Performance Study: Daggerboards & Fixed Keels

[yeloya]

Balance's positioning reminds me what we call "aspirine positioning" in marketing; "good to everyone, every day and for everything". This simply doesn't exist. The same boat cannot be good either with or w/out daggerboards, design is a whole. If we take out the daggerboards of a Catana and add a keel, or add a daggerboard to Lagoon 450 removing the keels, what's gonna happen ?
It's virtually impossible to create exactly the same conditions for two boats to be compared and talking about 0,2 kts of speed difference or 1-2 degrees of difference in leeway . It doesn't make sense to me. Even a slightest difference in sea state, current or a second of stronger or lighter wind during the test would make this difference, if not more.


Cheers


Yeloya

[thinwater]

Having built speed polars, you need to remember that practically none of the data is actually what is on the curves. You use GPS and instruments to continuously log data, and then a program takes all of those data points and interpolates and extrapolates them on to curves.

• This averages out all of the gust and tiny current variations, for both cases. Seastate must be controlled, but will average out if enough data is used.
• You are NOT making a run in 14 knots and a run in 16 knots. You are making may runs, on many courses, at many speeds, and then connecting the dots. So long as you cover all of the courses within a few knots of the full range, the interpolation is very accurate.
• The loading (gear and stores) needs to be the same.
• Sail trim is a big variable. In this case, windward trim with boards and keels is different.
• You mark time slots where the boat was as well trimmed as you feel it can be. You don't want to include tacks or tuning time.
• The wind indicator must be calibrated. This can be done with a calibrated meter, but is often done by motoring up wind and down wind repeatedly.

It's unlikely conditions will make a huge difference, because so much data is required, collected over many days. Trim is a separate matter.

[admiralslater]

I have sailed a great deal on boats with both arrangements and own two (I know I know) with boards . There are real advantages to both . The advantages of daggerboards are the performance ones that have been mentioned plust the ultimately reduced draft when anchouring etc . The down sides for cruising imo as follows, requires deeper water to go up wind ,reduce interior room , interference with deck layout and requires extra equipment to handle raising and lowering. Also most cannot be beached ,I say most because the Gerard Danson Outremers have skeg with a small foot on them that allows beaching .
Fin keels ... welll some are better than others . Original Pdq36s without the hard top and out boards actually went to weather quite well . Not like a dagger board boat but ok . Some designs I have seen dont have much down there at all.
The advantages imo are ability to sail in the water you can float in ,which is very useful in places that have flats like the Bahamas and the Keys etc . Hauling is easier as is beaching. Protection of appendages is also great .
When searching for the boat that ended up being the Outremer we did not excluded fix keel boats .
The early post talking about the polar chart that stoped at 45 degrees hit the nail on the the head ,the biggest difference between board and keels is in this range

[catsketcher]

I once talked to a guy who had a Leopard or similar and we were talking about a lagoon anchorage at Middle Percy Island. I told him he would have to dry out and he said he was not comfortable with it in his boat - it had keels.

I think there are a couple of reasons why my daggerboard boat is no worries on the hard - she has an overlap of glass on the bottom, very small 100mm deep keels (which you can't see when she sits on the sand), kick up rudders and retractable outboards. We beach her lots, there have never been times we have seen other boats drying out and not done the same if we wanted.

Daggerboards make real sense to me on a 38ft outboard powered boat with kick up rudders. The two boards are small enough for me to lift out on my own and they require no huge tackle to raise and lower (I push them down with my hand/foot most of the time). They have the bottom 300mm cut off and reglued back on to allow a fail safe and I have almost never touched with them down. They take up no usable space in the interior as they are offset and make no noise (nice cases). I am really happy with boards and would never want keels in a million years.

(I almost always run aground doing less than 2 knots - first the depth alarm goes off - if sailing - and this is incredibly uncommon - we tack. If motoring into Hill inlet or somewhere sandy and calm I take a look over the side - or maybe I am up top conning - no worries, the alarm goes off at 2m. Then it keeps getting lower, no worries if it looks fine, then one rudder kicks up a bit - that is okay - then if the other kicks up I know that I have to get out and push or we stop and anchor. In calm conditions it is perfectly safe - done it at least 40 times.)

But if my boat was 50ft long and had diesels the choice would be harder. I can run over fishing bouys probably better than a minikeel boat because most of the sailing is downwind and that means boards up. So if I run over a log the rudder fuse lets go and the rudder pops up as we hear the rumble underneath and I go "What happened?" and then go and push the rudder down. That may not happen on a keel boat. The log, (fishing float more likely here) could wrap around the keel, diesel leg or non kick up rudder.

So for the large cats, daggerboards get big, you have diesel legs or shafts and then wonder about protection. A 40ft daggerboard Schionning that is circumnavigating installed a deadwood for the diesel (like a trawler) but that increases wetted surface for light winds. So the advantages of daggers probably are accentuated for a smaller (sub 40-45ft depending on displacement) outboard powered and kick up rudder cat. Shaft drive diesels are probably better for daggers than legs as you can run the shafts back so that they get protection from the hull bottom when beached. Those choices are the ones that a more performance orientated owner will want anyway so the choice is made easy for some.

I used to have a centreboard in a small tri I owned as a kid. It was more of a pain than the dagger boards and probably slowed me down more. I ran aground with the board down much more on the tri than on my cat - I always have the depth sounder on and as we don't have logs in Oz the boards will mostly only get hurt by fishing floats and the bottom.

cheers

Phil

[44'cruisingcat]

Originally Posted by Saleen411

I spoke with Phil at the Annapolis Boat Show a couple years ago.

While discussing $$$ for his cat, he informed me that I could probably save about $45,000 if I ordered the Balance 451 WITHOUT daggerboards.

I was like REALLY?.....we could do that?....hmmmm. That's significant. If I were to order that yacht today, I still couldn't say if I would opt for the daggerboards considering the cost and modest performance gains.

That price difference is ridiculous, and completely unjustifiable. There's either obscene levels of profiteering, or the builder simply doesn't want to do daggerboards.

[44'cruisingcat]

Originally Posted by Thumbs Up

There are a couple things about this study that fail to quantify the advantages of the daggerboard model. In the offwind part of the tests, they said that they left the daggerboards down so that part of the study is obviously flawed. ]

Exactly. It seems to me that a comparison in which the daggerboards were not used correctly is either a waste of time or was biased from the start.

[Thumbs Up]

It makes sense now why the study was skewed. Phillip Berman (the multihull company) wrote it and has a stake in Balance Catamaran (China) as well. The Balance (with or without boards) is aimed at a niche market which is small compared to the total catamaran market which is their bread and butter. They just need to promote the catamaran lifestyle. These guys are catamaran brokers who are breaking into manufacturing. But mostly they want to sell used boats, and most of those don't have daggerboards!

[Thumbs Up]

I just reread the article. He is the owner of Balance. He is promoting the daggerboards if you read what he says. But the study was done by "Wolfson Unit for Marine Technology and Industrial Aerodynamics" (whoever that is but they don't sound like sailors). Anyway, they never mention VMG comparisons which is what matters. He can make something building these boats, make a bunch more selling them, and get paid again reselling them. is that a win win win?

[admiralslater]

Originally Posted by 44'cruisingcat

That price difference is ridiculous, and completely unjustifiable. There's either obscene levels of profiteering, or the builder simply doesn't want to do daggerboards.

I am not defending Mr Berman but having been intensely involved with the development of the daggerboard package for my Pdq 36 I dont think his number is quite so crazy as it sounds .
You will get some people who will say”a bit of ply wood some 2x4s and your done “ .These are the same folks who will be repairing in a couple of weeks . A few will get it right but that is not good enough in production.
Our boards are hollow with carbon ribs and seven feet long , the trunk has rebates for gides on each side and is slim enough to go through the side deck ,it also transfers loads from thehull to the main bulkhead through which it passes .
The lay up and installation was over 100 man hours using the most skilled people in the plant. Then the hardware need to raise and lower the boards .
And we have not even dealt with the development costs.

The result was fantastic ,in full race trim with good crew we can tack with good vmg about 85 degrees , if pinching about 80. The boards can be ajusted under full load . We actuall only use one board at a time so they are raised and lowered at every tack .
You may not think 45000 is worth it for boards and that is fine . But that does not mean they are over priced.
I dont want to get stuck in the weeds on this ,I just wanted to express my thoughts

[44'cruisingcat]

Originally Posted by admiralslater

I am not defending Mr Berman but having been intensely involved with the development of the daggerboard package for my Pdq 36 I dont think his number is quite so crazy as it sounds .
You will get some people who will say”a bit of ply wood some 2x4s and your done “ .These are the same folks who will be repairing in a couple of weeks . A few will get it right but that is not good enough in production.
Our boards are hollow with carbon ribs and seven feet long , the trunk has rebates for gides on each side and is slim enough to go through the side deck ,it also transfers loads from thehull to the main bulkhead through which it passes .
The lay up and installation was over 100 man hours using the most skilled people in the plant. Then the hardware need to raise and lower the boards .
And we have not even dealt with the development costs.

The result was fantastic ,in full race trim with good crew we can tack with good vmg about 85 degrees , if pinching about 80. The boards can be ajusted under full load . We actuall only use one board at a time so they are raised and lowered at every tack .
You may not think 45000 is worth it for boards and that is fine . But that does not mean they are over priced.
I dont want to get stuck in the weeds on this ,I just wanted to express my thoughts

I've built and fitted boards and cases to a couple of boats including my own. It's done 37000 miles without needing any repairs.

I'd certainly be happy to be paid $45000 for them. That would represent something over $40000 for less than a month of my labour.

[admiralslater]

As I said earlier for some people it is doable . But on production boats it means have reproducible results . Different interior and deck molds and diferent cabinets. 2 moulds each for board and trunk.
If you are as skilled as I am sure you are . Give your self a raise .

[thinwater]

No comments on centerboards?

[mark_morwood]

Originally Posted by thinwater

No comments on centerboards?

I suspect that like me, very few people here have experience with centerboards on catamarans so can't offer much in the way of informed comment so are keeping quiet. Yeah I know, when has that ever stopped anyone! :-)

I don't think I've ever knowingly seen a catamaran with centerboards, though I do know they exist. Sorry.

[cuffy]

The Wolfson unit, University of Southampton, have are probably one of the most respected yacht and ship research centres in the world.
Try google

[CGirvan]

Originally Posted by catsketcher

The two boards are small enough for me to lift out on my own and they require no huge tackle to raise and lower (I push them down with my hand/foot most of the time).

cheers

Phil

I'm interested in the dimensions of the boards you have as I'm toying with the idea of converting to daggerboards and haven't come up with a plan for how to adjust the boards depth.


If anyone has any links to info on controlling daggerboards I would really appreciate it.


Thanks


Colin