Are Dagger Boards Worth it?

[Don Lobo]

howdy there cat people

seems the benefits of dagger boards are

1) you can point more upwind when they're down

2) you can reduce your draft to about 2' when they're up

3) when they're up, you have less drag and might go faster

4) you can choose more or less sideways drift depending on conditions

I'm wondering if these benefits are worth having yet another system that could fail, break, cause problems. Also, they take up a little room in the hulls.

please share your thoughts... are they worth it?

cheers!

Lobo

[Chotu]

Applying the same logic, why would you want to have another system like sails that can break?

Might as well just get a power boat because then you only have to worry about the engines.

You get dagger boards because you like to sail And to make your way to Windward well. They are also great in the event of the perfect storm. You can pull those up, pull your rudders up, and you’re not going to trip over yourself and flip the boat from the wave action.

The only reason not to get them is because you don’t care about sailing performance and because you want more room inside the boat. And more simplicity. Just like you mentioned. To me, those will be unacceptable trade-offs. Especially when it comes to the safety factor.

[rob denney]

There is no doubt about the benefits. What is not considered so often is the effect of an impact (logs, containers, big sea animals) on high performance boats.

Either the case cracks and leaks, the board breaks, followed by impacts to the prop and rudder or the boat comes to a halt. In which case anything not braced or tied down (including the crew) doesn't.

It is simple to make efficient boards that kick up in a collision. It is asking for trouble not to.

[catsketcher]

I really should put this down on a webpage, because it is a good question that gets asked a fair bit.

For those sailors who desire better performance, daggerboards are well worth any trade offs.

As well as pointing higher, you also go faster. This is because daggerboards produce less drag to equal the sideways force produced by the rig. Minikeels need to act at a higher angle of attack to produce the same amount of lift. This causes more induced drag. Also because the hulls crab sideways more, the hulls also have more drag. So you not only have less leeway with daggerboard, you go faster through the water. Add on a large reduction in wetted surface area and daggers are great for speed.

Most of the time during cruising, the daggerboards are up. This is because cruisers tend to run downwind. You would think this is where minikeels would catch up. But they have more wetted surface so are again slower. On a beam reach I might have my two boards half down but on a broad reach they are almost all the way up.

One other problem with minikeels that daggers get around is the shift in the centre of pressure. Some minikeel cats are a pain to helm in a seaway downwind - you go up and down all the time with the helm. This is because you can't raise the daggers so the CLR stays forward (really about midway), just when you want it aft a bit (you want lee helm until you are at deep angles). Also the centre of pressure in a foil can shift depending on the angle of attack. On a short chord foil like a dagger this 5-10% shift is negligible. On a 3.5m long minikeel this is a much longer distance, contributing to a shifting CLR. So a dagger cat with daggers up is much more compliant downwind.

Rob and I disagree totally about the safety aspects of daggers. When going fast, the daggers are usually raised as you are sailing downwind. Our cruising cat only gets pushed hard when I can bear away to reduce loads - that means a broad reach and that means boards up. So going fast is very safe almost all of the time. None of my friends have lost boards by running into things in the last 25 years. My cat does lots of sailing and I am yet to break a board. I did break a dagger in my tri, but that was a design that made it hard to lift the dagger and I had it down when motoring in a calm, (because it intruded into the very small cockpit), not something any cat would usually do.

My first multi (another tri) had a pivoting centreboard, and I am very glad not to have such a feature on any subsequent boat of mine. A tiny bit of shell can stop rotation, you get a really large hole in the bottom that is structurally inefficient and the things make knocking sounds underway and at anchor. As for a surface piercing centreboard - I think the engineering challenges would be significant. I know of two designs that did use them, a Sedlemyer and an alloy Fitzgibbon, but neither were at all fast. The first Australian beach cats (like the Yvonne and Quickcat) used to have centre mounted swing centreboards but this style did not make it into the 70s or 80s in higher performance types.

Make sure your cat can take the ground. It is not hard to make the bottom tough enough and make kick up rudders so that a dagger cat can take the ground well.

Other things I like about my daggers

- I can reach the bottom of my hull without getting my head wet. Makes it easier to clean the hull in winter.
- I can easily remove the daggers for painting. This means I can pre-emptively antifoul and keep the daggers (and the case as well) cleaner.
- Mine never make any sound
- They look cool
- They take up very little interior space because they are slightly canted and mounted on the outside of the hull centreline.
- I can dial up the amount of helm I want. If I am on a reach and the helm gets heavy it is because I haven't got enough board down.

Lots of people like daggers - you just have to work out if you are one of the people who will like them.

cheers

Phil

[Tupaia]

Upwind - obvious, daggerboards are more efficient.



Downwind. A cat with boards is virtually impossible to broach when surfing (not like a mono broaching) but turning due to the rudders cavitating and pivoting around the mini keels.

[captmob]

I raced Cats for years in the late 70’s Hobie 18 changed everything. Excellent engineering and much improved handling. A little learning curve on tacking but keep the boards. Just my humble opinion.

[Redreuben]

Can anyone comment on the practice of just using the windward board on a beam reach ?

[Paul Howard]

I have owned a 39ft. catamaran (for 16years) with fixed keels that I sailed about 60,000 miles full time cruising and local cruising.
I now own a 37ft catamaran (for 6years) with daggerboards and fixed rudders that I have cruised Cuba and the Bahamas and do local cruising and club races.

The fixed keels on the heavy cat (1992 Manta 38 extended) were good for full time cruising. We could dry out on any beach or sandbar with no more preparation than positioning it on a rock free area. We have anchored over sandbars in Brazil to let the tide set us down for a scrub and check of saildrive zincs.
The boat ran straight, occasionally surfing off the wave tops at over 20knots. We have sailed round Cape Horn and north of the Arctic Circle and many places between.
The cat with keels was much faster than the monohull we circumnavigated the world in and also much more comfortable and secure in extreme weather. We have been at sea on that cat in winds gusting over 60knots, having hove-to for up to three days at a time, lay to a sea anchor, etc. We had a couple groundings that slightly damaged the keels, though the repairs were easy and not serious or requiring immediate attention.

I like sailing the boat with daggerboards. Much more responsive, lighter, more fun to sail, as it is about half the displacement of the fixed keel cat we had previously owned.
My wife says the daggerboard cat is 'too bouncy' on the open sea on long passages when compared to the much heavier (nearly twice the displacement) fixed keel catamaran. But I like keeping the daggerboard boat light to get the performance.
I have lay hove-to with the daggerboard cat in winds about 35knots, the windward board about 3/4down, when we chose not to push to windward in that wind. The boat lay quietly and made slightly more leeway than when hove to with the keeled cat.
I have had some groundings, none at high speeds, lift the daggerboards and you are free. My fixed rudders are about 28" deep, with the rocker of the hull not that deep, so I cannot dry out on a sandbank like I could with the cat with keels where the keels were about three inches deeper than the rudders.
Boats are a compromise.

[Tupaia]

Originally Posted by Redreuben

Can anyone comment on the practice of just using the windward board on a beam reach ?

Depends on the cat. we only have one board port hull.


Firstly you would not have the board(s) down at all on a reach.



Upwind the theory is that having the windward board down would release if you lifted the windward hull.


Where you intentionally fly a hull you would need to have the leeward board down.

[rob denney]

Originally Posted by catsketcher

Rob and I disagree totally about the safety aspects of daggers.

Not at all! I think we are in total agreement about both the safety and performance aspects.
Where we differ is in 1) whether there is anything in the ocean to hit, 2) how fast you need to be going for a collision to be a problem and 3) whether there are situations when this speed will be exceeded with the board(s) down.

1) is pretty obvious to me. There is a lot of big stuff floating or just submerged out there.
2) is open for discussion. But if we agree that hitting something big near the hull/board interface will stop the boat almost instantly, then the effect on the crew when sailing/stopping at 5 knots can be compared to walking into a bulkhead, shroud, table edge or over the bow. At 10 knots it is equivalent to running full tilt. Any faster than this, the results are obvious.
3) maybe some sailors always lift their boards at more than 10 knots speed, but most don't. eg "If I am on a reach and the helm gets heavy it is because I haven't got enough board down."

Performance cats sail with the apparent wind ahead of the beam regardless of the true wind, which is anything from a broad reach to hard on the wind, depending on 'performance'. In this scenario, some board is required.

It is not trivial to make kick up daggers, but can be done with a bit of thought and ingenuity. Either in the hull where they are a potential source of leaks or, more logically, between the hulls where there are several other advantages besides kicking up.
The fact that no one does is in the same "peculiar behaviour of cruising multihull owners/designers" basket as swept back shrouds making it difficult and damaging to sail ddw

[Chotu]

The solution my designer chose to the problem of hitting something at speed with the board is just making the board weaker than the case/trunk.

My boards are just a big piece of foam with a little bit of glass around them. Uni directional where important for the loads.

The case is much, much stronger. It has a little bulkheads that hold it onto the hull, Manny wraps of TRIaxial, etc.

So the idea is the board breaks when you hit something and absorbs the impact. Not too hard to make a new board. Especially when you have another one on the other side as a male plug.,

[Redreuben]

I crew on Corsair and the like little trimarans, on virtually any point of sail and speed where the board is generating lift the boats need to be luffed or squared away to adjust the board up or down.
I assume this is the case with cruising cats too ?

[Redreuben]

@Rob denny. Hey Rob, I assume your solution to swept back shrouds is the free standing mast ? I understand the solution, not sure if I’m convinced, in the era of asymmetrics on multi’s not many sail dead down wind anymore but I guess cruisers might.
In the smaller boat racing scene I’m seeing textile rigging giving more resilience and reliability than wire that just goes “bang”. Lol
Daggers and boards outside the hull, must admit this fascinates me, have seen a lot of work on this over the years from canting forward and ventilation fences to imitating Whale “tubles” on the leading edge but nothing seems to complete with the endplate effect of a hull bottom.
What are your findings on the Harry’s ?

[macieknan]

Phillip Berman of The Multihull Company has an informative article and a vid on that topic that I highly recommend. He is an experienced builder making and selling cats with both options and was able to articulate pros and cons, attempted to measure some of these performance gains and generally offers sound perspective on this topic.

https://www.multihullcompany.com/art...s/&ved=2ahUKEw

Myself, i would consider this as a one of many features and would not reject a boat based on that single criteria.

[Redreuben]

@macieknan. That link didn’t work for me.