Desperately in need of a solution for a vibration-ratlling noise when motoring at certain RPM on my CAL 2-25 with Yanmar YSM-8 hp. I first thought problem stemming from cutlass bearing, prop shaft or even engine mounts. Changed cutlass bearing, corrected shaft, replaced engine mounts. My problem now seems nailed down to what seems to be vibration between rudder shaft and rudder tube. This is not easy to determine as there is no obvious void or wear when I shake the rudder from underwater. Tried inserted Mylar sheets between post and tube which did not work (the sheets were swept away). Heard of a solution involving injecting epoxy in the tube or perhaps having a sleeve or some kind of bushing made to be inserted between rudder tube and rudder post. Anyone with similar experience and solution would be most appreciated.
Cal 2-25 vibration when motoring
- Thread starter leclaira@videotron.ca
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Yes indeed, I had the two-blade propeller checked, they did make a vert minor adjustment but nothing significant.
I was actually told by the prop shop that a three-blade propeller instead of two would create less vibration but also told from another reputable guy on the Eastern Seaboard that for such a small motor it would not make a heck of a difference. In any event, I still think right now that the problem is between rudder post and rudder tube.
Can you feel it in the wheel? Seems to me that a harmonic like that would be felt by hand. just a thought..
It is probably nothing to worry about if it only occurs at a certain motor speed. My YSM-12 single cylinder horizontal (big brother to your Yanmar) does not like to idle less than 850 or 900 RPM and has harmonic vibrations at double that speed at 1700 to 1900 RPM. She is smooth at all other speeds. I have a three blade Campbell Sailor propeller (12”dia, 7”pitch) but she behaves the same if the reduction gear clutch is engaged or not. Don’t run it at those speeds. My motoring / motor sailing speed is 2500 to 2600 RPM or about 5 to 6 knots depending on sea state. That is about 85% of the full load 3000 RPM.
Your YSM-8 has a bit less power and a bit faster full load speed and may have vibrations at different speeds.
Your YSM-8 has a bit less power and a bit faster full load speed and may have vibrations at different speeds.
Problem is, the rattling (very intense) does happen over an appreciable RPM spectrum meaning I cannot run the motor at speeds that would otherwise be quite useful, at more than idle or slow speed but less than cruising speed. Unfortunately I don't have a rev-counter to be more accurate in my description. You are right though about the problem disappearing when I run the motor at running speed (about 5.1 knots). I may attempt this fall (prudently) injecting epoxy in the rudder tube after covering the rudder post with mold release. I may consider buying a 3-blade propeller as well. The prop expert in this neck of the wood told me a three-blade propeller does create way less vibration and he has solved many vibration problems by having customers switch to three-blade. But again, I have spent already quite a bit of money to try and solve this problem. I enjoy motoring with this small Yanmar once-cylinder, which so far has been very reliable.
Instead of Mylar shims you could try stainless steel shims, such as these: http://www.mcmaster.com/#catalog/119/3739/=nx4mdc You might need to experiment to get the thickness you need. Something like .003" (part # 2317K13) or .004" (part #2317K14) could work.
I'm not sure how your tiller cap and top bearing surface (i.e., where the post comes up into the cockpit) are set up, but after cutting the sheet to the correct width to fit the circumference of the rudder post and the depth that you want, you would cut a series of short vertical tabs in the top of the sheet. After putting a little Teflon grease on the shim stock, curve it around the rudder post and insert it in the gap, being careful not to crinkle it and also not to cut yourself on the sharp edge of the shim. Then, when you've inserted it all the way down to the depth where the tabs begin, bend over the tabs on to your rudder post bearing (or what have you). The tabs will keep the shim from dropping out, as happened with your attempt with the Mylar strips.
BTW: I know of a guy on the east coast who tried the epoxy technique on his Catalina 30 and at present has a rudder solidly epoxied in place! I'm sure others have done it successfully but I think I'd pass. I don't see why you couldn't make the stainless shims work just fine (as they do on my own boat) for a lot less money and hassle. You might want to add them on the bottom bearing surface of the rudder as well, though that might involve either going for a swim or waiting until your next haulout.
Thank you to both of you for the advice. As I read on another forum thread about a very similar Cal model, the 2-27" (quote) "there is no bearing in the rudder shaft tube of a Cal 2-27. It was simply glass laid up around a waxed shaft". This is also the case for my 2-25 which would explain why over a long period of time (mine is 1978) as there is wear in the tube and no bearing whatsoever to provide support, thus it rattles. I think I will go with you advice to insert stainless steel shims (with your described recipe of tabs to support it). Not being an expert, I am also very hesitant at venturing into the injection of epoxy in the tube.
Please report back on how it goes with the stainless shims. I'll be interested to hear your results.
Have you definitely been able to isolate the vibration to the rudder? Do you get the same vibration when you are sailing without engine on or when the engine is not in gear? In my 2-25 there are grease fittings in the rudder shaft but you have to crawl in through the lazarette to get to them. also the tube is open at the top about 8 inches below were the shaft goes up through the cockpit. Is there a lot of lateral play when you try to shake the rudder by hand?
as far as a three bladed prop, I replaced my two blade with a three blade and am very satisfied with the results, seems to have much more power and control. Had to have it re-pitched once to get max RPMs. In my opinion well worth whatever slight increase in sailing drag.
as far as a three bladed prop, I replaced my two blade with a three blade and am very satisfied with the results, seems to have much more power and control. Had to have it re-pitched once to get max RPMs. In my opinion well worth whatever slight increase in sailing drag.
Re: Cal 2-25 vibration when motoring
Have you definitely been able to isolate the vibration to the rudder? Do you get the same vibration when you are sailing without engine on or when the engine is not in gear? In my 2-25 there are grease fittings in the rudder shaft but you have to crawl in through the lazarette to get to them. also the tube is open at the top about 8 inches below were the shaft goes up through the cockpit. Is there a lot of lateral play when you try to shake the rudder by hand?
as far as a three bladed prop, I replaced my two blade with a three blade and am very satisfied with the results, seems to have much more power and control. Had to have it re-pitched once to get max RPMs. In my opinion well worth whatever slight increase in sailing drag.
I think I nailed it down to the rudder post-tube but one is never 100 per cent sure until a solution that works has been found with this kind of problem. I don't get that rattling sound when I sail without the engine on and very little vibration when I rev up the engine on neutral. I found the grease fitting you are talking about to grease the rudder tube. I did put a waterproof grease (but not a very thick high viscosity grease). It made no difference. There is not a lot of lateral play when I try to shake the rudder by hand but the rattling seems to come from inside the tube anyway. I am glad to hear your three blade prop is a great improvement. Did it also make a difference when you switched from two blade to three blade in terms of overall level of vibration felt in the cockpit? I must admit that my two blade prop is not very efficient when I motor off the dock, it pulls on one side in reverse and does not provide for very secure maneuvering.
Have you definitely been able to isolate the vibration to the rudder? Do you get the same vibration when you are sailing without engine on or when the engine is not in gear? In my 2-25 there are grease fittings in the rudder shaft but you have to crawl in through the lazarette to get to them. also the tube is open at the top about 8 inches below were the shaft goes up through the cockpit. Is there a lot of lateral play when you try to shake the rudder by hand?
as far as a three bladed prop, I replaced my two blade with a three blade and am very satisfied with the results, seems to have much more power and control. Had to have it re-pitched once to get max RPMs. In my opinion well worth whatever slight increase in sailing drag.
I think I nailed it down to the rudder post-tube but one is never 100 per cent sure until a solution that works has been found with this kind of problem. I don't get that rattling sound when I sail without the engine on and very little vibration when I rev up the engine on neutral. I found the grease fitting you are talking about to grease the rudder tube. I did put a waterproof grease (but not a very thick high viscosity grease). It made no difference. There is not a lot of lateral play when I try to shake the rudder by hand but the rattling seems to come from inside the tube anyway. I am glad to hear your three blade prop is a great improvement. Did it also make a difference when you switched from two blade to three blade in terms of overall level of vibration felt in the cockpit? I must admit that my two blade prop is not very efficient when I motor off the dock, it pulls on one side in reverse and does not provide for very secure maneuvering.
After reading your description of things, I would not suspect the rudder system as being at fault. If you had slop between the rudder tube and the rudder post you would observe this under sail as well, and also when you wiggle it. You say it is just fine under sail and there is not a great deal of movement. I would move on to something else.
A one cylinder diesel is not going to be as smooth in the first place. I don't doubt you are picking up some vibration in the rudder tube but it is almost certainly some kind of transmitted resonance that, as you have already stated, disappears at certain RPMs.
Your original post speaks of a "corrected shaft." What did the "corrections" entail? I had a bronze prop shaft that was very slightly bowed in my Catalina 30 and it caused symptoms along the lines of what you described. After replacing it with a new shaft the problems vanished. Did you actually remove the shaft and take it to a machine shop that verified it is true? Also, did you check to see the strut itself does not have any play where it is attached to the hull?
All other things being equal, I would expect the three blade prop to be smoother than your two blade. So that's something you could consider, but only after you have made absolutely certain that the entire drive train is aligned and in good order.
As for the boat pulling in reverse, that sounds like garden variety prop walk. Nothing unusual there.
In any case, I don't think I'd be worrying about the rudder.
A one cylinder diesel is not going to be as smooth in the first place. I don't doubt you are picking up some vibration in the rudder tube but it is almost certainly some kind of transmitted resonance that, as you have already stated, disappears at certain RPMs.
Your original post speaks of a "corrected shaft." What did the "corrections" entail? I had a bronze prop shaft that was very slightly bowed in my Catalina 30 and it caused symptoms along the lines of what you described. After replacing it with a new shaft the problems vanished. Did you actually remove the shaft and take it to a machine shop that verified it is true? Also, did you check to see the strut itself does not have any play where it is attached to the hull?
All other things being equal, I would expect the three blade prop to be smoother than your two blade. So that's something you could consider, but only after you have made absolutely certain that the entire drive train is aligned and in good order.
As for the boat pulling in reverse, that sounds like garden variety prop walk. Nothing unusual there.
In any case, I don't think I'd be worrying about the rudder.
Thanks for your observations and advice, my strut is very sturdy and very strongly bolted to the hull. My shaft is bronze type and somewhat vintage (I understand this is really some kind of alloy with bronze in it). I took it to a machine shop and they had a look at it and were of the view that it is true. I was told or read somewhere that stainless steel shafts are better-stronger however. Cutlass bearing as I mentioned earlier is new and so are engine mounts (Vetus). I intend to proceed in the fall with inserting the stainless shims. Although the rudder does not have a lot of play when inspected underwater, the tiller is a little loose and does not keep course the moment you take your hand off it. I agree with your assessment about the need to ensure the drivetrain is in good order. Engine shaft alignment seems ok although not necessarily as precise as the .006 textbook recommendation. An important prop shop has offered to trade in my two blade prop for a three blade prop for a reasonable price and is firmly of the view that the three blade will dampen a lot vibrations. I will make the switch and report back about my success or lack of.
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