Brittle 45 year old plywood
17th September 2014 at 12:53pm #1175Martin WardParticipant
A few weeks ago I was having a bonfire and decided to burnt some very old (45 year old plywood). I discovered two things – Firstly that the old very dry and painted plywood went up like a bomb – Secondly when I tried to snap the wood it broke along glue lines (ie along the area that the deck beams) with such ease I couldn’t believe it.
Many of the old plywood OK’s still in use may be in a simplier condition. No I’m not saying that old ply OK’s will suddenly brust into flames but the brittleness of the wood really shocked me! Many rescue boats tow dinghies back to shore by holding them alongside. This continual bumping along side the rescue boat could cause very brittle plywood to snap. There must be a great deal of pressure between the curvature of both boats and with the lack of fenders used my almost all rescue boats the really ol boats in the OK fleet my not get the extra carefull handling they need.
I was wondering whether anyone has come across this issue and has experience in whether plywood just gets to a point that it gives up or alternatively has anyone got any thoughts regarding full inflatable rescue boats and whether they are kinder to the hulls of old boats?
What do you say to a rescue crew that won’t tow you on a line?
Martin Ward23rd September 2014 at 5:52pm #7629Alan PriceParticipant
Don’t worry.Be happy
46 year old 1211 got trailered nearly 700 miles down here a couple of years back and gets trailered 8 miles each way to the Etang for a sail. So far there are no problems. Obviously i avoid sailing her in big winds these days but i have the dart/sprint15 for that stuff.
I think you are familiar with CVRDA. This great crowd have many a really old ply boat between them and some of them have never been restored but still sail largely problem free.25th September 2014 at 7:32pm #7630davecooperParticipant
I agree with Alan: I think 45 year old boats are much more likely to have trouble with glue giving up than plywood giving up, for sure some of the glues used weren’t immortal. I wonder if the ply you were breaking had’nt trapped water against the deck beam (for instance,if the boat was left upside down for any length of time) and the deck rotted where the water was trapped?
Dave28th September 2014 at 10:42am #7631Bob BourneParticipant
I’d agree, long term, trapped water is a killer, but also skimping on deck framing (for instance) can also cause problems.
If a boat has been ‘lightened’ at any time in its life by re-decking with thinner ply and less framing, then what can happen, is the ply gets stressed beyond what it is capable of absorbing at the glue joints on the frames. The larger ‘unsupported’ area can be bent just by leaning on it, causing the ply to fracture ‘internally’ around the frames, deck beams or whatever, it may not be visible, and still ‘sound’ enough in use, but when removed, it is obviously weakened as you note in in your original post.
Answer – , use lots and lots of frames, or thicker ply………
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