Western Star Posted April 21, 2016 Share Posted April 21, 2016 I am building 7mm baseboards using 6mm exterior grade birch ply. The design uses slots and tabs with half joints were cross-members meet within the structure. I cut all of the parts for one board at the end of last year and stored the parts on a flat workbench (which is larger than any of the parts). Over the winter some of the parts have developed a twist along the long edge. Simple question:- how can I reduce / minimise the twist on the individual parts? thank you, Graham Link to post Share on other sites More sharing options...
The Nth Degree Posted April 21, 2016 Share Posted April 21, 2016 Graham, could you soak the parts and shove them behind a radiator? Link to post Share on other sites More sharing options...
RMweb Gold colin penfold Posted April 21, 2016 RMweb Gold Share Posted April 21, 2016 The hard anwer in my experience is that you can't. I built one board with one slightly twisted element thinking it would be OK. The whole board ended up twisted. I removed and replaced the twisted element and all was well. Your time is more valuable than your money, dont spend hours building a layout on a flawed baseboard - replace the twisted stuff and start again. Link to post Share on other sites More sharing options...
RMweb Premium Jol Wilkinson Posted April 21, 2016 RMweb Premium Share Posted April 21, 2016 Graham, I don't think you can very easily. They will probably have absorbed - unevenly - some moisture and that has caused the distortion. You would probably need to steam them for some time and then clamp them to remove the distortion. It would probably be easiest to replace the distorted items. Jol Link to post Share on other sites More sharing options...
RMweb Gold chris p bacon Posted April 21, 2016 RMweb Gold Share Posted April 21, 2016 Unless time is an issue, I'd put them in the room they are to go in with some weights on them. They've absorbed moisture and when they lose that you can possibly manipulate them back into shape. If time is an issue I would be inclined to remake them. Link to post Share on other sites More sharing options...
Osgood Posted April 21, 2016 Share Posted April 21, 2016 In contrast to maybe 20 years ago, modern day exterior grade ply seems to be pretty dire stuff. For anything crucial I resort to marine ply and grimace at the cost. Link to post Share on other sites More sharing options...
Nearholmer Posted April 21, 2016 Share Posted April 21, 2016 I thoroughly agree with Osgood. Presuming that there is a BS or EN dealing with plywood, it seems a miracle to me that some of what is sold is deemed compliant. Beware especially some superficially very good looking stuff that has fairly dark-coloured outer layers, and somewhat lighter inner layers. I bought a sheet of 9mm, from a very well known 'chain' builders merchant, and was "wowed" by the smoothness of the finish and the apparent quality. What a fffffff......flaming disappointment! Never has plywood warped so enthusiastically. Added to which, the lovely smooth outer layers have a tendency to delaminate from the inner layers. The older, duller-looking, less fine-surfaced stuff was infinitely more stable. I'm given to understand that this evil plywood comes from China, and if that is true, it is a great pity it didn't stay there. K Link to post Share on other sites More sharing options...
Osgood Posted April 21, 2016 Share Posted April 21, 2016 Not all marine ply costs telephone numbers - the dog's danglies (with LLoyds ticket) is big bucks, but other equally good products are available. I buy from a long-established local timber merchant (Read Timber in Norwich) who recognise that not many will pay silly money or require a Lloyds ticket, and therefore stock a best value for money grade. They source this from a distributor down Bristol way I believe, so it will be available nationwide. Link to post Share on other sites More sharing options...
RMweb Gold chris p bacon Posted April 21, 2016 RMweb Gold Share Posted April 21, 2016 I'm given to understand that this evil plywood comes from China, and if that is true, it is a great pity it didn't stay there. K The ply that the diy chains buy up is indeed from China where its main use is as shuttering for concrete pouring. As you can guess it's purchased on price not quality. I buy mine from a timber merchants where if you are Joe Public they will ask you what the purpose is before pointing you in the right direction. Link to post Share on other sites More sharing options...
JeffP Posted April 22, 2016 Share Posted April 22, 2016 Why is mdf not favoured? Once built, with a coat of varnish, dead stable. Link to post Share on other sites More sharing options...
Western Star Posted April 22, 2016 Author Share Posted April 22, 2016 Why is mdf not favoured? Once built, with a coat of varnish, dead stable. I agree with you comment Jeff... however the resulting board is not as forgiving as one made from ply of equivalent thickness. My previous layout was made in 4' x 2' sections using 6mm thick material (as are the current ply baseboards), the downsides to me are:- 1/ drop / knock a board and watch the MDF split along the sheet, particularly where there is a right angle joint; 2/ screw heads can pull through easier than in ply; 3/ PVA type glues are a no-no for joints as the water content can induce twisting. I used 3/4" square PAR for re-inforcement of all joints between top and sides of the MDF baseboards.... and then found that some of the long runs were failing, the MDF was splitting along the sheet whilst the PAR remained attached to both pieces of MDF. I had primed the MDF after assembly with finishing coat of oil-based gloss paint so not a case of water ingress. Try fixing screws through the sides / tops into the PAR after doing the scenery! Link to post Share on other sites More sharing options...
3 link Posted April 22, 2016 Share Posted April 22, 2016 I buy my 9 mm birch ply from a local timber merchant at £33 per 8x4 sheet , how does this price fair with you chaps around the country? Link to post Share on other sites More sharing options...
devondynosoar118 Posted April 22, 2016 Share Posted April 22, 2016 About what they charge here in not so sunny Devon, £36-50 depending on where you go and what grade. I too prefer ply to MDF. Link to post Share on other sites More sharing options...
gismorail Posted April 22, 2016 Share Posted April 22, 2016 I buy my 9 mm birch ply from a local timber merchant at £33 per 8x4 sheet , how does this price fair with you chaps around the country? That's about the price around the northwest area and north Wales I get mine from a local builders merchant delivered for about that price. Compared to Wickes /B&A its cheaper and far better quality Link to post Share on other sites More sharing options...
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