"New To Me" Gavin DPV rigging questions

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OrcasC205

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I had planned on waiting until after I finish Tech 1 to start looking at DPVs, but a friend just gave me his old Gavin DPV when he was cleaning out his garage. It has newer SLA batteries and the original brushed motor and everything appears to work. I took it down to the ship canal today to test buoyancy and trim and, in fresh water, it took 5 lbs of lead to get it to be just barely positive (which I understand is the goal at the surface since the body o-rings will compress slightly at depth.) I figure I'll use it until I figure out what I really need in a DPV -- heck, it was free anyway.

My question now is how to do the rigging for the tow cord and the tow leash (for stowing it during the dive or if it breaks down.) I want to have the tow cord length be adjustable when I am starting out so I can find the right length. I'm comfortable tying a taught-line hitch to make the length adjustable, but I'm not sure where on the Gavin to attach the tow cord. There are cutouts in the struts that I could loop the tow cord through and route them around the outside of the shroud. Or I can loop it around the handles with the fixed side on the trigger side and the adjustable loop on the non-trigger (left) side, but in that case the large, adjustable loop could come off the handle.

For the tow leash, I've seen it recommend to attach it under the hose clamp used to attach the front handle, but I am concerned with the PVC body that having a line under the hose clamp will cause the PVC to distort when it is tightened down which might cause the nose o-ring to not seal. Am I being overly paranoid?

Thanks for any help or photos of how you've got your vintage DPVs rigged.
 

Ouvea

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The primary tow cord that attaches to your crotch D-ring should allow for a comfortable arm extension. This permits you to be horizontal/in trim and still be pulled by the crotch D-Ring. You do not want the DPV to tow you by the arm (tow cord too long). This will tire your arm/should very quickly and doesn't permit you to maneuver the DPV efficiently. Inversely, you don't want to tow cord too short as you'll be scootering around at a 30-40 degree angle creating drag and you'll most likely feel the prop wash across your body.

In regard to the tow leash. It should be long enough to to allow your DPV's nose to sit very close to the butt of your tank. You should clock the attachment point so that when you release the DPV, the tow leash is at the 6 o'clock position. When correctly setup, the DPV sits in-line, behind your tanks horizontally.

Regarding the hose clamp pressure. My buddy used a Gavin for a very long time, prior to switching to the current XJS. He never had any issues with the DPV and never flooded the DPV. I have seen a flood due to dislodged o-ring and a failed high speed shaft seal. I dont think I've seen one occured due to distorting the actual DPV body.
 

rjack321

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Which model do you have?

You will want to make it just barely positive in salt water too, Typically you'll have a small chunk of lead or pouch you add along the batteries close to the center of gravity for salt and remove for fresh. Make sure your lead and batteries are clocked correctly, the scooter handles should lay at 3 and 9 o'clock at rest and once turned on the prop torque should rotate the body so the right hand handle is at 12 o'clock.

You don't really need a tow leash at the nose (unless you actually want to tow it a lot). You do need a piece of stiff 2" webbing with a loop in it that you can slide your hand through as a temporary storage hold. And a long enough tow cord that you can slip it through that webbing and more permanent stowage. There is nothing wrong with the paracord under the hose clamp to a bolt snap though. If you burn a small hole in the 2" webbing you can attach the tow clip there so it doesnt flop around. You won't deform the PVC tube or cause leaks.

Towcord wise, using a tautline hitch is rather more modern than tying into the handles. One alternative used back in the day was to tie the cord long with a girth hitch at each end. Then loop the excess around one of the handles until the length was correct.
 
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OrcasC205

OrcasC205

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Which model do you have?

I have the short tube with one battery set (2xUB12180), but my friend also gave me a long tube with the bulkheads to build a double battery set (4xUB12180) if I want -- just need to add latches to that tube.

You will want to make it just barely positive in salt water too, Typically you'll have a small chunk of lead or pouch you add along the batteries close to the center of gravity for salt and remove for fresh. Make sure your lead and batteries are clocked correctly, the scooter handles should lay at 3 and 9 o'clock at rest and once turned on the prop torque should rotate the body so the right hand handle is at 12 o'clock.

When you say "clocked correctly", should I have the battery installed so that it is upright when the scooter is at rest, or when it is underway and the torque has rotated the right handle up? And should I have the lead underneath the battery so that it helps counteract the torque (like the lead in a sailboat keel?)

You don't really need a tow leash at the nose (unless you actually want to tow it a lot). You do need a piece of stiff 2" webbing with a loop in it that you can slide your hand through as a temporary storage hold. And a long enough tow cord that you can slip it through that webbing and more permanent stowage. There is nothing wrong with the paracord under the hose clamp to a bolt snap though. If you burn a small hole in the 2" webbing you can attach the tow clip there so it doesnt flop around. You won't deform the PVC tube or cause leaks.

I've got the stiff 2" webbing which is held in place with a stainless hose clamp. I went ahead and made a tow leash out of paracord and mounted it under the hose clamp and put a bungee loop to clip the tow leash off to.

Towcord wise, using a tautline hitch is rather more modern than tying into the handles. One alternative used back in the day was to tie the cord long with a girth hitch at each end. Then loop the excess around one of the handles until the length was correct.

I think I'll give the girth hitches a try for now -- that was how the towline was attached when I got the scooter.

Thanks for your help!
 

rjack321

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When you say "clocked correctly", should I have the battery installed so that it is upright when the scooter is at rest, or when it is underway and the torque has rotated the right handle up? And should I have the lead underneath the battery so that it helps counteract the torque (like the lead in a sailboat keel?)


I think I'll give the girth hitches a try for now -- that was how the towline was attached when I got the scooter.
Clocking refers to how the weight is offset (very slightly) in the tube. It's normally assisted by having the extra lead to get it neutral stuck onto the underside / bottom side (facing down in the ocean) of the batteries. You can mount the batteries in any orientation, terminals up, down, or sideways - that doesnt have anything to do with how the scooter will want to sit naturally in the ocean.

You want the body to sit right side up, handles at 3 and 9 o'clock when at rest. When you pull the trigger you want enough of that overall battery and lead weight to be shifted downwards in the tube so that the right hand handle rotates up to the 12 o'clock position. If that weight offset is perfect, you can then basically drive it from the now 12 o'clock handle with a couple fingers. And you aren't muscling against the torque of the prop.

Ya the taut line hitch is a "modern" approach to tow length adjustment down to millimeter increments. The Gavin traditionally did the wrap thing. If you are using a short body, once it's completely unwrapped you thread the now excessively long tow cord through the front strap and tada you can tow it behind you. That won't work with any gavin body bigger than a short, since it'd require an insanely oversized tow cord just to avoid the front clip.
 
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OrcasC205

OrcasC205

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Thanks! That makes sense now. It looks like I can put the weight under the batteries shown in the photo below to keep it upright at rest.

IMG_2726.jpeg

This is how I have it rigged so far -- had to build a little cradle for it out of scrap lumber.

IMG_2728.jpeg

Looking forward to trying it out soon!
 
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OrcasC205

OrcasC205

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One more quick question... I assume a length of cave-line is useful for attaching the hitch pin clip that is used to lock out the trigger? Or is there a better way to not lose it during a dive?
 

rjack321

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One more quick question... I assume a length of cave-line is useful for attaching the hitch pin clip that is used to lock out the trigger? Or is there a better way to not lose it during a dive?
On mine (long ago) I'd put the hitch pin through the loop of towcord going around the right hand handle. You could in theory make a little leash for it but then you run the risk of it getting into your prop. Most people just put a spare pin into the tow cord up there at the right side handle. You can bend them all the way "closed" plus use a thick-ish cord. So they really don't fall off very often, you're more likely to drop it than have it fall off actually. They are cheap though. Another good place for a spare is your wetnotes.

Assuming you want to stop and drift or look at something for a few minutes you'd typically just keep the right hand on the right handle for ~1-3 min stops. For ~5-10min stops you would leave the tow cord on your crotch strap but move your right hand to the front scooter strap and just swim it along by the nose.

For 10+min stops and "stowing" it. That's when you would pin the trigger, turn down the prop pitch, clip off the towstrap to the front loop. Then push the whole scooter behind you and clip the nose to your butt Dring. Its a bit of a production so usually only full stowed when you really don't anticipate using it for awhile. That's partly why losing a trigger pin isnt really that common, it comes off at the start of the dive and doesnt get re-pinned until the end of the dive most of the time.
 

Whitrzac

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There is a standard handle/twist grip conversion available for them too
 
https://www.shearwater.com/products/teric/

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