Gavinscooters : HPDE or PVC

Constantino · August 4th, 2006, 05:59 PM

What are the differences ?
The pros / cons ?

Thanks,
Ricardo

DRE · August 5th, 2006, 12:09 AM

Quote: (Originally Posted by Constantino)

What are the differences ?
The pros / cons ?

Thanks,
Ricardo

AFAIK, he no longer makes the PVC ones but replaced them with AL backends.

graham_hk · August 5th, 2006, 02:37 AM

Tell George what sort of diving you are doing and let him tell you what scooter you need. Tends to work out better than you telling him what you want LOL

PVCs are slightly more efficient but less hardwearing
HDPE are slightly less efficient but much more hardwearing and suited to everday diving particularly where boats are involved

Cheers, Graham

Constantino · August 5th, 2006, 03:45 PM

Thanks.
HPDE - ocean (eventually cave).

Nevertheless, I thought it would be usefull to understand a little more about the subject.

From where does the efficiency diference come from ? Length (ratio) ? Shape ?

Thanks for your input,
Ricardo

graham_hk · August 6th, 2006, 04:36 AM

The PVC allows more water to flow through the props because there is more space between the shroud and the body

Derk · August 8th, 2006, 01:50 PM

Hi Graham,

given the shape of the PVC-Tail, I do not believe in a better waterflow to the props...
Anyway, noone will be easily able to proof any hypothesis on a topic with flow involved

best,
Derk

Quote: (Originally Posted by graham_hk)

The PVC allows more water to flow through the props because there is more space between the shroud and the body

OkiMike · March 31st, 2008, 09:15 AM

What's the difference between the "normal" tail and the Aluminum option? I looked through the Gavin manual but couldn't find anything useful on the subject.

Indeed, the whole site needs to be flushed down the drain and begun anew.

Dvdwoude · March 31st, 2008, 08:29 PM

The ALU back-end is made for deeper diving...

On the the Gavin site (Exploration, sea scooters. Fort Lauderdale, FL.) is info for the PVC and HDPE back-end(s):

On all versions of the scooter, the motor seal becomes at risk beyond about 550 feet, the bodies are subject to bowing at 700 feet and crushing at about 1100 feet.

In both the HDPE and PVC (nose and tail material) versions, the flex will become an issue in the 900 foot range, which becomes a moot point due to the risk to the seal and the chance of leaking around the o-rings if the body flexes (a major issue at all depths with HDPE bodies, which we do not use for that reason).

Between 450 and 650 feet, the flex in the PVC bodies is between 5/100 and 8/100 of an inch.

August 4th, 2006, 05:59 PM	#1 (permalink)
Constantino(Offline) New Member Join Date: Feb 2006 Location: Portugal Posts: 65	Gavinscooters : HPDE or PVC What are the differences ? The pros / cons ? Thanks, Ricardo

August 5th, 2006, 12:09 AM	#2 (permalink)
DRE(Offline) New Member Join Date: Nov 2005 Location: Mineola, NY Posts: 162	Quote: (Originally Posted by Constantino) What are the differences ? The pros / cons ? Thanks, Ricardo AFAIK, he no longer makes the PVC ones but replaced them with AL backends. __________________ www.dirtydiving.com - DIR is not a 4-letter word!

March 31st, 2008, 09:15 AM	#7 (permalink)
OkiMike(Offline) New Member Join Date: Feb 2007 Location: Okinawa, Japan Posts: 77	AL tail What's the difference between the "normal" tail and the Aluminum option? I looked through the Gavin manual but couldn't find anything useful on the subject. Indeed, the whole site needs to be flushed down the drain and begun anew. __________________ "Hard work pays off in the future. Laziness pays off now."

August 5th, 2006, 02:37 AM	#3 (permalink)
graham_hk(Offline) Pinoy ako pinoy Join Date: Nov 2005 Location: here, there and everywhere Posts: 779	Tell George what sort of diving you are doing and let him tell you what scooter you need. Tends to work out better than you telling him what you want LOL PVCs are slightly more efficient but less hardwearing HDPE are slightly less efficient but much more hardwearing and suited to everday diving particularly where boats are involved Cheers, Graham

August 5th, 2006, 03:45 PM	#4 (permalink)
Constantino(Offline) New Member Join Date: Feb 2006 Location: Portugal Posts: 65	Thanks. HPDE - ocean (eventually cave). Nevertheless, I thought it would be usefull to understand a little more about the subject. From where does the efficiency diference come from ? Length (ratio) ? Shape ? Thanks for your input, Ricardo

August 6th, 2006, 04:36 AM	#5 (permalink)
graham_hk(Offline) Pinoy ako pinoy Join Date: Nov 2005 Location: here, there and everywhere Posts: 779	The PVC allows more water to flow through the props because there is more space between the shroud and the body

August 8th, 2006, 01:50 PM	#6 (permalink)
Derk(Offline) New Member Join Date: Feb 2006 Location: Germany Posts: 85	Hi Graham, given the shape of the PVC-Tail, I do not believe in a better waterflow to the props... Anyway, noone will be easily able to proof any hypothesis on a topic with flow involved best, Derk Quote: (Originally Posted by graham_hk) The PVC allows more water to flow through the props because there is more space between the shroud and the body

March 31st, 2008, 08:29 PM	#8 (permalink)
Dvdwoude(Offline) New Member Join Date: Aug 2006 Location: the Netherlands Posts: 94	The ALU back-end is made for deeper diving... On the the Gavin site (Exploration, sea scooters. Fort Lauderdale, FL.) is info for the PVC and HDPE back-end(s): On all versions of the scooter, the motor seal becomes at risk beyond about 550 feet, the bodies are subject to bowing at 700 feet and crushing at about 1100 feet. In both the HDPE and PVC (nose and tail material) versions, the flex will become an issue in the 900 foot range, which becomes a moot point due to the risk to the seal and the chance of leaking around the o-rings if the body flexes (a major issue at all depths with HDPE bodies, which we do not use for that reason). Between 450 and 650 feet, the flex in the PVC bodies is between 5/100 and 8/100 of an inch.