Drilling holes in grp

[RunAgroundHard]

Morgans Cloud, aka Attainable Adventure Cruising, has done a lot of work on JSDs and the mounting brackets, rectangular plates on the quarters. The analysis is backed up by engineering. Worth a look if you have not already done so. Of course, that is a different design to your eyelets, which spreads the load over a larger area than I assume your eyelets do.

The article* is called "Jordan Series Drogue Attachments And Launch System", updated February 22, 2023, original June 1, 2013 by John Harries. Also some good information on the comments section.

* For clarity (in case anyone is not aware), the article can be found at www.morganscloud.com but needs a subscription to access.

 

[thinwater]

Morgans Cloud, aka Attainable Adventure Cruising, has done a lot of work on JSDs and the mounting brackets, rectangular plates on the quarters. The analysis is backed up by engineering. Worth a look if you have not already done so. Of course, that is a different design to your eyelets, which spreads the load over a larger area than I assume your eyelets do.

The article* is called "Jordan Series Drogue Attachments And Launch System", updated February 22, 2023, original June 1, 2013 by John Harries. Also some good information on the comments section.

* For clarity (in case anyone is not aware), the article can be found at www.morganscloud.com but needs a subscription to access.

Remember that Morgan's Cloud is an aluminum boat. Different.

 

[RunAgroundHard]

Remember that Morgan's Cloud is an aluminum boat. Different.

It wasn’t only about his boat. There was discussion on GRP laminating to increase strength, clamping, load distribution and even bolting patterns and sizes. Perhaps I have quoted the wrong article, but all these subjects have been discussed on the site.

 

[zoidberg]

Thanks for that, RAH, if intended for me.

I've been a subscriber to MC for some years, and have followed in depth the very long list of comments about this topic. In particular, I dug deep into the excellent contributions from several experienced engineers.... and then dug even deeper.

I've 'run the numbers' in respect of the laden displacement of my modest boat, and shared them with the engineers various - including some with real practical/professional expertise on 'bolted fasteners' and load-sharing.

I'm well aware of Don Jordan's suggestion of a simple stainless steel strap. Do we have any validated specifications for a pair of s/s straps appropriate to the laden displacement of my boat? Or John Harries' boat - either of them? Or anyone else's boat....

What about the necessary dimensions of the straps' ends, where the shackle fits? How thick? How wide? How to check for potential fracture sites...?
And while we're on about shackles, joining the bridle arms to the straps, where does one find reliable specifications matched to 'Design Loads'? And would such shackles, if available, be constructed of stainless steel - and what grade? Or a different steel alloy - and which one is optimum? And why presume a STEEL shackle?

What about a line of s/s bolts into the hull? How many is enough - and what does 'enough' mean? A straight line, or staggered? A circular pattern? Or square? What's the optimum spacing? Equal 'proload' on each, or progressive, and between what limits? Why?

What Factors of Safety should be applied to each item.... and why?

Don Jordan was a professional aviation engineer. He wasn't an amateur in calculating allowable loads and cumulative stresses. There are all sorts of engineers, and not all of them have Don's expertise and pro experience in dynamic structures. Some of them - most of them, I'd hope - would say 'That's not my area of knowledge. Go find someone who does understand the mechanics of such systems'. With respect, thankfully there ARE engineers who do offer some guidance, which is 'hoisted in'.

Perhaps underlying some of all this is the lingering unspoken "Why don't you just do it the same way as everyone else seems to? And as I would.....?" I've noted time and again, over 50-odd years of sailing, a strong 'reactionary' impulse to adoption of something different. Just a few seem to ask 'why' and look to ways of doing stuff just a little better. Like Don Jordan....

 

[thinwater]

It wasn’t only about his boat. There was discussion on GRP laminating to increase strength, clamping, load distribution and even bolting patterns and sizes. Perhaps I have quoted the wrong article, but all these subjects have been discussed on the site.

True.

In fact, Matt has discussed the benefits of spreading the load using composite chain plates, which are NOT straps, they are more like a fan.

 

[zoidberg]

Someone will along any minute to tell us that JSDs are really only for 'blue-water boats' in far off oceans, despite Don Jordan inventing the things in response to the Fastnet 79 disaster and report.

I've crossed that stretch under sail 12 times. The next time will be the Thirteenth....

This is what that stretch of sea can look like, from the nearest point of land downwind.

 

[dunedin]

Someone will along any minute to tell us that JSDs are really only for 'blue-water boats' in far off oceans, despite Don Jordan inventing the things in response to the Fastnet 79 disaster and report.

I've crossed that stretch under sail 12 times. The next time will be the Thirteenth....

This is what that stretch of sea can look like, from the nearest point of land downwind.

Forecasts are so much better these days that a coastal cruising yacht that properly researches the multiple forecast models and acts accordingly is extremely unlikely to get caught out in an unforecast severe storm when doing a passage of under 5 days, and generally should be able to divert to shelter if any surprises come up in the 3-5 day horizon when underway.

 

[zoidberg]

Now there's an Act of Faith....

But OK. This li'l lobster doesn't expect to get into trouble sufficient to need a JSD while coastal cruising.
Nevertheless, I'm really looking forward to Raytheon inventing a 'Beam me up, Scottie' badge.....

 

[thinwater]

Someone will along any minute to tell us that JSDs are really only for 'blue-water boats' in far off oceans, despite Don Jordan inventing the things in response to the Fastnet 79 disaster and report.

I've crossed that stretch under sail 12 times. The next time will be the Thirteenth....

This is what that stretch of sea can look like, from the nearest point of land downwind.

I've tested chutes and JSDs to gain data in up to gale conditions. But the only time I have used a drag devise in anger (off figure of speech, that) was when it was blowing hard enough that I wanted to delay arrival until daylight, not because I felt any danger. I can also imagine you might use a drogue for comfort. In those cases, it will be easier and safe to attach the bridle to the winches. The load won't be that high and chafe can be managed with padding. Or good stern cleats. Unless there are big breakers the loads will not exceed genoa sheet loads.

 

[zoidberg]

...when it was blowing hard enough that I wanted to delay arrival until daylight,.... Unless there are big breakers

'Blowing hard'.... 'until daylight'.... 'big breakers'.....

I don't recall ever getting to choose the size of breakers in the night, but respected research by the Wolfson Unit/So'ton University shows that a breaking sea of Critical Height 60% of boat length WILL capsize the boat, if struck beam-on.

Around this part of the world, I/we get a whole lot of breaking seas of that size and larger.... much larger. See #46. That's why 'I'm a believer' in JSDs to keep my wee boat and my soft little pink bod end-on to those seas.