View Full Version : U-74 trip report.
Been planning this trip now for 3 months, conditions now seemed favourable but perhaps not perfect. The weather somewhat overcast with the odd glimmer of sunshine, the sea is rolling but we are on our way nonetheless.
3.5 miles out of Dunbar harbour we catch our first glimpse of a buoy on the now rolling sea.
Onboard ‘The North Star’ business is run by father & son team, Jim and Iain Easingwood who now located the wreck of the UE74 submarine with the aid of a sounder & years of seagoing experience.
A new shot line is dropped on to the wreck from the North Star with 4 buoys attached for our dive.
Once kitted up, we await the return of the first wave of divers, bad reports suggest the visibility is 1 meter or less, not what I wanted to hear but I hadn’t come this far to bail without having a splash at it.
Inching forward towards the motorized ramp & into the North Sea fully equipped with twin 10’s pumped to 250 bar & a side slung 7 liter with a 60% nitrox mix, I took my first full stride & splashed.
The water was cold, some 6-7 degrees, which was soon forgotten as the task ahead unfolded, descending the shot line.
First stop at 5 meters for a standard bubble check, all’s well the rest of the descent went without a hitch lasting 4 minutes before the seabed came in to view.
Only 4 meters away lay the U74, easily found following the rest of the shot line, which had bent in the slight currant away from the wreck.
The visibility seemed to be better than the previous divers had experienced, around 3-4 meters & looking good.
We hit the starboard side first, slightly forward of the conning tower, travelling along to the bow & returning over the deck area exposed us to the now moving currant.
I missed the opportunity to film the torpedo or cylinder, which lies off the port side due to my own now forgetfulness.
I film the bow section, along the deck & on to the conning tower.
I remember the sight glasses from previous research & easily or perhaps accidentally find them on the conning tower being somewhat inspected by a large shrimp.
The deck gun is behind the conning tower, standing tall from the deteriorating deck pointing towards the erect periscope.
Time is close to 17 minutes with a planned 19 minutes bottom time we head back to the shot line.
We find it easily, but there are now 2 shot lines, we are 4 divers in 2 pairs of buddies.
I remember chuckling to myself as the other 2 divers ascend the wrong shot line, no harm done, as we know both make it to the surface, or so I assume.
On the shot line, I notice my back gas is very low, I had monitored it through the dive but now it has taken a rather drastic dip in the less than favourable direction.
I double check both gauges to make sure my manifold is open, both read the same, this is bad news as they are now reading 70 bar & I have 15 minutes of deco ahead, not counting the accumulative deco I will face on the way up.
I now notice my Air2 is leaking air from my back gas out in to the North Sea & continued to do so for the remainder of the dive, I suspect it did this all through the dive going by the rate in which my air dropped but I hadn’t noticed this.
I have to make it to 15 meters so I can change to my deco gas, im in a hurry up the line, slightly more than usual, my buddy seems less than impressed when im hovering 1 meter above the intended first stop & indicates I should descend slightly.
I haven’t informed him of my unfolding problem, as I have no need to burden him with the stress, I have calculated roughly that I will make it on the air I have left.
Upon reaching 15 meters, I switch to my 60% mix & breathe a sigh of relief.
I now have 33 bar left in my back gas on my air integrated computer.
We reach our 6 meter stop only to discover we had chose the wrong shot line, at 6 meters our line had stopped short of the surface.
I signal for my buddy to bag up, as I have my camera & low on air, I think it will be easier for him than myself.
He inflates the bag but while doing so descends the line with our now accumulative weight on it.
The top buoy is no more than a 2-litre fender & not near buoyant enough to support us both.
He moves off the shot line only to disappear within a few seconds into the gloomy green water now being spurned on by the currant.
I remain on the line at 6 meters to complete my decompression, a further 3 minutes elapse before im all clear to ascend the last 6 meters & only 2 minutes from the surface.
I have a feud with my video camera & stage bottle during this time while attempting to locate my DSMB, tucked neatly under my deco gas & now in an almost unreachable position.
I have chosen the wrong DSMB; my orange one is located on my other side in a mirror image position, less the stage bottle & camera.
I have inadvertently tangled my camera, reel line & my decompression regulator together. My head is now twisted to the right in a bid to keep hold of my reg.
I choose to free ascend the remainder with a watchful eye on the boat position; I inch closer to the surface before committing to breaking it.
I surface to some welcome glorious sunshine beating down upon me, I see my buddy’s DSMB some 150 meters away, cast by the current, he has 1 minute of decompression left to do.
The North Star swings in to position where im picked up by the motorised ramp, I board before we pick up my buddy.
The boat ride back in is slightly bumpier than the way out, perhaps it was more noticeable as I was drinking coffee & eating some home made cake, both supplied courtesy of Marine Quest.
All in all a great day out, some good diving, a good boat team & above all with a great bunch of guys.
It has been worth waiting for.
10/10
sounds good, but eventful!! Glad you enjoyed it Stewart!!
45 meters depth.
19 minutes bottom time.
first stop, 24 meters for 2 minutes.
second stop, 18 meters for 4 minutes.
third stop,15 meters for 1 minute.
gas switch at 15 meters to 60%, ppo2 is 1.6.
fourth stop, 12 meters for 5 minutes.
fifth stop, 6 meters for 10 minutes.
2 minutes to surface from 6 meters.
total run time, 43 minutes.
Great stuff, stew! :D
Sounds like a memorable dive.
alexmaclennan
25-03-07, 23:55
Sounds very exciting. Glad you're all back safe :) .
alex
i also had a great day out stew, cheers for the dive buddy;)
i also had a great day out stew, cheers for the dive buddy;)
wehey hey!!
Chris has arrived at last.
now go introduce yourself in 'Jimmys pub'. :)
great dive matey... more to come. ;)
alexmaclennan
26-03-07, 09:50
Stewart, I assume you used some form of dive planning software for that dive profile. It seems pretty complex to work out in your head. Which did you use? Why choose that one?
alex
One i have used previously is the Gap Planner, punch the figures in and it tells you the rest. Good bit of kit but haven't invested in my own copy yet.
Stewart, I assume you used some form of dive planning software for that dive profile. It seems pretty complex to work out in your head. Which did you use? Why choose that one?
alex
i used Gap planning software.
its very expensive & like Mogwai i have not invested in a copy... yet (perhaps)!
if im diving <40m i use decocheck as its free usage to 40m & capable of mixed gas. £50 to buy an activation code.
>40m i need something else, Gap fills the Gap, pardon the pun.
£120+ depending on what version your after, there are loads.
i find it very user friendly & i like the way it lays out the slate run times & stops.
ohh, did i mention you can have a free 2 week trial of gap software where you can choose any mixtures & any depth?
a PDF printer could come in very handy for anyone exporting GAP files ;)
using the 60% mix, knocked 12 minutes of my deco time. the water was 6-7 degrees so this helped me to get out quicker.
if i had used my computer i could have left the water 2 minutes earlier than 43 minutes.
Yup, thought it looked like a GAP profile, have ran that profile a couple of times and have printed it off. Need to get myself twins etc first before really looking at investing in GAP but that is a way off :)
i used Gap planning software.
its very expensive & like Mogwai i have not invested in a copy... yet (perhaps)!
if im diving <40m i use decocheck as its free usage to 40m & capable of mixed gas. £50 to buy an activation code.
>40m i need something else, Gap fills the Gap, pardon the pun.
£120+ depending on what version your after, there are loads.
i find it very user friendly & i like the way it lays out the slate run times & stops.
ohh, did i mention you can have a free 2 week trial of gap software where you can choose any mixtures & any depth?
a PDF printer could come in very handy for anyone exporting GAP files ;)
using the 60% mix, knocked 12 minutes of my deco time. the water was 6-7 degrees so this helped me to get out quicker.
if i had used my computer i could have left the water 2 minutes earlier than 43 minutes.
If you only get a 2 week trial, did that mean that you printed off every dive profile permutation that you could think of during that time? :eek:
I presume it's not one of the free trials that you can dupe by resetting your PC's clock? :o
Q.If you only get a 2 week trial, did that mean that you printed off every dive profile permutation that you could think of during that time?
A. now would i do a thing like that?
if i were that clever, i would have got the trimix tables also ;)
Q.I presume it's not one of the free trials that you can dupe by resetting your PC's clock?
A. not a chance, you would have to align the moon & stars to the exact time of the next lunar landing, based on the radius curve of my coffee mug & even then its not garunteed.
each activation code is specific to your computer, you cant dupe this.....
but if you can, i know a guy who may be interested.
Lizardland
27-03-07, 02:07
Well done, Stewart. Sounds like a good dive, a bit of excitement at the end is always good :)
Gutted I missed it.
Cheers,
Stuart
Gutted I missed it.
something about throwing a teddy if memory serves me well :)
Stewart, regarding duping the code, I would not recommend this, however I am pretty sure it is doable. There are plenty of keygen and keymaker programmes out there for software with a hell of a lot more security than something like this.
If you were that way inclined I would do a few googles, either that or get on a geek forum and ask a pasty faced individual to help write one for you. They love that shit!
Lizardland
27-03-07, 10:54
something about throwing a teddy if memory serves me well :)
Oh it's long gone :)
Though my weekend made up for it, as long as I don't think too much about paying £3.50 a pint!
Cheers,
Stuart
Deep Seeker
27-03-07, 12:12
I use the free version of GAP software. Version 1.2.2 . In terms of comparison to my old Aladin Air L and my Sunnto Vytec it's at least as conservative and I can adjust various settings to make it more or less conservative. It allows any mixed gas you wish to throw at it although I imagine however that it is not quite as user friendly as the latest versions. You also need to correct it with a patch to make it 'Build 310' but this looks to be available from the download page anyway.
I personally think the software is excellent and would find it difficult to justify paying the cost for the latest version unless there was a safety issue. But given I never rely on just one deco planner and so far GAP has been pretty conservative I don't see any problems with it. It isn't supported by GAP any longer even though it is avaialble on their website but at the end of the day it's not like diving with long deco (or any diving...!) doesn't come with inherent risks in any case!
Cheers
Nick
IanStevenson
27-03-07, 17:42
45 meters depth.
19 minutes bottom time.
first stop, 24 meters for 2 minutes.
second stop, 18 meters for 4 minutes.
third stop,15 meters for 1 minute.
gas switch at 15 meters to 60%, ppo2 is 1.6.
fourth stop, 12 meters for 5 minutes.
fifth stop, 6 meters for 10 minutes.
2 minutes to surface from 6 meters.
total run time, 43 minutes.
I'm going to ask a really stupid question now, but help me out please :)
I learned to dive on PADI tables then converted to BSAC. I mostly dive on my computer (Suunto Gekko) but plan on PADI tables if needed - air/nitrox as appropriate. I recently got some BSAC 88 tables just to have them around really. I dive a single cylinder and only plan no-stop dives at present, although I am qualified to 40m.
It looks to me like you could plan this dive on BSAC 88 tables (on air!) with only 2 minutes of stops at 6m.
Sooo..... now for the stupid question......
Why are you planning dive with 21 minutes of deco (thats accelerated on 60% for most of it too!) when the tables say you can do it with 2 mins at 6m... **** THERE IS AN ERROR IN THIS CALCULATION - READ THE REST OF THE THREAD TO FIND OUT MORE ***
Are the BSAC tables just considered hopeless by modern standards? Or hopeless beyond the no stop time? Or are you just being very conservative?
What sort of course do you go on to find out the stuff that makes you dump the 88 tables?
I have no plans to dive to 45m on a single cylinder with no redundancy, or until I have a lot more training and experience, or possibly ever, because what I really like is looking at fish in the shallows. I'm just asking out of curiosity!
Ian
Just got round to reading this Stewart. Great report! I was on the edge of my seat!
It looks to me like you could plan this dive on BSAC 88 tables (on air!) with only 2 minutes of stops at 6m.
Sooo..... now for the stupid question......
Why are you planning dive with 21 minutes of deco (thats accelerated on 60% for most of it too!) when the tables say you can do it with 2 mins at 6m...
Ian,
Buhlmann tables say 15 minutes of stops with an 18 minute BT.
Buhlmann tables say 21 minutes of stops with a 21 minute BT.
US Navy tables say 9 minutes of stops with a 20 minute BT.
with these figures it would take just over 2 hours to remove the N2 from your body.
using 60% removes the N2 at a far greater rate by replacing it with O2.
if i were doing a 2nd dive i could cut the surface interval down to just over 1 hour.
it also makes the dive a lot safer giving the fact most tables are only a guideline, they dont take into account how much personal stress you endure or how hard you have been working, thus elevating N2 or even Co2 without knowing it.
the US navy tables are designed more for the 'elite' fitness group
the navy also have the appropriate top side cover to deal with situations which may arise. this is why they have such a short deco penalty.
i dont have a copy of the BSAC 88 tables at hand, but i would be more than worried if they suggested a 2 minute stop was safe.
Hi,
just had a quick look into the BSAC tables.
For a dive to 45m with 19min bottomtime I get:
19min @ 45m
3min ascent to 9m (first stop)
gives 22min dive time (look at the definitions at the first page of the tables!)
22min dive time and 45m gives 1min @ 9m and 3min@6m (4min deco) :eek:
Could be totaly wrong tho....
DECO2000 (anyone else knows them? ;))
1min@12m, 3min@9m, 6min@6m and 13min@3m (23min deco)
But I am only an Oceandiver.....
Lars
WTF are these BSAC tables. I just ran a simulation on my vyper out of interest: with the following results(based on air only):
45m for 19 minutes gave a deco time of 26 mins with a ceiling of 8m,
moved up to 24m, was then at 29mins ceilin 8.5m
at 18m 30mins ceiling 8.3m
at 15m decompression time was up to 31mins with a ceiling of 7.4
at 12m 31mins and 6.7
then 6.0m for 29mins
Continuing to let it run between 6m and 3m and I couldnt surface until 65mins elapsed
Bearing in mind that the vyper does not allow for deep stops or for gas switching, I would say that the tables Ian looked at are either dangerous or have been read wrong. And that deep stops have now been proved to be effective, as well as switching to higher mix of o2 speeds up decompression time as well as allowing a safety margin. I am with Stewart on this one!!
IanStevenson
27-03-07, 23:57
I'm quite happy to believe that I read the tables wrong especially since I don't use them often. I have however re-read the instructions that come with them and I can't figure out what I did wrong.... I agree with lars that I didn't account for travel times which would be a serious error if planning the dive so actually I agree with his result of 1min at 9m and 3mins at 6m.
If someone can help us figure out what we're doing wrong with the BSAC 88 tables that would be great... They seem to agree OK with my PADI tables for no-stop diving - they are a little more generous with bottom times but the discrepancy is measured in minutes.... They are fairly in line with my Gekko for no stop dive times too.
I should ass I have no experience of diving to or planning dives to this depth - I was just interested in why the tables that just popped through my letterbox gave a different picture to you guys....
So can anyone help figure out where Lars and I are going wrong with BSAC 88 tables?
Ian
There is free software available on the net that will let you run various dive times and mixes. All you have to do is run a search for them. This may give you a bit more insight into what is going on and possibly point you towards the correct answer.
IanStevenson
28-03-07, 09:37
Cheers for that Mogwai, but I don't really need to be able to plan such dives, I was just interested in the discrepancy between the official tables I paid for and have trained for and what people were using in practice. I kind of assumed that the printed tables would be reasonable - BSAC don't seem to be killing divers left right and center after all. This may be because no-ones using them to plan this sort of dive though, which was kind of the question. Seems I'm not the only one either - I think my working may be in the right ballpark because someone has posted similar concerns here
http://www.bsacforum.co.uk/forums/showthread.php?t=151
(Gord - hope a cross-forum post is OK here - I know they are usually bad manners but I can't find a better non-forum source to post)
It shows plans for the same dive on BSAC 88 tables and various deco software packages. Again BSAC88 gives a little bit of deco, but the software solutions have in water times which are twice as long.
Seems that the '88 tables are being questioned by some folks...
NOTE THIS POST IS FROM A POSITION OF IGNORANCE - PLAN YOUR DIVES WITHIN YOUR OWN KNOWLEDGE AND TRAINING AND DON'T USE ANYTHING I SAY!!!
Lizardland
28-03-07, 11:35
BSAC 88 tables have always been a bit liberal. The model they were based on was never released so no-one could check how they worked (unlike Buhlmann, VPM, RGBM, etc) and the RNPL table predecessors were horrendously unreliable. I wouldn't touch them with a barge pole and I don't know anyone who uses them for deco diving.
Even straight Buhlmann with no safety margin still wants 10min of deco. I'd be a bit concerned doing that dive on air with the deco from the BSAC88 tables.
Cheers,
Stuart
IanStevenson
28-03-07, 19:04
BSAC 88 tables have always been a bit liberal. The model they were based on was never released so no-one could check how they worked (unlike Buhlmann, VPM, RGBM, etc) and the RNPL table predecessors were horrendously unreliable. I wouldn't touch them with a barge pole and I don't know anyone who uses them for deco diving.
Even straight Buhlmann with no safety margin still wants 10min of deco. I'd be a bit concerned doing that dive on air with the deco from the BSAC88 tables.
Cheers,
Stuart
Hmmmm - I'm regretting buying them now! I only bought them because my PADI tables don't show any deco on them so I wanted them for planning a slate as a backup to my computer on dives that could concievably go into deco if things went a bit wrong. Sounds like they're not a very good though!
Ian
Lizardland
29-03-07, 00:49
Hmmmm - I'm regretting buying them now! I only bought them because my PADI tables don't show any deco on them so I wanted them for planning a slate as a backup to my computer on dives that could concievably go into deco if things went a bit wrong. Sounds like they're not a very good though!
Ian
At the risk of offending a lot of people, BSAC88 aren't worth the paper they are printed on. They are so out of date they need to be confined to a museum.
If you want emergency deco tables then get a set of Buhlmann tables which are very reliable (IANTD sell them on a plastic sheet for taking underwater). You should be able to download a set of Buhlmann tables from the internet for free. They are well tested (most European CMAS divers learn on them) and reliable for short deco times.
There are also plenty of deco programs out there that take the hassle out of dive planning too.
Not that I'm plugging it: www.lizardland.co.uk has my deco software on it :D It's free.
Something else to bear in mind is ratio deco too. Do a search on the internet for it. It's basically a set of simple rules that you can use for working out deco in your head. It works on the basis that there is a relationship between time spent on the bottom and time spent on deco. For example, I know that for every two minutes I spend at 36m then I need to do 1min of deco at 6m because there is an approximate 2:1 ratio between bottom time and deco (NB, that's for the gases that I use with my rebreather, with air it will be different). Similarly, I know that at 48m it changes to a 1:1 ratio i.e. every minute of bottom time is 1min of deco. It's a really good way of working out deco for things you haven't planned for.
Cheers,
Stuart
alexmaclennan
29-03-07, 08:44
Not that I'm plugging it: www.lizardland.co.uk has my deco software on it :D It's free.
Other good stuff also on Lizardland website including very pointed opinions about kit setup.
alex
[QUOTE=IanStevenson;6644]Cheers for that Mogwai, but I don't really need to be able to plan such dives, I was just interested in the discrepancy between the official tables I paid for and have trained for and what people were using in practice.
Yeah, didn't expect you to use them to plan dives, just thought they might help to illustrate the point you were making. Would not expect anyone to do this type of diving without the appropriate training. Is interesting stuff though :)
very interesting dive report stewart my ambition to dive a u-boat just got stronger i,m still in the 30m range thou. :rolleyes:
very interesting dive report stewart my ambition to dive a u-boat just got stronger i,m still in the 30m range thou. :rolleyes:
if i remember correctly, it was you who spurned me towards this in the first place.
thanks :)
I realy enjoyed the Sub dive Stewart, bloody cold tho'. I ran the GAP profile using 60% on the dive, and the stops do seem conservative compared with say the Buhlmann tables etc.
What I would say is that I am far more comfortable decompression diving on what seems to be conservative run times than trying to get out the water too quickly, even though I do like my beer.. After breathing high O2 content mixes I also feel a lot better after the dive as well..
Interesting discussions guys..
Regards
Jim
Hi,
just had a quick look into the BSAC tables.
For a dive to 45m with 19min bottomtime I get:
19min @ 45m
3min ascent to 9m (first stop)
gives 22min dive time (look at the definitions at the first page of the tables!)
22min dive time and 45m gives 1min @ 9m and 3min@6m (4min deco) :eek:
Could be totaly wrong tho....
Lars
Dunno about *totally* wrong... I've not got the tables to hand and it's too late to go dig them out(!)
But.. from memory your "bottom time" *is* your dive time, therefore your 19 minutes is from starting your descent to arriving at the first stop, which of course makes the tables a lot less aggressive than they first seem.
Having said that, BSAC 88's are commonly agreed to give very little deco penalty on first dives, I would normally use something like GAP for a dive to this depth, or do it on computer and add a few safety stops ;)
Like I say, it's late and I should be asleep, remind me on Sunday to check if I'm correct! :D
Cheers,
Smudge
Hi,
just had a quick look into the BSAC tables.
For a dive to 45m with 19min bottomtime I get:
19min @ 45m
3min ascent to 9m (first stop)
gives 22min dive time (look at the definitions at the first page of the tables!)
22min dive time and 45m gives 1min @ 9m and 3min@6m (4min deco) :eek:
Could be totaly wrong tho....
DECO2000 (anyone else knows them? ;))
1min@12m, 3min@9m, 6min@6m and 13min@3m (23min deco)
But I am only an Oceandiver.....
Lars
Ok, having had a quick shufti at the tables to remind myself!
45m with a 19min *dive time*,
Your max descent rate is 30m/min, so as always with BSAC tables rounding up you allow 2 minutes to get down there from the surface.
To ascend the 29 metres to your stop, at your maximum rate of 15m/min will take another three minutes, so your actual *maximum* bottom time is now 14 minutes.
But can you do a 15m/min ascent? Do you know the ascent rate of your computer? If you are going to use BSAC tables this way then you need to find out! Most people who would use the tables would add a minute for extra safety and call it three minutes.
Equally, the maximum bottom time we talked about is just that, a maximum, so most people would plan on leaving the bottom a minute before the maximum. Hey presto you now have a bottom time of twelve minutes... and the tables stop looking *quite* as aggressive ;)
And of course you can write on your slate, "leave bottom @ 14 min OR at XX Bar" doesn't matter then how narked you are, how confusing the deco info is on your computer, you know if you can read a run time and an SPG then you can get out on time...
That's not to say I would reccomend doing this type of diving on BSAC tables, personally I wouldn't, but if I had kit failures which left me BSAC 88's or no dive, I could.
The profile above would imho work, I would add a 1@9 stop and add another one or two minutes at 6, because I'm not 19 and superfit anymore (stop laughing at the back :p ) and I'd probably swap onto a 50% mix in a pony at the first stop.. but then you have to remember the tables were written when people saw sex as safe and diving as dangerous, it was broadly accepted that pushing the limits of the tables was asking for trouble... hence it was also expected that divers would add their own extra safety margin...
Don't write them off just yet, BSAC 88's have seen an awful lot of safe dives, it just depends how you use them!!
re:the origional blog.
had a problem with my manifold immediatly after the sub dive, finally got it stripped down this week (professionally) & inspected.
there was a problem with the open & close valve seat restricting airflow which even had MDE scratching their heads.
i still dont fully understand the problem myself, however.
this has since been replaced & i tested them today, good as new :)
i noticed the problem when i went to get them filled, i couldnt fill them as they were already full????
yup, exactly my thoughts too.
so it looks like i did the sub on a single 10 litre cylinder as one of them would not fill as it was already full :eek: