Rigging a small boat for diving

[Groundhog246]

Braunbehrens once bubbled...


Not sure about where you get this info about the Danforth, but it's true that the Danforth can "swim" if there is enough speed. This is especially true of the aluminum Danforths.

Partly personal experience. I had a steel Danforth pull out (5 to 1 scope and chain) when the wind shifted. The boat had moved about 50 feet and built up enough momentum that the anchor would not set again and we ended up ON the beach. It was a nice sand bottom, which should have been near ideal holding. That anchor went in the dumpster at the marina and I bought a Bruce the next day.

I'm also not sure that "get the next size up" is such a good idea. I used to subsribe to that idea, but now I think that you are better off using that weight in chain, rather than a larger anchor.

Most companies base their recommendations on low to moderate windspeeds. Not sure why they want to sell you a smaller anchor. If you read the fine print many suggest one size up if you're likely to experience strong winds. Personally, I've anchored in the evening with 5 knots winds and woke up at 3am with 40 knots. Certainly chain is a key part, too many with a piece of rope on an anchor with no chain.

As for the 7 to one scope, I don't think so. Sure, this is what's recommended, but I frequently anchor in over 100 ft of water. I'm not going to carry 700 ft of rode, that's just plain silly. We typically get away with a lot less, but then there is some data that the deeper your anchor the less scope you need.

7 to 1 is for max holding, aimed at heavy winds, 5 to 1 usually adequate, 3 to 1 as the earlier post suggested is IMHO foolish. Never heard of using less in deeper water. I've seen a heavy weight shackled to the joint between rope and chain used to reduce rode length, similar effect to longer chain, usually when anchoring where there's not much room to swing.

 

[speardivertampa]

Tommed,
I was in about the same situation as you. I have a 22' Grady, and everything was about the same. As far as tank racks..roll controll all the way. The adjustable ones are great because you can pop them out and change them if a buddy has those lp120 giants. I mounted 2 four tank holders on my stern gunnels. I read through the responses, and I dont think that I am repeating a thought, but we dive with 3 divers. Each diver makes 2 dives (or 4) and sits out 1 dive (or 2). This way you always have someone on the boat, and everybody gets their dives in. (we usually dive in <60ft, so we can usually do 4 dives a piece w/120's and 'trox. )
Hope this helps, that you understand my dive pattern suggestion, and trust me you will love the freedom of being able to dive from your own boat.

Good Luck,
Chris

 

[Braunbehrens]

Groundhog246 once bubbled...

I had a steel Danforth pull out (5 to 1 scope and chain) when the wind shifted.
we ended up ON the beach.

Most companies base their recommendations on low to moderate windspeeds.

I've anchored in the evening with 5 knots winds and woke up at 3am with 40 knots.

7 to 1 is for max holding, aimed at heavy winds, 5 to 1 usually adequate, 3 to 1 as the earlier post suggested is IMHO foolish.

The Bruce is the fastest setting of the two, Bruce and Danforth. If you really went a long distance and it didn't set I would suspect something was amiss. Maybe it wasn't a "real" Danforth, maybe it was fouled, and maybe it was one of those with the sliding shaft so it was being dragged backwards. In all the tests I've seen the Danforth sets pretty well. Also, the Aluminum danforth can be adjusted for sand or mud, apparently the two require very different angles for optimum ground tackle.

I'm looking at a chart for anchor sizes, and it is based on a 30 knot wind. I don't think too many people dive in those conditions... It's always good to have a good storm anchor of course, if the size of your boat warrants it.

The amount of scope, and the weight of the anchor all come back to a problem that is specific to diving...pulling the anchor back on board. If I let out 7 to one scope, add 2 boat lenghts of chain and go one size up on the anchor, then I'll have to wait at least an hour, maybe more, to pull it up after diving. Otherwise the chance of getting a bend in your shoulder is just too great. In my case, the boat is not big enough for a winch, so it's arm power.

I've used the buoy trick before, but I'm worried that this might drag the anchor along the reef on the way up, and it can't be used if there are other divers or boats around.

Speaking of weight, here is something to consider.

For a 22' boat, the chart I'm looking at says that you need a 5 pound Danforth (right on the cusp though, 12 would be safer), an 11 pound Bruce (cusp again, go to 16.5), or a 4 pound Danforth Aluminum Fortress.

For chain you'd wan to use about 20 ft, or 16 pounds. Total weight with the Bruce, 32 pounds.

I can't help but feel that with short scope, a 4 pound Aluminum and 35 feet of chain you are better off than with a 16 pound Bruce and 20 feet of chain. Same total weight!

I have no data to back this up, but I might switch to this kind of ground tackle and compare the two.

BTW, the next bigger size Fortress (Aluminum Danforth) is only 2 pounds more!! Intriguing to say the least.

 

[Groundhog246]

My danforth was a "Danforth" stee, no angle adjustments. I do carry a Fortress as a stern hook/lunch hook. The water was very clear and not all that deep. The anchor dragged about 100 feet before we went aground. The water was clear and shallow and you could see it fluttering along on the bottom.

You may not enter the water in 30 knots, heck you might not even leave port in 30 knots, but around here at least, it can go from 5 knots to 30 knots or more with no warning at anytime of the day. I did a shore dive last summer, when we entered the water there was no wind and no current. After 30 minutes of diving a longshore current started to pick up, by the time we exited the water (45 minutes) there was quite a current, we were 100 ft down the beach from our planned exit and it was blowing 20 to 25 knots. We knew it would be windy and could have guessed the approx direction, as that's about the only cause of a curent at this site. I've been caught out in thunderstorms, with about 5 to 6 minutes from the first hint of clouds and rumble in the distance till the wind and rain was fully upon us.

I agree on the rode weight/retreive issue. We happen to own a sailboat and when we've a lot of rode out, or the anchor really well set, will lead the line back and wrap it around a winch. Not all that fast, but makes it light work.

 

[Braunbehrens]

Well, I'm sure glad I got a Bruce, not a Danforth! Come to think of it I've heard a couple of stories of Danforths dragging, but not Bruce anchors.

Your post really shows that selecting an anchor is very much dependent on the boat you have and the conditions you are likely to experience. If I had a way to pull up the anchor that didn't use arm power, or if I had the luxury to stick around for a couple hours after the dive, then I'd most definitely get a nice big anchor and lots of chain.

I've actually toyed with the idea of putting some kind of winch on the boat, but I think it's just too small.

 

[Stone]

I've only been diving from my own boat for a year (steel danforth and 10 ft of 3/4" chain). My boat (old, heavy 25' Chriscraft inboard) handles 5/6 feet pretty well, but we usually plan dives based on 3 ft or less.

Most of our dives are 80 to 110 ft. I usually put out 2:1 and sometimes 3:1. Current is rarely a problem; if the full length of the chain is on the bottom, I don't worry (most of the time the chain is in a clump).

I will have to investigate the "Bruce" anchor.

 

[Stone]

I always use the anchor ball. I have yet to have a problem clearing a wreck or reef. Every once in a while I will move the anchor to a better position.

 

[Braunbehrens]

Stone once bubbled...
I always use the anchor ball. I have yet to have a problem clearing a wreck or reef. Every once in a while I will move the anchor to a better position.

Just to clarify. You hang a ball on the anchor rode and motor towards the anchor. The ball goes down somewhat and the anchor ends up popping up attached to the ball.

So you say that you use this method and you have never hooked another part of the wreck or reef?

If this is true then it is good news indeed. I always worry that the anchor might rake across the reef with this method, but maybe it goes straight up.

Sure would save my back and shoulder...

 

[Groundhog246]

Braunbehrens once bubbled...

Just to clarify. You hang a ball on the anchor rode and motor towards the anchor. The ball goes down somewhat and the anchor ends up popping up attached to the ball.

So you say that you use this method and you have never hooked another part of the wreck or reef?

If this is true then it is good news indeed. I always worry that the anchor might rake across the reef with this method, but maybe it goes straight up.

Sure would save my back and shoulder...

Are you talking about breaking the anchor loose? Or pulling in all the rode? With the Bruce, I've never had any problem breaking it out of the bottom. I just shorten up till the rode is almost vertical, and if it's doesn't come loose, snub the rode and give the boat a shot forward.
If it's hauling in all that rode, nothing I can think of, other than a winch, is going to make it lighter.

I'm not in an area with reefs, so can't comment on that issue. In areas known to have snags that like to keep an anchor hooked, I often put a retreival line with a float on the back of the anchor. For that a light poly line and a small float are adequate.

 

[Groundhog246]

Stone once bubbled...
I've only been diving from my own boat for a year (steel danforth and 10 ft of 3/4" chain). My boat (old, heavy 25' Chriscraft inboard) handles 5/6 feet pretty well, but we usually plan dives based on 3 ft or less.

It's not currents, or even waves I particularly worry about, it's wind. I've had more than one boat drift down on us (usually at night) when anchored with too small an anchor, a poorly designed anchor or not enough rode and winds have shifted direction or increased. If you're in a spot where your actually hooking on a reef, then any scope at all will keep you there. It's a little hard on the reef though (and we talk about poor buoyancy damaging reefs) when you hook in with an anchor. Part of a rail on a wreck at Toby ripped off not long ago when an anchor hooked on.

Have you boating experience prior to that year? Or taken any courses? I haven't been diving for all that long, but I've been around boats since I was a kid and owned several on and off for 25 years. If your chain is in a clump, it doesn't sound like you've even "set" the anchor, just dumped the whole works off the bow. I really hope a squall does not catch you in the water, or you are likely to surface and no see your boat.