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Author Topic: Perfect trim U47?  (Read 2232 times)

Tom_DK

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Perfect trim U47?
« on: July 31, 2008, 10:30:21 PM »

Hi

I want to make a few modifications on my U47 with static dive.

- Change the acrylic glass to PVC
- Remove the ESC fot the piston tank and put in Engell's relay Printed Circuit Board...as I'm having small problems to FAST stop the engine on the tank when end switch is activated.
- Remove the 4 x AA cell batteries for the reciever and use the BEC from the main engine ESC.
- Make a perfect trim

And thats what I need some help to do. I would like that the U47 has a straight waterline both when submerged and at the surface. Now the bow always comes up first and that looks just aweful and none scale. I figured that I need some kind of additional material at the rear end of the sub to make it more floating, but what to use and where to place it and finaly how to trim it?

BR,
Tom
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andyn

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Re: Perfect trim U47?
« Reply #1 on: August 01, 2008, 12:45:55 AM »

This may seem like a stupid idea, but how about one of those air filled bags you seem to get a lot of in packaging nowadays shoved in the tail end?

Just an idea...
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Mankster

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Re: Perfect trim U47?
« Reply #2 on: August 01, 2008, 10:56:06 AM »

To trim it you need to first make sure you have her level when submerged and stationary, with ballast tank full. Simple matter of adding a bit of lead and moving it around the you balance the sub. Now when surfacing  you should be able to get to decks awash with the  sub still level (or very close as you have a central piston tank that emptiess from one end, not from the middle). When surfaced if you find that the bow is sitting too high, you need to add a little more lead to the bottom of the bow and some foam to compensate to the underside of the top deck. So when the top deck breaks the surface , the foam loses its buoyancy and the lead will keep the bow down.

bbdave

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Re: Perfect trim U47?
« Reply #3 on: August 01, 2008, 11:14:02 PM »

I thought they did surface bow first or is that wrong? looks like i may have to re-trim :o

To trim it you need to first make sure you have her level when submerged and stationary, with ballast tank full. S

When my tank is full she sits on the bottom i have the proportional switch which isn't very proportional as the first part of the fill is about 3/4 of the tank which sends her straight down. i think you sub guys need to hold a symposium for us mere mortals  needing to learn the black art ;D
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Mankster

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Re: Perfect trim U47?
« Reply #4 on: August 02, 2008, 12:01:12 AM »

I thought they did surface bow first or is that wrong? looks like i may have to re-trim :o

To trim it you need to first make sure you have her level when submerged and stationary, with ballast tank full. S

When my tank is full she sits on the bottom i have the proportional switch which isn't very proportional as the first part of the fill is about 3/4 of the tank which sends her straight down. i think you sub guys need to hold a symposium for us mere mortals  needing to learn the black art ;D

Is that the Engel XP switch? The idea with that is the sub should be pretty my at neutral buoyancy when the tank is 3/4 full, and the rest of it is to fine tune and park at the bottom. I dont think that switch allows you to stop at say halh a tank, its either empty or 3/4 full as you say.

bbdave

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Re: Perfect trim U47?
« Reply #5 on: August 02, 2008, 12:25:27 PM »

It is the xp with a bit of deft twidling though i can get it to stop at about mid way up the tower but all this messing about gives me hours of fun.

What will happen if i use my sub in a heated pool will it require more or less ballast to submerge i assume the water will be less dense due to chemicals etc

Sorry for hi-jacking the thread tom O0
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Mankster

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Re: Perfect trim U47?
« Reply #6 on: August 02, 2008, 02:24:37 PM »

Warm water is less dense than cold so your sub will be less buoyant, and sit lower in the water. Take a bit of foam and lead with you to fine tune. I dont think chlorinated water makes much odds over tap water in the bath that you may have used to trim the boat.

Subculture

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Re: Perfect trim U47?
« Reply #7 on: August 03, 2008, 07:44:35 AM »

You can upgrade the electronics to a fully proportional system that will work just like a servo.

bbdave

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Re: Perfect trim U47?
« Reply #8 on: August 03, 2008, 11:10:43 PM »

Where do i get one of those? would i need to alter the gear at the end of the tank which has the variable pot thingy on it
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Subculture

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Re: Perfect trim U47?
« Reply #9 on: August 04, 2008, 03:05:35 PM »

You would only need to modify your tank a little bit. This board uses a hall effect sensor to count the thread revolutions, rather than use a feedback pot.

As such this system is more flexible, with no pot to wear or get noisy/dirty.

All you will need to do to fit one to your engle tank, is epoxy a couple of magnets (supplied with the board) to the gearwheel which mates with the tanks threaded shaft. Fit the hall sensor to the tanks end plate/bulkhead, and wire in the board to the microswitches already on your tank.

I'd estimate no more than an hours work.

PM me your email, and I'll send you some information and details of these boards. They're made by Markus Rieger in Germany, and cost about 75 euro each.

Andy
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