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Old Nov 03, 2009, 10:54 PM
Datsmar
Gulf Coast of Mississippi
Joined Jun 2006
11 Posts
Discussion
KMB jet drives

Has anyone bought or used the KMB (Kehrer Modellbau Berlin) jet drives? They look like a durable units. The only other jet drives I can find are the Graupner drives. I have a 54" Island Class fiberglass hull I'm trying to power with something different.
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Old Nov 03, 2009, 11:44 PM
from downunder Downunder
col_426's Avatar
Hobart, Tasmania, Australia
Joined Feb 2008
83 Posts
Hello Datsmar,
I've used one of KMB's 33mm jet drives in a Cen Waveshark rebuild, and was very happy with it. They are very sturdy and well made. KMB were also very good to deal with. The pic shows the jet drive installed in the Waveshark.

Phillip
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Old Nov 04, 2009, 01:11 PM
Datsmar
Gulf Coast of Mississippi
Joined Jun 2006
11 Posts
Phillip

Great looking Waveshark. Looks like a pretty full hull. How does the jet unit mount to the hull? Looks like you have a plate that mounts to the hull that uses mechanical fasteners. Looks like the servos are mounted to this plate. What is the width and length of the hull? It must really run fast with the gas engine.

Lawrence
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Old Nov 04, 2009, 06:25 PM
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col_426's Avatar
Hobart, Tasmania, Australia
Joined Feb 2008
83 Posts
Quote:
Originally Posted by Datsmar View Post
Phillip

Great looking Waveshark. Looks like a pretty full hull. How does the jet unit mount to the hull? Looks like you have a plate that mounts to the hull that uses mechanical fasteners. Looks like the servos are mounted to this plate. What is the width and length of the hull? It must really run fast with the gas engine.

Lawrence
Thanks Lawrence. I've just posted a side shot showing the outboard end of the jet drive, you can just see the KAMEWA steering and reversing bucket on the right. The jet drive inlet is glued to the bottom of the hull, and epoxy resin has been poured around it to seal it and make sure it stays attached. At the rear, there is a 33 mm diameter hole through the transom where the outlet fits, and where the 'outboard' part of the jet drive attaches to the inboard section with screws. If you look at the picture of the KMB jet drive, you can see where the two sections come apart, and the transom of the boat fits in there.

The basic process is to cut the hole in the transom, slide the inner part of the jet drive in place with the flange poking out the hole in the transom, and pour the epoxy around the inlet on the inside (before making a hole in the bottom, saves having the epoxy run out the hole ). When the epoxy is set, then you can make the hole in the bottom and file it to size, and attach the outboard steering and reversing section.

The plate in the hull is just to attach the servos to, the top one is for the throttle, the bottom servo is for the reversing bucket, and the centre one is for steering. The jet drive itself doesn't connect to this plate at all.

The speed is pretty good with the nitro engine, although it probably isn't as fast as a serious prop setup, but I think this is typical for jet drives. I mainly did it for the novelty, and so that it's like a real jet ski. I am thinking of replacing the nitro engine with a brushless setup, partly for a bit more speed, and mostly because it's less messy than nitro.

It's a bit hard to see how the jet drive mounts in the pictures, but I can take some closer pics tonight if are interested.

Phillip
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Old Nov 04, 2009, 09:16 PM
Datsmar
Gulf Coast of Mississippi
Joined Jun 2006
11 Posts
Phillip

I woul appreciate any closer pictures on the drive and the servo mounts. I found a posting from 2007 with info on a dual drive PBR that KMB makes. I just think it would look really unique on the water.

Lawrence
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Old Nov 04, 2009, 09:19 PM
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Hobart, Tasmania, Australia
Joined Feb 2008
83 Posts
No problem, I'll take some pictures tonight and post them tomorrow for you.

Phillip
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Old Nov 07, 2009, 10:43 AM
Datsmar
Gulf Coast of Mississippi
Joined Jun 2006
11 Posts
Thanks for the added pictures Phillip. Nice contruction work. I can see the use of the flex cable for controls works well.

Would assume you don't have alignment problems or water leakage problems using them.
I think the KMB drives are shorter or more compact than the Grapner drives are, but not sure as Grapner doesn't give any details on there units that I can find.
I have written to KMB on which units would fit the best, the 28mm or 33mm, still waiting for an answer. I'll post some pictures after I get whatever installed.

Lawrence
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