Plank warpage

I have 2 dry , unrestored canoes which have extensive plank cupping . [ The planking has bowed away from the ribs except at clinch tack points . ] Is there a fix aside from replacing all the planking ?

 

Hi Dave,
The cupping is a result of too much moisture. I have had more than few come through the shop in this condition. One method that has worked for me is to remove the tacks , apply a little heat and mositure with a damp cloth. (not to wet) Then retack using a different tacking pattern to help the cupped areas lay down. It doesnt always work on very severe spots as the planking wants to stay in that shape. Sometimes it is easier to replank as you are already removing tacks.

 

The way the grain runs in the plank will determin how much much it will cup and warp. When wood gets wet it will swell and shink when it dries. On planking that has straight grain or quartersawn, most of that swelling and contracting will be in the thickness of the plank and very little in the width. As a result there is almost no cuping or warping.
On planking that is flat sawn, the most commen type of planking, the swelling and contracting will be in the width. this movement across the width of the plank will cause it to cup. Extra nailing may help reduce the cupping but the forces are still there and the plank may just split itself at the nail as it trys to expand and contract.
Working with old canoes that have flat sawn planking is always a problem. Do you replace the original cuped and warped planking with something thats better than the original and change the character of the boat or just try to reduce the warping by adding extra nails knowing that it will probley cause the planking to split even more latter on? There is no good answer there.
Rollin

 

Rollin, is this correct? I thought that (at least with US builders) the edge grain was what was generally used/desired. I know I haven't seen many canoes but to my knolledge all I've seen but one have been edge grain, only the Cedarwood had face grain. (also a Thompson that had some replacement face grain planking, which was badly buckled and needed to be replaced.)

Dan

 

Thanks for all the responses . It may help too know that the 2 canoes are of 1960's vintage , one a 15' Peterborough , the other probably a 12' Chestnut .