and check their flexibility.
Click to expand...

Hi itchenseadog

If we were on the hard, this is the way I would do it, much more direct. Problem is we're in the water right at the side of a well used visitor path. Perhaps we could find a quiet place to moor the boat and light a well filled BBQ, that ought to do it. Just need a piece of tube now.

Thank, stu
 
I should say that the pipe was 15" diameter and in two 15ft sections with a bolted flange to join them so that we could use the shorter section and boil it up quicker if we were bending shorter lengths. The 4" x 2" Rock Elm gunwhales were the most difficult as we had to bend them two ways. When bending the ribs we would have at least a dozen in the pipe at once. The youngest apprentice was the "runner" who would feed the bending teams of two men each side and one on the keel and woe betide the apprentice if he brought the ribs in in the wrong order by supplying us with a rib that hadn't been boiled long enough! Hands would get sore at the end of the day through handling the hot timber without gloves. I always used to enjoy "timbering up" as the hull would really start to take shape very quickly. One of the worst jobs was fairing off the planked hull which would take up to 10 men 3 days hard slog with hand planes
 
itchenseadog said:
Don't bother about "steaming" the ribs. Although tradition always says you have to steam them, the easiest and most effective way is to "boil" them. During my boatbuilding career (I am now retired) we used a pipe sealed at one end, placed at a 20 degree angle, filled with water and a fire at the lower end. When the water was boiling, we would put the 1 1/2" x 1 1/4" x 30ft rock elm or danta ribs into the water for about 20 minutes. We could then feed them over the top of the keel and bend up both sides of the boat where they would be temporarily clamped and tacked into place before planking.
The "boiling" method is far quicker than steaming and meant that we could bend the ribs around a 48ft motoryacht at 7" intervals in half a day. If the wood is left in the boiling water for too long you can boil the goodness out of the timber but the trick is to pull the ribs out occasionally and check their flexibility.
Click to expand...

Rampart?
 
You must log in or register to reply here.

Share this page

Top