Surface drive / prop pocket

scot · Post by **scot** » Oct 15th, '07, 20:06

Here's an interesting project. The guy built a 38ft Carolina style boat and incorporated a custom built surface drive unit into a pocket. Engine is single Cummins 450C. Not a Bertram but a neat looking ride and the drive line engineering is certainly unique. The boat has sopme interesting shallow water capacity. He says cruise is around 19kts and WOT is 24kts, not to bad for a 38ft boat with one engine.

http://www.youtube.com/watch?v=U60rx06Dmtk

Harv · Post by **Harv** » Oct 15th, '07, 20:43

That is one trick pony. The only change I would make is to extend the cockpit over the prop in such a way to keep the prop concealed even when it is raised upwards. That prop protruding from the transom looks like a surfire linecutter when fishing. The extension should overcome that problem.

In Memory of Vicroy · Post by **In Memory of Vicroy** » Oct 15th, '07, 20:53

It never stops amazing me how people can try to re-invent the wheel.....bet the seals in that surface drive will last a week, even if the dawg don't fall in the prop. I've been to outdrives a few times over the years, and the old tried and true straight shaft with nothing but a strut and cutless bearing and a prop is the best ever. No drive trains with oil seals underwater is the way to go. It's a "duhhhhh" thing, my frens.

UV

Rawleigh · Post by **Rawleigh** » Oct 16th, '07, 07:54

Can you say "Puppy puree"???

nic · Post by **nic** » Oct 16th, '07, 09:12

Scot,

To me there is no reason for a 24kn boat to have a surface drive.

Most conventional drives top out at 39kn or so due to drag, (imho), unless you are......can't remember his name "That's My Hon" 1980s Palm Beach 55kn until Jack Nicklaus bought it and threw out the MTUs and put in another cabin. The designer had US Navy connections and used air induction on the props apart from other hull refinements.

Also, and this is really important, there is no need for surface drives to be articulated. Betty Cook's team pioneered that type and everyone followed but you can have fixed shaft, (ie standard installation), surfacing propellors, with the exhaust dumping directly on top for low rev acceleration, developed by Sonny Levi originally and perfected by Dave Warren. I have driven them, they work. Conventional drives on the exact same 77ft hull and same 1150hp engines 32kn, fixed surface drives 38kn.

It is a business waiting to happen.

Nic

Rawleigh · Post by **Rawleigh** » Oct 16th, '07, 15:23

Knowing where he is located I would say that it was partly a draft issue. Most of those boats in the Outerbanks are single screw diesel with a skeg to protect them from grounding. They tend to be slower though.

Carl · Post by **Carl** » Oct 16th, '07, 17:40

I think the best reason for that guy to have a surface drive is because he wants one. Makes him happy and if he don't make Chop Suey with that pooch its cool with me.

I kind of like the drive articulating...put a bowl over it when its up and you got one hell of a blender. Just need the fancy umbrellas and your good to go.

UV, if everbody stayed with the tried and true we'd all be touting the benefits of our 31 Bertram sailboats, paddlewheel boats, steam engine boats etc. Gotta look forward...

That said...I ain't saving up for one just yet.

In Memory of Vicroy · Post by **In Memory of Vicroy** » Oct 16th, '07, 17:59

Well, the Grosbeak Propulsion System never really took off......but it's still out there.

UV

scot · Post by **scot** » Oct 16th, '07, 20:13

Nic,

I think the point the designer intended is 2 fold, first and foremost is draft and second is backing down with a single screw boat. As a general rule singles just won't go in a straight line backwards, it can be hair raising to say the least. He says it has 28 degrees movement either way and the boat is extremely easy to handle in reverse.

Plus I'm sure he can blow a really nice rooster tail behind the boat if he were so inclined.

It's an interesting boat and no small engineering challenge. Even if I wouldn't do it I still appreciate the guy's imagination and persistance.

If he likes the dawg he needs to put it on a rope, what a mess that would make!

nic · Post by **nic** » Oct 17th, '07, 04:56

Scot,

OK, part of me wants to recognise this guys passion and engineering skill and another part of me wants to put myself up for membership of the Mean Team. I don't like it. I don't care how shallow the water is and I like dogs.

I'm applying for membership.

Nic

Carl · Post by **Carl** » Oct 17th, '07, 06:43

Vicroy wrote:Well, the Grosbeak Propulsion System never really took off......but it's still out there.

UV

I forgot about that system UV, I would like to recant my statement as you are truly ahead of your time with that design. Wait and see...one day some huge conglomerate will see the genius in the design and give it a whirl, maybe the next step in the Newly Improved Bertram Empire, perhaps it will be seen on the next 63 footer, seems to have everything else...

bertram31.com

Surface drive / prop pocket

Surface drive / prop pocket

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