S.P.E.C. Boot and the MK 20

[lexvil]

So I bought 3 spec boots, NOS scubapro when they were mentioned in another thread, got them today. One I’m going to send to James79 so he can see about fabrication of new ones, one I just put on a mk20 UL, hand packed with silicone

Now if the weather cooperates I may get a chance to test it soon, a back up to the MK11T if I ever get to travel to warm water.

 

[p_kos]

That’s a great looking reg and I would guess possibly the only MK20 UL with a SPEC boot on it in existence right now.

 

[BoltSnap]

Very interesting. Report back after trying it in ocean please

 

[race890]

So I bought 3 spec boots, NOS scubapro when they were mentioned in another thread, got them today. One I’m going to send to James79 so he can see about fabrication of new ones, one I just put on a mk20 UL, hand packed with silicone
View attachment 644597 View attachment 644598 View attachment 644599

Now if the weather cooperates I may get a chance to test it soon, a back up to the MK11T if I ever get to travel to warm water.

Hi, did you or James79 manage to fabricate a SPEC boot design. I also have an UL Mk20; which I would like to put a boot on....(.but I am in Australia). Maybe some seal sealing silicone tape can be wound around to form a "boot"?
Also do you know the exact difference between servicing of the UL vs a std Mk20? I think it is just a couple of torque values when re-assembling.
Do you have a Mk20 UL service manual?

 

[lexvil]

Hi, did you or James79 manage to fabricate a SPEC boot design. I also have an UL Mk20; which I would like to put a boot on....(.but I am in Australia). Maybe some seal sealing silicone tape can be wound around to form a "boot"?
Also do you know the exact difference between servicing of the UL vs a std Mk20? I think it is just a couple of torque values when re-assembling.
Do you have a Mk20 UL service manual?

You’ll have to contact James to find the status of the boots, sorry but I don’t seem to have the service manual for the UL.

 

[Eric Sedletzky]

I'm just curious if enough pressure can be transferred through a thick boot covering the holes to increase pressure sufficiently to the innards?
At some point it would almost seem like it would become a rigid covering that wouldn't allow pressure to transfer enough to be depth compensating.

 

[lexvil]

I'm just curious if enough pressure can be transferred through a thick boot covering the holes to increase pressure sufficiently to the innards?
At some point it would almost seem like it would become a rigid covering that wouldn't allow pressure to transfer enough to be depth compensating.

Not sure what you mean but the grease transmits the pressure and the boot retains the grease. I was using the factory boot on the UL and James was attempting to duplicate the discontinued boot and we were trying to adapt it to a MK 25, result on the 25 was inconclusive for me, I sent the 25 to Johndiver in FL to continue testing, don’t know the conclusions.

 

[Eric Sedletzky]

What I mean is if the boot is too rigid like too hard of a plastic etc. if it would become too rigid to bend and flex enough under pressure that it would diminish the pressure transfer. I don't know how much pressure it takes to achieve a proper depth compensation or how much stuff has to move. Has anybody ever done a comprehensive test to see how or if this stuff works? I recall seeing a metal SPEC boot once that was OEM Scubapro on a set of MK5's and I thought to myself that it didn't look like it would work very well. These were big thick collars that were an add on at the time.

 

[lexvil]

I vaguely recall those early spec boots and can’t say for sure how they worked but the later ones have flex so that they expand when the reg is pressurized, the concept lives on in the Atomic sealed firsts.

 

[rsingler]

Yes, the roof has to be quite flexible to allow adequate exchange on pressurization. Breath to breath, not so much. Current lubes are much lighter in consistency, and will be lost over time and replaced with seawater if that volume reservoir isn't there.
In contrast, the big metal Mk5 SPEC was essentially a pathway outside the sensitive inner ambient chamber. Some silicone would be squeezed out the SPEC holes on first pressurizaton, but after that all the exchange of sea water and tenacious silicone took place inside the boot.
Modern boots have no holes, so the flexibility and volume must accommodate the net volume change when the piston head first moves.