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Old Aug 05, 2013, 11:01 PM
RC boat Rock Star
Kalamazoo, MI
Joined Apr 2004
2,950 Posts
The weight is going to vary a lot. Your hull has a heavy lay-up as it's made to take a beating and keep on ticking.
OK, also as an Engineer you have to throw into the equation the trim tabs also artificially make the boat longer and can move the CG forward, i.e., the longer the trim tabs the further forward the CG is moved. Mount them about 1/8" above the bottom as trim tabs level with the bottom can actually slow the boat down. This was shown on nitro boats where they could lose up to 8-12 MPH.
These older hulls were originally set up with the CG at 27-30% forward but those were with less powerful engines. Today's higher HP and torque engines force the boats to have a more forward CG. Play with used pop or water bottles to help determine how much weight may have to be added to get yours balanced out. Crude but it works.
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Old Aug 06, 2013, 03:28 AM
Registered User
Helsingborg, Sweden
Joined Jul 2005
267 Posts
Ron has, as usual, offered very good advice. My personal choice for changing the cg would be to use weight initially to find a good balance point where the boat runs well, mark it and then move the engine forward to achieve that point without the added weight.
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Old Aug 06, 2013, 08:56 AM
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Joined Sep 2009
264 Posts
Cheers to both of you for the advice. w3bby, the engine is as far forward as is possible so unfortunately I have no other option there.

I am using hot water pipe insulation for flotation with a 15mm hole through it, that allowed me to place some metal bars inside and shift the COG.

Currently the trim tabs are about 1mm from the bottom between 1/32" and 1/16". I can move them up if needed but I will try them out as is.

The thread on the aly support is really not cut well with large tolerances. You can just about see the angle and gaps on the tabs.

Thanks again,
Bermylizard
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Old Aug 06, 2013, 11:48 AM
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Joined Sep 2009
264 Posts
Laziness was speaking earlier when I said I would try the tabs as low as they were. Ever hear: "The lazy man works the hardest?"

Well I have raised the tabs, as I know I will have to anyway, why waste a run proving what I was already told.
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Old Aug 06, 2013, 01:06 PM
RC boat Rock Star
Kalamazoo, MI
Joined Apr 2004
2,950 Posts
No, I haven't heard that one, just variations.
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Old Aug 06, 2013, 01:10 PM
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Joined Sep 2009
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My girlfriend says "The lazy man's girlfriend works the hardest." What it refers to is for example:

Someone throws rubbish at the trash can cause they are too lazy to get up. They then miss and have to get up and walk past the trashcan to pick up the paper. Ultimately they end up working harder as they were too lazy to do it right the first time. I am guilty of this=)
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