SPRUNG PLANK

[Vitalba]

Right on the waterline of Vitalba`s steeply raked transom is a plank which sprung by about .375" at the top edge only. This tapers to nothing about afoot or so along the plank. In other words the plank has twisted or rather straightened as it requires to twist in order to adhere to the profile of the transom.
The plank is attached to the transom and its doubler by three screws the bottom two are no.12 by 2" and the top one is no.14 (.246"dia.) which has sheared where the thread meets the shank leaving the threaded portion still embedded. Whether the "untwisting" of the plank caused this or it happened when the the plank was "pulled down" at some stage is unknown. Subsequentlythe gap was filled with a large qty. of epoxy now removed. There seems no way to use a clamp to pull the plank into position but fortunately 24" forward are the anode mounting holes and by attaching an 8 foot lever by means of a bolt through one of these the plank can sprung back to within .125" of its original position. By altering the entry angle of the top (broken) screw the counterbore in the plank can be reused for a new no.14 by 3.5" Bronze screw.
I am concerned however that in trying to pull the plank into position I shall either split the plank or shear the screw.
Would dampening and/or heating the last couple of feet of the plank be really worthwhile and if so how to do it ? And is it worth doing a trial run with a large washer (to spread the load) with or without heat/steam. Planks are .875" thick Mahogany.
Comment and Bright Ideas greatfully received. VITALBA

 

[covenanter]

you need to do it in stages, you need to steam it, or wet it quite a bit, then pull it in with clamps or screws part of the way. leave it to dry out for a day or two then repeat again a bit more. It should pull in flush. If you try to pull it in dry it will always want to spring back out, and will eventually.

 

[fisherman]

I watched Luke Howell at Gweek ( working sail) steaming a plank in situ, using a flexible pipe pushed over the end. Can you let the plank go enough to do that?

 

[cliffordpope]

[ QUOTE ]
using a flexible pipe pushed over the end.

[/ QUOTE ]

Plastic bag and a wallpaper stripper.

 

[1937rogerdon]

A wall paper stripper pad gives a lovely head of steam, which you can concentrate on the area in question

 

[Vitalba]

It seems that a Wall Paper Stripper is the answer and to spring the plank back in stages allowing it dryout in between. This will certainly reduce the loading on the screws and the chances of splitting the plank.
One last question: approximately, for how long should I steam ? or what is a guide as to when the plank is ready to be pulled in ?
Many thanks for your inputs thus far. VITALBA

 

[Tranona]

Up to one hour per inch of thickness seems to be the norm.

 

[cliffordpope]

The thing about bending by just applying a wallpaper stripper, or slipping on a polythene bag with a steam pipe, is that you don't have to bother about applying any rule about time. Give it 10 minutes and then apply a bit of pressure. Test again after another 10, and so on. That way you only steam for the minimum time needed to make the bend safely. You can bend half way, then give it a bit longer if necessary.