Hull speed and weight of sailboats?

Question

by the way, thanks for answering my questions. My question is this. If a boat length has a finite hull speed, then how much should weight really factor into a boat decision. I am using this argument in my head to justify a 7000 pound 28' pearson Triton.

Answer 1

I see The Usual Suspects got here first and I have no quibbles with the three previous posters and commend a Triton as a great first bullet proof boat.as to weight/length

there's a bunch of factors, but weight usually = strength. A J28 is probably only 4,000 pounds, will sail circles around a Triton and would be suicide to take out in conditions that Triton likes. There is also the consideration that a cruising/live aboard boat gets loaded down with stuff............almost every cruising boat I see pull into St Thomas from its first passage paints it waterline higher!  You put 2,000 pounds of food water books people dogs wind generators and what not on a Triton and it barley notices......2,000 pounds on a J28 and it bogs right down.....

yeah, and spend the money on a good marine surveyor for the Triton.........probably nothing really wrong with it but there's likely 6 or seven 1,000 dollar things need doing that surveyor will catch........

Answer 2

As mentioned above, The main factors involved in hullspeed are the waterline and the pressure that the rig can generate in the wind.  The biggest drawback you'll find is that it may require a bit more wind to get her up and going and that light air days may be a bit of a bore.  If you've got some larger light sail inventory, you can overcome that problem.

I've got a 28 foot sailboat with a curb weight of 6700 lbs;  not much different than your choice.  It's capable of very good speed in moderate air.

The biggest thing you'll want to pay attention to, as far as performance is concerned, is to have a balanced helm.  Once your on your upwind leg, with the headsail trimmed, adjust the main so that there is only a slight weather helm on the boat (about 1/8 of a turn on the wheel).  This ensures that the boat is travelling through the water in the most efficient manner.  On a downwind leg, a broad reach is one of the best points of sail.  Keep the jib cars forward and make sure that the main isn't blanketing the headsail.  Beyond these basic starting points, it's just a matter of experimenting with the sail trim to see what she likes best.  Good luck and have fun.

Answer 3

Chad...that's a great boat! Very forgiving of inadvertant error.  Weight is a function of motion (less tender or tippy) and seakindliness...if you will...how skitterish the boat is. A light boat is not very forgiving. The more she weighs the better she will split a wave and ride through. Some light boats slam onto the top of each wave and skip over them.

Any boat can exceed it's THEORETICAL hull speed if pushed hard enough.

Hull speed correlates to waterline length in the theory.

Theoretical Hull Speed= 1.34 (sq. root of waterline)

for a 25ft waterline...1.34x5=6.7  knots THS

To push a displacement hull past it's THS you need a strong rig and strong nerves. It takes a lot of wind and wave push. You are risking breaking the rig but if it holds up...the boat will slowly start to get deeper set in the water. It's called submarining...and your waterline length is increasing as well.  The key is to stop before the deck is awash! hehe

Here's an example of how the boat is sucked into the water....take the tap on your kitchen sink...turn it on full blast...rest the middle knuckle of your index finger against the edge of the aerator...the water should be skimming along your finger...if your finger is relaxed enough, it will be drawn into the stream of water. That's what happens to a displacement boat as it begins to exceed THS...it gets drawn into the water.

Answer 4

Hull speed is th square root of the water line length in knots.

This is one of the limiting factors in he speed a boat can attain.

Weight and shape , wetted surface , surface condition, vessel surface are other factors. in how easily it can attain that hull speed.

A condition that you should consider in a 40 year old boat is its condition. Be sure to have a competent survey done.

Pearson Triton is a good boat. Well shaped, well designed, easily driven hull. it will not exceed hull speed but will attain it easily. It is stable too.

Answer 5

I second Dave's opinion on the Triton, it's a great boat. Back when Pearson was building them, nobody really knew how strong Fiberglass would turn out to be, so they really overbuilt the boats. I used to race on a Pearson Wanderer, and my parents had one too. If the Triton you're looking at is in good shape, it's definitely a good boat still. Built like a tank, good heavy weather performance, good form stability. Just don't expect it to be a light-air boat.

I only have a few minor disagreements with Dave's post. For one, the squat he mentions usually only happens in shallower water. you also get stern slip if you're too close to a bulkhead or another boat - your stern will get drawn toward them.  The other thing is that while a heavy displacement boat generally has better rough weather handling upwind, that weight can become a hindrance downwind. If your boat can't accelerate when it's hit with a puff downwind, you're more likely to broach, whereas a lighter displacement boat will accelerate down the puff.

Everything's a tradeoff and there's no perfect boat, but it's hard to go wrong with a Pearson.

Answer 6

The theoretical hull speed is like the previous poster said 1.34 x sqrt (waterline).

although there's a few points to consider, waterline at rest is not the same as when sailing, IE, heel the boat over and the water line usually increases due to shape of the hull.

heavier boats may not have enough sail area to overcome drag to reach hull speed.

another is although most sailboats are thought to be displacement rigs, on some of the lighter rigs you can get them to semi plane. IE surfing.