What's your SurfGF and how does it compare to your (Rec) GFHi?

[dmaziuk]

Question:
Would someone surfacing, say, with GF95 after a NDL dive be as aggressive as someone surfacing with GF95 after 2 hours of decompression?

One would think that the latter has some slow compartments heavily loaded, albeit below 95, compared with the former who has virtually no loading of slow compartments?

I wonder if anyone ever surfaces with GF95 after an NDL dive unless they run out of gas and have to do a CESA. I mean, deep bounce dive to the NDL would probably do it but you'd have to skip your safety stop. In my logs SurfGF can get above 90% after 20-ish minutes at 25-ish msw, but once I ascend above 10m is drops down to low 70s within 5 minutes. And that's even before the safety stop.

 

[Wibble]

I wonder if anyone ever surfaces with GF95 after an NDL dive unless they run out of gas and have to do a CESA. I mean, deep bounce dive to the NDL would probably do it but you'd have to skip your safety stop. In my logs SurfGF can get above 90% after 20-ish minutes at 25-ish msw, but once I ascend above 10m is drops down to low 70s within 5 minutes. And that's even before the safety stop.

Dive to 30m/100ft on air for 20mins and you’ll be in deco territory.

But you’re right in that by definition a No-Deco-Limit dive means you cannot enter deco, so as you ascend you’ll be off gassing and the SurfGF will fall.

 

[LFMarm]

I wonder if anyone ever surfaces with GF95 after an NDL dive unless they run out of gas and have to do a CESA. I mean, deep bounce dive to the NDL would probably do it but you'd have to skip your safety stop. In my logs SurfGF can get above 90% after 20-ish minutes at 25-ish msw, but once I ascend above 10m is drops down to low 70s within 5 minutes. And that's even before the safety stop.

Indeed, I don't think it's possible unless you use unsafe ascent rates.

 

[scubadada]

I have exchanged many messages with Shearwater.

Diving to the GF high does take a normal ascent into account but not a safety stop. So, if you dive right to NDL and then ascend at 30 ft/min,, you will surface very close to the GF high. A safety stop will lower your surfacing GF to below the GF high.

The SurfGF is the instantaneous transport to the surface. The ascent will lower the SurfGF, the SS will lower the Surf GF, the final ascent will lower the surfacing GF.

 

[stuartv]

To emphasize what @scubadada said.

If you stay down until a Shearwater computer says your NDL is 0, and then ascend directly to the surface (no safety stop) at exactly 30 feet per minute, when you get to the surface, your SurfGF and your GF99 will be equal to the GF Hi setting you were using.

Further, in that scenario, when you start your ascent, your SurfGF will be HIGHER than your GF Hi setting. Only slightly higher, but higher nonetheless.

Does that mean you are "in deco"? No.

 

[BlueTrin]

Question:
Would someone surfacing, say, with GF95 after a NDL dive be as aggressive as someone surfacing with GF95 after 2 hours of decompression?

One would think that the latter has some slow compartments heavily loaded, albeit below 95, compared with the former who has virtually no loading of slow compartments?

This may be interesting