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Old 27-02-2010, 12:56   #16
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Daggerboards would only weigh slightly more than minikeels, if anything. And there is the option with a cruising boat (since you won't be flying a hull) of only having one, which would probably weigh less than a pair of minikeels.

There's no need to raise the board so far that you leave a slot in the hull - you raise it to the extent that it doesn't protrude beyond the hull, but it still fills the slot. So the drag caused by a raised board would almost certainly be less than that of a minikeel.

I've yet to see a minikeel boat that could match the daggerboard boats i've sailed on, on any point of sail.
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Old 27-02-2010, 18:18   #17
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Some owners are concened about racing but I am not interested in racing and if I am crusing i am also not concerned with matching all other cats on all points of sail. With adequate diesel drives and preferably shafts run your motors up to hull speed to go directly into wind or off a lee shore if necessary. .

An understated advantage of mini keels for cruising is the extra bouyancy (rather than weight its drag that is more the issue) and hence ability to have adequate tankage and carry cruising loads. I prefer to have what I need to stay away and be independent of resupply as long as possible.

44C I agree there seems to be evidence that only one daggerboard would do the job.

There is a trend with the current new generation cats being released to have both good speed and load carrying. This will be the trend and focus of designers as we go foward over the next few years.

One here http://www.sail-the-difference.com/f...up_results.pdf

There are plenty of racing designs available and current crusiers with inadequate load carrying. Just check blogs and websites where cruising for many is compromised by carrying jerrycans and chasing fuel and water.


Many cats have inadequate load carrying which is more a design issue and mini keels can help.

There are some new cats that can resolve this by design. Prefer to have what i need to stay away and be independent of resupply until necessary.

My view as I search for the right vessel (cat) for cruising.
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Old 27-02-2010, 19:41   #18
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There is a slight danger in comparing "mini keels" with dagger boards.
One first has define a 'Mini Keel' on a Catamaran.
Also to understand that it does not have the function of a monohull's keel.
In Australia and New Zealand dagger boards are a common feature on many designs of catamarans - for 2 major reasons :- 1. providing better windward performance and
2. providing the ability to go into very shallow water. At the same time the bottom of the hulls will often be provided with a flat area on which a sacrificial hard wood strip is fixed to allow the Cat to be beached. For some reason this flat area with its wooden strip was termed a mini keel, and this name has stuck; unfortunately a belief has grown that these "mini keels" improve sailing performance, the jury is still out ! One thing is for sure if the cat's hulls are deeply submerged then the Cat will tend to move as if it was fixed to a track, regardless if it has mini keels or none.
Dagger boards probably owe their origins to Lee Boards seen on many Dutch sailing Barges that made passage into the North Sea.
If only the modern day dagger board copied the design of Peter Southwell which had the case on the outside of the hull, with its lower opening above the waterline - which made it very easy to clean etc. (Peter Southwell the Island Spirit catamaran designer)
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Old 02-03-2010, 13:00   #19
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minikeels

There are a few different variations to the minikeel designs - the FP range of cats, I believe has the best solution! The minikeels are made with glassed in polyurethanefoam, which again are glued with Sikaflex into the recessed cassettes inside the hulls.

There are several benefits with this design, firstly safety, the keels are not part of the hull integrety and will sheer off if the boat hit an object in the water or go aground.

Secondly the volume of polyurethane creates a lot of buoancy, which can be used for payload.

Thirdly, replacement after keel damage can be done anywhere by anyone with next to no tools, just order a new keel from FP! This also makes the repair done by the insurance company a lot cheaper than if the hull itself would suffer damage.

All the same the boats sit comfy on their keels on the hardstand.

HAppy lead free sailin
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Old 18-03-2010, 05:40   #20
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It comes down to performance and access. Deep high aspect boards allow a performance multihull to match and usually exceed a performance monohull in windward VMG (even considering the affect of apparent wind on pointing ability). Retracted boards reduce wetted surface and increase downwind speed. Our 12,000# 44' performance cat regularly romps past 20 knots reaching, and beats all performance monohulls, and most racers, on or off the wind. These advantages loose relevance when the multihull is heavy (low cost, high speed, comfort - you only get two choices - we chose cost, speed, and spartan). Boards allow access into skinny water (we draw 15" boards up). Groundings are bad with or without fixed keels. Careful design and quality construction (and shallow draft / careful navigation) minimize risk. Multihulls support bigger sailplans, go faster, and do it all in skinny water, especially if they are light. Don't forget to consider beam. We carry a bigger sail plan, go faster, and are more stable because we are 28' wide overall and our waterline hull beam is about 30". Yes, dockage is a headache. Finally - props in the water slow any boat. A large light multihull can run retractable outboards, like our 2 - 9.9 Yamahammers.
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Old 18-03-2010, 06:45   #21
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DwightSusan,
Was your Wild44 hauled out in Rockport Texas last summer? If so we spent a little time drewling over it! One of the prettiest boats I've ever seen, so nice we even went to meet the builder in Corpus. AJ
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Old 18-03-2010, 07:01   #22
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Seems to be confusion on the boards, centerboards vs. dagger boards. What cruising cats use dagger boards, other than the F-boat trimarans? With centerboards that can rotate back on a pivot point if you strike something, doesn't that alleviate the concerns on leaking daggerboard trunks?
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Old 18-03-2010, 07:47   #23
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Here's the deal. Daggerboards or mini-keels each have significant adavantages and disadvantages. I wouldn't buy a cat based strictily on one or the other. Every boat is a compromise. Buy the boat that suits you, your significant other and your pocketbook. Live with the limitations. Every boat will have 'em. You either live with them or you sell the boat.

BTW, Canibul, many cats have daggerboards. I've seen very few that have centerboards. Mostly older designs, and I mean older by a lot, and also the Gemini 105. You might mitigate some damage with them but you tend to lose inside space and have a bit more complication than with a daggerboard. (i.e. pin/hinge maintenance and sometimes hoisting mechanisms)
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Old 18-03-2010, 09:43   #24
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I think Chris does a good job explaining a justification for why both are nice to have.

Atlantic Catamaran FAQ - by Chris White Designs

Are there daggerboards or centerboards to aid upwind performance?

Why are there fixed fins on the hulls of the Atlantic Cats?


What about rudder protection?

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Old 18-03-2010, 11:42   #25
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Its one thing to ground on shallow bottom. Quite another to hit a coral head at full speed. Think in terms of impact psi.
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Old 18-03-2010, 12:09   #26
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Discussions of boards seem (to a casual observer) to fall into two categories; there are the "You should not have them" and the "I like them fine" groups. The first seem to think the world would be better if there weren't any board -equipped boats around, while the proponents don't really care what other people decide. If performance were not an issue to catamaran owners, they would have a barge and get the use of all that wasted space between a catamaran's hulls. So performance IS an issue. Since remarks about tripping over a board in the ultimate wave, or being mowed down by a sea full of board eating containers have be equitably answered, I am left to wonder if most of the objections to boards are really rooted in deep feelings of unweatherliness!

Its a joke, folks: remain calm and compose a witty reply lest we sink to the level of the anchor warriors!
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Old 18-03-2010, 12:31   #27
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With a mini-keel
I would feel
Like I was able to
Stand on my own two feet.

Choosing a board
Won't leave me floored
Whilst I pass
My buddy boat from leeward.

But in any instance
While going the distance
Having no system beneath you
Will be an absence of resistance.
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Old 18-03-2010, 13:02   #28
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cchesley -

Excellent!
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Old 18-03-2010, 14:02   #29
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Quote:
Originally Posted by Canibul View Post
Seems to be confusion on the boards, centerboards vs. dagger boards. What cruising cats use dagger boards, other than the F-boat trimarans?
All of Bob Oram's designs have daggerboards, AFAIK all of Schionnings, Farrier's F41, many Chris White designs, Gunboats, some of Robin Chamberlins designs, and no doubt many more than these few I can think of in a couple of seconds.
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Old 18-03-2010, 14:16   #30
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Quote:
Originally Posted by Canibul View Post
Its one thing to ground on shallow bottom. Quite another to hit a coral head at full speed. Think in terms of impact psi.
Common practise is to make the bottom 300mm or so of the board "sacrificial", ie solid foam, lightly glassed, so it can break off in an impact. You make the daggerboard cases much stronger than the boards themselves.

Depending on the boat, rudders can be protected by allowing them to kick up if hit.

Remember, boards will only be fully lowered when sailing to windward in light conditions. At "full speed" the boards would not be fully down. If running downwind they would be fully raised.

Sailing at "full speed" around coral heads probably isn't the best practise anyway, but I feel safer around shallow water with retractible boards, kick-up rudders, and outboards than can be raised, leaving a boat that can float in less than 18" of water, than I do with fixed rudders, saildrive legs and mini-keels all hanging down and unable to be lifted.

I'm not saying mini-keels don't have advantages - they do. Like everything there are pro's and cons to both.
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