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Old Dec 18, 2012, 10:17 PM
mahoganyfan
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United States, NJ, Atlantic City
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Question
Trim tab position

Can anyone suggest how high up on the transome should trim tabs go that do not adjust?I have to move mine up from flush with bottom because the boat was plowing through the water.It is a 1/6 scale crackerbox brushless boat.
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Old Dec 19, 2012, 12:52 AM
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trim tabs

That would be a strong 1/16" from flush and also put some goop under trim tabs for water leaks. Also in c-boxes, the prop should be about 1/8" below bottom of c- box for a decent ride. Check CG, sounds a blonde hair to far forward.
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Old Dec 25, 2012, 08:49 PM
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CA, you can bend them up or down to adjust the blades but they should start even/flush with the transom. Bend the ends up to raise the bow and down to lower it.
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Old Dec 25, 2012, 09:05 PM
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trim tabs

Now to start with, at least 1/16" above transom as typed in above post and very carefully bent down if you can't afford the higher end tabs that have machine bolts to slightly bend tips down. Well, since your around transom, sharpen transom edges so water doesn't cling to boat.Tip, when bending some tabs, you can break transom or crack it. Best off to take tabs off and bend. Trial and error! I've found by looking from bow straight back to transom and thought tabs were flat, they weren't flush but actually were down angle and redid the upward tabs. That is why they should be 1/16" up from transom. Try it! Something else comes to mind about tabs being flush is drag which you don't need. You want the water to break free at the transom edge, not the tabs edge. The tip of tabs is for bow trim. You want the last 4 or 5" of boat to ride on. Enough said.
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Last edited by Mikedown; Dec 25, 2012 at 09:58 PM.
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Old Dec 25, 2012, 10:23 PM
Steps? What steps?
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United States, TX, Humble
Joined Jan 2010
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I've raced and won plenty with smaller Crackerboxes - what motor/packs and what prop does the OP run? Trim tabs are considered "drag tabs" and should not touch the water unless they are needed for minor trimming to keep the bow down. Take them off temporarily (seal the holes with tape) and see how the boat runs without them. If it still plows then either your CG is too far forward, the hull bottom is warped, or the prop you are using has too much lift. Octura x-series props worked best for me.

Once you get it running freely, mark the CG and re-install the tabs (1/16" above the bottom is good, slot the holes to move them up). Place a straightedge flat on the bottom and see if the tabs are pointed up, down or parallel with the straightedge. Start with them up slightly and see how the boat runs. Of course it's been a week since we've heard from him, perhaps the OP has the solution already.



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Old Dec 26, 2012, 06:15 PM
mahoganyfan
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United States, NJ, Atlantic City
Joined Nov 2010
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Thanks Guys

Thank you for all the info.I did as advised and repositioned trim tabs up further.I had to fill old screw holes and repaint.With trim tabs off boat already ran 100% better during test runs but bow would bounce up and down.Put trim tabs back on 1/16 higher than bottom of transome and boat runs fine,bouncing almost eliminated.I am still messing around with trim tab positioning (bending) but I think I am almost there.If I have to bend trim tabs signifigantly though, I will take off trim tabs then bend so as not to damage mahogany transome.Shortly I will be putting up video of boat running and any opinions of how boat is performing would be appreciated.Its not the fastest boat you guys have ever seen but it is quick enough for the size of the ponds here in southern New Jersey.
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Old Dec 26, 2012, 09:30 PM
Steps? What steps?
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United States, TX, Humble
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Be aware that a properly-running Crackerbox does porpoise a bit, it is the nature of the over-powered hull design. The original full-size boats do it too - check out the video:
Crackerbox Race Puddingstone Lake 2012 (5 min 2 sec)


If you eliminate the porpoising completely the boat will run too wet with slower speeds and higher amp draw. Enjoy the fun spectacle!



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Old Dec 26, 2012, 11:23 PM
RELAX. You'll live longer
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Brisbane- Australia
Joined Jul 2007
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Ya beat me to it Zozer.
If a Crackerbox ain't bouncing, she ain't running right.
Some of the best fun at our club is anything up to 10 Crackerbox boats bouncing around the course. Only small ones & all with the same motor & prop. But still great fun.

Great video too Zozer..
Cheers.
Paul.
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Old Dec 27, 2012, 03:00 AM
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Slightly off topic:
I watched the video and noticed all boats kept their 'lane' during the race.
Running in the outside lane makes you run much wider ovals.

How does this system work?

Regards, Jan.
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Old Dec 27, 2012, 03:14 AM
RELAX. You'll live longer
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Not sure on the full size ones Jan. It's either the rules or they don't like to cross the wake of another boat.
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Old Dec 27, 2012, 07:52 PM
mahoganyfan
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Bouncing during running

Thanks Zozer and 785boats.I have to go back then and retweak tabsuntil I get some bounce back.By the way Zozer,thanks for video.
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