Doppler
Active Member
I was recently asked by a client to "test dive" a HammerHead rebreather. My client is looking for an alternative to a European-built unit they have been recommending to various MilPro customers of theirs for several years. Various reasons for the need for an alternative, none of which are relative here, but my client has withdrawn its support of the "current model" and the HammerHead made the shortlist.
Anyhow, this may be useful to someone wondering which unit to buy... What follows is an abbreviated version of my final report to my client.
Hammerhead Expedition-Grade Rebreather
Summary of three-days diving/Xover in North Florida’s Cave Country, December 2014
Parameters of “Man Testing”
Mike and I are experienced rebreather divers with time on units from several manufacturers. Both of us are instructors / instructor-trainers on various different rebreathers.
The testing was carried out in Ginnie Springs and Troy Springs, Florida, December 3-5, with Randy Thornton from HammerHead -- who is also the owner of Sub-Gravity (a distribution company associated with HammerHead and various related products). Water temperatures were approximately 20 degrees (68 F) and visibility ranged from infinite to less than a metre (3 feet).
We each had our “own” unit and were given ample hands-on opportunity to build, disassemble, prep, and dive our units for this assessment.
Unit Specs
The two units we used were supplied by SubGravity: one several years old and Randy Thornton’s personal unit; the other fresh from the factory. Both were the HammerHead Extreme models (as opposed to the Classic) and both were similarly configured: Large canister (smaller size (hobo) available) in aluminum (machined Delrin an option for weight saving). Units fitted with 3.6 kg radial scrubber bucket, and Juergensen Marine RevC+ primary controller using a Shearwater Petrel setup as secondary (non-controlling). Each was also fitted with the patented DIVA (Dive Integrated Vibrating Alarm) HUD atop a Shrimp BOV manufactured/marketed through SubGravity for Golem Gear. Loop hoses were 11-inch. A little short from head to counter lung Ts for both me and Mike... perfect length from T to Shrimp BOV. (Since various hose lengths are in SubGravity options catalog, this does not seem to present and issue.)
The heads were fitted with three SG-22 oxygen sensors (Molex connectors) with the fourth spot in the sensor array left empty. The units were running eCCR (other options include manual and hybrid), using four available pre-programmed oxygen setpoints (0.4 bar, 0.7 bar, 1.0 bar, 1.2 bar).
Units were bolted to standard 6 mm stainless steel backplates and traditional three-point harness systems, and were fitted with back-mounted counterlungs (both over the shoulder and on the shoulder lungs are available but not tested by Mike or I). The wings supplied were SubGravity donut wings delivering approximately 150 N of lift, according to manufacturer's specs.
We used three-litre steel bottles for oxygen and diluent (air and ean32 used as diluent gas during the three days of diving).
Wearing O’Three 1-100 drysuits and thermal undergarments adequate for conditions, no additional ballast/weight was required. In fact, an aluminum backplate might be optimal for freshwater springs diving.
Conclusions
The unit itself is impressive, and behaved faultlessly during our initial testing.
Bayonet connectors for hoses and unit head facilitate assembly. This fastening method gives positive feedback and the design helps to eliminate the possibility of cross-threading which exists with current unit. Negative and positive tests where 100 percent passes. As were all in-water bubble-checks.
Scrubber is easy to pack (we used Intersorb® 812 throughout testing) and available in four sizes (2, 2.5, 3.6 and 4.1 kilos respectively). Housing for head and scrubber bucket VERY simple to put together and extremely robust using zero clasps or clips resulting in a positive connection and streamlined profile. ORings are integrated into various components, so fewer items to misplace, or forget. A plastic spacer is required for the slightly smaller bucket to work correctly and marry to the CCR's head when using the full-size canister.
The Shrimp BOV is a superior product and allows one-handed operation to open and close. Its operation is smooth, reliable, and much faster than the corresponding system supplied with current CCR units, and therefore may result in shorter bailout in an emergency.
WOB was excellent to good in all practical diver positions. Vertical head-down was challenging but serviceable. Both Mike and I tried unsuccessfully to over-breathe the unit under "normal" working conditions. The HammerHead, in our opinion, is superior in this regard.
The diluent and oxygen manual-add controls were super responsive, making dil flushes and manual setpoint control a breeze. eCCR controller was extremely stable through all depth changes although care must be taken on rapid descents. (I found this particularly apparent when doing a pre-dive oxygen flush at six metres, which was rectified by doing a partial dil flush a couple of times before heading deeper.) Expedition DIVA lights are visible with mask removed, vibration when outside operational range VERY apparent. Clearing flooded loop was simple even with BMCL (which is NOT the case with the current version of backmounted lungs in my personal experience). Set point adjustment, manual setpoint management, dil flushes, high setpoint recovery all exceeded performance expected of Vision units in my opinion. Low setpoint recovery (0.30 tested at depth) was immediate, and response time of cells was super fast.
Our opinion is, this is a superior unit, made to expedition quality in the USA. Since this unit uses more modular architecture with many more options available stock than from the current vendor it offers a much broader operating range. In combination with the recommended sidemount CCR, the HammerHead offers a perfect alternative to the current line of CCRs for us and the individuals and organizations who look to us for advice.
E&OA, December 9, 2014
Anyhow, this may be useful to someone wondering which unit to buy... What follows is an abbreviated version of my final report to my client.
Hammerhead Expedition-Grade Rebreather
Summary of three-days diving/Xover in North Florida’s Cave Country, December 2014
Parameters of “Man Testing”
Mike and I are experienced rebreather divers with time on units from several manufacturers. Both of us are instructors / instructor-trainers on various different rebreathers.
The testing was carried out in Ginnie Springs and Troy Springs, Florida, December 3-5, with Randy Thornton from HammerHead -- who is also the owner of Sub-Gravity (a distribution company associated with HammerHead and various related products). Water temperatures were approximately 20 degrees (68 F) and visibility ranged from infinite to less than a metre (3 feet).
We each had our “own” unit and were given ample hands-on opportunity to build, disassemble, prep, and dive our units for this assessment.
Unit Specs
The two units we used were supplied by SubGravity: one several years old and Randy Thornton’s personal unit; the other fresh from the factory. Both were the HammerHead Extreme models (as opposed to the Classic) and both were similarly configured: Large canister (smaller size (hobo) available) in aluminum (machined Delrin an option for weight saving). Units fitted with 3.6 kg radial scrubber bucket, and Juergensen Marine RevC+ primary controller using a Shearwater Petrel setup as secondary (non-controlling). Each was also fitted with the patented DIVA (Dive Integrated Vibrating Alarm) HUD atop a Shrimp BOV manufactured/marketed through SubGravity for Golem Gear. Loop hoses were 11-inch. A little short from head to counter lung Ts for both me and Mike... perfect length from T to Shrimp BOV. (Since various hose lengths are in SubGravity options catalog, this does not seem to present and issue.)
The heads were fitted with three SG-22 oxygen sensors (Molex connectors) with the fourth spot in the sensor array left empty. The units were running eCCR (other options include manual and hybrid), using four available pre-programmed oxygen setpoints (0.4 bar, 0.7 bar, 1.0 bar, 1.2 bar).
Units were bolted to standard 6 mm stainless steel backplates and traditional three-point harness systems, and were fitted with back-mounted counterlungs (both over the shoulder and on the shoulder lungs are available but not tested by Mike or I). The wings supplied were SubGravity donut wings delivering approximately 150 N of lift, according to manufacturer's specs.
We used three-litre steel bottles for oxygen and diluent (air and ean32 used as diluent gas during the three days of diving).
Wearing O’Three 1-100 drysuits and thermal undergarments adequate for conditions, no additional ballast/weight was required. In fact, an aluminum backplate might be optimal for freshwater springs diving.
Conclusions
The unit itself is impressive, and behaved faultlessly during our initial testing.
Bayonet connectors for hoses and unit head facilitate assembly. This fastening method gives positive feedback and the design helps to eliminate the possibility of cross-threading which exists with current unit. Negative and positive tests where 100 percent passes. As were all in-water bubble-checks.
Scrubber is easy to pack (we used Intersorb® 812 throughout testing) and available in four sizes (2, 2.5, 3.6 and 4.1 kilos respectively). Housing for head and scrubber bucket VERY simple to put together and extremely robust using zero clasps or clips resulting in a positive connection and streamlined profile. ORings are integrated into various components, so fewer items to misplace, or forget. A plastic spacer is required for the slightly smaller bucket to work correctly and marry to the CCR's head when using the full-size canister.
The Shrimp BOV is a superior product and allows one-handed operation to open and close. Its operation is smooth, reliable, and much faster than the corresponding system supplied with current CCR units, and therefore may result in shorter bailout in an emergency.
WOB was excellent to good in all practical diver positions. Vertical head-down was challenging but serviceable. Both Mike and I tried unsuccessfully to over-breathe the unit under "normal" working conditions. The HammerHead, in our opinion, is superior in this regard.
The diluent and oxygen manual-add controls were super responsive, making dil flushes and manual setpoint control a breeze. eCCR controller was extremely stable through all depth changes although care must be taken on rapid descents. (I found this particularly apparent when doing a pre-dive oxygen flush at six metres, which was rectified by doing a partial dil flush a couple of times before heading deeper.) Expedition DIVA lights are visible with mask removed, vibration when outside operational range VERY apparent. Clearing flooded loop was simple even with BMCL (which is NOT the case with the current version of backmounted lungs in my personal experience). Set point adjustment, manual setpoint management, dil flushes, high setpoint recovery all exceeded performance expected of Vision units in my opinion. Low setpoint recovery (0.30 tested at depth) was immediate, and response time of cells was super fast.
Our opinion is, this is a superior unit, made to expedition quality in the USA. Since this unit uses more modular architecture with many more options available stock than from the current vendor it offers a much broader operating range. In combination with the recommended sidemount CCR, the HammerHead offers a perfect alternative to the current line of CCRs for us and the individuals and organizations who look to us for advice.
E&OA, December 9, 2014
