Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 04-11-2009, 13:22   #1
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,326
Carbon Fiber for Jordan Series Drouge Attachment

My boat is cored on the deck and topsides (below the water line is solid), and I am fussing over how to get some very strong attachment points. The design guide calls for 7,500 pounds.

Cleats. There are 2 large stern cleats in solid glass, but they are not backed well enough. Because they are under a carpet liner and because of the corner they are in, it is not simple to add a big backing plate. Possible, though, by simply laying on more layers of glass. The cleats might have to be larger and changed to ss. Might not be able to repar the carpet, and it does not need replaced yet.

Chain plates on the sides. Accesible, but it is a cored section, so I would have some extra work there. Ugly too.

Carbon fiber chainplates. Accesible. I could place these a number of places. I eliminate corrosion and leakage issues. They will be nearly invisable. A bit more work, but not bad.

I have made reacher attachment points using Kevlar before, for the same reasons; Kevlar honey comb hull. They worked very well for over 15 years.

* Unidirectional CF sufficient to hold 12,000 pounds, perhaps. Will calculate.
* easy to spread the load over several square feet. I understand I can rely on ~ 600 pounds in shear for epoxy secondary bonding, so though only 12.5 in2 are required, I will get much more. I imagine 1 layer of 3-6 oz glass cloth will cover the fiber for bonding and protection.
* Line hole with ss tube and washers, sized to fit ~3/8" ss shackle.
* Pin is horizontal, canted inwards to match bridle angle. Shackle can swivel in verticle plane.
* Can be located in a transom posstion that is safer to reach (top step).

Your thoughts? Specifically, any experience in this application? It is certainly less demanding than a mast chainplate in terms of stress and cycling.
__________________

__________________
Gear Testing--Engineering--Sailing

Writing full-time since 2014.
Bookstore:http://sail-delmarva.blogspot.com/20...ook-store.html
thinwater is offline   Reply With Quote
Old 04-11-2009, 14:50   #2
Registered User
 
markpj23's Avatar

Join Date: Nov 2005
Location: Black Hills, SD
Boat: Now Boatless
Posts: 1,148
Images: 47
Is carbon fiber best suited to the type of load that your drogue attachment points will endure? I have no idea but that was the first question that came to mind.

I too have contemplated adding SS plates for this purpose. Does the solid portion of your hull include the lower transom step / steps? In my case it does and for that reason I plan to add the plates level with the top of the very last step. This also provides a more optimum angle for the drogue, as opposed to a top step mounting as you described.

It's a trade - off, accessibility vs performance angle. IF we're smart enough to rig things before it turns too ugly to descend the steps, then IMO lower is better. Knowing that things seldom go as planned, I can see the merits of a higher, more accessible mount. In my case dinghy interference would be an issue with a top step mount.

Where would you source your carbon fiber stock from? Will it hold up during its likely loading, etc, etc. I'll watch this thread with interest as the answers unfold.

Best of luck with it - and may you NEVER have to use it!

__________________

__________________
Mark
markpj23 is offline   Reply With Quote
Old 04-11-2009, 15:31   #3
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,326
Great comments. Thanks.

Quote:
Originally Posted by markpj23 View Post
Is carbon fiber best suited to the type of load that your drogue attachment points will endure? I have no idea but that was the first question that came to mind.

I too have contemplated adding SS plates for this purpose. Does the solid portion of your hull include the lower transom step / steps? In my case it does and for that reason I plan to add the plates level with the top of the very last step. This also provides a more optimum angle for the drogue, as opposed to a top step mounting as you described.

It's a trade - off, accessibility vs performance angle. IF we're smart enough to rig things before it turns too ugly to descend the steps, then IMO lower is better. Knowing that things seldom go as planned, I can see the merits of a higher, more accessible mount. In my case dinghy interference would be an issue with a top step mount.

Where would you source your carbon fiber stock from? Will it hold up during its likely loading, etc, etc. I'll watch this thread with interest as the answers unfold.

Best of luck with it - and may you NEVER have to use it!

Is carbon the best fiber? Well, it is used for chain plates, and that is a much more difficult application, with a lot of cycling. Certainly, other fibers would work. I am considering Kevlar as well. Some fibers would concern me regarding bonding.

Mounting low or high? Great question. What if I tear a hole in the hull down low? Very bad. I would be afraid to do that unless it was a part ofthe original lay-up and I was SURE I could make it bullet proof. Additionally, on my boat Houdini couldn't reach the inside in that area. If you can reach it, then it has some merit. I would add additional glass.

I have only used CF a few times (most resently to stiffen battens - Sail Delmarva: Search results for battens), and those times I have gotten the TOW from West Systems. I notice Defender has an interesting supply of fibers too. I have not nailed that down. In the case of the battens, carbons high modulous was of more interest than its strength. I wanted stiffness with minimum bulk, since I was constrained by the existing pockets. It has always performed very predictably for me.

Regarding which step, I imagine that is a boat-specific compromise, and your points make sense to me. In my case I have a catamaran with a wide base, so placment is less critical.

BTW, your dingy will not be on the davits when you are using the drogue, I think.
__________________
Gear Testing--Engineering--Sailing

Writing full-time since 2014.
Bookstore:http://sail-delmarva.blogspot.com/20...ook-store.html
thinwater is offline   Reply With Quote
Old 04-11-2009, 15:39   #4
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
The hull to stern joint probably isn't cored. I would make some carbon fiber chainplates, route a slit at the joint and mount the plates there. It's easy to spread the load over the side of the hull, just glass it in a couple of feet. Don't forget to reinforce the joint to compensate for cutting the slit in.

cheers,
Nick.
__________________
s/v Jedi is offline   Reply With Quote
Old 04-11-2009, 18:17   #5
Senior Cruiser
 
mikereed100's Avatar

Cruisers Forum Supporter

Join Date: Dec 2005
Location: Santa Barbara
Boat: 46' custom cat
Posts: 1,571
Images: 2
Another consideration is that when using a bridle some percentage of the force applied to the attachments will be in peel rather than sheer if they are fixed to the side of the hull. A slotted arrangement as Nick describes might be best, with some of the fibers on the interior of the hull, but now you are getting into a lot more work if the inside is not easily accessed. Another option might be to glass them to a gusset inside the hull. I've tried to work this out for my boat and keep coming back to stainless chainplates with hefty backing.

Mike
__________________
mikereed100 is offline   Reply With Quote
Old 04-11-2009, 18:34   #6
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,326
Yes, the pealing issue is relavant.

Quote:
Originally Posted by mikereed100 View Post
Another consideration is that when using a bridle some percentage of the force applied to the attachments will be in peel rather than sheer if they are fixed to the side of the hull. A slotted arrangement as Nick describes might be best, with some of the fibers on the interior of the hull, but now you are getting into a lot more work if the inside is not easily accessed. Another option might be to glass them to a gusset inside the hull. I've tried to work this out for my boat and keep coming back to stainless chainplates with hefty backing.

Mike
I suppose I did not put all of my thinking into my post.

Yes, the inside is accessible. Actually, the intention is to have some of the attachment on the underside of the deck - less pealing force, but still some. Thus, my intention was to reinforce the step and use it as a slot or gusset to keep the force directed in a controlled range.

Yeah, a SS plate is simpler. But part of the fun is the puzzling. And knowing when to stop if you can't puzzle it all out!

Another problem is that on my boat (photo of similar boat pic. 3 - View Boat Photos - YachtWorld.com) I suspect a chain plate would tend to crush the flange on the stern inwards.
__________________
Gear Testing--Engineering--Sailing

Writing full-time since 2014.
Bookstore:http://sail-delmarva.blogspot.com/20...ook-store.html
thinwater is offline   Reply With Quote
Old 06-11-2009, 08:00   #7
Senior Cruiser
 
mikereed100's Avatar

Cruisers Forum Supporter

Join Date: Dec 2005
Location: Santa Barbara
Boat: 46' custom cat
Posts: 1,571
Images: 2
I like your idea to use the reinforced step with a slot. There's really no limit to how much fiber and pucky you can slather on so I don't see why it wouldn't work. I agree that the cool factor of composite attachments is worth a bit more trouble.

Mike
__________________

__________________
mikereed100 is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Jordan Series Drogue vs Para-Anchor ? markpj23 Health, Safety & Related Gear 5 30-10-2011 21:17
Carbon Fiber Chainplates Zednotzee Deck hardware: Rigging, Sails & Hoisting 12 03-11-2009 06:29
Blackbird Carbon Fiber Guitar? markpj23 Fishing, Recreation & Fun 21 08-04-2009 16:24
Paint carbon fiber? mestrezat Deck hardware: Rigging, Sails & Hoisting 3 14-03-2009 21:49
carbon fiber shrouds and forestay dpollitt General Sailing Forum 4 13-05-2008 15:59



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:06.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.