series drogue size and count

[seandepagnier]

Consider this table from ocean brake:

Cones Displacement Lbs Price USD
130 6,600 lbs $1,312.20
140 12,000 lbs $1,386.90
150 18,000 lbs $1,497.00
155 30,000 lbs $1,639.40
160 33,000 lbs $1,706.30
165 40,000 lbs $1,773.30
170 50,000 lbs $1,840.20

It is odd to me, that at 6,600 you need 130 cones, but at 12,000 only 140 cones.

No idea how they determined this table.. but it seems very generous for the smaller boats if 170 is enough for a 25 ton boat. Any insight? My displacement is between 3000 and 4000 lbs, would extrapolate to needing 120 cones

I have 60 cones for a jordan series drogue which is obviously not enough, but these cones are very expensive ($10 each or more) I can get 24 inch drogues for $30. A 24 inch drogue should drag as much as at least 15 of these cones. So what if I just got 4x 24 inch drogues in addition to the 60 I have? Would you alternate them 15, 1, 15, 1, 15, 1, 15, 1 or 4,60 ? or would it matter?

My understanding is a single drogue is not great because it will load up and it's harder to keep a steady pull in the waves. Reports show that using 2 drogues is already significantly better. So what is the deal with using hundreds of drogues? Is this to make it easier to retrieve (they run around the winch) ? Why not have 10 or 12 decent sized ones rather than more than 100 tiny ones? It would cost less and weigh less.

Please let me know what I'm missing, where I'm confused (as usual)

[hpeer]

Sean,

Yeah, I don’t get it either.

My understanding is the Jordan type drogue is to nearly “stop” the boat while others (Gale Rider, Sea Break) are designed as “speed reduction” drogues meant to slow boats to a 3-6 knot speed.

I spoke to a gentleman who felt he deployed his drogue too early which caused him to be pooped badly, which created a whole string of bad events.

My personal strategy is to have 2 drogues I can deploy. 1 until it breaks then I have a spare. Or 2 if its really terrible and I need to slow more. Then I want them at different deployment lengths. I have not heard any convincing argument why my plan is not better than a Jordan. But also it is cheaper and easier to retrieve. The potential problem would be if the lines foul. But I would still have at least one.

[kmacdonald]

Looks like a misprint to me. Research it a little.
I'd follow their advice to the letter. A lot of thought and engineering went into that design and you aren't going to design a better one on the couch.

[hpeer]

Another table with different quantities. But similar in that the number of cones is not linear to displacement.

http://www.eglin.net/2bikes/wp-conte...ructions-2.pdf

[hpeer]

And another opinion.

Pros & Cons Between Jordan Series Drogue VS The Sea Anchors

[beetle]

It appears you do not understand the problem the Jordan Series Drogue is trying to solve. You might do well by reading the original engineer's/designer's paper and that would answer your question as to why one might want something like it.

[kmacdonald]

Originally Posted by hpeer

Another table with different quantities. But similar in that the number of cones is not linear to displacement.

http://www.eglin.net/2bikes/wp-conte...ructions-2.pdf

That looks accurate.

[beetle]

Originally Posted by kmacdonald

That looks accurate.

One what basis would that publication be more or less accurate? Accurate than what? Opinion in the absence of fact is not too helpful...

[kmacdonald]

The table shown in post #1 is obviously wrong. I know this from looking into a Jordan Series Drogue. Google it and it will become clear.

[beetle]

Originally Posted by kmacdonald

The table shown in post #1 is obviously wrong. I know this from looking into a Jordan Series Drogue. Google it and it will become clear.

Again - what's your source that the table from post #1 is obviously wrong? Suggesting that Google will somehow tell me what's wrong is silly.

[kmacdonald]

Read the Coast Guard report on the Jordan Series Drogue. It has the details on construction and number of cones to use.

[seandepagnier]

From the other site:

DISPLACEMENT CONE # LINE LENGTH* LINE DIAMETER ANCHOR WEIGHT
6,000 lb. 130 296 ft. 5/8" 15 lb.
12,000 lb. 140 312 ft. 5/8" 15 lb.
18,000 lb. 150 167 / 167 ft. 3/4", 5/8" 15 lb.

So 6000lb is 130 cones again, and 12000lb suggested 140 cones. I realize it is not linear but this doesn't really make a lot of sense that 10 more cones, and a 7% more drag force is all that is needed to deal with a boat twice the weight.

Using displacement is like rating an anchor based on the displacement which is not really valid either.

Originally Posted by kmacdonald

The table shown in post #1 is obviously wrong. I know this from looking into a Jordan Series Drogue. Google it and it will become clear.

https://www.oceanbrake.com/

Originally Posted by beetle

It appears you do not understand the problem the Jordan Series Drogue is trying to solve. You might do well by reading the original engineer's/designer's paper and that would answer your question as to why one might want something like it.

I have read about it quite a bit. I am asking why fewer larger drogues would not work as well. I understand clear advantage of 2 over one, and 3 smaller better than 2 and so forth.. but above 10 or 15 drogues it seems there are diminishing returns.

Otherwise.. why not have 2000 1 inch drogues? It _is_ absurd that one particular size drogue is "optimal" for every size boat. Its like saying giving the same vaccine dose to a 90lb adult vs a 450lb one is in both cases "optimal" and after all it's what they do, but again it's absurd, and there is lots of evidence that it doesn't work as well on these huge people. Maybe smaller boats should have smaller cones rather than fewer? Maybe the cones should get smaller and smaller toward the end?

[beetle]

I have read that report, I have built Jordan Series Drogues, I have deployed them. But again - on what basis is the first linked-to idea from Ocean Brake incorrect? Essentially the Ocean Brake model follows the USCG document on drogues that you mention. So what's wrong with USCG or Ocean Brake's in terms of number of cones to use or how they are constructed?

For what it's worth, I set up my drogues using spectra bridle and line, due to its low stretch and lower weight than the double braid originally suggested.

[beetle]

Originally Posted by seandepagnier

I am asking why fewer larger drogues would not work as well.

The principal of the Jordan drogue is to reduce shock load assuming that not all cones will be in the water (and therefore loaded up at the same time). As you reduce the number of cones you are increasing the chance (<- key word, 'chance') that not all cones will be loaded up at the same time as the boat surfs/surges down a wave. The hope (<- another key word, 'hope') is that there are sufficient cones in the water at any given moment to slow the boat down so it won't pitchpole.

And yes, a zillion tiny cones would be better than 200 bigger cones, which are better still than 20 big big cones.

So what's the issue? I had a joyous (evil!) time constructing lots of little cones, but it did work for me when I tested the result. If you want to build fewer and test it, perhaps it will work for you.

[kmacdonald]

Spectra is fine. The table in post #4 is for monohull boats. There may be a table for cats that is different. I would post links but am typing on a smart phone with limited signal. Out cruising. Posting tables without what they reference can be confusing at best. Always research yourself.