Permatrim Hydrofoils
- Thread starter SENSEI
- Start date
OK, We got rid of the cold Northers and water has returned to Perdido Bay! I was able to get the boat off the lift and over the sand bar. I ran about 60 miles with the new Permatrims.
I wish I could say--Permatrims solved all of the problems. But not so. There is a definately better handling at lower speeds--but the mileage suffers. There is a smoother transmission from definate displacement speed to planing speeds, with the engines trimmed own--bow down. I definately got the boat to plane down to 13 knots. I say down--because I found it better to get up on a plane at 19 knots and then slowly back down until the boat falls off a plane. However one has to give considerable power (read more fuel usage) between 9 and 13 knots to be on the semi plane in this range. The boat was "semiplaning better in the 10 knot range--but not as good as a C Dory.
What I see as most important is that the tunnel is kept open at 12.5 to 13 knots--and if one were in heavy seas (which I was not), the ride should be better.
There was no increase or decrease on the time from idle to 30 knots--still about 6 seconds.
What gets difficult to quantify is the difference at higher speeds. There is a bit of turberlance as you trim down which seems to buffet the motors around, so there is a sort of course vibration. The rooster tail seems less at full speeds. There is still a small rooster tail at 13 knots. But there is also a lot of water swirling around the Armstrong Bracket and the motor lower cowling at this lower speed. The steering is definately stiffer and cornering is slower at high speeds. The boat slides less on cornering, it stays level.
As you put the bow down, at high speeds, the horsepower required is increased and the RPM goes down and fuel consumption goes up, as you bring RPM back up. As you trim the bow up, you get to a certain place where cavitation occurs. I think that cavitation is slightly less than without the Permatrims.
Some numbers: These were close with both 90 gallons of fuel and 150 gallons of fuel aboard--no water, one person and most cruising gear aboard. There was various current and this was an average:
2700 RPM 12 knots 1.9 MPG motor trimed all the way down
2800 RPM 13 knots 2 MPG motor trimmed all the way down
3500 RPM 22 Knots 2.3 MPG neutral trim
3800 RPM 25 knots 2.2 MPG neutral trim
4000 RPM 27 knots 2.1 mpg Neutral Trim
4500 RPM 30.5 knots 2.0 mpg Neutral trim
4800 RPM 34 knots 1.8 mpg Neutral trim
4800 RPM 26 knots 1.7 mpg motor trimmed all the way down
5600 RPM 42 knots 1.4 mpg Motor neutral to slightly up. (I might have been able to take the speed up slightly more, but don't like to leave at WOT for a long time and didn't want further prop ventillation.
These upper numbers are very close to what I was getting before the Permatrims. I don't see any increase in fuel mileage. The speeds are less than when I first got the boat--since I have added a lot of gear and some windage.
I didn't put in the speeds of all of the way trimmed up, because as trimming up the RPM goes up and speed increases, but the mileage stays about the same--until cavitation occurs. Just before cavitation, the boat slows and MPG goes up.
The range of 8 to 10 knots takes a lot of power and the mileage goes down. If you get below 6 knots, then the mileage goes up, but turbine flow meters are not as accurate at low speeds. I did one run to Apalachacola (200 miles fuel to fuel) and got 2.3 mpg at 7 knots when running with trawlers. (Fill up to fill up)
The chop was 1 to 2 feet--the boat ran fine--in the 2 foot there was some minor bouncing and putting the bow down (motor down) smoothed that out--but at a cost of fuel consumption when the bow was all of the way down.
Marc had asked about "leverage to put the bow up with the Permatrims". My feeling is that you can bring the bow up slightly more with the Permatrims, but as it gets to a certain point, the prop cavitates. It is more likely to cavitate when in turbulant water--read rougher.
I will have to wait for a windier day to determine what happens with 3 or more foot seas and the permatrims. They definately accentuate the trim available.
Do they make any real difference--not in the up to two foot chop category. They don't make much difference in speed or mileage, and make steering a bit stiffer.
Bob Austin
I wish I could say--Permatrims solved all of the problems. But not so. There is a definately better handling at lower speeds--but the mileage suffers. There is a smoother transmission from definate displacement speed to planing speeds, with the engines trimmed own--bow down. I definately got the boat to plane down to 13 knots. I say down--because I found it better to get up on a plane at 19 knots and then slowly back down until the boat falls off a plane. However one has to give considerable power (read more fuel usage) between 9 and 13 knots to be on the semi plane in this range. The boat was "semiplaning better in the 10 knot range--but not as good as a C Dory.
What I see as most important is that the tunnel is kept open at 12.5 to 13 knots--and if one were in heavy seas (which I was not), the ride should be better.
There was no increase or decrease on the time from idle to 30 knots--still about 6 seconds.
What gets difficult to quantify is the difference at higher speeds. There is a bit of turberlance as you trim down which seems to buffet the motors around, so there is a sort of course vibration. The rooster tail seems less at full speeds. There is still a small rooster tail at 13 knots. But there is also a lot of water swirling around the Armstrong Bracket and the motor lower cowling at this lower speed. The steering is definately stiffer and cornering is slower at high speeds. The boat slides less on cornering, it stays level.
As you put the bow down, at high speeds, the horsepower required is increased and the RPM goes down and fuel consumption goes up, as you bring RPM back up. As you trim the bow up, you get to a certain place where cavitation occurs. I think that cavitation is slightly less than without the Permatrims.
Some numbers: These were close with both 90 gallons of fuel and 150 gallons of fuel aboard--no water, one person and most cruising gear aboard. There was various current and this was an average:
2700 RPM 12 knots 1.9 MPG motor trimed all the way down
2800 RPM 13 knots 2 MPG motor trimmed all the way down
3500 RPM 22 Knots 2.3 MPG neutral trim
3800 RPM 25 knots 2.2 MPG neutral trim
4000 RPM 27 knots 2.1 mpg Neutral Trim
4500 RPM 30.5 knots 2.0 mpg Neutral trim
4800 RPM 34 knots 1.8 mpg Neutral trim
4800 RPM 26 knots 1.7 mpg motor trimmed all the way down
5600 RPM 42 knots 1.4 mpg Motor neutral to slightly up. (I might have been able to take the speed up slightly more, but don't like to leave at WOT for a long time and didn't want further prop ventillation.
These upper numbers are very close to what I was getting before the Permatrims. I don't see any increase in fuel mileage. The speeds are less than when I first got the boat--since I have added a lot of gear and some windage.
I didn't put in the speeds of all of the way trimmed up, because as trimming up the RPM goes up and speed increases, but the mileage stays about the same--until cavitation occurs. Just before cavitation, the boat slows and MPG goes up.
The range of 8 to 10 knots takes a lot of power and the mileage goes down. If you get below 6 knots, then the mileage goes up, but turbine flow meters are not as accurate at low speeds. I did one run to Apalachacola (200 miles fuel to fuel) and got 2.3 mpg at 7 knots when running with trawlers. (Fill up to fill up)
The chop was 1 to 2 feet--the boat ran fine--in the 2 foot there was some minor bouncing and putting the bow down (motor down) smoothed that out--but at a cost of fuel consumption when the bow was all of the way down.
Marc had asked about "leverage to put the bow up with the Permatrims". My feeling is that you can bring the bow up slightly more with the Permatrims, but as it gets to a certain point, the prop cavitates. It is more likely to cavitate when in turbulant water--read rougher.
I will have to wait for a windier day to determine what happens with 3 or more foot seas and the permatrims. They definately accentuate the trim available.
Do they make any real difference--not in the up to two foot chop category. They don't make much difference in speed or mileage, and make steering a bit stiffer.
Bob Austin
Thanks Bob . Interesting findings . I appreciate the detail . I have question as to where folks are getting their Permatrins ? I think the 25 Cruiseship would benefit from one . I know that Bobs Machine Shop in Ruskin also make a similar product for alot less $ I wonder how they compare .
Marc
Marc
My experience with Bob's hydro has been very good.
It's amazing how I can now control bow angle.
I would assume because the permatrim is so much larger that the effect would be more pronounced then bob's, my concern is when is more too MUCH.
also they say because of it's size you can stand on the permatrim, but is the motor and mount made for that?
Of course there is the price thing, how much should a piece of cast aluminum cost.
just my 2 cents.
ignore it at your peril .......just kidding.
James
It's amazing how I can now control bow angle.
I would assume because the permatrim is so much larger that the effect would be more pronounced then bob's, my concern is when is more too MUCH.
also they say because of it's size you can stand on the permatrim, but is the motor and mount made for that?
Of course there is the price thing, how much should a piece of cast aluminum cost.
just my 2 cents.
ignore it at your peril .......just kidding.
James
james":24dei7n1 said:also they say because of it's size you can stand on the permatrim, but is the motor and mount made for that?
James
I certainly hope so, James, because that's been one of the tested safety options if I ever fall overboard while drifting and can't board using the swim step. Stand on the lower end where the Permatrim mounts and raise the motor. Heck if spousal attachment fell off, I'd probably use the same technique.
Don
Sneaks-- You might be better served if you stood on the cavitation plate and used the tilt function on your motor to give you a lift onboard...I know a guy, a pro walleye fisherman in the Dakotas, who fell in cold water while fishing alone. He couldn't get back in the boat until he got the idea of using his big motor to lift him up.
When I heard that story, I decided that would be my plan B. Even if all you could do is straddle the cavitation plate, it would get you up out of the water and higher than the transom.
Of course, this supposes that you have a trim button on the side of your engine.
Keith
When I heard that story, I decided that would be my plan B. Even if all you could do is straddle the cavitation plate, it would get you up out of the water and higher than the transom.
Of course, this supposes that you have a trim button on the side of your engine.
Keith
Marc, do you know anything about the tabs or whatever they call them , that I believe Volvo was making?I had some literature but have misplaced it.
here is a link to it
http://accessorycatalogue.penta.vol...de=192012837&childNode1=192013193&language=us
here is a link to it
http://accessorycatalogue.penta.vol...de=192012837&childNode1=192013193&language=us
Here is both sizes http://www.foreandaftmarine.com/TrimTabsVOLVO.htm
Not had any experience with them . Ill research however , they look
interesting............
Marc
Not had any experience with them . Ill research however , they look
interesting............
Marc
Wefings":2zvmofe3 said:
Marc, go with the biggest you can clear. I have 12 x 12 Lencos and they are scarcely adequate (no foil, though). The Lenco stroke seems to be shorter than the Bennett Hydraulic, and I think if I could just shove the tabs down a little farther I would be OK. But often times I am running with one all the way down to offset the passengers' weight. Once it is down all the way, there is no more I can do. I am a tab junkie too, and I firmly believe that you should have a good 10% of tab function that never gets used.
Please keep us up to date on the PermaTrim or whatever you use. I am thinking that might be cheaper than a tab upgrade, but have always been leery of how it might act in a huge following swell on the Columbia River bar.
Bob, its called the #B/T It used to be called True Tracker [stabilizer plate] . I think you can search it on their site . It looks like they recently changed it to add foils on the bottom and it looks slightly larger as well . I will try one , as the price is right !! I Think their site searches within itself, as I dont seem to get a url for the page.
Thanks Tyboo on the Tab advice , alot of folks will be using the boat so I dont want to make it so responsive one could get in trouble..........
Marc
Thanks Tyboo on the Tab advice , alot of folks will be using the boat so I dont want to make it so responsive one could get in trouble..........
Marc
Hello, I am new to this site and new to C-Dory ownership, in fact my C-Dory isn't built yet. I am awaiting the delivery of my 22 Cruiser. I can't wait. I have been boating for 14 years first on a 25' Oday sailboat and then a 25' Searay Sundancer, so I am a little unsure how different the 22 C-Dory is going to be for me ( I'm a little apprehensive). The other 2 boats were very heavy! Has anyone made a jump like that and how was the change? Also I keep hearing about the Permatrim - is it that big of a difference? I am getting the 115 Suzuki and the Bennett Trim Tabs - will I still need the Permatrim? I would truly appreciate any input.
Thanks Spiker
Thanks Spiker
Spiker,
You can always add a Permatrim or similar hydrofoil to your outboard drive later.
The C-Dory should seem lighter, more nimble, and responsive than your other boats, to my thoughts. The only characteristic of the C-Dories that needs some attention on your part is it's tendancy to pound at speed in chop. You can shift weight forward, but as you know, that must be done judiciously. You can engage your trim tabs to lower the bow, or you can use a hydrofoil, like the Permatrim, on your outboard drive leg.
Or, you can slow down and enjoy the trip without pounding.
Even though I have the larger C-Dory model, the TomCat 255, the bow can want to rise going at speed into higher seas. Also, the TomCat does not plane at the low speed that the 22's plane. The Permatrims (on two outboards) allows performance like a longer hulled craft. You can use them to plane at a lower speed, to keep the bow down, or up, or just to get more efficient thrust and better mpg by condensing the water flow atop the prop.
No need to worry, if you are not sure now, about Permatrims or not at this point. I had mine put on before delivery and am glad I did.
John
You can always add a Permatrim or similar hydrofoil to your outboard drive later.
The C-Dory should seem lighter, more nimble, and responsive than your other boats, to my thoughts. The only characteristic of the C-Dories that needs some attention on your part is it's tendancy to pound at speed in chop. You can shift weight forward, but as you know, that must be done judiciously. You can engage your trim tabs to lower the bow, or you can use a hydrofoil, like the Permatrim, on your outboard drive leg.
Or, you can slow down and enjoy the trip without pounding.
Even though I have the larger C-Dory model, the TomCat 255, the bow can want to rise going at speed into higher seas. Also, the TomCat does not plane at the low speed that the 22's plane. The Permatrims (on two outboards) allows performance like a longer hulled craft. You can use them to plane at a lower speed, to keep the bow down, or up, or just to get more efficient thrust and better mpg by condensing the water flow atop the prop.
No need to worry, if you are not sure now, about Permatrims or not at this point. I had mine put on before delivery and am glad I did.
John
mikeporterinmd
New member
spiker":2b93f9nn said:
The advice I've been given is that if you have tabs on a 22, you do not
really need a Permatrim. I'll play this summer with the tabs, but I
suspect we'll be fine.
As to the change: we went from a 30' Searay to the CD-22. So far,
I'm happy. But, we bought near the end of last season and so far
have not slept on the boat. Working on it, though, is much easier
than a Searay. I also enjoyed running it. As I watch fuel prices on
land creep fast $2.50, I'm also happy to not have a 20gph boat any
longer. I'm hoping we'll get back to joyriding more!
Mike
Warren,
Well, just remember that I am more of a casual user and Dr.Bob is somewhat of a detail-oriented specialist, well-versed in marine use/construction.
I know that using the Permatrims going upwind in a storm uses more fuel, but I can say that Roger and I both were so happy to be able to go fast without pounding in those heavy seas!!!
To me, having the option of more control is a blessing. I will usually go with equipment that increases my choices and control. To that end, the Permatrims are great.
I have not yet had all my instruments calibrated accurately enough to do the detailed analysis that Dr. Bob has.
I have only had the chance so far to use the boat in stormy seas, so no reasonable evaluation by me has been done.
I can tell you that I hang on to every word Dr. Bob types on here, because he's gone out and paid his dues, done the work, and thought it all out before posting!
But, I still love my Permatrims.....ouch!
John
Well, just remember that I am more of a casual user and Dr.Bob is somewhat of a detail-oriented specialist, well-versed in marine use/construction.
I know that using the Permatrims going upwind in a storm uses more fuel, but I can say that Roger and I both were so happy to be able to go fast without pounding in those heavy seas!!!
To me, having the option of more control is a blessing. I will usually go with equipment that increases my choices and control. To that end, the Permatrims are great.
I have not yet had all my instruments calibrated accurately enough to do the detailed analysis that Dr. Bob has.
I have only had the chance so far to use the boat in stormy seas, so no reasonable evaluation by me has been done.
I can tell you that I hang on to every word Dr. Bob types on here, because he's gone out and paid his dues, done the work, and thought it all out before posting!
But, I still love my Permatrims.....ouch!
John
Spiker,
Many of us have had much heavier boats--as well as both smaller and larger. There is a real spectrum of boaters. I would NOT get the permatrims for the CD 22, especially with the 115. The Bennett trim tabs will do what you want--put the bow down. One has to be a bit cautious in equating the trim tabs to the permatrims (another boating group tends to do this some what in error). The Permatrims are being put on the Catmarans, because one cannot put trim tabs on them. Permatrims, Doel Fins etc are also put on inflatables, boats which are underpowered and have a problem getting on a plane.
For the CD 22, you will trim the boat with the Bennett Trim tabs, and then fine tune the performance with the outboard trim. You want the thrust to be parallel to the water.
Marc--thanks, I found the "True Tracker" in the search. It is quite different than the Permatrims. The Permitrim bolts on the top of the cavitation plate with 10 1/4" bolts. The True Tracker bolts on the bottom of the cavitation plate, and has fins above and below the plate (looks cast?)--and is held on with apparently 4 (by the photos) bolts.
I would be concerned about the ability to run the 16" prop on the 150 Suzuki with a plate under the cavitation plate. It would be most interesting to see two boats side by side with the same props and engines to see how they worked. The Permatrims look to be a little larger, but the True trackers are a lot cheaper!--$45 vs about $140 per fin.
Many of us have had much heavier boats--as well as both smaller and larger. There is a real spectrum of boaters. I would NOT get the permatrims for the CD 22, especially with the 115. The Bennett trim tabs will do what you want--put the bow down. One has to be a bit cautious in equating the trim tabs to the permatrims (another boating group tends to do this some what in error). The Permatrims are being put on the Catmarans, because one cannot put trim tabs on them. Permatrims, Doel Fins etc are also put on inflatables, boats which are underpowered and have a problem getting on a plane.
For the CD 22, you will trim the boat with the Bennett Trim tabs, and then fine tune the performance with the outboard trim. You want the thrust to be parallel to the water.
Marc--thanks, I found the "True Tracker" in the search. It is quite different than the Permatrims. The Permitrim bolts on the top of the cavitation plate with 10 1/4" bolts. The True Tracker bolts on the bottom of the cavitation plate, and has fins above and below the plate (looks cast?)--and is held on with apparently 4 (by the photos) bolts.
I would be concerned about the ability to run the 16" prop on the 150 Suzuki with a plate under the cavitation plate. It would be most interesting to see two boats side by side with the same props and engines to see how they worked. The Permatrims look to be a little larger, but the True trackers are a lot cheaper!--$45 vs about $140 per fin.
Warren,
I wouldn't characterise my review of the Permatrims as not liking them.
I try and be objective with some numbers in my comparisons. I would say that for the average use, in less than 3 foot seas, the Permatrims would not make a lot of difference. I had the chance to run the boat slightly over 1000 miles without the Permatrims--and now I'll get a chance to run over 1000 miles with the Permatrims by then I'll have a solid opinion. I didn't take them off.
From what I saw, the boat will plane down 2 to 3 knots slower. This may be very significant in heavy seas. I have a report from another C Brat who may post on the forum that he found by powering up and increasing the speed with the Permatrims he was able to keep 18 knots in "Wind waves 2 to 4 ft. NW swell 4 to 6 ft at 11 seconds".
I am waiting for a windier day so I can try the Permatrims in similar conditions locally.
I wouldn't characterise my review of the Permatrims as not liking them.
I try and be objective with some numbers in my comparisons. I would say that for the average use, in less than 3 foot seas, the Permatrims would not make a lot of difference. I had the chance to run the boat slightly over 1000 miles without the Permatrims--and now I'll get a chance to run over 1000 miles with the Permatrims by then I'll have a solid opinion. I didn't take them off.
From what I saw, the boat will plane down 2 to 3 knots slower. This may be very significant in heavy seas. I have a report from another C Brat who may post on the forum that he found by powering up and increasing the speed with the Permatrims he was able to keep 18 knots in "Wind waves 2 to 4 ft. NW swell 4 to 6 ft at 11 seconds".
I am waiting for a windier day so I can try the Permatrims in similar conditions locally.