Altitude change

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kalailyliani
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Altitude change

Post by kalailyliani » Wed Aug 03, 2016 1:28 pm

I'm diving clear lake next weekend near Sisters, OR. The surface elevation of clear lake is 3,012′. Our dives will be <60' and we are planning a 2 tank dive.

Can someone direct me to a dive table or some info to calculate how long I must wait before going up to McKenzie observatory, which is 5,325 feet?

I'm new to diving and I know not to fly right after diving, but what's the rule on local elevation changes? Like, what if I lived 2000' above the dive site? Would i technically not be able to return home? :/

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Scubie Doo
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Altitude change

Post by Scubie Doo » Wed Aug 03, 2016 3:19 pm

I've never dove at altitude. But while in Hawaii it is easy to dive and drive up to altitude without thinking. A lot of people live at elevation in Hawaii and dive. However, that doesn't mean it is "safe". You should really take a course or get some training on diving at altitude. I have over 700 dives and I would take a course, even a private course just to ensure I was doing everything correctly. I know you can research online, but elevation is not something I would ever mess with unless I was 100% sure what I was doing. Just my opinion.

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Nwbrewer
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Re: Altitude change

Post by Nwbrewer » Wed Aug 03, 2016 4:05 pm

This book covers all the theory stuff about the physiology of diving at altitude, though it's not an easy read - https://www.amazon.com/Diving-Above-Sea ... 0941332306

When I looked a few years ago there weren't many classes available for altitude diving locally, and non from any of the instructors that I trust.

After all the reading I did on the subject, and discussing it with a few instructors, for anything in the 3K feet and under range, I've just done my dives with 32% on air NDL's and padded my stops by a bunch and called it good.

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WylerBear
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Re: Altitude change

Post by WylerBear » Wed Aug 03, 2016 4:53 pm

Check the DAN website. There's got to be at least one or two articles about going to elevation after diving. Also, you know you also have to adjust your dives for the altitude as well, right? There is a table in the PADI AOW manual with adjustments. Probably in other manuals as well. And assuming you are driving there from a lower elevation, when you get to Clear Lake you may already be a G (I think, it may be H)diver without ever having submerged so you need a surface interval before diving too. It seems like the last time I dove there by the time we looked around a bit and slowly set up our gear, we had killed at least an hour and were good to go. Have a fun and safe time. I've dove there twice now and probably won't ever do it again but it is a cool dive.
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defied
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Re: Altitude change

Post by defied » Wed Aug 03, 2016 6:55 pm

Your theoretical depth will be around 65ffw. You'll be fine. Safety stop at 15ffw.

Dive like usual, go slow on ascent.

D

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kalailyliani
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Re: Altitude change

Post by kalailyliani » Thu Aug 04, 2016 9:22 am

Thank you all - I did do a bit of research yesterday and watched a few videos on dive tables and know about the additional +2 pressure grade per 1000 ft of elevation (yay! learning :) ) I am actually driving down the night before the dive so I should be ready to go for the first one. I've just never been to the area and really would like to see what I can while I'm there when someone started questioning me about DCS and what nots for a change of 2k altitude so it made me all paranoid.

I'll be sure to do the safety stops and do slow ascents. I'm sure we'll discuss it more while we're there to determine if it's a good idea or not, but I just didn't want to go in blind.

Appreciate all the help!! :)

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60south
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Re: Altitude change

Post by 60south » Thu Aug 04, 2016 9:49 am

The easiest way is often to plan your dive as if you're doing it at the maximum elevation. That way you don't have to worry about surface interval times and altitude. This also adds some conservancy to the plan.

For instance, if you're diving at 3000ft but later ascending to 5300ft, just plan the dive as if you're already at 6000ft (rounded up). Do still use the 3000' safety stop depth (14ft).

http://www.divebuddy.com/calculator/altitude.aspx

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H20doctor
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Re: Altitude change

Post by H20doctor » Thu Aug 04, 2016 2:21 pm

The best way to learn about altitude diving is to take the class and get your altitude cert card...
That way you have the training you've taken the class and you know how to program your dive computer
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Norris
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Re: Altitude change

Post by Norris » Thu Aug 04, 2016 3:53 pm

Or ask divers about it like you have, and research what is out there. Either way will likely work.
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Furnari
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Re: Altitude change

Post by Furnari » Thu Aug 04, 2016 8:46 pm

I've done several dives at Clear Lake; as I recall it barely meets the criteria for an altitude dive (I could be wrong , however). While everyone is different, taking it easy on the dive, using a generous safety stop, breathing nitrox, and other conservative measures make sense. If you take your time breaking down your gear and packing your vehicle after staying the night, you should be fine ascending a couple thousand feet to do some sight seeing. The more time you give yourself, the better off you'll be. Maybe plan on having lunch before leaving? Also, avoid strenuous hikes around the observatory.

Are you staying in the cabins? IMO, the best diving is located out and to the left (east) of the cabins as that's where a lot of trees are within recreational depths. The rangers are generally assholes to divers and will direct you to the gazebo area west of the lodge (they won't even let you park in the main parking lot- true story). From there, you'll have a fairly lengthy swim to see the a decent number of trees. They tend to give you more leeway if you stay in the cabins; if so, find an entry along the path in front of them (as far east as possible).

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kalailyliani
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Re: Altitude change

Post by kalailyliani » Thu Aug 04, 2016 9:42 pm

No cabins... They were all booked. I'll make a note to go east of the cabins for the good stuff! Thank you :)! There will be a group of at least 8 of us diving. I can't wait! I bought a computer today and can't wait to use it :joshsmith:

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selkie
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Re: Altitude change

Post by selkie » Fri Aug 05, 2016 7:40 am

Belknap Hot springs resort is just down the road from Clear Lake. http://www.belknaphotsprings.com/
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kalailyliani
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Re: Altitude change

Post by kalailyliani » Fri Aug 05, 2016 9:42 am

we're just gonna camp in the middle of the woods... somewhere... out there.

Should be able to see the perseid meteor shower too :partydance:

i wish it was next weekend already!

Steiger
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Re: Altitude change

Post by Steiger » Fri Aug 05, 2016 9:10 pm

A lot of dive computers have an altitude function, check to see if you can set it for your current elevation.

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lamont
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Re: Altitude change

Post by lamont » Wed Aug 10, 2016 7:26 pm

Steiger wrote:A lot of dive computers have an altitude function, check to see if you can set it for your current elevation.


I'd agree with the suggestion made by 60south to plan and execute it like it was at 5,325ft instead of 3,012ft

Realistically that shouldn't matter much since you'll essentially be doing a "deco stop" of at least an hour or two between the time that you surface from the last dive to the time when you finally arrive at 5,325 ft -- and that elevation change is only 2.45 fsw of pressure change.

Although you want to keep in mind that at around 6,378 ft things will likely get a little bit riskier since if you ascend from sea level to that altitude you'll basically be starting out your day surfacing from a hugely long saturation 'dive' at sea level and could be pushing an overpressurization gradient in all your long compartments (pressure at that altitude is equivalent to 0.79 ATA) in addition to whatever you pick up on the dive.

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kalailyliani
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Re: Altitude change

Post by kalailyliani » Thu Aug 11, 2016 2:50 pm

Thanks everyone! i'm excited for this weekend.
The dive computer will indeed commodate the change in elevation and i'll talk to the DM about the dive plan tomorrow.

This newbie diver appreciates all the help!

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