Pilot House / Coach Roof Camber

[SeaJay]

I am interested in hearing the opinions of this group on the virtues of different roof cambers. My project is a 46' motorsailer to which I am adding a pilot house. The roof has a maximum span of 10'. I understand how to lay out the camber once the height is determined. However, I am uncertain about the amount of "pitch" from both functional and aesthetic perspectives.

The example I've been looking at is about 1:6 which just looks too rounded to my eye. I suppose you could build a cabin roof completely flat an it would still shed water just due to the motion and/or trim of the boat, but in practice, what is generally the minimum recommended camber? I've look in all of my design books and I'm not finding much guidance. Thoughts?

SeaJay

[TeddyDiver]

I recall smth like 1:20 mentioned in some standard as a minimum but thats just my memory..

There's also the strength issue. Give it an inch (but as much as your eye can stand).

[Paul Kotzebue]

Camber for a pilot house top will normally fall between 1/2" and 1" per foot of beam. So a 10 ft span would have between 5" and 10" of camber, depending on style, headroom, and structural requirements.

[Squidly-Diddly]

had......" The sides of the roof were raised a bit to allow easier entry and exit, to permit larger side windows, and to increase roof strength."....

a "pagoda" style roof.

Personally, I'd do whatever it takes to make the roof double as skydeck.

[SeaJay]

Paul,

The ratios you've given sound correct and are similar to what I've used in land based architecture for flat roofs, garage floors, walkways, etc. However, I want to be sure I'm understanding you correctly. You say a 10 ft. span would have a 5" to 10" camber. But since the camber is at the middle of the span, wouldn't the highest point actually be 2.5" to 5"?

Mark, Teddy, Squidly,

Thanks for the feedback. It is really handy to be able to ask questions in this forum. I agree that rounder is stronger but also that the "eye" must be satisified.

My boat has 1 1/4" of camber in 9 1/2'. I think it started out that way in 1979 (I don't think it has settled!)


An acquaintance has this Beowolf and he has about four inches in six feet - looks pretty good for that style of boat and delivers more headroom with a lower line from th side view. The thing to its right is flat and that looks bad, IMO and certainly requires more internal bracing.


There is a boat called an Albin that docks near me and doesn't pull off the high camber very well. Every day I pass that boat (it never runs) and think "that looks funny". It is totally subjective, of course, and a traditional build like the Beowolf with a plywood top can pull off four inches. The Albin, trying to deceive the eye that it has a low profile yet maintain headroom, has a certain cartoon look to it, to me.

[Joe Petrich]

Sometimes you can draw all you want and not figure out what will work. If you have the boat available get some cardboard and light framing material and mock up the design full size on the boat itself. That way you can see what it looks like and adjust it to suit your taste. There is no "proper" amount of camber for a pilothouse top. Strength and aesthetics generally dictate the shape.

[SeaJay]

Mark,

The 1-1/4" camber on your boat looks pretty close to what I am after...maybe just a touch more. The rounded roof at the bottom of your post is what I've been working with and I agree, it doesn't look right.

SeaJay

I do things Joe's way and I am the slowest builder EVER. I am generally happy that I have drawn and sometimes mocked up what think will work. He is right on target - It has to "fit" the boat. Get us some pictures as you go!

[Paul Kotzebue]

Originally Posted by SeaJay

Paul,

The ratios you've given sound correct and are similar to what I've used in land based architecture for flat roofs, garage floors, walkways, etc. However, I want to be sure I'm understanding you correctly. You say a 10 ft. span would have a 5" to 10" camber. But since the camber is at the middle of the span, wouldn't the highest point actually be 2.5" to 5"?

No, the highest point is 5" to 10". Boat deck cambers are generally given in inches of height per foot of beam (width).

[Brent Swain]

I give her 7 inches in six feet. Looks good. An extra inch of camber greatly adds to the stiffness ,and drastically reduces distortion in steel cabin tops. It also improves ultimate stability.

[SeaJay]

Brent,

What is the camber on Rosey?

http://origamimagic.com/boats/Rosy37/rosy_37.htm

That curve looks right to me. Is it really 7" in 6'?

SeaJay

[Brent Swain]

I have no idea, as she is not my design.

[SeaJay]

Sorry Brent, I thought that was one of yours. I just did a quick internet search to find some of your designs and landed on that site.