Advice on steaming oak frames

[joliette]

I have to fit some sister frames. Last time I tried laminating in situ and found this to be difficult and sticky! This time I want to try steaming. The sister frames will be approx 1 1/4 inch square oak x 3 ft long. I was thinking of making a steam box out of plastic drain pipe, insulating this with polystyrene and connecting it to my pressure cooker or kettle. Would this type of set up work? How long would I need to steam each frame for? Is it worth givng the oak an overnight soak in water before steaming? Any advice would be much appreciated.

 

[Lakesailor]

Have a look at This Thread I posted about just what you are suggesting.
In the end I re-did a bit of the strip using a wallpaper steam stripper (£23 Focus DIY) and using the plastic core pipes from bale-wrapping plastic (Silage bales) as they are much, much thicker plastic. If you can get some 4" soil pipe that is much thicker than drain pipe as well. The drainpipe tends to sag with the heat.
The kettle was marginal for providing steam and most automatic kettles will kill themselves if you try to force them to continue boiling. Usually a bit of plastic in the switch assembly will distort with the heat.

 

[KenMcCulloch]

1 hour in the steam box for every 1" thickness is the usual rule. If you can get the wood sawn from 'green' (freshly cut unseasoned) timber that is better, if not soak it in water for a couple of days first.

 

[Poignard]

I had to bend edgewise a piece of mahogany about 2" x 1".

I used a length of old cast-iron drain pipe. I plugged one end with cement and had the pipe sloping. I put some water in the lower, plugged end and heated that end with a butane blowlamp. The upper end was loosely plugged with rags. When the water boiled I lowered the timber in with a string tied to it. I'm not sure how long I steamed it for but probably an hour or so. Then I pulled it out and bent it round a former that I had made.

It worked very well.

The subject is well covered in "Amateur Boatbuilding" by Howard Chappelle

 

[absit_omen]

An alternative to building a steam box is to wrap the frames in rags and keep pouring boiling water on them for about 30 mins.

 

[cliffordpope]

Steam in a bag. Cut a suitable length of tough polythene from a roll of tubing (or staple an old fertilser sack round it), stuff the ends with rags, and feed in steam from a wall paper stripper. Clamp the wood into position on the boat and gradually apply force with wedges, clamps etc. If it is reluctant to bend, leave it a bit longer.
When bent into position, turn off the steam and rip the polythene away, and get fastening.
No need for burnt fingers carrying the wood from the steam box - do it in situ.
For long timbers clamp at one end, and slide the tubing along as you bend and clamp the wood into position.

 

[Peterduck]

Either steaming or boiling [and I prefer boiling every time] will dry the wood out, so the need to pre-soak it is important. Equally important is that the grain of the wood should follow the length of the piece, ie, not run out of one side. Sistering is a 'bodge' fix,and replacing the broken section of the rib with the new piece, scarphed together lower down the rib, is a better fix.
Peter.

 

[andrewbodenham]

4" drainpipe or similar as a steambox.
Steam from wallpaper stripper - the big ones you can hire are ideal. I used an old tin on a double-burner primus - pleasingly folksy but more of a faff. However you do it you need plenty of steam.
A proper scarph-jointed replacement is a much better job than sistering, and well worth the extra effort.
Selection of timber is critical. No point in wasting hours of labour if your materials are not 100%. Oak for steaming needs to be fresh cut (green, unseasoned) quarter-sawn, with the growth rings running in line with the planking. Grain must be parallel along the length of the rib - shouldn't be too hard with the short sections you need. Orientate so that the 'bark' side of the rib faces the centre of the boat. Worth tracking down a supplier who is interested in the project and who will cut exactly what you need, though you should expect to pay a premium for good service.
Steam for about 45 mins then check for flex. Should bend with minimal force. Position quickly and wedge / shore in place until cool. Cut scarphs and fasten into final position.
The ribs in the boat below were much smaller section than yours, but the technique is just the same. If sharp bends are involved have some spare stock, as a few failures can be expected.

 

[sue_bagnall]

I would recommend steam in a bag. We have just finished replacing all the frames in our 28” Dalimore
All you need is a length of plastic sheeting slightly longer than the frames to be steamed roll the long edge twice and staple them together. Insert the frame and seal one end by rolling the edge over and staple again. Put the frame in place as best you can and clamp. Insert at the bottom of the bag your pipe, we use the plastic plumbers pipe you can get from any DIY store. Cable tie in place. We used a burner and drum of water to create the steam. The hotter the better. It will normally take about 30min you will then be able to clamp it into place and get the shape you require. Leave to go cold before moving. If you can make up all the bags you need this saves time. As you can feed the pipe into the next frame etc. Hope this helps I have tryed to post a picture but it didnt work. Must be doing something rong?? andy ideas

 

[cliffordpope]

[ QUOTE ]
We used a burner and drum of water to create the steam. The hotter the better.

[/ QUOTE ]

Unless you are pressurising the system it can only be 100 degrees !

 

[joliette]

Thank you all for the helpfull advice.

The "sister" frames are in fact intermediate frames that I am fitting to reinforce the mast step, to prevent leaks. I had thought the leak problem was in the garboard (ref. my previous post), but on examination found evidence of movement along the 3 or 4 planks above this i.e. external cracks in the antifouling and internal rust stains from water ingress for a few metres along these seams.

So, to stiffen the whole structure up and spread the loads I am fitting 4 intermediate wooden floors with frames going up to the chain plates. These frames will have an oak strap fitted on top that will be fastened to the floor and mast step.

The good news is that a few of these frames are nearly straight, so will require hardly any steaming. I'll probably try the boiling water and rag technique for these. For the others and the oak straps I'd like to try boil in the bag providing I can find a way to get a steam supply down into the bliges.

Thanks
Mike

 

[Victorious]

Boil in the bag
Tube of cheap tarpaulin. (dont totally seal the joint.. If has to leak to enable a flow of steam and prevent puddle of hot water in the bag)
Wallpaper stripper supplies plenty of steam....even for big stuff like 22ft 2in boards
can be a tad tricky if frames pass under existing stringers but there are ways of doing it.
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