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[reefrich]

Hi guys

I have just started to trim my Ohio static diver (sheerline). I have manage to get it to submerge level but then the nose starts to surface and the tail end sinks. I have tried to increase the bouyancy in the tail but am struggling to get a perfect balance (level in the dive and surface).

Any tips you guys have to help would be great.

Cheers

[Mankster]

Start with surfaced trim - add foam (just) below the water line to get it level. Once you have set surfaced trim , flood your ballast tank - you want your boat to just settle on the bottom (add more lead if it doesn't).  Now add foam (just enough to bring the boat to neutral bouyancy) high up under to the top hull. Once you have found out how much foam you need, move it backwards and forwards under the top hull, till you find the spot where the sub is level submerged.

Remember with type of ballst tank, water sloshing about or pooling in one end when the sub is tipped will upset your trim -though a little forward motion (with a pitch controller) should setlte things out again.

[reefrich]

Thanks for that, I will give it a go.

[Subculture]

Also make sure you haven't got any trapped air under casing- that'll really mess you up.

[Turbulent]

I had one of these boats - first Sheerline boat I owned.

Follower Ramesh's (Mankster) advice & you'll not go far wrong, you need to get foam above the waterline - attach it to the underside of the Middile casing & a good lump in the bow. These boat are awful on the surface ref turning but when dived are very responsive.

Make sure you run slow when submerged or she'll porpoise like a bitch - also fit a leveller.

[Subculture]

Does it porpoise with a leveller?

[Turbulent]

Does it porpoise with a leveller?

Not as much, speed is the real key, you need to drive these long boats slow to reduce the drag.

[Subculture]

Curious. I've seen a couple of Eden/Sheerline Ohios in use. One was well out of trim owing to a replacement battery. The other was undergoing 'trials'. The Engel Lafayette, which although a smaller boat, has a very similar length to beam ratio, cuts through the water like a scythe and handling wise appears to without vices.

[reefrich]

Yes it did porpus with the leveller fitted, although it wasn't moving forward very quickly.

[Turbulent]

Curious. I've seen a couple of Eden/Sheerline Ohios in use. One was well out of trim owing to a replacement battery. The other was undergoing 'trials'. The Engel Lafayette, which although a smaller boat, has a very similar length to beam ratio, cuts through the water like a scythe and handling wise appears to without vices.

Lafeyette's a smaller boat, the proportions may be the same but the water is the constant - density etc.

Reefrich try running at different depths, I found mine was better a little lower in the water - about 3 inches of water above the fin, if you fit your scope onto a cork it will rise as you dive.

Keep at it, it's the hardest sheerline boat to drive but worth the effort.

[Subculture]

Agreed, but a larger model should be more stable, not less.

[snowwolflair]

Also make sure you haven't got any trapped air under casing- that'll really mess you up.

Water surface tension can cause "sticky" bubbles.  If you rinse your model with a very very dilute solution of Fairy liquid before use it will counter these. (not at the pondside though!)

[Turbulent]

Agreed, but a larger model should be more stable, not less.

Not this one.

[Mankster]

Its the weight and possitioning of the battery that makes this particular sub twitchy.

[Subculture]

Big lead acid battery up front?

Really the Ohio should handle very similar to a Vanguard, apart from the position and size of the vanes, and a small  difference in length they're very similar. The Ohio looks like the vanes are a bit smaller in relation to the size of the vessel, however it doesn't have a fixed shroud to counter, so that should help manoeuvrability.

Has this model got room underneath the cylinder?

[Turbulent]

no room under the cylinder.

Battery (12V) is in the bow, Trust me the Vanguard handle better by a country mile, but that has the batteries in the keel.

Fwd planes on the Ohio are only for show - not even linked up.

[admiral donuts]

I have an Ohio myself and have spent months trying to get a level static dive
lets not forget that the 12 inches to the foot scale models do not static dive
they always dive under way except for dry dock seal testing and hovering to fire missiles
This is acheived with the aid of lots of large fast pumps,trim tanks and crew
Seriously,lifting the module up 1 inch (yes,I still work in imperial) slinging a 12 volt sealed nim
stick pack underneath the module and moving the whole lot back as far as the upper
casing will allow seems to make this boat really docile
why not put this to sheerline for a second opinion

donuts

[RonP]

The trimming of any model submarine with a single ballast tank is very difficult and the bigger the boat the worse it gets. Part of the problem is that the tank is never empty nor full so water slushes around and upsets things. An easy answer is two place a free flooding tank at the bow and stern, the tanks shold be open at the top with a small inlet pipe on the underside. Place these for and aft
so that the underside of the tank is just below the surface waterline. These tanks will provide boyancy at the bow and stern when surfaced but will freeflood as you submerge and will drain when surfaced. They stabilise the boat no end when running surface and will give some lift when underwater. You can observe the idea when doing the washing up for the wife (cuz we all do dont we)
Take the collander and put it into the water right way up (little holes down) and it will sink very slowly. Turn it over wrong way up and it will go down like a housebrick.
Hope this helps
RonP

[Albion]

Ron, do you just put a hole in the bottom, say 1/16" of some piping to further restrict the draining?

sounds clever

[RonP]

I usually put a 3/16" pipe in the bottom as a start point and you can sleeve it down to suit but you could use a plastic tube of any size and a small aquarium valve to strangle it down.
It really does work well, although I use 2xpiston tanks and dont have the problem I have one of these little jobbies in the rear of my U-Boat so that it always dives and surfaces nose first.
As Alexander says----simples!