I've set up some doubles to get sorted with them trimwise and just generally comfortable with them prior to a TDI course in November.

I had a dive in them today and found that if I stopped finning I would roll slightly forward and quickly turn turtle on my left side. This of course meant that I had to skull with my fins to keep the "yaw" under control.... anyone had similar problems?

Gear is, (dunno how relevant)
2 x Faber 12s
40lb Halcyon evolve (torus)
2lb alloy plate
Drysuit and 8kgs of lead.

I can't see anyway that the rig isn't balanced I haven't put a tailweight on as I wanted to see whether I was top heavy or not without, as for reaching the valves... gonna have to put a tailweight on as I can only just reach the isolator so i'll probably have to put the bands further down the tanks (the top band is just on the break of the curve at the moment.

Any thoughts appreciated.

I have a home made tail weight with my rig, which is pretty much the same as yours bar the alloy plate, mine is stainless. It solved all my trim issues

What type of undergarmet are you using on your bottom half? I found that effects trim. I usually where just some thermal leggins and thats it.

Do you have chicken legs? or too much loose material in your DS around your legs and ankles? I have chicken legs so I use Gaiters, which helps to keep air out of my feet.

There are the problems and solutions that I found when I moved to twins.

Ant

I'm using the Xerotherm Artic top and bottoms with the booties by 4th elephant...
I have legs reminiscent of tree trunks.. well sapling at least , i keep a very minimal amount of air in the suit so my feet aren't feeling floaty..

You should probably keep the bands just at the point where they curve in. If you need to move the rig or down your back, you could loosen off the webbing for the arms and tighten the crotch strap (or the opposite to move it in the other direction)

Can't see why the rig would be tipping to the side; particularly as it sounds like the weight is low down (assume a weight belt?). Is the gear mounted centrally on your back (i.e. - arm webbing loops both the same length?)

My twins used to push my head down just a little too much and I used to have to compensate. Ditching the steel backplate and adding 3kg of tail weight fixed that completely.

Hmm.. I think there may be a bit of difference there, not much certainly no more than 20mm but I shall remedy this.

Yeah I'll be looking to make a 2kg tail weight asap and see if that helps.

For me, the tail weight made a dramatic difference. The first dive I used it, I reckoned it kept my head up too much, but after the 3rd or so dive, I worked out that it was actually bang-on. With the tail weight on I can trim out to pretty much any angle I want. So if there are any photos in circulation out there of me scooting along at 45 degrees and with dropped knees, , I can guarantee it's intentional

Nothing there that extensive application of photoshop couldn't cover up!

Just had a thought about the rotation problem..

If my legs were not at the same angle then I would be unbalanced yeah? So if I was focused on the fact that I was pitching forward then I may have been doing something strange with my legs such as having my left leg out further than my right which would have effectively increased my mass on that side inducing a roll??

Plausible??

Basically it comes down to the fact that your centre of gravity and centre of buoyancy are out of alignment.

Your centre of gravity should be around your belly button and your centre of buoyancy should be around that general area as well...you are head heavy...I had the same problem when I shifted to Steel Doubles.

To combat this I put my weight on a weight belt and adjusted my body position.

Pull your head right back, clench your arse cheeks together which pushes out your groin and keep your legs bent at 90 degree angle when not moving and arms out in front. Experiment with this position and you will get it.

A core piece of the GUE training was being videoed under water. Invaluable for spotting exactly what's right and what's screwing you up. Best done in a pool, as you've then got clear water, lots of light and plenty of right angle walls to reference against.

Put a 2.5 kilo tailweight on the doubles and they are now sorted! No roll, no head dive and spirit level trim.... Just gotta get more flexible.

Cheers for the advice guys!