Quote: (Originally Posted by
quickean)
In cold fresh water, I have good trim with the Meg with no additional weight using a dry suit and 3L fabers. Keep in mind small differences in how the cylinders are placed up or down make a decent difference in trim. I've been doing some 3 hour dives lately and my back is as comfortable at the start of the dive as it is at the end - no problems.
The fact that you can rise or lower the tanks on your unit is as a matter of fact a benefit of the "tube type" rebreathers compared to the rebreather having a shell in which one can only use one type of tanks and in wich one can't rise or lower the tanks to modify the gravity center of the machine .
the dolphin has a shell and in addition the main tank is located at the bottom of the shell which gets trim even worse.
All dolphin modifier have in addition enhanced the main tank size and made the trim absolutely terrible.
Last bad point many dolphin modifiers have mounted frames to be able to use back plates and wing, the result is that the shell and the tanks have been pushed a little bit more behind compared with the original unit where the shell was really in contact wih the diver's back.
All of that point made in terms of trim the worst rebreathers on earth (not the original ones but the modified one with big heavy tank, back plate etc).
I first tried to compensate this using a 2 liter tank for dil instead of the 5 liter original tanks and attaching a couple of lest bag on the top of the shell.
but the solution was not totaly satisfactory
later I thought of buying the hydrogom shell but I eventualy decided not to.
I designed a really ligth epoxy-fiberglass shell because the ligther the shell is best trim one get.
And the hydrogom is really too heavy IMHO
then I designed the shell so that the bottom tank is as close as possible to the diver's body
the back plate is attached on the shell itself so that the rebreather components are as close to the diver's back as possible.
And of course I installed a lead bar on the top of the shell just behind the diver's neck.
This 4 kilos bar can be pulled out easily by the diver and dropped in case of loop drowning.
Lastly I mounted on the back plate harness (on the diver's shoulder) 2 lest pockets containing 2 kilos lest bags also droppable.
the result is perfect, I can dive perfectly horizontaly without any effort to keep this underwater attitude it is just great .
for me it is just as a dive re-birth really.
So what I did is not the best that can be done of course, I just say this to discribe how things can be bettered in terms of trim
I think that it is capital for anyone to chose it's rebreather or to built or modify a unit taking all those points in account.
I've change a lot my habits compared with what I did at the begining,
For me the ligther the rebreather is and the closer to the diver's bag the better the trim is
last thing we can all reduce the lest we carry, and reducing the belt lest is a key point to better the trim.
regards
jean mi