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Tunnel Hull

Old 12-11-2006, 11:12 PM
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jhunter
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Default Tunnel Hull

Howdy, I just got my hands on what I believe is a Dumas 24" Tunnel Hull with a K&B 3.5 outboard. Don't know squat about boats being a flyer, and I have a few questions. One, how far should the motor turn from side to side? I imagine the steering should be somewhat limited due to the speed. Two, I need a bracket to mount on the engine to anchor the throttle cable, which I assume, is the standard Du-Bro flex cable, and the cable slack should be around 2" ? Anybody have a part number and a source? The fuel tank, 6 oz, should go into the middle or aft bay? Steering control should be flex for pull/pull or solid rods? I bought an Enya no. 3 glow plug and have some heli 30% fuel, this OK? Any and all advice is gladly wecomed, and MERRY CHRISTMAS!!!!! I attached a few photos also, thanks.
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Old 12-12-2006, 12:15 AM
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TIA
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Default RE: Tunnel Hull

Is there a screw missing that holds the carb on?
Old 12-12-2006, 12:31 AM
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Default RE: Tunnel Hull

OK, I'm going to be scrolling up and down a lot!
The motor should swing 15-20 degrees in each direction more is okay.
Steering setup is optional. I've seen dual cables use, a solid 4-40 thread at the end rod hooked up to only the right side with the servo set up to pull and fancy Kevlar thread like what the flyers use on a servo wheel.
Your #2 is right.
the 6 ounce tank is fine if you're just going to play with it or else you can throw an 8 ounce for more run time.
the plug I don't know about as I'd have to look up what heat range it is but the Heli fuel will do the job.
I don't know what you do and don't know about your new boat but 2 things to remember if you already haven't found out. #1 is that the engine runs in reverse so you'll have to swap your starter wires around. Don't forget to put them back before trying to start your plane. If you do forget, you'll be far from the first to do this! #2 is that the threads that hold the propshaft assembly has left-hand threads, not right so this way you won't have to start swearing because you can't get it off when it comes time to lube the flex cable.
Old 12-12-2006, 12:43 AM
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Default RE: Tunnel Hull

OOOOHHHHHH, I knew the part about rev. the starter but didn't think about the L/H threads! All the carb screws are in place, they go below the casting a bit. What bay for the tank and do you have a P/N and a source for the bracket to hold the thro cable? And please tell me more about motor maint, lube a cable? I guess I should tear the motor down and inspect etc. What kinda cable lube? Thanks.
Old 12-12-2006, 12:45 AM
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Default RE: Tunnel Hull

I'm using the [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCW31&P=7]OS Throttle clamp[/link] to hold the throttle. I'd suggest Sullivan gold cable over the Dubro flex cable for throttle as it's stiffer. 2" slack is about right. As for turning, I limit mine via the controls on the TX. Use a metal geared servo with at least 80 oz. As for cable or rod, it's up to you. I've used both and like the rod. Two are used on each side with a wheel collar to hold it together. Makes for fast changes. Tank placement is up to you. CG should be around 30% from the transom forward. This should be done without fuel. Plugs I'm using are MC9 or KB 1L.

Take the motor apart and check bearings. Might want to put new ones in there. Make sure to grease the cable before starting each day of running. That or drill a small hole in the lower into the upper plate to put a 50/50 mix of 80/90 and STP.

Get a x1440 b/c prop, 65% fuel and hang on!!! Mine was radared at 46.3 mph with a K&B SS motor early this summer.

G-1 - the carb is held in by set screws.....
Old 12-12-2006, 11:52 AM
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Jerry Dunlap
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Default RE: Tunnel Hull

In looking at the photos, the engine seems to be set rather deep. You want the c/l of the propeller even or slightly above the bottom of the sponsons.

A balancec/sharpened M440 or X440 also works well on that boat.

JD
Old 12-12-2006, 10:33 PM
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Default RE: Tunnel Hull

Jerry, I placed a straight edge on the sponson and it lines up with the prop hub dead center. I disassembled the engine today and everything looks in great shape, a low time engine. The K&B owners manual I downloaded mentions a removable plate at the PTO for greasing the flex shaft, this motor does not have this plate. What is the standard procedure to grease the shaft? The book says before every outing you must service the flex shaft wit a 50/50 mix of STP and 20-50 wt oil. I will use the 4/40 rods for the pull/pull steering, and balance 30% from the transom. Thanks for the replies, J
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Old 12-12-2006, 10:47 PM
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Default RE: Tunnel Hull

To lube the flex shaft, just unscrew the stub shaft bushing, remove the flex shaft, apply the grease, and stick it back in the lower unit. Retighten the stub shaft bushing, of course.

JD
Old 12-12-2006, 11:53 PM
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Default RE: Tunnel Hull

Next time you have the lower / power head apart, drill a hole in the lower.


Then use a hobby syringe to inject a mix of 80/90 and STP into the hole before each run.


Beats tearing it all apart before each run.
Old 12-13-2006, 12:17 AM
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Default RE: Tunnel Hull

The K&B owners manual also says to initially set the carb at 4-1/2 turns out. Try it at 3-1/2 turns othyerwise it will be too rich.
When I had mine, I tried all kinds of things to lube the cable with from flex cable grease to the 20w50/STP mix. Ask 100 people and you'll find about that many types of lube that they like.
Old 12-13-2006, 01:19 AM
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Jerry Dunlap
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Default RE: Tunnel Hull

The reason I usually remove the cable after a day's running is to inspect the cable for broken stands.

JD
Old 12-13-2006, 10:39 PM
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Default RE: Tunnel Hull

Thanks for the info guys, I will drill the hole in the lower plate, seems like the best way to service the flex shaft. Is it necessary to plug the hole? Probably OK being open, but it doesn't hurt to ask.
Old 12-13-2006, 11:39 PM
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Jerry Dunlap
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Default RE: Tunnel Hull


ORIGINAL: jhunter

Thanks for the info guys, I will drill the hole in the lower plate, seems like the best way to service the flex shaft. Is it necessary to plug the hole? Probably OK being open, but it doesn't hurt to ask.
The hole doesn't need to be plugged.

JD
Old 12-14-2006, 12:09 AM
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Default RE: Tunnel Hull

Thanks JD.

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