Jordan series Drogue Attachment

[Boston Blackie]

Not a good idea. Jordan conservatively suggests the chaiplates, bolts and backing structure needs to be strong enough to hoist the fully laden vessel. Would you feel safe hoisting your vessel from the aft end of the toerails?

[alctel]

Originally Posted by Boston Blackie

Not a good idea. Jordan conservatively suggests the chaiplates, bolts and backing structure needs to be strong enough to hoist the fully laden vessel. Would you feel safe hoisting your vessel from the aft end of the toerails?

Yes, I think so. Provided it was pulled from the back along the longitudinal direction and the attachment points were bolted longitudinally to the toe rail.

It's through-bolted through the aluminium and then the deck and then the hull, every 6 inches or so.

[Boston Blackie]

We have the same aluminum toerail construction on our J42. Rod Johnstone does not suggest high loading such as preventers to the bolted toerails. What is the grade of your toerail throughbolts? In confused late storm seas you will not be just experiencing shear loads parallel to the toe rail. There will be maximal lateral inboard stress in the bridle leg the stern is slewed toward. This will be putting ALL the twisting load on the aftermost toerail throughbolt. When it shears you will unzip the rail from the deck.

[alctel]

Originally Posted by Boston Blackie

We have the same aluminum toerail construction on our J42. Rod Johnstone does not suggest high loading such as preventers to the bolted toerails. What is the grade of your toerail throughbolts? In confused late storm seas you will not be just experiencing shear loads parallel to the toe rail. There will be maximal lateral inboard stress in the bridle leg the stern is slewed toward. This will be putting ALL the twisting load on the aftermost toerail throughbolt. When it shears you will unzip the rail from the deck.

Hmm ok. Did you use stern mounted chainplates?

[Boston Blackie]

Originally Posted by alctel

Hmm ok. Did you use stern mounted chainplates?

Yes, we did. Have posted a pic of ours separately. The key is that the ultimate God-Forbid load bends the plate in toward the hull. Also note our oval slot which allows the shackle to swivel. Off- axis loads derate shackle WLL significantly.

[thinwater]

The concern about zippering is valid, but remember that outward pull will be taken by the other bridle arm. Up or down is possible, though.

There is another important point here, though, and that is choosing the correct bridle length. In simple theory, longer is better, providing more turning force. In practice, that results in one leg taking the load every time the boat yaws, an it will. Every time the leg goes slack there is a shock load and the potential for chafe.

I don't suppose there is one answer to this question. 1:1 is too short, 2:1 seems practical, and 4:1 is probably too long.

[Boston Blackie]

Hi Thinwater,

Our bridles are 30' double braid Dacron, according to Jordan's design. Overall length of the drogue is 300' in three cowhitched sections of decreasing diameter. I believe most of the stress is taken by the inward angled lead, given our transom beam. I did massively beef the internal laminate and added backing plates.

Cheers,
Blackie