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Hi all about 6 years ago i built a John Starks GP-12VS tunnel hull painted it and left it on the shelf now im about to mount the outboard looked at the plans nothing there to show o/b elevation. Would i be correct to assume for a starting point to mount prop shaft center line even with sponson bottom ? It would be great for anyone to chime in who has built this tunnel. Happy easter to all. Regards Andris Golts.
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Andris,
Not familiar with your hull. What are the dimensions and what motor, lower & esc are you going to use? In general for most tunnels starting at the prop center even with the bottom is what most do. From there I generally go vertically,
Mic
Mic Halbrehder
IMPBA 8656
NAMBA 1414 -
Just started my first Tunnel Hull, so not a specialist, but this makes sense to me and is how I will set it up for a start;
Hope that's of any help...Wisdom is knowing how little we knowComment
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I think I have the article in my collection of Radio Control boat Modeler. I will try to scan threw them in the next few days to get a correct answer from the article.
If it was me I would start with the out drive up about 1/8 on an inch and slightly tilted up.Comment
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Thanks to all for the reply to my post .Mic the tunnel is 22'' in length with a 14'' beam motor is a sv27 1600kv on 4s with a 70 amp Hacker esc turning a x437 3 blade prop. Randy the GP-12V3 is John's second tunnel design that was not published in R.C.B.M . Regards Andris Golts.Comment
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Iam doing a 35" Tunnel hull going Electric. Brushless Outboard Trying to find what steering servo to use and linkagesComment
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For a 35 inch tunnel I would use a 1/4 scale or two 160 inch ounce servos on 6 volts or 5 cell Nimh. I sell the HS645MG or HS-5646WP and run two if them in a big boatComment
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Thanks for the replyComment
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Andrew, I've made a costly mistake setting up a tunnel in the past (and this may only be unique to my particular hull), but after burning up several spec motors I came to the realization that my hull (a fairly rare Herb Stewart) was that the sponson design caused the boat to run quite nose-high. This of course caused the hull to rotate on the CG axis and consequently rather severly submerged the prop causing lots of load on the motor. It looked good on the setup board, but underway it was a whole 'nother story. I'm sure Mic can chime in here and add more to this.2008 NAMBA P-Mono & P-Offshore Nat'l 2-Lap Record Holder; '15 P-Cat, P-Ltd Cat 2-Lap
2009/2010 NAMBA P-Sport Hydro Nat'l 2-Lap Record Holder, '13 SCSTA P-Ltd Cat High Points
'11 NAMBA [P-Ltd] : Mono, Offshore, OPC, Sport Hydro; '06 LSO, '12,'13,'14 P Ltd Cat /MonoComment
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i think its a common mistake to have the prop too low on any type of tunnel or catamaran for that matter. sometimes the best position, looks like the prop wont even touch the water when its at speed, but it does...Comment
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Last year at the Nats my boat was not set up yet, It preformed like $#!^. I spent severt trips to the lake and after it was all said and done this is what works best for me. I am happy now I can not get any one to race me now that I have it dialed in.
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22 X 14 wide sounds like a flying wing! 1600 on 4S with a 437/3 should work fine if your not over 5-6 lbs wet. As for prop height unless your centerline on a setup board is not much below the sponsons I can't see a problem. Smaller prop and let it work. I have found I tend to run too high sometimes. Spinning out will tell you in a hurry. Take some lap times with a stopwatch and lower vertically 1/8th inch at a time and you might see times go down as you lower. The watch will keep you honest as we all seem to revert to straight line speeds that are not what you need to heat race.
Randy is spot on for servos on a larger tunnel.
Mic
Mic Halbrehder
IMPBA 8656
NAMBA 1414Comment
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My boat is old Stinger tunnel hull that has not been touched.. Iam looking start out 6s and work into a HV setup. What outboard conversion is the best to use?
7.5 hull. 35'Comment
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Hear is my build for a boat that size. Schultz is no longer in business.
http://forums.offshoreelectrics.com/...cat-conversionComment
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