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Hi Warren,
It is exactly what I was looking for, thanks a lot!!!!

I am almost done with the spare hull, so this is going to be next!
Cheers,
Nic

the subject needs corrected its the main block 75mm not a 57mm 

Hi Nic,

Spring back of a curved lamination after removal from the mould is proportional to the thickness of the individual laminations and inversely proportional to the square of the number of laminations, if all the laminations have the same young's modulus.  The proviso isn't true if you are using different woods for the skins and the core (but Young's Molulus doesn't vary all that much between species), and the 'rule' also assumes equal thickness laminations, but it's probably close enough to say springback is something like 1/n squared.

So a two layer plank will spring back about a quarter (1/2 squared) of the crown of the mould and a three lamination plank will spring back about a ninth (1/3 squared) of the crown of the mould.  My experience is that the 1/9th estimate is pretty good.

Warren Nethercote
KC 3786

Thanks Bob,
I think I will go with the epoxy and make things simple!
If you have any information on how much crown to put in the gluing process so I get the right one post cure, I am interested

Take care!!
Nic

Most everyone now is building planks with an epoxy system like West System. Back before these systems glue was used. I’m not sure which type though. The only problem I can see is getting enough gluing pressure, that is proper clamping, while it’s in prebend ( the over bending necessary to get the desired crown after the glue dries).
Bob

Hi,
Quick question to the group of building experts!
Has anyone ever used PPU glue to build a plank?
It is a polyurethane glue i used to build sailboat nasts in the past.
I believe it is known for being flexible and not crack when flexing
Thanks,
Nic
KC5508

I won one at the NA’s raffle a few years ago. So far so good.

One more thing concerning proposal two, iceboaters are not a particularly litigious group however who ever builds these tiller heads had better have some really good liability insurance since they are going to have to be marketed as a safety device.

The three new proposals are interesting. I think number three, hull number removal is great and about time.
Number two makes sense as long as existing sails are legal and don’t have to be retrofitted. I am totally against number two, the tiller release requirement. If you want one great, go for it but don’t require it. There can’t be too many sources for them and they’d probably be expensive. The other thing is what’s the standard, at what force must they release and who is going to check them and how would you know the new toy you just bought is setup correctly. How about shear bolts, would they be okay? Too vague and too expensive.
Bob

Hi Bob,
I never really had any issue in gusty winds. I am able to let go the sail if I need.
I have to admit I prefer to get the mast to bend !!!
Take care,
Nic