Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 18-03-2010, 14:49   #16
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
I am concerned that there would be tangling and then chafe problems.

Quote:
Originally Posted by erasmos View Post
the wind comes from the left.. west of course.. Im from the North atlantic..
Those are bad problems, since then you can loose the whole system.

The bow brake would certainly get around the sea anchor rode, with side to side shifts.

The stern anchor would likely get under the boat and foul the rudder, since the boat is generally moving aft at 0.5-2 knots (surging on line stretch).

It is a puzzler, all right. This is an advantage of the JSD, since there are many elements and they start near the boat. When there is slack, it sinks. The draw backs are cost, bulk, and difficult retrieval, but it is a darn clever solution.

I had mused over the idea of using a Seabrake and warps together:
* Advantages. Simplicity, can deployed in stages, gives braking elements both close astern and 1/2 wave length out (as you pointed out). Redundancy.
* Disadvantages. Chafe between the warps and Seabrake rode. Much worse, if the warps are weighted, which they must be. Fatal drawback.

A bridle long enough and weighted with chain might give some of these advantages, but the Seabrake would tend to pull it out of the water. I wonder, at what length does a bridle present a tangling risk?
__________________

__________________
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 18-03-2010, 18:20   #17
Registered User
 
erasmos's Avatar

Join Date: Mar 2010
Location: Greece
Boat: Nantucket Clipper 31ft (1979)
Posts: 36
..if the parachute doesnt work due chafe, side to waves or bow drifting, and added the trouble of retrieval (the Fiorentino anchor also suffers from troubles being retrieved in severe storms even if it has a retrieval buoy).. the JSD in a stern setup naturally is preferred choice. Even perhaps, what people have been using since the dawn of time, weighted warps in different lenghts and poles.

In regards to weights, one of the issues facing the chute is that it will simply not work in some borderline conditions:

"CHAIN AT THE SEA ANCHOR
If you are planning on cleating the main rode to your boat (with SUBSTANTIAL chafe protection) then we recommend using a short length of chain at the Sea Anchor to aid deployment and create some catenary effect. Chain at the Sea Anchor helps keep the Sea Anchor down. During slack cycles the chain causes the Sea Anchor to swing down and maintain some tension in the rode.
MID-SCOPE CHAIN
Although our instruction manual illustrates chain mid-scope, input from the field (to the Drag Device Data Base by Victor Shane) suggests it does not have the effect we had believed. One report we received tells of a 40' sloop in a hurricane with 200' of rode, 40' of chain with a 45# CQR mid-chain and then another 200' of rode. The report is that the rode and chain were straight and the anchor was thrashing about the chain. Placing chain mid-scope is the busiest place, requiring thimbles in the rode ends and shackles to join the chain to the rode. For these reasons we tend to lean away from mid-scope chain.

CHAIN AT THE BOAT
This is where chain can provide the most benefit. It prevents the rode from chafing through (which is our biggest concern). You can let out a few feet in moderate conditions to well over 100' in severe conditions.
There are a few things you need to be aware of:

Remove the anchor from the end of the chain - if you are unable to remove the anchor you MUST use a short length of chain as a "stand off" to keep the anchor flukes away from the rode because an anchor which is thrashing about could chafe through the rode with its flukes.

The chain MUST be snubbed to the deck cleats to off load the windlass. We carry Stainless Steel Chain Grabbers for this purpose (they fit 5/16" to 1/2" chain).


Once you are set on the Sea Anchor it is virtually impossible to adjust the amount of chain which is out so you must determine the sea conditions and let out the appropriate amount when the Sea Anchor is initially set. (See the section "Bridling with Chain").


The down side to using chain at the boat is that the chain can do damage to the chocks, bow roller, etc. but we believe the trade off of not having to be concerned with the rode's chafing through is worth the possible damage." (from para anchors site)


..to theoretically 'fix' the chafe problem facing the parachute anchor (apart from not hitting the half wavelength), its line has to hold a secondary brake near the bow. It then puts complications and restrictions into length variation so 'manufactured solutions' suggests chains on the rodes which obviously is a kind of secondary solutions to the problem.

In my diagram above obviously there are troubles with a stern floating sea brake (head to wind)

JSD in general perhaps is superior to these but you loose important momentum in a storm being taken downwind being held longer in the strong wind and waves (especially if a front is moving slowly.. like the center of a hurricane). Additionally being cockpit to rogue waves its very possible to having rogue waves slam the cockpit and snap all rodes just by the shock loads.

So why hasnt brakes and seaanchors represented a 'too serious' problem yet too actually do something?

Perhaps we are somewhat dealing in hypothetical situations here because modern technology enables people to avoid the occasional freak storm. Also engine powers helps. Think if both fail? One looks for a bullitproof system for a medium sized cruiser when heaved to even in rogue waves. I see room for improvement in the field though obviously there are numerous issues still to be solved.
__________________

__________________
"But more wonderful than the lore of old men and the lore of books is the secret lore of ocean." -- H. P. Lovecraft
erasmos is offline   Reply With Quote
Old 19-03-2010, 16:54   #18
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
You bring some interesting points.

Quote:
Originally Posted by erasmos View Post
"CHAIN AT THE SEA ANCHOR
If you are planning on cleating the main rode to your boat (with SUBSTANTIAL chafe protection) then we recommend using a short length of chain at the Sea Anchor to aid deployment and create some catenary effect. Chain at the Sea Anchor helps keep the Sea Anchor down. During slack cycles the chain causes the Sea Anchor to swing down and maintain some tension in the rode.
MID-SCOPE CHAIN
Although our instruction manual illustrates chain mid-scope, input from the field (to the Drag Device Data Base by Victor Shane) suggests it does not have the effect we had believed. One report we received tells of a 40' sloop in a hurricane with 200' of rode, 40' of chain with a 45# CQR mid-chain and then another 200' of rode. The report is that the rode and chain were straight and the anchor was thrashing about the chain. Placing chain mid-scope is the busiest place, requiring thimbles in the rode ends and shackles to join the chain to the rode. For these reasons we tend to lean away from mid-scope chain.

CHAIN AT THE BOAT
This is where chain can provide the most benefit. It prevents the rode from chafing through (which is our biggest concern). You can let out a few feet in moderate conditions to well over 100' in severe conditions.
There are a few things you need to be aware of:

Remove the anchor from the end of the chain - if you are unable to remove the anchor you MUST use a short length of chain as a "stand off" to keep the anchor flukes away from the rode because an anchor which is thrashing about could chafe through the rode with its flukes.

The chain MUST be snubbed to the deck cleats to off load the windlass. We carry Stainless Steel Chain Grabbers for this purpose (they fit 5/16" to 1/2" chain).


Once you are set on the Sea Anchor it is virtually impossible to adjust the amount of chain which is out so you must determine the sea conditions and let out the appropriate amount when the Sea Anchor is initially set. (See the section "Bridling with Chain").


The down side to using chain at the boat is that the chain can do damage to the chocks, bow roller, etc. but we believe the trade off of not having to be concerned with the rode's chafing through is worth the possible damage." (from para anchors site)


..to theoretically 'fix' the chafe problem facing the parachute anchor (apart from not hitting the half wavelength), its line has to hold a secondary brake near the bow. It then puts complications and restrictions into length variation so 'manufactured solutions' suggests chains on the rodes which obviously is a kind of secondary solutions to the problem.

In my diagram above obviously there are troubles with a stern floating sea brake (head to wind)

JSD in general perhaps is superior to these but you loose important momentum in a storm being taken downwind being held longer in the strong wind and waves (especially if a front is moving slowly.. like the center of a hurricane). Additionally being cockpit to rogue waves its very possible to having rogue waves slam the cockpit and snap all rodes just by the shock loads.

So why hasn't brakes and seaanchors represented a 'too serious' problem yet too actually do something?

Perhaps we are somewhat dealing in hypothetical situations here because modern technology enables people to avoid the occasional freak storm. Also engine powers helps. Think if both fail? One looks for a bullet proof system for a medium sized cruiser when heaved to even in rogue waves. I see room for improvement in the field though obviously there are numerous issues still to be solved.
Clearly, chain or even worse, an anchor, attached at mid-rode is trouble. As the quote pointed out, this is a "busy" part of the rode and there should be ample chance for the anchor to slice through something. For the same reason (and someone will object) the current wisdom is that a kellet on an anchor line is a bad idea. It has less benefit than a bigger anchor, more chain, or more rode, and can really jump around. Perhaps there is some benefit when short scope is required in moderate conditions, but if things get worse, the catenary will straighten and you're cooked.

Chafe at the bow - or stern, for that matter - is interesting. In my case, I use a bridle and chafe gear on the bridle - no chafe. My system, for moderate size catamarans, is well proven over many years.
Sail Delmarva: The Ultimate Chain Hook for Catmarans...
Sail Delmarva: Anti-Chafe Gear
Although this show the bow and not the stern, the situation is very similar and the cleat placement is similar.

However, I won't speak to mono-hulls. The issues are different, complicated by snubbers and bow sprits and sailing at anchor. These are not catamaran issues. We worry about other things... sea anchors and drogues, since heaving to and lying a-hull are poor plans in wild conditions.
__________________
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 19-03-2010, 18:32   #19
Registered User
 
sabray's Avatar

Join Date: Aug 2008
Location: Wash DC
Boat: PETERSON 44
Posts: 3,169
I'll try my hand here. Chafe is bad it also can quickly chew up a line suprisingly fast. My current thinking is to install 2 chainplates if you will on the stern of my Peterson so the jsd will lead outside of all chafe points. Could you deploy a sea anchor the same way? I think yes. I am thinking a 3 rd line to the jsd so that it could be pulled port or stbd. On my boat it looks like that would run through a hawse pipe where chafe would occur but not critical this would be a point for balancing the load. I have and do use a killet. Never seen issue with it. Seems to help if it's blowing 35 I run it out to 2 3rds the rhode weight is about 30 lbs. I should sit down and caulate the advantage. I prefer though knowing I did that bit extra. That's where science meets reality. I'm happier using the killet if it starts stinking out. From a skippers performance point it stands that I am evaluting the conditions and makiing proactive choices. That over all is the critical point. The gear is checked and evaluated. Then we modify as the circumstances permit.I do how ever like the idea of getting the chafe points eliminated when using any line attached to the boat.
__________________
sabray is offline   Reply With Quote
Old 19-03-2010, 22:01   #20
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
I think the drogue has to ride deep - otherwise it may be messed up by a wave behind us just when we need it most.

Thinwater - great post - THX.

b.
__________________
barnakiel is offline   Reply With Quote
Old 20-03-2010, 10:27   #21
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
All of the drogues I tested ran shallow under load

Quote:
Originally Posted by barnakiel View Post
I think the drogue has to ride deep - otherwise it may be messed up by a wave behind us just when we need it most.

Thinwater - great post - THX.

b.
The great tension brings them up and the chain is just enough to keep them from coming out. Also, the great length of rode also helps, as it resists going sideways through the water.

Parachutes are actually rigged with a float to prevent sinking, but their size keeps them from coming out completely. This approach won't work on the drogue, because they move throug the water too quickly.

I didn't test the JSD, I only reported the data. However, I believe it would run deeper, which is one of its strengths.

I appreciate the thanks. It took some time.
__________________
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 20-03-2010, 14:51   #22
Registered User

Join Date: Jun 2008
Posts: 64
Thinwater, thanks for actually taking real test data, with measured drag and everything. I can actually compare the different devices.

Todd
__________________
zydecotoad is offline   Reply With Quote
Old 20-03-2010, 19:45   #23
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
riding to shallow

Well ten, what if we use barn-doors like on a trawler net? Or beter yet - design a sinker to drive the set deeper the faster we go?

Should not be too difficult - such sinkers are used in fishing, aren't they?

b.
__________________
barnakiel is offline   Reply With Quote
Old 20-03-2010, 20:55   #24
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
That's interesting thinking...

Quote:
Originally Posted by barnakiel View Post
Well ten, what if we use barn-doors like on a trawler net? Or beter yet - design a sinker to drive the set deeper the faster we go?

Should not be too difficult - such sinkers are used in fishing, aren't they?

b.
... I just don't know where to go with it.

Clearly, a surging load is more complicated than a steady load. A simple planer would be trouble. Also, it's not desirable to have too much downward pull - it could prevent the stern from rising. We just want to prevent the drogue from coming out of the face of a wave.
__________________
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 21-03-2010, 10:52   #25
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2005
Boat: Outbound 44
Posts: 4,560
Tom
It might be interesting to take the diagram you have and just show enlarged the 0-12kts section. If you have a drogue out and are going greater than 10 or 15 kts, you really have some serious problems.

Paul L
__________________
Paul L is online now   Reply With Quote
Old 21-03-2010, 13:33   #26
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Quote:
Originally Posted by thinwater View Post

We just want to prevent the drogue from coming out of the face of a wave.
Not good enough, mates. The wave travels faster than the drogue and a breaking one may turn your drogue into a pile of messy hardware. I think the drogue has to sail deeper - say the depth equal to the wave's height (not exact, just an idea). This could prevent the drogue being carried on by the white water.

???

b.
__________________
barnakiel is offline   Reply With Quote
Old 21-03-2010, 14:05   #27
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
You're right - my explanation was inadequate.

Quote:
Originally Posted by barnakiel View Post
Not good enough, mates. The wave travels faster than the drogue and a breaking one may turn your drogue into a pile of messy hardware. I think the drogue has to sail deeper - say the depth equal to the wave's height (not exact, just an idea). This could prevent the drogue being carried on by the white water.

???

b.
Unless the drogue runs at least as deep as the troughs between waves, it does as you suggest and eventually comes out of the face of a wave... which was my point.

Practice seem to shows that it is not required to run very deep, but practice also shows that drogues that are pulled on short tethers do exactly that when the load really comes on. The trouble with a very long tether is that there may be too much stretch.

I've never read discussion about the potential benefits of anchoring a drogue closer to the waterline, to reduce the upward pull. I have low atachments on my transom (to allow mooring lines to pass under my tender) and have wondered if they might improve the deployment of a drogue. They are probably strong enough (SWL ~ 1,000 pounds) since they are only slightly redirecting the load and not carrying the full load. The angle would be different - aft rather than across.

Sail Delmarva: Easy Mooring with a Dingy on the Davits
__________________
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 21-03-2010, 14:11   #28
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
True enough. But sometimes we are trying to illustrate the obserd!

Quote:
Originally Posted by Paul L View Post
Tom
It might be interesting to take the diagram you have and just show enlarged the 0-12kts section. If you have a drogue out and are going greater than 10 or 15 kts, you really have some serious problems.

Paul L
However, I can imagine hitting 20 knots with warps in the water, if surfing starts, and we want to know what the load is then.

Really, the relevant range for warps and a 12-foot sea anchor are SO different, they don't belong in the same discussion or graph.

I think the important take-away is to see when each provides ~ 500-800 pounds pull, since combined with hull drag, that is the most force the wind can provide, and when each provides 2,000-4,000 pounds of pull since that is what a wave strike can impose.
__________________
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 21-03-2010, 16:04   #29
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,324
I should add that all of the actual data was between 0-10 knots.

Quote:
Originally Posted by Paul L View Post
Tom
It might be interesting to take the diagram you have and just show enlarged the 0-12kts section. If you have a drogue out and are going greater than 10 or 15 kts, you really have some serious problems.

Paul L
I believe the extrapolations are reasonable, but I fairly certain the data below 10 knots (except for the chutes) is accurate.
__________________
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 21-03-2010, 17:13   #30
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Quote:
Originally Posted by thinwater View Post

... 2,000-4,000 pounds of pull since that is what a wave strike can impose.
Dynamic? Static?

Pull = pounds (per ft)?

Meaning - what do we understand by X pounds of pull? I think the wave is moving, so the static PRESSURE (e.g. pounds per sq ft) could be in pounds, but as the water travels at a specific speed ... so - how do we interpret the quoted number?

I am sorry to ask here as I might probably find on the net, just trying for a shortcut.

THX
barnie
__________________

__________________
barnakiel 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
Heavy weather tactics. Anyone want to share experience with sea anchors or warps? spencer53 Weather | Gear, Reports and Resources 72 04-03-2013 15:42
Yachtworld Asking Prices VS Actual Sale Price - or What is the Markup ? talus Dollars & Cents 108 06-08-2012 15:06
An Actual Shower stall 2divers Monohull Sailboats 62 09-06-2011 23:31
Towing Near Miss Knottygirlz The Sailor's Confessional 20 28-11-2007 11:16
Towing service irwinsailor Seamanship & Boat Handling 4 26-06-2006 14:42



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:02.


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.