HP100 doubles trim/buoyancy

[rhlee]

I just bought of a set of HP100 doubles (used) and am wondering about people's experiences with them w.r.t. trim and buoyancy. I normally dive with a HP80 single with a SS BP wearing 5lbs on the upper cam band and 10 on a belt. I'm wondering where I should start out in trying to get the trim figured out with the doubles.

According to the specs I found, the HP80 is -2.5 empty and the HP100s are -1.3lbs empty. So, if I figure correctly, with just the doubles and backplate, that is something like 8.5lbs negative not counting the manifold and the bands (for which I don't have a good guess) which leaves something like 15lbs left to distribute (is this alot? I would have expected to have to use less lead with doubles...).

Should I expect these to be head-heavy? Also, what is the DIR perspective on using weight belts with doubles (yes, I know this isn't in the DIR sub-forum since my main question is about the doubles themselves)? Is that kosher or is it frowned upon? It seems like people go to great lengths to move weight to places other than the belt, and I'm wondering if there is a reason for it.

thanks.

 

[MSilvia]

A lot of it will depend on the manufacturer of the HP100s. I have Asahi HP100s, and they seem to be aconsiderably more negative than any of the specs I've seen for PST tanks.

In any case, I was used to diving a 6lb SS plate with an STA, an old steel 72, and 12 lbs on my belt. When I put the doubles on the plate, I was significantly negative and head-heavy with no weight belt. It sucked out loud, so I slid the bands as high as I could, put on an aluminium plate, and am now very close to neutral, nicely trimmed, and very happy in that rig with no belt.

As far as I'm concerned, I try to get weight off my belt because I have enough gear-related crap to deal with without lugging a freakin' weight bench around with me. When I was diving a 2-piece 7mm suit with an AL80, I needed 36 lbs on my belt. Trust me when I say diving dry with steel and no belt is a huge improvement.

 

[texdiveguy]

I dive double st lp85s and a 5.5 ss backplate on my Zeagle Tech BC with a Bare drysuit and undergarment and use no additional lead.

 

[rhlee]

thanks. I'm diving dry too. The tanks are PST HP100's (the older kind that are rated at 3500 not the E7's that are rated at 3442). The bands are already up as high as they will go (the top band starts right where the tank starts to curve up).

texdiveguy, how is trim with your double 85's and SS plate? it seems liek those should have similar characteristics as the HP100s. Do you have any head heaviness problems?

 

[texdiveguy]

thanks. I'm diving dry too. The tanks are PST HP100's (the older kind that are rated at 3500 not the E7's that are rated at 3442). The bands are already up as high as they will go (the top band starts right where the tank starts to curve up).

texdiveguy, how is trim with your double 85's and SS plate? it seems liek those should have similar characteristics as the HP100s. Do you have any head heaviness problems?

No, I trim out real well with the 85's.....and you are right, they are sim. to your hp100s.

 

[JeffG]

Also, what is the DIR perspective on using weight belts with doubles

If you need the weight, use it. Nothing wrong with using a weight belt.

 

[rjack321]

with Worthington HP100s I use a 5# SS plate and 8lbs on a belt. Drysuit, 200gm undies, 5'8" 142lbs.

There is nothing wrong with a weightbelt under a harness. Move weight around to get your trim in order, that's A1 priority

 

[texdiveguy]

with Worthington HP100s I use a 5# SS plate and 8lbs on a belt. Drysuit, 200gm undies, 5'8" 142lbs.

There is nothing wrong with a weightbelt under a harness. Move weight around to get your trim in order, that's A1 priority

I am a bit surprize you are needing the extra 8lbs. with st doubles and the ss backplate.

 

[cool_hardware52]

I just bought of a set of HP100 doubles (used) and am wondering about people's experiences with them w.r.t. trim and buoyancy. I normally dive with a HP80 single with a SS BP wearing 5lbs on the upper cam band and 10 on a belt. I'm wondering where I should start out in trying to get the trim figured out with the doubles.

According to the specs I found, the HP80 is -2.5 empty and the HP100s are -1.3lbs empty. So, if I figure correctly, with just the doubles and backplate, that is something like 8.5lbs negative not counting the manifold and the bands (for which I don't have a good guess) which leaves something like 15lbs left to distribute (is this alot? I would have expected to have to use less lead with doubles...).

Should I expect these to be head-heavy? Also, what is the DIR perspective on using weight belts with doubles (yes, I know this isn't in the DIR sub-forum since my main question is about the doubles themselves)? Is that kosher or is it frowned upon? It seems like people go to great lengths to move weight to places other than the belt, and I'm wondering if there is a reason for it.

thanks.

The first task is to determine your total weighting. Expect to be quite a bit negative at the start of the dive, you need to consider the weight of the gas (~16lbs) and you need to consider how much gas you might want in your suit during your shallow stop. If you are used to fairly short exposures with single tanks you may find you want to add more gas to your suit during longer exposures.

You might end up 20+ lbs negative.

Only after you get your total weighting nailed is it worth playing around with trim weighting.

Tank Type, tank position, plate position, body type, undergarment and drysuit, weightbelt, fins, gas in the legs etc. can all effect trim.

Wing shape play a part to. Some wings have more lift low, some more in the middle, some at the top.

I find pools a great aid. The horizontal bottom is good reference when dealing with trim issues.

Good luck,

Tobin

 

[rjack321]

I am a bit surprize you are needing the extra 8lbs. with st doubles and the ss backplate.

Its cold here! I carry the same SS plate and 22lbs with a single