DIR Diving Blog

DISCLAIMER – DO NOT FOLLOW THIS, IF YOU PLAN DECOMPRESSION DIVING YOU SHOULD BE PROPERLY TRAINED AND PLANNING YOUR OWN DIVES.

Been playing with some deco planner calculations.

30/30
Av depth 33m
Time 40mins
Comes out with 17 minutes of deco

21/35
Av depth 33m
Time 40mins
Comes out with 36 minutes of deco

While we are thinking of using 21/35 we have to bear this in mind, we will be looking at different profiles.

Add in the 50% bottle and we have

30/30
12 mins deco

21/35
21 mins deco

Well back from diving weekend in Portland which was a lot of fun. We did 4 dives over the course of the days and spent the rest of the time chatting away. We met up with Bob Cooper, And and Greg for a curry on saturday night and the same crew along with Howard on sunday night.

Appparently the original DIR videos are a must see!

Dive 1 – Countess in the harbour. Skipper was Jay on Top Gun. After a bit of stress getting fills we managed to all get sorted. Plan was to use my AL80 as a bottom stage as it had 32% in it. Not a bad dive I led the team for a good chunk of it and we dropped into the holds for some swim throughs. Was rather silty so I ended up backing us out of the hold as I couldn’t see the way through and wasn’t laying line. We carried on and finally bagged off and ascended. Clare had some grief with her inflator constanly bubbling into her wing so didn’t have a good dive.

Dive 2 – The Frognor. The trip out was on Goose which is a cool boat! We descended down the shot towards the wreck and had a bit of a drama. Clare didn’t get hold of the shot and had to fin to keep up with the descent and was knackered when we reached the bottom. We re-ordered at the bottom and I then led the dive. The wreck was quite broken up and we toured round it trying to pick out features. Lots of fish life. It was quite dark and the lights worked a treat. As team dives go it was very good. At 40 minutes we started our ascent. We hit our ascent rate quite well although it seemed a bit fast between 21-15m. We did the gas switch onto the 50% at 21m although I forgot to immediately bag off and had to be reminded by Fraser. The rest of the ascent then went very well with us arriving at the surface bang on schedule.

Dive 3 – The Ailsa Craig. Again out on Goose. We had a long trip out so I was careful not to over heat on this one. I carried the kit onto the boat before getting changed. We descended down the shot with Clare leading which was a good thing as she had a nasty sinus squeeze. We then toured round the wreck, it was quite small and we saw the boilers etc. Had a nasty moment where a loose rope got caught round my leg – as I swam over it I thought “hmm that slack line looks dangerous”! I freed myself and swam on. We ended up slightly deeper than our average depth so left 2 minutes earlier than planned. On the ascent I ran deco and it all went as planned. I padded in the extra 2 minutes around 6 and 3 and we surfaced at 60mins.

Dive 4 – Bow of the blackhawk. One of those dives where it just didn’t quite come together. There was a bit of a current and I just found myself bumping into Clare and Fraser. Didn’t really enjoy it and ended up with weird head down trim near the end of the dive which then vanished on the ascent.

Overall an excellent weekend and more valuable experience for us working as a team. We did all the planning for these dives as per our tech-1 course and I felt it was really coming together.

Ok so lets discuss gas planning

33m average depth dive

Back gas
All gas useable – ascend from wreck
Minimum gas using stage
1 min for emergency
1 min for ascent to 23m
1 min ascent 21m
1 min for gas switch onto back gas
4 x 60 x 4 = 960 litres / 24 = 40 bar.
Full 12’s but assume 220 bar fill. Less min gas we
have 180 bar.
Assume 4.3 ATA’s for 5 mins with a SAC of 20 = 430
litres /5 mins = 18 bar/5
This allows 10 segments or 50 mins bottom time maximum

Deco gas
AL80 with 200bar of 50%
Multiply by 2/3 = 133 bar available
SAC * 5 * ave ATA for deco = 15 * 1.5 * 5 = 113 litres
/5mins
133 x 11.1 = 1476 = 13 segments = max 65 mins deco

Planned this weekend (27th and 28th August) is 4 wrecks dives out of Portland using Breakwater dive center. We will be diving:

Sat
10.30 Countess
15.00 Frognor

Sun
09.00 Ailsa Craig
14.00 Blackhawk (Lulworth)

Planning to take a stage on all 4 dives but we have time for fills saturday morning (fingers crossed!).

Myself and Fraser met up and did three dives out of Swanage. Two were on Killer Prawn and the the third one was under the pier.

Dive 1 was on the Kyarra. We descended the shot with the tide still running slightly. As we reached the wreck we were greated with 6m+ visbility and we could make out the wreck and structure clearly. My previous two dives on this wreck had both been rather gloomy with the ambient light going at 20m in one case. This time the wreck really came alive with the good visibility. We set off towards the bow of the wreck aided by the current. We past through several overhanging parts of the structure with Fraser leading the way. I found a Lobster followed by the most enormous conger eel I’ve ever seen. We carried on towards the holds and in one we found a huge amount of broken crockery, bottles, buttons and even a roll of lino! We carried on and found the anchor chain and the metal tubes the chains ran through were decaying so you could see the chain both in and out of them. At this point the tide turned and we started to get pushed towards the stern. We went with the follow and at the end of our bottom time we left the bottom to start deco. Truly stunning dive.

Dive 2 and we were due to dive the Valentine tanks. The skipper Mike explained the difficulty of finding them i.e. bloody small object compared to a wreck! We dropped in and went down the shot in a howling current. It really was a case of hanging on to the line or being swept off. We near the bottom and billowing clouds of silt envelope us. It’s clear that the shot has come off the wreck and we’re just at the seabed. Fraser sets off into the current pulling his way along the bottom with his hands. I followed him struggling to keep up. After a couple of minutes we decided we aren’t going to see the tanks so we head off with the drift. It was actually a really good drift dive. I saw 4 undulating rays, couple of dogfish, lots of crabs and a variety of other life.

Dive 3 was then under the pier once the boat got back to the harbour. Not a bad dive actually although the tide had moved out so we had a bit of a hike back through the shallows.

Overall an excellent day out. Killer Prawn is a very good dive boat and the skipper Mike Marsh was excellent.