Mahogany planks cupping HELP

fergal.b

I picked up my 16' x 4" x 1/4" planks for the deck of my boat I have them stored in the hall of the house but brought two outside yesterday to start measuring up they were left out overnight and today I noticed a cup in one of the planks it's not fixed in place yet but I don't want this to happen to anymore as it will be a pain to fix them down "they will be epoxied onto plywood"
So my question is are there any tip's or tricks that I can use to stop this happening.
Cheers.

jack of all

Probably not suitable for your application but when running of a some custom skirting in the past which was wide and only in red deal I routed some grooves (6 x 6mm or something like that) on the hidden, back face. This took out any stresses in the boards and allowed me to fix the boards flat as they were now somewhat pliable across their width.

galwaydude18

The reason they cupped is leaving them outside overnight in a moist atmosphere where the timber soaked up moisture from the air and created an unequal balance in the wood. Moist on the outside and drier in the middle of it. It won't be moist to touch.

Also are you leaving them in the hall anywhere near by a radiator?

fergal.b

They are not near a rad but the house is quite warm, the ones in the house are still fine it's just the one outside that cupped so now I'm afraid to bring the rest outside "much to the delight of the wife:D" incase they cup, will they flatten out as they acclimatise to been outside and take on more moister, should I spray them with water would that help or bring them back in to dry out again before I fit them




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galwaydude18

They might flatten back if you bring them back in and dry out a bit. Worth a try but to be honest I would nearly split it in the width at this stage depending on how cupped it is. Can you post a pic of how cupped it is?

fergal.b

I had it clamped down all day so it's a bit better but you can still see the difference in the two.

galwaydude18

fergal.b wrote: »

I had it clamped down all day so it's a bit better but you can still see the difference in the two.

Clamping won't cure that to be honest. I would defo split that in half to reduce the cupping effect.

recipio

Its inevietable that thin ,wide boards will cup. I take it you are not screwing them down to the plywood - that would flatten the cupping. ?
Otherwise you could run a saw kerf on the concave side , stopping within 2 mm of the top of the cut and they will flatten with hand pressure. Of course you could rip them down the middle ?!

fergal.b

Yep I don't want to screw it down or have more joints than needed so a run with the saw on the underside might be my only option. I will be using some raptor composite nails in the gun as these can be sanded and are almost invisible so they might help to hold down the planks while the epoxy sets.




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1chippy

A lot will be down to where in the tree the planks were cut. I had the same problem with some of mine. It would look a disaster if you go ripping the boards. you would end up with even more of those tricky joints as you pull them round. If they are not overly cupped you could try planting it on with the edge touching the face and srew a batten from side to side, then cover the screw holes with the next board.

fergal.b

1chippy wrote: »

A lot will be down to where in the tree the planks were cut. I had the same problem with some of mine. It would look a disaster if you go ripping the boards. you would end up with even more of those tricky joints as you pull them round. If they are not overly cupped you could try planting it on with the edge touching the face and srew a batten from side to side, then cover the screw holes with the next board.

How are you getting on with yours, any photos

recipio

Fergal,
forgot to say you can permanently flatten a board using the saw kerf technique by glueing a slip of wood into the kerf and clamping it down to a flat surface until the glue is set. It needs to be a snug fit and that means using a thicknesser to make the slips - did you get that Emco thicknesser up and going yet ?

fergal.b

I'm keeping the planks in the house then measuring them up and fitting them straight away so they don't get a chance to cup, the raptor nails seem to be doing a good job holding the planks down while the epoxy sets,so far so good.:)

The INCA is going well very happy with it and getting a good finish with the planer, I didn't get the thicknesser with it but I can get by without it.

recipio

Nice ma-chine ! Out of interest are the boards nailed clinker style/overlapping or nailed straight on to plywood. Do you not get problems with splitting if they are nailed and glued on to plywood. ?

fergal.b

They are just nailed/pinned by 18 gauge by 16mm nylon polymer pins so too small to cause splits the epoxy sets in a few hours after that nothing will move same as the hull below but there will be a 4mm gap between each plank on the deck
You can just make out the little dots where the pins are.

1chippy

fergal.b wrote: »

How are you getting on with yours, any photos

Not much to show really, put on the shelf for a while. Putting an extension on the workshop at the moment and a couple of new machines so enough to keep me busy.

fergal.b

1chippy wrote: »

Not much to show really, put on the shelf for a while. Putting an extension on the workshop at the moment and a couple of new machines so enough to keep me busy.

Not to worry you will get there at some stage. I just did the first test run of the engine yesterday just to make sure there are no leaks before it's all planked as it will be a pain trying to fix anything through just the hatch opening. So far so good except for the alternator belt slipping

https://www.youtube.com/watch?v=43f8x8CZ4l0

fergal.b

So far so good.