Read many posts on the 22'ers using a Permatrim, has anyone put one on a 25' cruiser? I'd really like to get away from using my trim tabs to force the bow down in rough conditions. Like many others, I do not enjoy the boats behavior in quartering or following weather... its down right spooky and the tabs extended that far down enhance the issue. Thanks for any advice.
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25' C-Dory Cruiser--Permatrim
- Thread starter Fishbum
- Start date
I don't know about the Permatrim, but I have had a Doel-fin on my Honda 130 since it was new. I do think it adds lift. I haven't noticed any problems with following seas. The boat seems to handle pretty well as long as the trim tabs are completely in the up position. I've found that having the trim tabs down at all in a following sea creates problems.
Lyle
Lyle
I am considering putting the Permatrim on my CD 25. But you need to trim the trim tabs up in following seas, as you would with the Permatrim. It is the bow down, not the trim tabs which cause handling problems in following seas. If you trim the bow up in following seas, the CD 25 is a well behaved boat.
I'm definitely thinking about it, I have twin Yami 80's. I have oversize trim tabs I put on weeks after taking delivery in 2003.
The reason I believe it will help is that my boat runs most efficient (max speed at a given throttle in the 15-17 nmph range) when the engines are trimmed all the way down to their stops and the attitude adjusted with the trim tabs. In other words, if I try to raise the engines slightly or even to level with the hull bottom, then use the trim tabs to readjust the attitude, the boat runs slower at the same throttle setting. I believe the permatrims will help in 'neutralizing' the added weight of twins.
I'm on the fence because I'm not all that sure the slight increase in efficiency will pay the $300 it will cost me, payback may be 10+ yrs away! :|
The reason I believe it will help is that my boat runs most efficient (max speed at a given throttle in the 15-17 nmph range) when the engines are trimmed all the way down to their stops and the attitude adjusted with the trim tabs. In other words, if I try to raise the engines slightly or even to level with the hull bottom, then use the trim tabs to readjust the attitude, the boat runs slower at the same throttle setting. I believe the permatrims will help in 'neutralizing' the added weight of twins.
I'm on the fence because I'm not all that sure the slight increase in efficiency will pay the $300 it will cost me, payback may be 10+ yrs away! :|
I am not sure what the trade off is--when you put on any "fin" and push the bow down, it is increasing the drag in the water. The point is well taken with the weight of the twin 80's that you have to raise the stern. On the other hand, with the single 130, I feel like I don't have enough power, but that putting on the permatrim may slow the boat slightly.
On the Tom Cat, putting the bow down really slows the boat and makes it much less effecient---but different types of hulls. The boat planes at lower speed, but I don't think I got any increase in effeciency at any speed.
On the Tom Cat, putting the bow down really slows the boat and makes it much less effecient---but different types of hulls. The boat planes at lower speed, but I don't think I got any increase in effeciency at any speed.
Right Bob on the drag. If I add Permatrims, I expect to use them more than the trim tabs, except for lateral adjustments. I would also expect the Permatrims, in my situation, to add less drag than the smaller surface area trim tabs that also have less effect since they are closer to the fore/aft fulcrum of the hull. I would hope to be able to run the outboards trimmed up a bit closer to neutral attitude to allow the props to be more in line with the water flow direction. So in my case it's a matter of which dominates, the extra surface area drag of the Permatrims vs the increased efficiency attained by the prop angle over what I have now.
I'm inclined to go ahead with the Permatrims because I'd rather spend $$ on this company to save ANY dollars to the oil companies, even at a net loss for some time...
I'm inclined to go ahead with the Permatrims because I'd rather spend $$ on this company to save ANY dollars to the oil companies, even at a net loss for some time...
William and Beth Tucker
New member
Hey yall! Yall are so far over my head in boat knowledge that i don't even know what yall are talking about in most cases>>>What about installing them things on a 25 C-Dory with twin 90 Hondas ?? tucker
Bill,
The twin older Honda 90's would probably weigh slighly more than the twin Yammie 80's, so if the Permatrims help the boat with the Yamaha's they should help your boat. (the "help" would be lifting the stern, pushing the bow down).
I would wait to see what they do for the boat with the 80 hp Yahama's.
The twin older Honda 90's would probably weigh slighly more than the twin Yammie 80's, so if the Permatrims help the boat with the Yamaha's they should help your boat. (the "help" would be lifting the stern, pushing the bow down).
I would wait to see what they do for the boat with the 80 hp Yahama's.
I don't understand the difference between Permatrims and trim tabs (other than the latter allows for lateral adjustments). It seem like they function in much the same way. Or is there some dynamics with Permatrims due to the proximity to the prop? Could someone explain how they work and the benefits?
Thanks,
Thanks,
The two trim tabs on the boat (electric --Lenco--or hyraulic--Benett or Instatrim-) are on each side of the transom, so they can rais the transom on one side or the other, by pushing down. Pushing up on the transom, will both correct lateral (side to side ) trim, and fore and aft trim by pushing downward on the bow.
The Permatrim accentuates the motor's thrust. If there are two engines, then the Permatrim can do some of what the trim tabs will do. But with the single engine---as I have--the effect is not lateral, just lifting or allowing the stern to be depressed and oppositely moving the bow.
The CD 25 (and 22) both do better in chop with the bow down so that there is a sharper surface, and less flat surface--less pounding. Some engine fins run in the water--the Permatrims only run on top of the water on my Tom Cat--the engines are probably a couple of inches higher than on the CD 25. Some boats, like inflatables and other small boats use the plastic "Dolfins"--which are foil shaped and do have some upward and downward effect. I see the Permatrim (at least in the Tom Cat, as having mostly a downward effect, by directing the prop wash more down, raising the transom and thus lowering the bow. In the Tom Cat,with the widely spaced engines, this can also effect lateral trim (Trim tabs cannot be used on the Tom Cat, because of the bracket and twin engines.
Usually trim tabs are used to achieve the trim or level riding of a boat--both laterally and fore and aft--they will help a boat get on a plane faster by pushing down on the stern, and lifting the stern. Then the engine is trimmed so that it is parallel to the water surface--where the boat is running faster with the most effecient speed (the reasons for watching tachs, boat speed and fuel consumption). If the trim tabs are not getting teh bow down as much as we think it should, the option is to add the Permatrim, which will also increase the effect of rasing the stern and depressing the bow--as we want to do in the c Dory 25.
The Permatrim accentuates the motor's thrust. If there are two engines, then the Permatrim can do some of what the trim tabs will do. But with the single engine---as I have--the effect is not lateral, just lifting or allowing the stern to be depressed and oppositely moving the bow.
The CD 25 (and 22) both do better in chop with the bow down so that there is a sharper surface, and less flat surface--less pounding. Some engine fins run in the water--the Permatrims only run on top of the water on my Tom Cat--the engines are probably a couple of inches higher than on the CD 25. Some boats, like inflatables and other small boats use the plastic "Dolfins"--which are foil shaped and do have some upward and downward effect. I see the Permatrim (at least in the Tom Cat, as having mostly a downward effect, by directing the prop wash more down, raising the transom and thus lowering the bow. In the Tom Cat,with the widely spaced engines, this can also effect lateral trim (Trim tabs cannot be used on the Tom Cat, because of the bracket and twin engines.
Usually trim tabs are used to achieve the trim or level riding of a boat--both laterally and fore and aft--they will help a boat get on a plane faster by pushing down on the stern, and lifting the stern. Then the engine is trimmed so that it is parallel to the water surface--where the boat is running faster with the most effecient speed (the reasons for watching tachs, boat speed and fuel consumption). If the trim tabs are not getting teh bow down as much as we think it should, the option is to add the Permatrim, which will also increase the effect of rasing the stern and depressing the bow--as we want to do in the c Dory 25.
Seahooked wrote:
What also matters with trim tabs or Permatrims is the efficiency of the hull through the water at various speeds, boat weights (loading) and rpms. Whichever (or combo) can produce the best hull through the water efficiency at a given speed and rpm will result in the best mpg fuel usage. For my boat/engine combination, I'm banking on the Permatrims doing the same job as the trim tabs but with less induced drag to hurt the efficiency of the hull moving through the water. I will probably keep both engines at the same angle and use the trim tabs just for lateral (side to side) adjustments.
I may not have said it well, but I hope you got the idea.
I'll take a shot at this one. The 'smoothness' of the ride is a result of the attitude of the boat as it goes through chop, doesn't matter if its accomplished with trim tabs, Permatrim(s), none or both in combination. If you're going too slow to get the bow down (or boat level enough) with the trim tabs and/or Permatrims, then the boat will tend to slap in the chop rather than slice through it.One more question: If running in chop in my CD25, would I expect a noticably smoother ride with trim tabs extended and the motor trimmed to push the bow down with a Permatrim fin, vs the same seneario without the Permatrim?
What also matters with trim tabs or Permatrims is the efficiency of the hull through the water at various speeds, boat weights (loading) and rpms. Whichever (or combo) can produce the best hull through the water efficiency at a given speed and rpm will result in the best mpg fuel usage. For my boat/engine combination, I'm banking on the Permatrims doing the same job as the trim tabs but with less induced drag to hurt the efficiency of the hull moving through the water. I will probably keep both engines at the same angle and use the trim tabs just for lateral (side to side) adjustments.
I may not have said it well, but I hope you got the idea.
I installed Permatrims on twin motors but haven't tested the boat yet. Besides being able to bring the bow down by re-directing the flow of water and thrust, my main hope is that the foil effect of the Permatrims will lift the stern by a few inches. This would allow the boat to plane at a lower speed when we need to slow down in rough conditions but still need to keep moving efficiently. Reducing wetted hull area should reduce overall drag and give the boat a lighter feel in general. At least for our boat, the weight of the engines/fuel/batteries is more than the hull was designed for, so it tends to squat somewhat at midrange speeds. I have my fingers crossed here, since I've drilled 12 holes through 2 brand new cavitation plates! I'll post my results this Spring. Mike.
OK, I'll re-open this thread. I received my Permatrim today. I have a Honda 150 on Fan-C-Dory. All of the installation pictures I see on the net show the thing mounted above the cav. plate. The pattern on the model I rec'd mount under the cav.... Has anyone here done it on a 150/135 Honda ?
We have twin 90s on our 25 and I have a set of permatrims waiting for install now. I plan to put them on in the next few weeks. I researched the He.. out of them and I think it is worth the investment and a great supplement if not nearly a replacement for trim tabs (with twins). Can't wait to try them and I know there was at least one other Brat with twins and permatrims.
This past summer I felt that the Fan-C-Dory struggled a little to much to get over the hump and up on plane, and even then wanted (I felt) to ride bow high. I have Lenco TT's on it, but think that they would be better if they were shaped like the Bennett, and/or the next size larger.
Thanks for the reply. The Permatrim you have must be different than mine. The instructs for mine say mount it below the cav. plate. It has a hole that looks like it is made to fit above the trim fin (between it and the cav plate) but to get it there I have to loosen the trim tab to let it down so the Permatrim thickness will fit between the trim tab and the cav. plate. When I do that and slide the Permatrim forward to where it "looks" like it should go (the hole in the Permatrim aligns with trim tab adjust circle) the flare of the motor leg forces the Permatrim down to much for Permatrim to fit between the cav. plate and the trim tab.
No answer at Shipyard Island Marina, guess I'll wait till Monday - nap time !
No answer at Shipyard Island Marina, guess I'll wait till Monday - nap time !
Installed Permatrim's on ShiRoz 2 years ago.
Benefits: Helped in the Harbor as it has made the boat more responsive in throttling both motors while maneuvering in the harbor.
Boat is more responsive in turning while cruising.
We have not seen a decrease in gas mileage.
It is has made it easier to balance the boat while having passengers in the boat and shifting while underway.
Overall it has been a value added addition to the boat.
Benefits: Helped in the Harbor as it has made the boat more responsive in throttling both motors while maneuvering in the harbor.
Boat is more responsive in turning while cruising.
We have not seen a decrease in gas mileage.
It is has made it easier to balance the boat while having passengers in the boat and shifting while underway.
Overall it has been a value added addition to the boat.