I wanted to find out, How can i get my Hunter H33 go faster under power? Would changing propeller help, or are there any other tricks somebody knows?
Thanks,
Oleg
Thanks,
Oleg
going faster
- Thread starter olegedelman
- Start date
Power sailboat racing has not yet taken off. Speed gains can be measured in hundreds of dollars per fractions of knots so it would be a costly proposition with no trophy at the end. Keep the hull clean and the engine in a good state of tune and motor sail when a little speed is desired.
Prop
Well as asked what is your present speed and RPM"s when motoring and what prop do you now have.
See what prop you now have and than ask what others have on this forum for your model and compare with them,that is what I did with my 07 H-36 and what I found out the wrong prop pitch was installed from my dealer and I was not happy with motoring speed which was around 6knts full power and if conditions were calm.
I did change to a pitch that other 356/36 same boat that others had and went one step better and got a 3 blade flex o fold and been very happy with sailing and motoring very much improved.
I now have no problem doing6.5 to 7 knts motoring and sailing depending on wind 6 to 7knts no problem.
Nick
Well as asked what is your present speed and RPM"s when motoring and what prop do you now have.
See what prop you now have and than ask what others have on this forum for your model and compare with them,that is what I did with my 07 H-36 and what I found out the wrong prop pitch was installed from my dealer and I was not happy with motoring speed which was around 6knts full power and if conditions were calm.
I did change to a pitch that other 356/36 same boat that others had and went one step better and got a 3 blade flex o fold and been very happy with sailing and motoring very much improved.
I now have no problem doing6.5 to 7 knts motoring and sailing depending on wind 6 to 7knts no problem.
Nick
Top speed...
for a displacement hull sailboat is calculated at 1.34 times the square root of the waterline.
In everyday terms, more like just the square root of the waterline will give you a good top cruising speed (dirty hull, fully loaded with gear, full tanks, etc.).
Alternate choice is the MacGregor 26! :dance:
for a displacement hull sailboat is calculated at 1.34 times the square root of the waterline.
In everyday terms, more like just the square root of the waterline will give you a good top cruising speed (dirty hull, fully loaded with gear, full tanks, etc.).
Alternate choice is the MacGregor 26! :dance:
The fastest you can go in clam water is around 7.7 knots. You can get her going much faster on the down hill side of a large wave however.
Re: Prop
at 2800rpm, i get about 5.8-6 knots. i think that is slow for a 29hp engine. its a sail drive, how do i find out if i have correct pitch? i would like to get closer to 7 knots if that is at all possible. I have a 3blade prop from the factory; i assume they give you the least expensive one considering its a Hunter.
at 2800rpm, i get about 5.8-6 knots. i think that is slow for a 29hp engine. its a sail drive, how do i find out if i have correct pitch? i would like to get closer to 7 knots if that is at all possible. I have a 3blade prop from the factory; i assume they give you the least expensive one considering its a Hunter.
Re: Top speed...
so waterline at 29.5 will give me a cruising speed of 5.43 knotts. i cant get any faster?
so waterline at 29.5 will give me a cruising speed of 5.43 knotts. i cant get any faster?
If you follow the formula on the Wikipedia page you have a theoretical hull speed of 7.27 kts. That is the speed of the boat through the water, not over ground. Is your knot meter calibrated? Are you using GPS speed, which is speed over ground? Are your bottom and prop clean?
The other factor to consider is the fuel cost for pushing the boat to hull speed. Once the bow wave starts forming the fuel efficiency will take a nose dive. The faster you go the more water you are pushing and a wave forms with the boat in the trough. As you try to exceed hull speed the boat starts to climb the wave which means the boat is both pushing tons of water and trying to go up hill. That takes a lot of fuel.
Planing hulls as found on power boats are a different matter, they are designed to get on top of the bow wave and then plane. Most sailboats are displacement hulls that can't get on plane with out a lot of horsepower and lift, think a modern sport boat with a spinnaker up surfing down a wave.
thank you everybody. This gives me some things to think about. I am considering taking it to Bahamas so every improvement to speed under power is a big plus. I don't think MacGregor can make that journey.
Suggest you do some reading on the design and engineering of displacement hulls vs. planing hulls. With a displacement hull there is a theoretical hull speed that is a function do the length at the water line. Within practical limits of horsepower it wouldn't matter what size engine or how much horsepower you have you cannot consistently exceed hull sheet. And remember this is the theoretical speed assuming clean hull and suitable sea conditions. It is possible that when surfing down the face of a wave you could exceed hull speed but as others have pointed out this is a temporary condition.
Before everyone jumps- notice I said within practical limits.
That is why a sail boat hull is shaped the way it is. So when it heels you present a longer water line thereby increasing theoretical hull speed. The benefit of this hull shape is that it tends to take rougher water better. The downside is that unlike a planing hull you can't apply horsepower to make the boat rise up out of the water and ride on that water / air interface.
Before everyone jumps- notice I said within practical limits.
That is why a sail boat hull is shaped the way it is. So when it heels you present a longer water line thereby increasing theoretical hull speed. The benefit of this hull shape is that it tends to take rougher water better. The downside is that unlike a planing hull you can't apply horsepower to make the boat rise up out of the water and ride on that water / air interface.
i got and understand all that, but cruising boat is loaded up with all kinds of stuff especially if one to live on it. that is why i asked this question. Fully loaded i'm no where near my theoretical speed, thats where i thought a different prop design (other than what is supplied by a manufacturer) would somewhat improve my speed. Going 10-20 miles i wouldnt care, but going 300+ , if i need to motor for a while, any small improvement would help.
A few things to check on.
How are you measuring speed? Knot meter accuracy is + or - a significant amount and depending on calibration could be even worse.
This site is full of threads on tachometer Inaccuracy stories so check that. If you are trying to measure your speed and engine output against each other using two accuracy suspect devices you may be guessing at best.
Once you've dealt with those to the point where you have reasonable idea of speed and wide open throttle RPMs then you can start to look at other factors.
As others have said
Hull cleanliness can be significant factor.
Prop pitch would be where I'd look next. Make sure its within specs. Props are expensive and unless you really have hungering for a new one, pitch is a far lower cost thing to check. I will say I did replace my 3 blade fixed with a 3 blade feathering max prop. With that I got better motoring performance in forward (pops right up to hull speed) way better reverse performance and picked up about 1/2 knot sailing speed because it feathers under sail. That said it was $3 grand for the new prop.
You will find tons of threads on here regarding that conversation and as many opinions on various brands of props that people love.
How are you measuring speed? Knot meter accuracy is + or - a significant amount and depending on calibration could be even worse.
This site is full of threads on tachometer Inaccuracy stories so check that. If you are trying to measure your speed and engine output against each other using two accuracy suspect devices you may be guessing at best.
Once you've dealt with those to the point where you have reasonable idea of speed and wide open throttle RPMs then you can start to look at other factors.
As others have said
Hull cleanliness can be significant factor.
Prop pitch would be where I'd look next. Make sure its within specs. Props are expensive and unless you really have hungering for a new one, pitch is a far lower cost thing to check. I will say I did replace my 3 blade fixed with a 3 blade feathering max prop. With that I got better motoring performance in forward (pops right up to hull speed) way better reverse performance and picked up about 1/2 knot sailing speed because it feathers under sail. That said it was $3 grand for the new prop.
You will find tons of threads on here regarding that conversation and as many opinions on various brands of props that people love.
Our 2004 Hunter has a non-sail drive 3 bladed Prop and the 3YM30 engine, @2800 rpm I get about 5.9kts, @3000 rpm 6.1, the engine I believe is good for continuous power up to 3400 rpm, so to get more speed run the engine at higher rpm, fuel consumption goes up disproportionate to speed increase. The Yanmar is a relatively high revving engine, I don't believe that re-propping for more speed at 2800 rpm is the best solution, but a prop expert can discuss your situation better, the best this forum can do is advise as to who is good in your area.
Motor Sailing however, will yield the best performance, you will achieve higher speed at a lower rpm even in light winds. except of course, straight downwind, which only works well on a H33 or E33 with engine on. Humor aside, motor sail for best performance on a long passage. We will keep a sail up even in no wind conditions to make our boat more visible to others.
I don't believe a folding prop is the answer for faster motoring, but is for faster sailing with engine off. Also boat hulls seem to be slower at the end of the season, compared to the beginning.