What's My Hull?

[David Rive]

Last summer I bought an OA 38. I was under the impression it is a FD hull, but the more I look at it, the more I think it looks like a semi-displacement profile. Does anyone know for sure?

 

[Tad Roberts]

It's a semi-displacement hard-chine hull designed by Ed Monk Jr. But it's too heavy, short, and underpowered (with twin 120 Lehmans) to do more than 8 knots economically.

 

[David Rive]

Thanks Tad. You have confirmed what I thought. I have Lehman 135s and I am very happy to loaf along at the hull speed of 7.5 knots.

 

[Max Simmons]

Dave, same boat here but 135 Perkins. Most definitely SD. What kind of fuel burn are you seeing at 7.5knts?

 

[David Rive]

Hi Max,

I have not put enough miles on her yet to figure that out. The PO told me she gets around 2 gph at 7 kts, but that may have been a sales pitch. I will figure it out this summer. What kind of consumption do you get? I would assume the Lehmans and Perkins would be pretty similar.

 

[markpierce]

Dave, same boat here but 135 Perkins. Most definitely SD. What kind of fuel burn are you seeing at 7.5knts?

Gee, I'd think one of those engines could achieve hull speed as a single-engined configuration, even though one knot below would be much economical.

 

[Nomad Willy]

Mark when these boats were built in the 70's and early 80's fuel was cheap and they were designed to run at 10 or 11 knots burning about 8 to 10gph. Now few can afford to feed a boat that much fuel. So yes most trawlers only use the power of one engine most all the time. If one was to change the shape of the stern below the WL a bit so the hull becomes closer to a FD even less power would be required.