Trimming

[choice]

I am trimming out my U177 and have found that even though it seems balanced left to right and bow to stern, it seems to be prone to an easy rollover.
With very little effort, it will list to either port or starbord at an angel of about 30 degrees.
This seems totally amazing to me as it has around 7.5 kg of iron in the belly. I would think that would keep her upright under just about any condition.
Does anyone have an idea why this is occuring, or what I can do to correct it?
All ideas would be much appreciated.

[JWLaRue]

Under what conditions are you

Under what conditions are you seeing the rollover? Is it while stationary or while running?

What is the total weight of the boat?

It sounds like you do not have enough separation between the center of gravity and the center of buoyancy.

-Jeff

[koeze]

Try to lower your centre

Try to lower your centre of gravity. Lower the heaviest parts like batteries and ballast to the lowest possible point. Do you have a standard Engel boat of do you have a custom tower which is heavier than the original.

If it is an Engel boat also contact them. I heard that they are very good in support.
If you are quick you can look here MarineRC This forum is shutting down shortly but there are a lot of Engel builders there and Sergio there has built the Engel U177.

EJK

[choice]

My boat has not seen

My boat has not seen the open water yet, so the problem I am seeing is while the boat is at rest.
If I'm careful when sitting the boat in the water, it will sit upright, but the slightest nudge will cause it to roll to either side without preferrence.
The ballast is of course sitting in the lowest section of the boat, and the battery rests on top of that, there is no alternative location as the U177 has twin ballast tanks which occupy the remainder of the room in the WTC.
My boat is the standard Engel version, nothing custom has been added that might cause instablilty with added weight above the waterline. I did have to place a small amount of lead within the WTC to achieve the proper trim, would estimate perhaps 3-4 ounces which seems rather small in comparrison to the 7.5 kg of the iron ballast that comes as part of the kit. The stock ballast is rounded on the bottom to match the curvature of the lower hull.
I have been in contact with Sergio, through the marine RC site, who has a very nice 177, but there is a language translation problem that prevents him from giving any detailed advise.
I have also written to Gregor Engel, but I have had mixed results with receiving replies to my inquiries.
The instability is a real mystery to me as all the real weight is in the very bottom of the boat. It seems to be trimmed and stable until I try to float it with the top deck in place.
Thanks to both of you for taking the time to read and reply to my message, and I will be looking forward to any further ideas you may be able to offer.

[bob the builder]

The ballast is of course

The ballast is of course sitting in the lowest section of the boat, and the battery rests on top of that, there is no alternative location as the U177 has twin ballast tanks which occupy the remainder of the room in the WTC.

Did you say your batteries are sitting on top of your ballast tank?

It sounds to me like you may want to switch your ballast tank to sit above your batteries. They are a stable weight that will aid in trimming the model statically. The more of your heavy components that you can keep lower in the boat, the better. If you're using a gear reduction, make sure that the motors are off-centered towards the keel, and not towards the sail. If you can't change your internal workings, it sounds like you may need to add foam under your waterline, as high up as you can get it, and then counteract it with your formed lead ballast in your keel.

The further you get your center of bouyancy from your center of gravity, the better. Lowering your heavy components, or adding lead to the keel will lower your CG, and adding foam just under the waterline will raise your CB.

Hope this helps.

If you have the capability, I'd recommend posting a picture of your internals so everyone can see what you've got to work with.

If you don't have the capability, just let me know and I'll see what I can do about helping you out.

[choice]

Hi Bob

No, sorry for the

Hi Bob

No, sorry for the confusion, the battery sits on top of the ballast keel, not the ballast tank.
I am attaching a photo that is rather old, but shows the basic layout.
On top of the ballast keel is a plastic mounting board, and the battery sits on top of that along with main switch, pressure switch, servos, and such.
I went to rather great pains to make sure that it matched the plans exactly so that I wouldn't have the problem that I seem to be having.
Thanks for offering to lend your expertise, I cuold definately use some.

[JWLaRue]

How much does that battery

How much does that battery weigh? It *looks* like it may be providing too much weight too high up.

A quick test would be to remove the battery and see how the boat reacts to rollover.

-Jeff

[choice]

The main battery weighs 4.6

The main battery weighs 4.6 lbs.
The plans don't specify a weight for the battery, but the one I have fits the prescribed dimensions exactly, (5.95"x3.7"x2.0")and is rechargeable lead-acid as the plans indicate.
The model does not become unstable until the top deck is added. I have not added any weight or fittings to the top deck other than what is called for in the plans, and the sail has plenty of holes to allow water to escape.

[raalst]

Just an obvious point ]

[color=#000000]Just an obvious point ]

[choice]

Hello Ron

It's a good point,

Hello Ron

It's a good point, but there really isn't anything to remove topside, other than the sail and deck gun. I haven't added anything not included on the plans.