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Boat Forum / Building / August 2007Removing 3 bladed prop on an Alberg 35
I bought an Indigo 3 bladed prop last week for my Alberg 35 with the original Atomic 4, as the existing prop succumbed to electrolysis I went down to the boat yesterday, worried that I might not be able to loosen the old hub's grip on the shaft. It was also a 3 bladed prop. That was actually easy after about 5 minutes with a map gas torch. I seem to have only about an inch of space between the end of the prop shaft and the rudder (post). The hub is about 2-2,5 inches thick. I've tried swinging the rudder from stop to stop, but don't seem to be able to find an angle that will allow the old prop to come off, or, for that matter, a new one to go on. Others must have encountered this problem and found a solution..... At this juncture it seems to me that I either have to dismount the rudder to gain an extra inch or so, or I have to unmount the engine and pull the prop shaft forward a couple of inches (if that's even possible ) I am hoping that I missed something perfectly obvious as I was working late and was tired.... any help appreciated. Thanks, Jonathan Wye  SignatureI am building my daughter an Argie 10 sailing dinghy, check it out: http://home.comcast.net/~jonsailr >I bought an Indigo 3 bladed prop last week for my Alberg 35 with the >original Atomic 4, as the existing prop succumbed to electrolysis [quoted text clipped - 21 lines] > >Jonathan Wye Sorry to say but there are only two ways to get more room, both of which you've mentioned. I believe most people would prefer to pull the rudder.. I'm not familiar with an alberg 35 rudder but if you are taking it off is thee a possibility you could have it modified with a little larger cut out in case you want to remove things sometime in the future? There is an Alberg user's group - google "alberg 35" but they didn't have anything to say about removing a propeller. Apparently not a popular pass time. Bruce in Bangkok (brucepaigeATgmailDOTcom) It's called poor engineering and it is unfortunately, very common. The engine and propshaft should be offset to allow shaft removal without the rudder and there should be adequate clearance between the rudder and shaft for removing the prop. Additionally, there should be at 2 inches clearance between the outer diameter of the prop and the bottom of the boat to prevent pounding from prop turbulence, but too often these things are not done for cost savings. You may be able to remove the coupling from the gear box and gain a bit of clearance as well, but pulling the rudder has the advantage of being able to use a prop puller as well. Steve >I bought an Indigo 3 bladed prop last week for my Alberg 35 with the >original Atomic 4, as the existing prop succumbed to electrolysis [quoted text clipped - 21 lines] > > Jonathan Wye > It's called poor engineering and it is unfortunately, very common. The > engine and propshaft should be offset to allow shaft removal without the [quoted text clipped - 38 lines] > > I am building my daughter an Argie 10 sailing dinghy, check it out: > >http://home.comcast.net/~jonsailr Cut the prop shaft in the boat. Take out a 2" long section. Take off prop. When re-installing, use a sliding coupler to join the two pieces. This assumes you even have enough room to do this cutting. > Cut the prop shaft in the boat. Take out a 2" long section. Take off > prop. When re-installing, use a sliding coupler to join the two > pieces. This assumes you even have enough room to do this cutting. Woah! This is up there with some of the worst advice I've encountered on this newsgroup. -- Roger Long >> Cut the prop shaft in the boat. Take out a 2" long section. Take off >> prop. When re-installing, use a sliding coupler to join the two [quoted text clipped - 5 lines] > -- > Roger Long Ya, I kinda cringed when I read it. Alignment questions aside, that would have to be one strong coupler. >>> Cut the prop shaft in the boat. Take out a 2" long section. Take off >>> prop. When re-installing, use a sliding coupler to join the two [quoted text clipped - 8 lines] >Ya, I kinda cringed when I read it. Alignment questions aside, that would >have to be one strong coupler. Why? Isn't that just a twenty five horse motor? This is a boat, not an electrical generating station. Casady >> Cut the prop shaft in the boat. Take out a 2" long section. Take off >> prop. When re-installing, use a sliding coupler to join the two >> pieces. This assumes you even have enough room to do this cutting. > >Woah! This is up there with some of the worst advice I've encountered on >this newsgroup. There isn't any room to do it anyway. The shaft nearly hits the rudder in the rear and there is only a couple of inches between the engine coupling and the packing gland. Unless you wanted an Alberg 33 with the open back cockpit for racing :-) Bruce in Bangkok (brucepaigeATgmailDOTcom) What limits/prevents the rudder from swinging to the side. If it is steering linkage, that can be unhooked to allow more movement, If it is the mechanical attachment of the rudder itself, you're toast. Who installed the last one and could you talk to them? Gordon I once chartered a Hunter 37 (IMS) with just this arrangement. And it did in fact come loose, luckly with the coupling attached to the prop side so it didn't leave the boat. >> Cut the prop shaft in the boat. Take out a 2" long section. Take off >> prop. When re-installing, use a sliding coupler to join the two [quoted text clipped - 5 lines] > -- > Roger Long Jonathan, This is a very common issue with the long keel boats that have the propeller in an appature. It is a toss up. If the heel casting unscrews, then dropping the rudder is really pretty simple. Take all the head fitting off the rudder, unscrew (2 as I recall) the big screws that hold on the heal casting and down it comes. I actual fact, if you keep track of the shims, pulling a U4 forward an inch and an half is usually just about as hard. The problem if there is one is the exhaust pipe. The hoses and wires will usually pull that far, but if the muffler can't be moved with the engine (some can) then you don't want to mess with that during the season. It may take you out of commission for longer than it is worth. Matt Colie Lifelong Waterman, Licensed Mariner and Perpetual Sailor > I bought an Indigo 3 bladed prop last week for my Alberg 35 with the > original Atomic 4, as the existing prop succumbed to electrolysis [quoted text clipped - 21 lines] > > Jonathan Wye >Jonathan, >This is a very common issue with the long keel boats that have the [quoted text clipped - 39 lines] >> >> Jonathan Wye There is an Alberg group - google for it -- that has an article about converting to wheel steering that has a pretty comprehensive section on removing the rudder. Bruce in Bangkok (brucepaigeATgmailDOTcom) >I seem to have only about an inch of space between the end of the prop >shaft and the rudder (post). The hub is about 2-2,5 inches thick. I've [quoted text clipped - 7 lines] >I am hoping that I missed something perfectly obvious as I was working >late and was tired.... any help appreciated. .. >Jonathan Wye There *IS* the Medieval option. Accomplished with a Sawzall upon the defenseless rudder. Then made good with epoxy/glass, complete with two inch set back for NEXT time :-) Brian Whatcott Altus OK. >>I seem to have only about an inch of space between the end of the prop >>shaft and the rudder (post). The hub is about 2-2,5 inches thick. I've [quoted text clipped - 15 lines] > >Brian Whatcott Altus OK. That is a point. The User's group listing says that the rudder is solid mahogany.... Bruce in Bangkok (brucepaigeATgmailDOTcom) >>There *IS* the Medieval option. Accomplished with a Sawzall upon the >>defenseless rudder. Then made good with epoxy/glass, complete with >>two inch set back for NEXT time :-) Got to be the way to go. You bust a corroded exhaust system and it will be a major pain. Leave the engine alone. There are a zillion powerboats that take a chain saw to get the engines out. I think you can usually remove something like an A-4 without doing that. I have a chain saw and a sawzall. And an open boat. And you can drill out the rivets with those aluminum hulls. Same as aircraft repair. Casady On Aug 15, 4:40 am, brucedpa...@gmail.com wrote: > On Wed, 15 Aug 2007 02:45:36 GMT, Brian Whatcott > [quoted text clipped - 24 lines] > Bruce in Bangkok > (brucepaigeATgmailDOTcom) I will defend my suggestion although it sounds impractical for the Alberg. A coupler properly made, probably from SS about 1" ID larger than the shaft with deep holes drilled and then milled to size will be as well balanced as the original. A few barnacles on a prop would produce a far greater imbalance. I have been amazed at how my 3 bladed prop does not shake even though it gets covered with barnacles. I hit a mast from a dismasted Laser this past year and made a huge ding in one blade and it still turns smoothly. This causes me to believe that it is alignment, not balance that is most critical and a well made coupler would maintain that alignment. Besides, you can always re-align the shaft (fairly easy on my S2). >> >There *IS* the Medieval option. Accomplished with a Sawzall upon the >> >defenseless rudder. Then made good with epoxy/glass, complete with [quoted text clipped - 11 lines] >than the shaft with deep holes drilled and then milled to size will be >as well balanced as the original. If what you want is to get in the water, thirty minutes with a rasp and sandpaper might do it. No sawzall needed. Or is it covered with glass? Casady >A coupler properly made, probably from SS about 1" ID larger >>than the shaft Surely you meant OD. Makes more sense that way. Casady >I will defend my suggestion although it sounds impractical for the >Alberg. A coupler properly made, probably from SS about 1" ID larger [quoted text clipped - 8 lines] >alignment. Besides, you can always re-align the shaft (fairly easy on >my S2). Here's a little engineering insight. If a drive shaft is lightened by drilling out an axial hole whose diameter is one half the outer diameter - the shaft's strength in torque is reduced by 5% and its weight is reduced by 25% This is important in aircraft construction. So as applied to cutting and shutting a propellor shaft, if its diameter is x, and it is cut then bridged with a coupler, the coupler's diameter ought to be just over twice the shaft's diameter, to bridge across the gap. As to passing the torque into and out of the coupler - the ideal connection is splines, the more the merrier, within reason. But this is unlikely to be an option. Another option, much simpler to arrange, is two well-fitted bolt holes at right angles to each other, at one shaft diameter back from the cut, and the other at two diameters back if possible. This is likely to be weaker than the original torque capability. There is another option, which will be familiar to you from examining an old style (English) bike pedal crank. A flat is worked on the shaft, and the pedal crank has a hole to pass the shaft. But it also has a hole at right angles to the shaft through which a cotter bolt with a tapered flat passes to bear on the main shaft's flat. The cotter, when bolted tight, eliminates slippng between the two pieces, so a wear point is eliminated. If an eccentric hole can be drilled in the coupler, so a cotter bolt can bear on the shaft, it would stop relative motion. But there are many other ways you could concieve of connecting a shaft into and out of a coupler, I'm sure. Brian Whatcott Altus OK >There is another option, which will be familiar to you from >examining an old style (English) bike pedal crank. I had one like that, back in 1960. Loathed those cotters. And they were tacky. Oh, so British. Then there was the cotterless cranks with insufficient room for a standard bolt. Head was too big. I got one from the Datsun dealer that fit. Casady >>I will defend my suggestion although it sounds impractical for the >>Alberg. A coupler properly made, probably from SS about 1" ID larger [quoted text clipped - 38 lines] > >Brian Whatcott Altus OK I think the point you are missing is that although a coupling may very well cope with the torque there just isn't any room to fit a coupling of the type you describe at either the propeller or the engine end. One might possibly use a larger cutlass bearing running on the O.D. of the coupling but that would just add complications to a system that should be as sim0le as possible. The most logical answer is(1) remove the rudder, or (2) saw the cutout in the rudder larger. Bruce in Bangkok (brucepaigeATgmailDOTcom) >Here's a little engineering insight. If a drive shaft is lightened >>by drilling out an axial hole whose diameter is one half the outer >>diameter - the shaft's strength in torque is reduced by 5% and its >>weight is reduced by 25% This is important in aircraft >>construction. Driveshafts are usually tubes and not rods. Always for cars and big ships. It is only the smaller boats that lack the space. Casady >>Here's a little engineering insight. If a drive shaft is lightened >>>by drilling out an axial hole whose diameter is one half the outer [quoted text clipped - 6 lines] > > Casady uh what have you been taking? drive shafts on cars are tubes may be on other things; i have only seen one driveshaft on a boat that was tube and it corroded til it fell apart. mostly you find a ss shaft machined to speck for the boat and the power out put of the engine. but go ahead and use spring steel tube drive shafts it will give me business. >>I will defend my suggestion although it sounds impractical for the >>Alberg. A coupler properly made... >Here's a little engineering insight. If a drive shaft is lightened >by drilling out an axial hole whose diameter is one half the outer [quoted text clipped - 6 lines] >the coupler's diameter ought to be just over twice the shaft's >diameter, to bridge across the gap. ... >Brian Whatcott Altus OK I knew, sure as sure, as soon as I wrote "engineering insight" there would be a screw-up. And there was. If you want to maintain torque capacity though a coupling, it doesn't need to be TWICE the shaft diameter. That's three times the cross section area, at about twice the distance from the axis. The coupler diameter doesn't need to be even 1.5 times the diameter of the shaft. 1.3 times the shaft diameter would do it. So a coupler whose diameter is about one inch bigger than the shaft could handle up to a three inch shaft, if well connected. Yeah Baby! Brian W > I bought an Indigo 3 bladed prop last week for my Alberg 35 with the > original Atomic 4, as the existing prop succumbed to electrolysis [quoted text clipped - 21 lines] > > Jonathan Wye Well, the m marina figured it out. Apparently with enough patience one could align the prop and rudder and "turn" it off. I had thought something like this might be the case, as I was tired and it was late when I got to the prop last weekend. Also, some years ago I got hit by a Mack truck (literally) and sometimes I have trouble with certain 3 dimensional space/configuration problems. This might have been a bit of that, too. In any event, the new prop is on, and the boat is back in the water. Wish I could have gotten down this weekend to try it out. thanks for all the interesting commentary :) Jonathan SignatureI am building my daughter an Argie 10 sailing dinghy, check it out: http://home.comcast.net/~jonsailr >> I bought an Indigo 3 bladed prop last week for my Alberg 35 with the >> original Atomic 4, as the existing prop succumbed to electrolysis [quoted text clipped - 38 lines] > > Jonathan I'm glad you found a solution. Having said that, what year was all of this assembled? Maybe removing the rudder, looking for corrosion on the pieces and giving everything as good cleaning and greasing would be a good idea. |
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