Thread: Cambered Foredeck Construction

The simple way to make a deck crown with a single crown for reference, is to use a straight edge and parallel the boats' centerline with it on the deck beam. Using the same crown on a beam of different length will not work, especially if employing plywood decking.

This type of deck will have a straight centerline and the deck will also be relatively straight, depending on how much sweep is in the sheer. This doesn't look right to many, but works.

If you want a sheered deck line, you have to spring a batten down the boat's centerline, from the crowned beam and sympathetic, slightly sprung battens to blend into the sheer. This is much harder for the novice to get their head around, but looks a lot better. This is a compound curve deck and will require diagonal plywood planking, strip planking or even carvel or tongue and groove. It also requires some additional beams to hold the sweep in the deck planking. Strip planking is the easiest of these to do, as the strips can sweep with the sheer and roll with the crown at the same time. If the sweep isn't severe, then plywood can be forced (sometimes) if enough beams below exist, to hold the plywood to the shapes.

It might be helpful if you posted some pictures. I'm pretty sure I understand your wishes, but many may be lost, especially after my post.

In the very eyes of a boat's deck, the crown tends to flatten out a lot and this can be weird looking, plus can trap water too. There are a few different methods to make deck crowns, that don't have these problems, though they're difficult to describe. The two most common techniques are the "projected camber" and the "constant camber" methods. The projected camber method uses a subdivided circle, projected to the width (beam) and rise (height of the crown) desired, at each station or deck beam. This is the traditional way. The constant camber method uses a common curve, but it's drawn differently at each station or deck beam. This is more user friendly, as you make one template for the widest portion and this is moved to each beam or station and a new curve drawn at each with the same template.

Thanks PAR,

You have certainly understood what I was getting at, and I understand your explanation.

In the mean time I have been in touch with the designer and his explanation was similar to yours. He also said it didn't matter too much which path I chose as as long as it looked OK. I have been playing around with different beam curves and battens and I am pretty sure I have resolved the problem.

I started out with a constant camber template and moved it fore and aft till I found a point where things looked like they were not quite sitting right, which was pretty much identical to where I had placed the intermediate beam in the first place. I then modified the curvature slightly, and it really only took shaving about 6mm off the beam at the inwhale and blending it back into a fair curve towards the kingplank to get things to align correctly at the inwhale again. From here I ran battens from different directions, gazed at it from a distance with wine glass in hand, looked some more wtih a second glass, and decided it all looked OK.

So I have ended up following option 1 in my original post and only had to do a minor tweak. I am happy with how it looks and I think it was easier to do than to explain. The bulbous effect I was concerned about hasn't really materialised to any concern, and I put this down to the fact that the sheer curvature is not especially pronounced, and the deck camber is also fairly gentle.

A curvier lady would have been more trouble, but isn't that always the case!

Thanks for your guidance, you would have headed my down the right path anyway.

Cheers, Cameron.