Folding vs Fixed Prop STW?

[Davidasailor26]

More data points at

Folding and feathering propeller test

Which is the best folding or feathering propeller for you? Emrhys Barrell compares 15 props in a test of speed, thrust, drag, stopping speed and propwalk

www.yachtingmonthly.com

At 5 knots the drag of a fixed prop is about 25% of the drag of a bare hull. A feathering prop is barely on the chart, and folding prop is too small to plot.

Also seems to address the age old question of whether a freewheeling or locked prop is better.

 

[jon hansen]

P.H.R.F. : pin head racing federation. into the wind i'm dfl, off the wind i win every time on corrected time. i would never race around the bouys. can't win. the modern guys don't like us old CCA boats, for good reason.

it ain't right. i didn't make the rules. still............... my trophies look nice on the mantle

i never raced much. will never again. racing aeolus is like having a barn dance on your mom's dinning room table. not easy on the wood

PS: i have read bethwaite 40 times. it's really all about the wind. the captain that places his vessel in the stronger winds, wins every time. aeolus is set up to sail to it's rating. the boat is prepped. fresh sails. i understand the wind better that almost everyone, almost. and i'm 'dennis conner' smooth at the wheel.
having rockstar friends for trimming and tach helps too. it's all about the crew. constantly tweeking all the details.

 

[jon hansen]

100 year old design. locked sailing prop in rudder aperture.

plus smooth bottom

 

[Kings Gambit]

Regarding the handicap penalty for a folding or feathering prop, that number 3 sec per mile was pulled from somewhere where the sun don't shine. That's also true for all the other adjustments. There is no empirical data to support 3 seconds per mile vs 6 or 9.

Folding and feathering props cut drag, less drag more speed. I don't know that one brand is significantly better than another. The difference is most noticeable at low speeds.

When it comes to motoring, feathering props beat folding props because the blade shape is better in reverse. I've had a Martec Folding Prop and a Max Prop Feathering prop, both worked well. The Max Prop works exceptionally well in reverse.

So. I just checked the 2020 Southern Cal PHRF adjustment to standard ratings. A two-blade fixed now gets a +4 sec/mile adjustment. Going from fixed to folding would incur the -4 sec/mile penalty. I believe it was 3 sec/mi earlier. It’s 9 sec/mi for the 3-blade prop. So, sun does not shine in sunny Southern California? More like where you are nicht?

 

[jon hansen]

do you think they do some sort of testing? OR are they just some group of guys that really just throw darts at the wall. king's, i suggest it's more towards the later. there is no testing. they don't want the casual sailor to show them up. there are no test that i've ever heard of.

one design sailboat racing is the only fair ish game out there.

 

[jon hansen]

every region has different rating numbers for the same vessels. why is that? there is no science. lots of politics. oh yeah, lots of politics. no science, no tests.

 

[dlochner]

So. I just checked the 2020 Southern Cal PHRF adjustment to standard ratings. A two-blade fixed now gets a +4 sec/mile adjustment. Going from fixed to folding would incur the -4 sec/mile penalty. I believe it was 3 sec/mi earlier. It’s 9 sec/mi for the 3-blade prop. So, sun does not shine in sunny Southern California? More like where you are nicht?

And they determined this number how? Was there any tank testing? Real world analysis? Or did the measurers get tired of the complainers and gave them an extra second?

That is my point. PHRF measurers figure out the ratings based on their judgement, no real data collection or analysis.

 

[jon hansen]

thankyou Dave!!!

 

[Kings Gambit]

And they determined this number how? Was there any tank testing? Real world analysis? Or did the measurers get tired of the complainers and gave them an extra second?

That is my point. PHRF measurers figure out the ratings based on their judgement, no real data collection or analysis.

Just recall that PHRF means Performance Handicap Racing Fleet, so it’s empirical. Yachts racing with folding props do better on average than boats with two-blade fixed props by 4 sec/mile on the race course. No data there? Just thousands of races.Ever tried making a buffer? You can follow the formula for the # of grams of dihydrogen potassium phosphate and the # of grams of monohydrogen potassium phosphate needed in a certain volume of water to make a buffer with a certain pH. Does it EVER come out to that pH in practice? No. Must add a little acid or a little base to get there. Sometimes you must “tweak” by trial and error to get something right by looking at the measured outcomes.

 

[dlochner]

Just recall that PHRF means Performance Handicap Racing Fleet, so it’s empirical. Yachts racing with folding props do better on average than boats with two-blade fixed props by 4 sec/mile on the race course. No data there? Just thousands of races.Ever tried making a buffer? You can follow the formula for the # of grams of dihydrogen potassium phosphate and the # of grams of monohydrogen potassium phosphate needed in a certain volume of water to make a buffer with a certain pH. Does it EVER come out to that pH in practice? No. Must add a little acid or a little base to get there. Sometimes you must “tweak” by trial and error to get something right by looking at the measured outcomes.

Ask a measurer to show you the data. Ask them what statistical procedures they used to determine the ratings. Ask them how they know they are correct in the ratings and adjustments.

The answer you get will be the sound of crickets in the desert.

It is very easy to scam the PHRF ratings, the guys at the top of the fleet know how to do that. It has very little to do with any empirical data.

 

[jon hansen]

no, it's political.

 

[Kings Gambit]

Regional PHRFs have governing boards of members from SCYA-member clubs and harbor associations; bylaws and rules.Yes, there is a chief handicapper; but ratings can be appealed, and thus reviewed, An owner may appeal his own yacht’s rating, or act as a third party challenge to another owner’s yacht. Appeals and decisions are made public. Meetings are announced and are public to members. What? All of these super-competitive a-holes are in cahoots to game the ratings against everyone else? Where would some of the big names like Disney and Conner fall in this spectrum of skullduggery?

Where is the line? How would you do it? Run a series of controlled experiments on every yacht? Who pays?

 

[Davidasailor26]

Regional PHRFs have governing boards of members from SCYA-member clubs and harbor associations; bylaws and rules.Yes, there is a chief handicapper; but ratings can be appealed, and thus reviewed, An owner may appeal his own yacht’s rating, or act as a third party challenge to another owner’s yacht. Appeals and decisions are made public. Meetings are announced and are public to members. What? All of these super-competitive a-holes are in kahoots to game the ratings against everyone else? Where would some of the big names like Disney and Conner fall in this spectrum of skullduggery?

Where is the line? How would you do it? Run a series of controlled experiments on every yacht? Who pays?

I agree. PHRF is very unapologetically not a scientific process of measuring boat characteristics. There are other rating rules that do that. PHRF makes a projection of a boat’s performance based on similar boats, then adjusts over time based on observed performance.

Curious that a handicap board would up the adjustment to 4 seconds though. The standard PHRF adjustment, or split between any boat, is in 3 second increments. Wonder why they think they have precise enough data to change that adjustment by just one second per mile.

 

[jon hansen]

Dave, your a master teacher. you write eloquently. you have great 'street smarts'. the tens of thousands of kids you have helped guide while they all squirm and connive. some just refuse to want to learn i suppose. enjoy listening to how you teach. your great.
king's. your a good man. always kindly share. but understand, in all those clubs, groups, boards, ...........................
there is not one sailor, designer, captain, ................. they are all trained to do other things.

it just is.

"More sail"

 

[Kings Gambit]

I agree. PHRF is very unapologetically not a scientific process of measuring boat characteristics. There are other rating rules that do that. PHRF makes a projection of a boat’s performance based on similar boats, then adjusts over time based on observed performance.

Curious that a handicap board would up the adjustment to 4 seconds though. The standard PHRF adjustment, or split between any boat, is in 3 second increments. Wonder why they think they have precise enough data to change that adjustment by just one second per mile.

I wondered that myself, about the 1 second -increment change, instead of 3 sec. I am not presently a member, so have not been getting the "news."

 

[BarryL]

Hi Guys,

Some interesting stuff here.

Some more or less random comments and thoughts from me.

If you're a cruiser, someone who enjoys being on a boat and going places, and doesn't really care if you get there in 3 hours or 6 hours, who will motor when the wind is light, who won't constantly adjust your headsail sheet, car position, backstay, traveler, etc, and doesn't care if you're going 6.1 or 6. kts, then a fixed 3 blade prop is probably OK for you.

If you race, and race in light air, then you NEED a low drag prop.

PHRF - it isn't perfect, and it isn't always fair. But, it's the best game in town for people who want to race but don't want to race one design, and who aren't going to get freaked out if they don't win all of the time. Face it, there is NO way to make it 'even' for different types of boats in all weather conditions. I do a lot of PHRF racing. Single handed, double handed, fully crewed, windward leeward, distance racing, etc. I do it all. I do it casually on my boat. I do it pretty seriously on a friend's boats. I have raced one design, etc. Sometimes you get lucky and the wind favors you. Othertimes you get unlucky and there is no way you're going to win. If that is going to really bother you then PHRF racing is not for you.

I am the vice commodore for my sailing association, the Mt. Sinai Sailing Association. We run over 35 races a season. We have maybe 25 total boats that race in a given year. Everything from J80 to Catalina 42. We have 4 divisions. We try (very hard) to make it fair (and fun) for everyone. If the wind is 5 kts or less the slow boats are not going to be competitive. If the wind is 15 kts, the well sailed 'slow' boats (With good crew and good sails) are going to correct over the fast boats. That's just the way it is. We do a spring series, summer series, and fall series, each with 4-8 races. Over the SEASON, the well sailed, well prepared boats will win over the rest of the fleet. To me, that says that PHRF works. Any singular race may have a different result, but over time, the better sailed and prepare boats will win.

If you have an better system then PHRF I am all ears.

Personally, I like that we all try to get together after the race to share a snack, a beverage, and some stories about sailing.

Barry

 

[Jumpstart]

I'm going to be kind here. But Mr Hansen and Lochner made statements and accusations that are patently untrue.
1. PHRF isn't perfect.
2. Not all PHRF areas are the same. In fact most don't actively handicap. They just copy numbers out of the national PHRF book.
3. PHRF areas usually use an average wind condition for the area when assessing handicaps. Thus the difference in ratings sometimes between areas.
4. The smaller the PHRF region the less reliable the handicaps.
5. Most area give a 6 sec/mi credit for a 2 bladed prop. That is 2 boat lengths/mi in 10 knots of air.
6. Boats that either perform well in light air or or heavy air tend to have uneven results. Most PHRF areas have liberal weight limits but do limit crew weight so light air boats can't put 15 on the rail when the wind pipes up.
7. PHRF groups assume that you have boat prep, sails, and crew competency equal to the rating band you are competing in. Handicappers being experienced racers assess that. Around here if you rate around hundred you better have good crew, newer laminate sails, a smooth and clean bottom and an experienced skipper. Absent that you won't be competitive. That holds true for any handicap system.

I'm really sorry that you guys are unhappy about not winning unless it is a luck dog day for you. My guess is that no current rating system is going to make you happy. I've worked hard to optimize my boat, train a crew, and buy the best sails I can afford ( not to be confused with the most expensive sails). I'm still learning every time I go out. I have raced on 35 different types of boats in the 37 years I've been racing. I have also given back to the sport serving on a regional handicap board for 30 years and on the US Sailing national board and national appeals board. I'm most proud of the people who started racing with me and have gone on to buy and race boats. I will always take on crew that want to learn.

I've raced in IOR, MORC, IMS, Americap, IRC, ORR, and this year ORC. Pretty much have seen the positives and negatives of all the modern handicap rules. The big difference is that I take the handicaps for what they are and try to succeed within limitations. You guys seem to think the handicap systems should conform to how you want to outfit your boat and race. Good luck with that. You are much better at whining about inequities of handicap racing on a sailing forum. That's fine if you want to cruise but don't complain about the people who want to race.

 

[jon hansen]

i stand by everything i say. you might want to reread what i wrote. i never whine.
i said that the people on these groups are not designers. are you a yacht designer.
was a member of NCYC from 62' til 16'. i know your playground. i have well over 1,000,000 miles at sea. i qualify as a sailor. i am high trained at my sailor skills. i've been captaining these vesssels we play on since i was fourteen. 35 different types of boats? and you, the decider of things, were the captain of these? what are your marine credentials?
i think you make my case.
i like your boat. i like it's name. i too have been seconds from death. a skilled surgeon saved my life.
look at the picture of my 66' boat bottom. the boat will sail to it's PHRF rating.

the OP is claiming that his local PHRF rating should be used the exactly understand the drag of different props. that is plain wrong. cause PHRF is not science. now is it. the boards are not manned by marine designers are they. professional seaman? they do no science.

they are filled with nice guys (yachtsman) that that try their best, sort of.
i stand by my statement that it is politics. why, first hand observation!
i was rarely at the club, if ever? why? i was gone out at sea

 

[jon hansen]

what part of my boat do you think is not ready to race? i have never asked for any changes in the rules cause i'm not race ready? i played in PHRF. i won in PHRF. you are making stuff up about me and my boat.


and then there is my Ascow. you ever sailed on a fast boat?

 

[Jumpstart]

Never claimed to be a yacht designer. If you don’t think PHRF committees look at VPPs of similar boats also look at ratings from measurement handicap systems you are uninformed . 1mm miles is impressive. I’m guessing that was as a professional mariner not racing sailboats. Never raced an A scow but have helmed a 68’ sled in 6 Mac races. Aren’t A scows one design boats and don’t qualify for PHRF because they aren’t a cruiser racer or have an auxiliary? Great for inland lakes but might sink in something like a Mac race. I’ve crewed on a variety of boats including a couple at NCYC as part of my handicapping duties. Learned more on the rail about relative boat performance than driving my boat. My current boat was at NCYC at one time. At the end of the day, PHRF with all of its flaws still has the largest critical mass in the US and has lasted longer than any of the systems. Please suggest a viable alternative to PHRF for racing different designs and keep the cost to a reasonable yearly fee. BTW there is a way to see the relative difference a fixed prop makes according to science. Go to the ORC web site and find 2 sister ships with fixed and folding props. You can look at the difference at different wind speeds and get an idea. Average out the differences and voila, you have the one number difference. Unfortunately their are other factors that come into play like. Is the prop offset (C&Cs, Sabres) blade size, strut location relative to the keel etc. You might conclude there is no straight line answer. Also for that level of accuracy you will have to spend a lot more than $40