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Problems with CG due to large tanks.

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Problems with CG due to large tanks.

Old 07-20-2022, 09:55 PM
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Default Problems with CG due to large tanks.

Both me and my flying buddy has encountered problems with shifting CG due to fuel moving around in large fuel tanks. The problem appears around half empty tanks when all the fuel move backwards during high alfa in landing or take of. Should we start using a number of small tanks instead of one large and most often long stretched tank avoid this problem? I would be happy to hear of your experiences and thoughts on this matter.

Jannica in Sweden
Old 07-20-2022, 10:46 PM
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Consider making or purchasing a custom kevlar or fiberglass tank with baffles inside which will only allow the fuel to move fore and aft very slowly.
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Old 07-21-2022, 01:14 AM
Joseph Frost
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Position your tank to make sure you are not tail heavy on half or less, towards the end of the flights. Nose heaviness is no problem with turbine models, a standard thing on full tank.
Old 07-21-2022, 05:09 AM
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I have couple CARF models with their tanks. The longer tanks have a baffle in the middle to prevent the CG from shift as the fuel sloshes around.

You could use bladder (IV-bag) tanks. They might be better for the type of flying you like to do.
Old 07-21-2022, 11:12 AM
Len Todd
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The CARF main tank that came with my Ultra Flash had a chunk of glue come loose inside and plug my fuel line, and I use clunks with 3/16" IDs.. The vendor replaced it with a non-OEM tank. When I trashed the OEM tank, I cut it open and found that the baffle was not glued very well. So, ... now when I get a baffled tank, I look very closely at the internals to ensure against internal issues.
Old 07-21-2022, 04:59 PM
Joseph Frost
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That sounds just about right about some fuel tanks and the effects of the smelly stuff we fill them with. Well designed shape of the f/tank (as on pic) can also help the CG issues, but one of these in my early turbine days was so pourest it actually swetted the fuel through out its whole body! LOL. After good clean up I have given it couple of coats of slightly thinned down epoxy, easy fix.
Another headed tank I bought from a major jet supplier was so badly put togeter it flooded my model with large content of JetA!, luckilly on the ground.
Never rely on what you buy, you are sometimes better off making your own fuel tanks out of fruit juice bottels from the suopermarket, lot cheaper as well and you can finish them off to your own standard.

Great shape of f/tank to minimize CG problem.
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