MacGregorSailors.com

DrV – The condensed version...

The hull speed is simply the maximum speed that a displacement hull can move through the water without needing and extaordinary amount of power to go faster.

When guests ask this question when sailing, for a laugh, a friend and I invariably repeat in unison “The hull speed in knots equals 1.34 times the square root of the length in feet at the water line”.

Simply, to understand it, put these two facts together...

1. the larger a wave is, the faster it travels through water, and
2. the longer the hull is, the larger the wave it can make.

So therefore, to make a boat faster, make it longer at the water line, so it can make a larger wave, so it can move faster through the water with that wave. The largest wave it makes is the sum of the two waves that come, one from the bow, and the other from the stern.

If you wanted to double your speed from hull speed, you would need 2^6 power, or 64 times more power. For example, if you needed 50 hp at hull speed, you would need 3200 hp to double your speed! (Actually more, in practice).

As Russ points out, this all changes once you start to plain on the surface, as our boats do.

If that is still not clear, just ask.

-Brian.

Note that this only happens at a water/air interface and is peculiar to displacement-hull boats – so you can't make a submarine, or airplane faster by making them longer.

I put barrier and anti-foul on my daggerboard, and inside the daggerboard trunk as far as I could reach when it was new, so I didn't have the opportunity to notice whether or not it increased friction, but in any case I do relieve the pressure on it when retracting while sailing. The anti-foul I used (Micron) has a waxy finish, so I doubt it increased friction on the trunk.

I normally keep the DB retracted when docked, so only the bottom 12” or so remains wetted, but since it is out of direct light, there has been little fouling in fresh water. I think it's not a bad idea to do the daggerboard to protect it and prevent growth, or to make it easier to remove growth. My dealer advised me to do the rudders as well, but I'm happy I didn't take his advise on that- they spend most of their lives fully retracted and out of the water.

-B.

Re slower on a beam reach. Mines like that too. The new jib helps. It does not get blanketed by the main as easily.
I am going to order a main from Judy too. I think that will help the boat.
Ix

Putting Soggy Paws in the water in another month. Any recommended waxes/finishes/etc. for the hull prior to launch?

seahouse wrote:I put barrier and anti-foul on my daggerboard, and inside the daggerboard trunk as far as I could reach when it was new, so I didn't have the opportunity to notice whether or not it increased friction, but in any case I do relieve the pressure on it when retracting while sailing. The anti-foul I used (Micron) has a waxy finish, so I doubt it increased friction on the trunk.

I normally keep the DB retracted when docked, so only the bottom 12” or so remains wetted, but since it is out of direct light, there has been little fouling in fresh water. I think it's not a bad idea to do the daggerboard to protect it and prevent growth, or to make it easier to remove growth. My dealer advised me to do the rudders as well, but I'm happy I didn't take his advise on that- they spend most of their lives fully retracted and out of the water.

-B.

Id imagine barnacles would create a little more friction than af paint. I did the db as well and decided not to do the rudders for the same reason; Also someone mentioned they had done theirs in blue af and when they use the stern swim ladder they come out of the water blue as well. If you're planning on slipping I'd definitely af the hull. If not there are lots of marine waxes out there.

Do bottom paint every two years - or as needed. I'm thinking more of the hull normally - but not always - above the water.

yukonbob wrote:Id imagine barnacles would create a little more friction than af paint. I did the db as well and decided not to do the rudders for the same reason; Also someone mentioned they had done theirs in blue af and when they use the stern swim ladder they come out of the water blue as well. If you're planning on slipping I'd definitely af the hull. If not there are lots of marine waxes out there.

Collinite Fleetwax. 870 liquid cleaner-wax is what I use most, but it does have a fine abrasive. The 925 liquid fiberglass boat wax I believe is similar, but without the abrasive. And the 885 past wax is the toughest, but harder to apply.

http://www.collinite.com/marine-wax/

http://www.collinite.com/assets/Uploads ... tguide.pdf

I've got one also, but I understand any kind of spinnaker is not a one-person job.

DrV wrote:

Boblee wrote:My favourite sail is the spinnaker up to probably 15knots of wind

Wow!
That's all I can say.
Already have anymmetrical spinnaker, your post gives me a push to start thinking about how to rig a spinnaker.
(Came from official dealer even with proper line, but no manual whatsoever how to rig and even to raise it. Shall I install a new halyard?).

I remember few times last summer I was sailing downwind (and that was still slow, from 1.5 to 4 kts depending on wind!) , so you gave me a solid reason to install it.

but after that I get yelled at too much,

Why? No heeling involved! Why would anybody be unhappy? Or do they start to give you advices how to go faster?

[quote="dlandersson"]I've got one also, but I understand any kind of spinnaker is not a one-person job.

[quote="DrV"]

I fly mine with ATF sock single-handed several times a year.

And you clearly are not a ordinary person. ah is.

Newell wrote:

dlandersson wrote:I've got one also, but I understand any kind of spinnaker is not a one-person job.

DrV wrote:
I fly mine with ATF sock single-handed several times a year.

Thanks for the kudos, no, not particulary braggin just saying so that ordinary folks won't think it's impossible.

Flying the asym solo is not difficult.

Just don't try it if you are timid with heel and don't loose it when you get an unexpected gust of wind.

The spin is a special sail that acts like a parachute with wind.

Once she gets a mouth full, she tends not to let go of it....

Things can get quite hairy, quite fast...

http://www.youtube.com/watch?v=s0Bti3FUoDg

http://www.youtube.com/watch?v=0EIyKcoYaMY

http://www.youtube.com/watch?v=Fm0i8F6rMII

G

Very nice videos!

Do you have a close-up shot of the bowsprit? I have a brand-new assym and bowsprit from BWY but haven't had the chance to use them yet - any hints you can provide on how the bowsprit is best mounted would be great.

I've got a trade show to do in Tacoma, WA next weekend and am taking the opportunity to drag the M there for a week - then in June will be taking her to Bayfield, ON for a family get-together, hopefully will have time to get up to Georgian Bay. Can't wait for these trips - so far, opportunities to sail the M have been way too limited!

- Clay

seahouse wrote:I normally keep the DB retracted when docked, so only the bottom 12” or so remains wetted, but since it is out of direct light, there has been little fouling in fresh water. I think it's not a bad idea to do the daggerboard to protect it and prevent growth, or to make it easier to remove growth. My dealer advised me to do the rudders as well, but I'm happy I didn't take his advise on that- they spend most of their lives fully retracted and out of the water.

After 4 seasons of scrubbing nasty slime off the bottom of my unpainted bottom, I pulled the dagger out of the trunk to examine it. It looked great. I expected the 12" wetted portion to be full of slime, but it wasn't. A little dirt but not bad at all. So, I guess being in the trunk keeps it from fouling.

I would NEVER paint the rudders unless I was going to leave them down for weeks which I don't do.

--Russ

The nice thing is if you leave them down and they get slimy, I just leave them up next time. We had a smaller berth last year on the end for a while. I'd leave them down in case someone decided to take them off for me with their boat. There is a huge case of twofootitus where we are, and too much money. I've seen guys buy a 35 ft Bayliner as a first boat cause their buddy has a 28. Needless to say this guy managed to remove all of his rod holders (complete with rods) and VHF antenna off the side of his boat docking one day. Luckily the steel fishing trawler next to him didn't even really mind.