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Old 09-04-2010, 11:09   #46
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Yes, anything can be pushed fast through water when you apply enough force to it. It is very relevant however because you first need enough wind to overcome the drag and reach hull speed while a modern fin keel design needs less wind and is probably faster because it is lighter (higher K factor). Once hull speed is reached, you still need to more power from the sails to sustain that speed and that translates to more sail area, more stress and more heel. Heeling translates to less power from the sails so you need more surface area, leading to more heel etc. It is an equation that can't be won by a heavy displacement full keel boat.

HOWEVER: I do agree that as you go down in boat length, a heavy displacement boat becomes better for cruising. The reason is comfort and strength. It is more difficult to make something small very strong. In other words: for cruising, I would not buy a 42' Island Packet but might buy a 33' Island Packet. I would possibly buy a 42' Beneteau First but wouldn't buy a 33' Beneteau. I would sail a 33' Island Packet anywhere (within reason, not around Cape Horn) and same for a 42' Beneteau.

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Old 09-04-2010, 12:44   #47
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What I try to say is that a spade rudder can be made just as strong as a skeg hung rudder.

ciao!
Nick.
Hi Nick,

The important part is "can be made just as strong". Unfortunately in the real world very few are, Sundeers and maybe a few others excepted.

That leads me to prefer a skeg hung rudder on most boats in my budget.

I like the breakaway design you mentioned. I had a boat with a skeg hung rudder with a balanced section protruding below the skeg that was a breakaway. That small balanced section really balanced the rudder and you could steer the boat with two fingers in most conditions. But if you hit something hard you would still have a rudder, assuming the breakaway really did.
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Old 09-04-2010, 13:21   #48
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Some examples of modified full keel island packet , Morgan outisland. Yes you can sail in light winds. We just did Fl West coast Key west to Tampa without starting engine. Sailed daytime only anchored off beach. Winds averaged 5-10 speed averaged 4 kts.
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Old 09-04-2010, 13:37   #49
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Offshore racing rules make no distinction based on rudder type. History says all boats must carry a true spare.
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Old 09-04-2010, 14:14   #50
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Keel Types.....

I'm not a naval architectic, nor yacht designer....I majored in physics, but took just enough engineering classes to be "dangerous"
So, I leave the intricacies to the likes of Hinckley, Douglas, McCurdy and Rhodes, (all 3 of whose boats I've sailed offshore), Dashew, Perry, etc....

But, without arguing over opinions, nor quibbling over the minute details, I have a few comments to make/agree with.....

Quote:
Originally Posted by Dockhead View Post
But don't confuse keel type with bottom type. They're different things.
A cruising boat needs some depth in the forefoot and some profile to the hull, which does cost some speed but gives a comfortable motion and better tracking. There is no contradiction between this and an efficient bulb keel. Our boat is great downwind -- easily driven yet tracks like a freight train. The autopilot easily deals with following seas.
And....

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When you design a fin keel you end up with more draft. Dashew had a problem with that because he wanted the Sundeers to be able to sail shallow areas too. This forced him to enlarge the rudder (something he wanted anyway for reasons of maneuvering under power) so that the rudder plays a bigger role in tracking and preventing leeway.
While I agree with the above points, they are specific comments on the general fact that vessel / yacht keel design is not done in a vacuum.....

The entire hull, keel, and rudder designs/shapes/lengths/depths/etc. are designed and engineered together.....it is not wise (nor likely) for any vessel designer to make arbitrary descisions on one aspect of the underwater design (such wanting shoal draft), without engineering/designing the entire vessel for this goal.....

And, therefore, while it is fun to discuss the various pluses and minuses of different designs, we should all keep in mind that most of us are not naval architectics nor yacht designers.....and while I (and many of you, as well) do understand there are many variables (some sublte and some blatant) which affect a particular yacht's performance, etc. perhaps blanket statements of opinion on a public forum need to be highlighted as such, and not factual......
(Gosh, that's a weird sentence!!!)
What, I'm trying to say is that my opinion agrees with some others opinions here.......
In my opinion, a well designed fin keel / spade rudder sailboat is my favorite for offshore sailing, no question in my mind (whether a Hinckley I sailed on for years 30+ yrs ago, a Sundeer which I've always loved, or my current Gerry Douglas designed 47' sloop...)
But, others have different opinions, and they are entitled to them.....even if they're wrong....


Oh, and my spade rudder (only 6" shorter than my fin/wing keel) is designed / built similarly.....its bottom 1/3 is designed to break away in the event of a catostrophic impact......
Quote:
Originally Posted by s/v Jedi View Post
It also has an engineered weak point so that you are left with 2/3rd of the surface area if something needs to break during a grounding.
What I try to say is that a spade rudder can be made just as strong as a skeg hung rudder.
And, I couldn't agree more about a spade rudder being made just as strong as a skeg-hung rudder.....


I'm going to try to attach 2 photos here.....

The first is my boat in the slings showing the underwater design, 6' draft fin/wing keel, and spade rudder.....(~9700 lbs lead keel)

The second is a sistership, showing the exact same hull design and rudder, although this one was the deep draft 8' draft fin keel....(a few hundred lbs. less ballast, but deeper)

(I spoke with the designer, Gerry Douglas, a year or so after I bought my boat.....and he informed me that unless I was racing hard to windward, I'd never notice any difference in performance at all, and even then the 8' deep draft version would only have a slight advantage in keeping from being pushed leeward, but no actual improvement in pointing ability.....)

I hope some appreciate my contribution here....
John





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Old 09-04-2010, 18:43   #51
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Yep - spade rudders can be build as strong as skeg-hung ones. The point is, most of them are not.

But if a boat comes from the drawing board of one who wanted and knew how to design it strong (and then the boat is built in a boatyard that knows how to build it strong) then there is no issue.

b.
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Old 18-11-2010, 09:09   #52
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osmosis

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@Pete7 - I'm quite taken with Moodys, they seem to be a cruiser's yacht, but they only seem to come in "large" these days. Ideally I'm looking (I think) for a 36' boat. I took a boat plan of a bavaria in sizes 30,33,37 & 39 and laid them out in the garden to get an idea of size.

I think that the internal layout is going to be a big factor in choosing a comfortable boat. I plan to go cruising for months at a time. The Moodys seem to have a big aft cabin (stateroom?? ) and I'm not planning to spend my life sleeping, but I like the Moodys nonetheless.

Some of the older boats like Westerlys seem interesting, even in the 33' versions.

Is age all that important? I get the impression that just about every GRP boat eve built is still floating around (excepting accidents). I know that the Moody 31s are a 1980s boat but I get the impression that those GRPs that have not succumbed to osmosis seem to last really well.
I have been in the boat building business for over 40 years and have hear just about evrything to be said about osmosis and I can tell you the word was invented by the paint people to make money. The worst case \i have seen was an old westerly centaur after 35 years in the water it had about 40 % of the underwater part of the hull in blisters and a total weight of 156 kilos of water in the laminate. dried it out repaired the blisters and back in the water. Not a 1/4 of a knot faster and no more comfortable. I rest my case.
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Old 18-11-2010, 09:18   #53
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I have been in the boat building business for over 40 years and have hear just about evrything to be said about osmosis and I can tell you the word was invented by the paint people to make money. The worst case \i have seen was an old westerly centaur after 35 years in the water it had about 40 % of the underwater part of the hull in blisters and a total weight of 156 kilos of water in the laminate. dried it out repaired the blisters and back in the water. Not a 1/4 of a knot faster and no more comfortable. I rest my case.
Thanks for that. What's your opinion of bilge keels?
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Old 18-11-2010, 09:20   #54
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Well I have delivered Bilge and Fin, Deep, Long,Bulb and without bulb keels and can only say that with a production boat you can have any 2 of 3 things in a yacht. You can have either speed and comfort(big cost) comfort and safety (smaller cost) If you want the speed you will have to work hard for it in ANY yacht and you wont do it with just 2 of you. If you want comfort and safety for cruising you can acheive this with one or two crew. The idea is if you are racing you want to get there as fast as poss but if you are cruising you want to enjoy the trip, have a meal on the way, perhaps do a bit of fishing and arrive fresh and not knackered therefore DO IT SLOWER so the choise of keels is yours. All the best Pete and Sally in our Colvic Watson M/S ketch rig that sails like a brick in anything less than a gale but has a wheelhouse that is centraly heated and warm in winter in those gales.
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Old 18-11-2010, 09:40   #55
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... you can have any 2 of 3 things in a yacht. You can have either speed and comfort(big cost) comfort and safety (smaller cost)
Speed is of no concern at all to me.

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All the best Pete and Sally in our Colvic Watson M/S ketch rig that sails like a brick in anything less than a gale but has a wheelhouse that is centraly heated and warm in winter in those gales.
I've been looking at Colvics and I like them a lot. There was a Countess 33 ketch with bilge keels that looked very nice although the interior needed considerable updating. I'm reasonably good at woodwork and the wife can sew and upholster so, short of pulling bulkheads out, gutting the interior and freshening it up holds no fears.

Unfortunately, we're still building the cruising kitty at the moment so it is a case of look and learn for us at present.
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Old 18-11-2010, 09:52   #56
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colvic

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Speed is of no concern at all to me.



I've been looking at Colvics and I like them a lot. There was a Countess 33 ketch with bilge keels that looked very nice although the interior needed considerable updating. I'm reasonably good at woodwork and the wife can sew and upholster so, short of pulling bulkheads out, gutting the interior and freshening it up holds no fears.

Unfortunately, we're still building the cruising kitty at the moment so it is a case of look and learn for us at present.
Have a look at the colvic watsons as they are alot of boat for the money. We have more room below on ours than most 45 ft yachts. We have it all, washing machine, spin dryer,central heating,dvd,tv,sterio,computer,generator. Its just like a house on the water. If you want to see what the inside is like drop me a line with your e-mail and I will send some pics for you. Regards Pete at psg1640@gmail.com
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Old 18-11-2010, 09:57   #57
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Quote:
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I have been in the boat building business for over 40 years and have hear just about evrything to be said about osmosis and I can tell you the word was invented by the paint people to make money. The worst case \i have seen was an old westerly centaur after 35 years in the water it had about 40 % of the underwater part of the hull in blisters and a total weight of 156 kilos of water in the laminate. dried it out repaired the blisters and back in the water. Not a 1/4 of a knot faster and no more comfortable. I rest my case.
Well, never built a boat but was in the business and have been sailing and fixing boats for 35 years. Remember when "osmosis" was first becoming an issue back in the seventies. Was in a yard in Florida painting my bottom and watched a really nice Camper Nicholson down the way get treated for blisters. I watched as they started grinding, found complete delamination, and ended cutting away so much glass you could climb into the main cabin through the side of the hull.

I agree that technically, osmosis is not necessarily the cause of the problem but blisters are real and not an invention of the paint companies. 90% of the blister problems are pretty minor, cosmetic only and can be ignored for years but some of them, if left untreated, can become a serious structural issue.
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Old 18-11-2010, 10:11   #58
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osmosis

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Well, never built a boat but was in the business and have been sailing and fixing boats for 35 years. Remember when "osmosis" was first becoming an issue back in the seventies. Was in a yard in Florida painting my bottom and watched a really nice Camper Nicholson down the way get treated for blisters. I watched as they started grinding, found complete delamination, and ended cutting away so much glass you could climb into the main cabin through the side of the hull.

I agree that technically, osmosis is not necessarily the cause of the problem but blisters are real and not an invention of the paint companies. 90% of the blister problems are pretty minor, cosmetic only and can be ignored for years but some of them, if left untreated, can become a serious structural issue.
I agree with you about the sort of delamination and dry glassing you are talking about but must explain that as far as osmosis goes it is not a problem to the integratie of the yacht. It is the dry glassing that is the big problem with dry glassing is too little resin I am afraid I have seen quite a few early yachts from the usa with this problem.
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Old 18-11-2010, 10:15   #59
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"speed is of no concern at all to me"

What a very weird thing to say. I see the quest for speed under sail as a sign of good seamanship and an effort to most effectively use the forces and gear at hand.
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Old 18-11-2010, 11:12   #60
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I agree with you about the sort of delamination and dry glassing you are talking about but must explain that as far as osmosis goes it is not a problem to the integratie of the yacht. It is the dry glassing that is the big problem with dry glassing is too little resin I am afraid I have seen quite a few early yachts from the usa with this problem.
Well first, can't blame this one on the USA. Camper Nicholsons are made in the UK but to be fair, have seen plenty of US made boats with boat pox as well.

Also I looked closely at the work on the C.N. and the glass did not appear to be resin starved. Not sure if the delamination was due to glass layers that didn't bond during production or if the blisters had spread that badly.

I have seen many boats with blisters as large as 5-10 cm that were full of dark brown, acidic fluid that, from all accounts I have read, is a result of a reaction between the salt water that has penetrated the glass and unreacted resin or other chemicals used in the resin or layup process. And in many of these boats I have seen blisters and brown goo down into 2-3 layers of glass which was of course delaminated.

Maybe a moment to clarify terms. Technically osmosis is defined as molecules of a solvent (like water) passing through a permeable material, moving from an area where there is more solvent to an area where there is a less solvent ie concentrated solution. So in the case of boat blisters, the initial formation of the blisters is due to a reaction in the resin with moisture that entered the laminate by diffusion. Then after the an initial, small pocket of concentrated acidic solution forms it is enlarged by water entering under osmotic pressure trying to dilute the liquid in the blister.

So, osmosis doesn't start the reaction but is the mechanism that causes the blister to enlarge and poke out on the bottom and, over time to accelerate the penetration into the layers of glass causing delamination and weakening the structure.
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