Tech 40 Trim and buoyancy

[Windmutt]

Yeah, while technique can help with a lot of things, if your rig isn't setup to properly trim you out there isn't much you're going to be able to do. In my Intro-to-Tech course we spent 3 dives making small adjustments between wing and backplate adjustments for the tanks before finding the hole positions that worked best for trimming me out naturally. Most backplates have 3 hole positions you can run the tank's bolts through. If you're in the top, move it down one. If you're using the middle, move it to the bottom. Similarly, many wings can also be positioned in multiple places. These adjustment options exist because they need to for proper trim. Not everyone will trim out in the same way using the same adjustment positions.

An arched back, head up, and feet and arms out can only do so much. Sometimes the answer is to fix the gear. If your instructor doesn't understand that I'd be worried about what else they don't understand.

Great feedback. That’s what I suggested to my instructor, but he said several students have passed with the current rig configuration of his rental to me.

 

[Marie13]

Great feedback. That’s what I suggested to my instructor, but he said several students have passed with the current rig configuration of his rental to me.

Just because it worked for them doesn’t mean it’s going to work for you. Sounds like you need to look for another instructor.

 

[flymolo]

There are a lot of variables to consider. First - What is your height and build?

My personal experience is HP100s are shorter doubles and tend to make people very head heavy. A lot of people unconsciously dive heads-up position to try to offset this. When diving doubles you now have the weight of the manifold + 2 first stages at the top of your head.

For me a tail weight as low as possible is absolutely essential. it's literally the only way I can trim out HP100s. How much weight might be a function of how head heavy you.

Before trying that you should also try loosening your harness to drop tanks lower on your back and make sure you're using the bottom bolt position on your backplate (this raises the plate but drops the doubles lower on your back). I've found a lot of people have their shoulder traps a lot tighter than they need to be. Mine are pretty loose which you compensate for by cinching down the waist strap and snugging up the crotch strap.

Also already mentioned but make sure the top band is right at the crown/break of the tanks. This will also drop the doubles lower on your back.

+1

 

[crofrog]

So my wife and I struggled with double hp100s as well. Here are the steps we took to fix it:

1. Move the backplate down as far as you possibly can and still reach your valves. My back plate is 3" farther down my back than it was when I started. I was very balanced in a single tank with where it was, but it required a significant adjustment for doubles.
2. Switched to an AL backplate and move the weight from the AL backplate to a halcyon v-weight pouch with 5lbs added into the tail section of the pouch.
3. This is the biggest one descend to 30ft and over inflate your drysuit while dumping your wing. Ascend to 20ft while venting your drysuit with out doing anything drastic to get all of the air out. This significantly reduced the amount of "squeeze" we were diving with and balanced the air between our shoulders and feet significantly more. It was basically impossible to get all of the air out of your feet so having a bit more air in the drysuit allowed a better balance between the shoulders and feet for where the air was. This also resulted in both my wife and I diving about 5lb's heavier so back to the steel plates.
4. Wear a hood, my Santi 9mm hood is about 2.5lb positively buoyant.
5. Switch to double HP133s instead because they trim out better than HP100s. Double HP133's are ~3.5lb lighter in the water at 500psi than double Faber HP100, move that weight to your tail weight / hip belt.

So to summarize, lower the tanks down the back as far as possible, add weight to the tail, make sure your not overly squeezed, and realize that if you're underweighted it can create a lot of weird head heavy stability issues because you can't lean into your trim and you're forced to try and get more and more air out of your drysuit.

 

[Marie13]

@crofrog

The OP has rented gear from his instructor who refused to make any adjustments because other students had no issues with the way the gear is currently set up.

 

[crofrog]

@crofrog

The OP has rented gear from his instructor who refused to make any adjustments because other students had no issues with the way the gear is currently set up.

Well that's just not how any of that works. If you can't even adjust the harness to move the plate around you're basically never going to find balance.

Once you know what balance feels like you can dive rigs that aren't perfect but you have to learn what it feels like first, and for my wife it basically impossible with out adjustment. If she stopped moving when in the perfect diver positions (hands out in front, head up, back arched, etc etc) she would just fall face first in the water unless she was about 25 degrees positive trim.

 

[Marie13]

Well that's just not how any of that works. If you can't even adjust the harness to move the plate around you're basically never going to find balance.

Once you know what balance feels like you can dive rigs that aren't perfect but you have to learn what it feels like first, and for my wife it basically impossible with out adjustment. If she stopped moving when in the perfect diver positions (hands out in front, head up, back arched, etc etc) she would just fall face first in the water unless she was about 25 degrees positive trim.

That’s why there have been multiple suggestions for him to find another instructor.

 

[Windmutt]

I think it’s best to scrap what I’ve invested and restart the course with a new instructor. The advice validated what I suspected based on my recreational experience leading up to this course. I’m also investing in my own gear. I was being charged $100/day for the twins and Regs.

 

[Marie13]

Yeah if the instructor isn’t interested in helping you even get trimmed out by adjusting gear for you, then that’s a big red flag. Expensive as heck for the rental, too, seems to me.

Suggest you spend some time getting used to doubles before you give the course another try.

 

[jlcnuke]

I think it’s best to scrap what I’ve invested and restart the course with a new instructor. The advice validated what I suspected based on my recreational experience leading up to this course. I’m also investing in my own gear. I was being charged $100/day for the twins and Regs.

$100/day for a set of doubles and doubles regs, for the class (s)he's charging you for on top of that??
Yeah, I can rent doubles with wing and regs for $40/day in Florida.... while not taking a class.