permatrim questions
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Marty-
Great observations and conclusions!
From my experience, any outboard powered boat from 25 feet and under benefits greatly from a Permatrim because it
1. lengthens the apparent length of the boat to the water and waves, smoothing the ride,
2. provides a great lever to optimize trim,
3. levels the boat and holds the bow down to cut chop,
3. enables earlier planing when accelerating, and
4. provides slower planing speeds.
5. Also, a nice big hydrofoil, regardless of its make, also makes for a larger platform from which to re-board the boat after an unscheduled swim, etc.
(Several of these benefits named above overlap, but I've tried to show the full range of the Permatrim's benefits.)
Joe. :teeth :thup
Great observations and conclusions!
From my experience, any outboard powered boat from 25 feet and under benefits greatly from a Permatrim because it
1. lengthens the apparent length of the boat to the water and waves, smoothing the ride,
2. provides a great lever to optimize trim,
3. levels the boat and holds the bow down to cut chop,
3. enables earlier planing when accelerating, and
4. provides slower planing speeds.
5. Also, a nice big hydrofoil, regardless of its make, also makes for a larger platform from which to re-board the boat after an unscheduled swim, etc.
(Several of these benefits named above overlap, but I've tried to show the full range of the Permatrim's benefits.)
Joe. :teeth :thup
Joe,
No argument on any of your list, however I do wonder about the increased pressure from the longer (and heavier) lever arm on the tilt and trim motor of the smaller (ie 40hp size outboard on a 22 when these engines are basically designed for a smaller boat, more the size of the 16. (This is really ironic because this is the first time I have come up against a possible reason for running a single, like a 90, on the 22.)
So specifically, #2, #3, and #4 are applying pressure on those trim motors when these things are going on. Is that going to cause an early failure in some component of the trim tilt mechanism? This is assuming that with a Permatrim on, these pressures are generated in regular use. I would also assume that #5 would be a very rare occasion for use in that process.
Joe Said:
I’d be interested in input from anyone with experience in using the P-trims on twins on the 22’s or 25’s or from the mechanical, Engineering, technical folks here too. I think David and Val came up with a really good question, that has not been addressed before.
Harvey
SleepyC :moon
No argument on any of your list, however I do wonder about the increased pressure from the longer (and heavier) lever arm on the tilt and trim motor of the smaller (ie 40hp size outboard on a 22 when these engines are basically designed for a smaller boat, more the size of the 16. (This is really ironic because this is the first time I have come up against a possible reason for running a single, like a 90, on the 22.)
So specifically, #2, #3, and #4 are applying pressure on those trim motors when these things are going on. Is that going to cause an early failure in some component of the trim tilt mechanism? This is assuming that with a Permatrim on, these pressures are generated in regular use. I would also assume that #5 would be a very rare occasion for use in that process.
Joe Said:
I’d be interested in input from anyone with experience in using the P-trims on twins on the 22’s or 25’s or from the mechanical, Engineering, technical folks here too. I think David and Val came up with a really good question, that has not been addressed before.
Harvey
SleepyC :moon
Harvey-
You might try talking to a Technical Rep. from Yamaha and/or another manufacturer about the stress issue.
My gut feeling, however, is that they would be conservative in what they recommend to avoid giving you the "green light, and then suffering a failure for which they might be held responsible in some way.
My association with mechanical engineers has always taught me that they overbuild everything by a factor of 4 to 10 (if possible) to avoid any failure. (!)
Of course, it's the hydraulics that will be really tested (other than the anti-ventilation plate), and there's where the issue lies.
Probably the approach you're using of asking for practical experience from persons using hydrofoils/Permatrims on the 40-60 hp motors is the most realistic and pragmatic approach possible, and also the most likely to give good advice and predictive information.
Also, don't forget you have TWINS, so have TWO MOTORS to divide the Workload, Stress, and any additional Wear between.
(Put than down in your covered list of reasons to prefer twins to singles that you keep next to your computer!) Ha! :lol:
Joe. :teeth :thup
You might try talking to a Technical Rep. from Yamaha and/or another manufacturer about the stress issue.
My gut feeling, however, is that they would be conservative in what they recommend to avoid giving you the "green light, and then suffering a failure for which they might be held responsible in some way.
My association with mechanical engineers has always taught me that they overbuild everything by a factor of 4 to 10 (if possible) to avoid any failure. (!)
Of course, it's the hydraulics that will be really tested (other than the anti-ventilation plate), and there's where the issue lies.
Probably the approach you're using of asking for practical experience from persons using hydrofoils/Permatrims on the 40-60 hp motors is the most realistic and pragmatic approach possible, and also the most likely to give good advice and predictive information.
Also, don't forget you have TWINS, so have TWO MOTORS to divide the Workload, Stress, and any additional Wear between.
(Put than down in your covered list of reasons to prefer twins to singles that you keep next to your computer!) Ha! :lol:
Joe. :teeth :thup
Two answers
1) Many, many people run these on CD 22's and I've never heard of a problem with them. I had them on my 22 with twin Honda 40's and like others, feel they were one of the single biggest improvements I made to the boat. I also have them on the Tomcat I have now.
2) The permatrims don't add a lot of drag and it's drag on the lower leg that would create the angular motion required to put excessive pressure on the tilt and trim cylinder. The lift (upwards force) is mostly going to be carried through the lower leg to the engine and then to the boat through the motor mounts. Also note that a lot of angular force is applied when the prop is spinning since going forward, that pushes at the bottom of the lower leg and in reverse it pulls the lower leg out.
IMHO, there's nothing to worry about with regards to the permatrims creating torque as I'm confident any torque they might create is lower than what the prop itself creates.
1) Many, many people run these on CD 22's and I've never heard of a problem with them. I had them on my 22 with twin Honda 40's and like others, feel they were one of the single biggest improvements I made to the boat. I also have them on the Tomcat I have now.
2) The permatrims don't add a lot of drag and it's drag on the lower leg that would create the angular motion required to put excessive pressure on the tilt and trim cylinder. The lift (upwards force) is mostly going to be carried through the lower leg to the engine and then to the boat through the motor mounts. Also note that a lot of angular force is applied when the prop is spinning since going forward, that pushes at the bottom of the lower leg and in reverse it pulls the lower leg out.
IMHO, there's nothing to worry about with regards to the permatrims creating torque as I'm confident any torque they might create is lower than what the prop itself creates.
I've looked at these things and thought about them for my 26' Venture w/twin
90's and factory trim tabs. After some deliberation, and the fact I have no
problem getting on plane or trimming the bow down in head seas using my engine
tilt and trim tabs, I cannot see why I need more underwater or surface drag.
Is there any study showing how much stern "lift" occurs with permatrims vs the
factory trim tabs?
Maybe the smaller CD boats are stern heavy?
I do believe anything non-adjustable providing stern lift (permatrims?) in a large
following sea is a detriment (C-Dorys having such a flat aft section with a sharper
bow) possibly contributing to a broach which is an existing potential problem with
this hull design to begin with.
I'd like to see data, like some R & D figures, rather than opinions before I decide to
strap these things on my engines.
Aye.
90's and factory trim tabs. After some deliberation, and the fact I have no
problem getting on plane or trimming the bow down in head seas using my engine
tilt and trim tabs, I cannot see why I need more underwater or surface drag.
Is there any study showing how much stern "lift" occurs with permatrims vs the
factory trim tabs?
Maybe the smaller CD boats are stern heavy?
I do believe anything non-adjustable providing stern lift (permatrims?) in a large
following sea is a detriment (C-Dorys having such a flat aft section with a sharper
bow) possibly contributing to a broach which is an existing potential problem with
this hull design to begin with.
I'd like to see data, like some R & D figures, rather than opinions before I decide to
strap these things on my engines.
Aye.
Permatrims are not really non-adjustable they do adjust with engine trim. I didn't have trim tab on my 22 (with twin Honda 40's) and I ran it for several years without trim tabs (in many different sea states, including following). I then had them installed and ran several years with them. Unlike trim tabs which can be a problem in following seas if not retracted, my experience (not opinion in this case) is that permatrims have no to little contribution to broaching in following seas as they don't extend downward from the hull but rather run close to parallel to the water surface. The main downside is a little extra drag (maybe a lost of a kt or two at the top end). Also relative to trim tabs, they don't provide much lateral trim. So if you need to correct for uneven weight distribution port to starboard, trim tabs are much more useful.Foggy":11g7xfpo said:
It would be almost impossible to do a scientific study on the affect of how something like the Permatrim affects the ride and handling of the boats. There are way too many variables, and parameters.
I cannot speak for the 26, since I have not owned one. On the 25, I ran the boat with just trim tabs, and then with the permatrim, and it made a significant difference in the ride going into the chop.
No issues handling down wind and waves. The extreme conditions I had in Johston Straits, with 40 to 50 knots of wind against current, and seas which were at least 8 feet, and in some cases over 12 feet, with a short period. The motor was trimmed up, and I stayed on the back of waves, with occasionally powering down, and going to the back of the next one. The beauty was that it was easy to match the speed of the boat with the wave trains. I have been on semi displacement boats, where the tenancy to broach was very serious. My experience win handling the C Dory 22 and 25, was that the Permatrim improved the handling down wind/down wave.
As for the "load" on the trim system; as Roger notes, it is the thrust of the motor forward, with is the largest factor--not the size of the antiventillation plate. The Permatrim should be running right on the surface of the water, not under the water, at planing speeds. Many boats do not mount the engine properly, and this alone can give handling problems. Note, not only is there technique in handling the c Dory, but also optimal set up of the boat and engines.
I cannot speak for the 26, since I have not owned one. On the 25, I ran the boat with just trim tabs, and then with the permatrim, and it made a significant difference in the ride going into the chop.
No issues handling down wind and waves. The extreme conditions I had in Johston Straits, with 40 to 50 knots of wind against current, and seas which were at least 8 feet, and in some cases over 12 feet, with a short period. The motor was trimmed up, and I stayed on the back of waves, with occasionally powering down, and going to the back of the next one. The beauty was that it was easy to match the speed of the boat with the wave trains. I have been on semi displacement boats, where the tenancy to broach was very serious. My experience win handling the C Dory 22 and 25, was that the Permatrim improved the handling down wind/down wave.
As for the "load" on the trim system; as Roger notes, it is the thrust of the motor forward, with is the largest factor--not the size of the antiventillation plate. The Permatrim should be running right on the surface of the water, not under the water, at planing speeds. Many boats do not mount the engine properly, and this alone can give handling problems. Note, not only is there technique in handling the c Dory, but also optimal set up of the boat and engines.
I like what I am seeing. Thank you, BigMac, Rogerbum, Joe and Bob. It's reassuring to see the difference as positive and lots of hours without problems. One concern I have is that if the P-trim is going to take 1-2 knots of the top end, and I'm already slow, I just get slower -- partial solution, If it is only noticeable at the top end, I don't cruise there anyway, but is it causing drag that is going to translate into extra fuel burn? Most of my cruising now is at slow cruise (5-6 knots) so should not be an issue. My thinking on adding the p-trim is that I'm a bit stern heavy and they might help with some lift on the stern. Probably not too noticeable at the slow cruise speeds.
Harvey
SleepyC :moon
Harvey
SleepyC :moon
I'm having trouble swallowing the idea that adding more horizontal surface area
aft (permatrims), on a boat already with a flat hull aft and a somewhat "V'd" bow, is
more stable and less likely to broach in heavy seas compared to adding more
vertical surface aft.
Trim tabs can be elevated to null their lift going down a big wave.
Engine(s) can be trimmed up to help also. With a permatrim added here,
the horizontal lift is modified slightly, but not nullified.
I think some hard data is in order.
Aye.
aft (permatrims), on a boat already with a flat hull aft and a somewhat "V'd" bow, is
more stable and less likely to broach in heavy seas compared to adding more
vertical surface aft.
Trim tabs can be elevated to null their lift going down a big wave.
Engine(s) can be trimmed up to help also. With a permatrim added here,
the horizontal lift is modified slightly, but not nullified.
I think some hard data is in order.
Aye.
Hey guys this has been a good one for me as well. My first 16 Cruiser experience was a one month trial with out tabs or fin, I agree with what someone said eairler, this boat should not leave the factory without both. The boat I found had trim tabs already installed and I was really impressed with their performance. I looked into the archives of this sight and felt I should install the fin as well. No one at my marina had heard of a Permatrim but they had a Doelfin so I went that way. It was like getting religon, when I see wake or chop I just pull the bow down and she just cuts threw as if the boat was designed to do it. I used the tabs to adjust my left / right trim and the fin to pull the bow up and down. With the much lighter 16 these components are not optional and I speak from many hours of personal experience.
Bob I think you wrote you had a dolefin and switched to a peratrim is there that much difference between these to fins ?
Bob I think you wrote you had a dolefin and switched to a peratrim is there that much difference between these to fins ?
I simply indicated it really did have much effect in practice. Others have indicated that unretracted trim tabs do have an effect.Foggy":1xuq27n7 said:
Yep. And they are a non issue in following seas IF one remembers to bring them up.Foggy":1xuq27n7 said:
I guess actual experience on a 22CD with and without a permatrim in following seas doesn't count as hard data. :roll:Foggy":1xuq27n7 said:
Harvey, the permatrims don't affect mileage any noticeable amount. They probably do have a very minor effect but I certainly didn't notice it. The major impact I did notice was the huge reduction in bow rise when transitioning from putting along to cruising. E.g. a 22CD without either trim tabs or a permatrim has a low of bow rise on a hole shot. For about 3 seconds it can be difficult to see over the bow as the boat transitions to on plane. With the permatrim, that bow rise is very negligible. The boat also plans at a kt or two lower speed.hardee":12arq3a4 said:I like what I am seeing. Thank you, BigMac, Rogerbum, Joe and Bob. It's reassuring to see the difference as positive and lots of hours without problems. One concern I have is that if the P-trim is going to take 1-2 knots of the top end, and I'm already slow, I just get slower -- partial solution, If it is only noticeable at the top end, I don't cruise there anyway, but is it causing drag that is going to translate into extra fuel burn? Most of my cruising now is at slow cruise (5-6 knots) so should not be an issue. My thinking on adding the p-trim is that I'm a bit stern heavy and they might help with some lift on the stern. Probably not too noticeable at the slow cruise speeds.
Harvey
SleepyC :moon
Our summer cruise of Southeast Alaska in 2012 was our first with the Permatrims installed. In the 2300 miles cruised that summer the only negative effect was a very slight loss of wot speed & increased tenancy of having the tow line to the Mokai sucked into the prop in reverse if the motors had any up trim at all. During that cruise & since with the Permatrims installed most of the time the motors are trimmed so the Permatrims are kept level with the bottom of the boat with the exceptions of trimming down for going into the chop or when heavily loaded in the stern & only trimmed up for shallow water running. I have yet to even come close to a broach with our CD22 either with or without the Permatrims & consider their addition one of the most positive I've made. We also have the Bennet Trim Tabs & contrary to some other reports of their use, I prefer to not only use them for leveling at speed but also prefer when needing trim going into chop or other bow down trim to start with their creased trim & only going to the Permatrim motor trim, when I need the that extra trim for conditions or boat load. & yes I've experimented with the combination of trim tab & Permatrim use extensively with my decribed mode working best for me.
Foggy, I would put my overall use of the Permitrims & their lack of negatives more in the hard evidence category & my opinion of their use in combination with trim tabs in the soft, but your welcome to put either anywhere you please.
Jay
Foggy, I would put my overall use of the Permitrims & their lack of negatives more in the hard evidence category & my opinion of their use in combination with trim tabs in the soft, but your welcome to put either anywhere you please.
Jay
This is my real life experience. We installed a Permatrim on our original Suzuki DF70. I really liked the way the boat reacted to just a small adjustment of the trim. I didn't notice any additional drag.
We upgraded to a new Suzuki DF90 the second season and had trim tabs installed with no Permatrim. The boat's reaction to trimming with the motor tilt trim + trim tabs was nowhere close to the action we got from the PT. So much so that I ended up installing the PT on the new motor which resulted in a drastic change in the ability to adjust the bow up and down with immediate results. I use the trim tabs mostly for lateral trim, leveling the boat out. Plus, we didn't notice any additional drag or loss of speed at the top-end. We've reached 30 mph at WOT lightly loaded in flat water conditions, which is about the max most 22's reach from what I've seen.
I'm a firm believer in Permatrims and would not want a motor without one on a C-Dory. Again, this has been our experience on our boat. Whether one chooses to install or not is a personal choice. To each his own.
We upgraded to a new Suzuki DF90 the second season and had trim tabs installed with no Permatrim. The boat's reaction to trimming with the motor tilt trim + trim tabs was nowhere close to the action we got from the PT. So much so that I ended up installing the PT on the new motor which resulted in a drastic change in the ability to adjust the bow up and down with immediate results. I use the trim tabs mostly for lateral trim, leveling the boat out. Plus, we didn't notice any additional drag or loss of speed at the top-end. We've reached 30 mph at WOT lightly loaded in flat water conditions, which is about the max most 22's reach from what I've seen.
I'm a firm believer in Permatrims and would not want a motor without one on a C-Dory. Again, this has been our experience on our boat. Whether one chooses to install or not is a personal choice. To each his own.
hardee":2gja27y6 said:
Well Harvey, so you mostly cruise at 5-6 knots and your concern is that you are already stern heavy and you don't want to lose 1-2 knots at the top end, Maybe, when you repower, you should consider a single 70-90hp with a Permatrim and a light weight kicker. Just a thought. :shock: