u-joints on prop shaft?

[goodoldwoody]

Hi

I've often wondered about this very question. Since every time our boat encounters a wave, rolls or heels the the alignment goes out enough so that you at least hear a different tone.
Trouble with all this is a sailboat is a compromise and unfortunately by the time you've finally got your particular compromise sorted it's time to think about buying a new boat.
I'm just trying to keep mine safe and reliable and yet I seem to spend a lot more time & money maintaining it than sailing it to exotic locations.

Cheers Woody

[Cheechako]

Originally Posted by goodoldwoody

Hi

I've often wondered about this very question. Since every time our boat encounters a wave, rolls or heels the the alignment goes out enough so that you at least hear a different tone.
Trouble with all this is a sailboat is a compromise and unfortunately by the time you've finally got your particular compromise sorted it's time to think about buying a new boat.
I'm just trying to keep mine safe and reliable and yet I seem to spend a lot more time & money maintaining it than sailing it to exotic locations.

Cheers Woody

Yes, I've wondered too if it is hull flex/alignment or the rush of water/side load current around the prop changing the sound. Seems to me Ujoints or etc are a good thing if you have room.

[Barney21]

I suggest you go the UJoint rout as you will get them from a local wreckers no specialised part if you have an issue. Buy a couple of extra UJ s as spares if you are only young .!! You will need the 2 flanges off the old tailshaft have a machine shop cut the splines on your shaft or if you have the space just get the tailshaft shortened to suit your application.
Remember when getting the shaft cut to size allow enough slip on the splines about 25mm I suggest this will allow the shaft to find its own centre plus a bit each end . This will stop any vibration setting in and is really a nice fix and not a speialty item which you may have to buy some bits for at some inconvenient location. Coat the splines with "Never Seize" or similar, you can use the same to pack the UJs.
If you can find a Toyota 4x4. The small Ute/Pickup would be my choice for all the reasons above, they will spin for years will plough the bottom for longer than your prop will last!

[Kiwi.]

Originally Posted by Hoghead

There would be several advantages:
No alignment issues. This is important to me as I have little faith that the "mechanic" in Subic can align the engine properly.
The engine could sit horizontal, or in any attitude required to fit
Beta engines have the gearbox output from 3.5 - 5" lower than the crank centreline so a drive shaft simplifies clearance issues.
Engine mounts are easy to fabricate
Any change in alignment when the boat goes into the water, or the mounts sag is a non issue
There must be a reason why this is not more common..................

You still need to align the output shaft of your gearbox parallel to the prop shaft, so no, you cannot mount the engine in "any attitude required to fit".
Universal Joints at an angle put an acceleration into the output shaft through half a rotation and then slow the output shaft down for the second half of the rotation. This can be very damaging if there is any significant rotating mass (for example a propeller) on the output shaft. The trick is to use two U joints and for them to be installed at exactly opposite angles, the best way of doing this is for the engine output and the prop shaft to be parallel, then the second U joint reverses the variable velocity induced by the first universal joint.
Note it is often stated that there should be a small difference between the angles, often quoted as 3 degrees. This is so that the needle rollers in the U joints slowly proceed around so that the wear occurs evenly around the joint. I wouldn't worry about this in a wooden boat, things will flex enough to ensure the U joints have some procession.
Constant Velocity joints (CV) are different, you only need one.
One of my favorite "weird" boats uses U joints see https://www.tradeaboat.co.nz/reviews...-one-of-a-kind

[Lepke]

One issue with boats and u-joints, working u-joints can make noise the is amplified by the hull. In commercial fishing, the noise was sometimes enough to turn off fishing.

[Hoghead]

Originally Posted by Captndave1

Good solution, I think.
Unrelated, what hull # FD12 is yours.? I am familiar withe FD 12s, I had the opportunity to sail on hull #24 for several thousand miles with the Owner/Builder of FD12s, Mr, Will Ekholt including 8 trips from Tampa to Cuba and the Grand Caymans.
The FD12 is an excellent boat, I very much enjoyed sailing the boat
I hope all goes well with your project.

I own hull #1, and yes an excellent boat which is why I am spending the money on a new engine

[Hoghead]

Originally Posted by Kiwi.

You still need to align the output shaft of your gearbox parallel to the prop shaft, so no, you cannot mount the engine in "any attitude required to fit".
Universal Joints at an angle put an acceleration into the output shaft through half a rotation and then slow the output shaft down for the second half of the rotation. This can be very damaging if there is any significant rotating mass (for example a propeller) on the output shaft. The trick is to use two U joints and for them to be installed at exactly opposite angles, the best way of doing this is for the engine output and the prop shaft to be parallel, then the second U joint reverses the variable velocity induced by the first universal joint.
Note it is often stated that there should be a small difference between the angles, often quoted as 3 degrees. This is so that the needle rollers in the U joints slowly proceed around so that the wear occurs evenly around the joint. I wouldn't worry about this in a wooden boat, things will flex enough to ensure the U joints have some procession.
Constant Velocity joints (CV) are different, you only need one.
One of my favorite "weird" boats uses U joints see https://www.tradeaboat.co.nz/reviews...-one-of-a-kind

I understand how both U and CV joints work, and my comment about engine attitude was to simplify the installation of a new engine to the existing shaft.
In my case the gearbox elevation of the Beta 90, depending on the final box selection, is 86 - 125mm lower than the crank centre line. I therefore would have to raise the engine on bespoke mounts if installing the traditional hard mounted method.
I am also concerned that there might be clearance issues to do it the traditional method.

Using U or CV joints, allows me to position the engine horizontally on the boat centre line, in line with the shaft, on simple mounts. The angle will be about 8 degrees in a single plane so well within the range of the joint(s)

Given that I already have a bi-directional thrust bearing, it is much easier to use a jackshaft, changing alignment is not a concern, and alignment expertise is not required.
The more I think about this, the more I like the idea.

Some great engineering data from NTN on CV joints here - note the sliding shaft:
http://www.ntnglobal.com/en/products.../pdf/5603E.pdf

[Pigpen Pete]

We have used a traditional* automotive tailshaft assembly complete with universal joints, spline, centre bearing etc to link the engine, which is amidships, to the standard traditional SS marine propellor shaft.* The SS prop shaft has a 2-way thrust bearing clamped to the hull before it exits through the hull.
This rig was installed prior to launching in 1992 and after more than 20 years cruising, including circumnavigating from Sydney (Aus) via Lofoten, it still works fine. We grease the universals from time to time if they get a bit noisy and have replaced the thrust bearings once.
As said above this arrangement, together with the use of an external cutlass bearing, completely removes any alignment issues. We also were advised to set up the assembly with a few degrees of bend to keep the universals moving.
The engine mounts take no thrust and we used soft automotive Ford Fairlane mounts which greatly reduces vibration and fatigue.
The standard tailshaft assembly was quite cheap to have made up. We keep it painted and generally rust free.

[boden36]

A friend of mine years ago made a unit from a VW Kombi drive shaft with CV joint on each end. The joint units looked the same as on my Scatra system.
When I changed the engine in our boat the length of the shaft between the joints needed adjusting. An engineering shop made a new splined shaft for it.

Regards,
Richard.

[Hoghead]

Originally Posted by boden36

A friend of mine years ago made a unit from a VW Kombi drive shaft with CV joint on each end. The joint units looked the same as on my Scatra system.
When I changed the engine in our boat the length of the shaft between the joints needed adjusting. An engineering shop made a new splined shaft for it.

Regards,
Richard.

VW Combi is also known as the Type 2
Interesting if that is what Aquadrive uses

I have Porche 930, and VW Type 2 CV joints left over from a Speedster project that I have been eyeing up today. Boat torque will be about 550-600 Nm (405 - 442 ft. lbs) depending on the finial gearbox ratio I settle on.
Still have not found a TQ rating on my joints and it would be nice to use something I have

[Elie]

After years of frustrations trying to align my hard to reach the shaft coupling I finally installed an Aquadrive coupling and push bearing. It was a bit complicated to fit the the structural bulhhead(in stainbless steel!) to support the push bearing. But, once installed, all problems of alignment and engine supports are gone: No vibration with heavy Brunton Autoprop propeller. Having installed greasing zerks(machine shop work) there is no problem at all... just the pleasure and with a PSS shaft seal, all maintenance, water intrusion are all gone... I would recommand highly this type of solution.

[a64pilot]

Originally Posted by Hoghead

VW Combi is also known as the Type 2

Interesting if that is what Aquadrive uses



I have Porche 930, and VW Type 2 CV joints left over from a Speedster project that I have been eyeing up today. Boat torque will be about 550-600 Nm (405 - 442 ft. lbs) depending on the finial gearbox ratio I settle on.

Still have not found a TQ rating on my joints and it would be nice to use something I have

Automotive shafts are usually specified to hold ridiculous amounts of torque, cause you can do things like race the engine up and dump the clutch, or be spinning on ice then suddenly hit dry pavement etc.
Boat drives rarely or almost never have such shocks

[Oceanride007]

You mentioned no room for a shaft seal, have a look at Deep Sea Seals, mine on a 1.25" shaft is 135mm.
Plenty of evidence that either U or CV will work but if you have the luxury of a common bedplate, I'd take everything out, line it up properly and do a Solid coupling. The Bed plate itself could be pussy footed. Alignment for the novice when you can see and measure it is not hard. Even feelers and 6" rule is enough.

[Barney21]

Originally Posted by boden36

A friend of mine years ago made a unit from a VW Kombi drive shaft with CV joint on each end. The joint units looked the same as on my Scatra system.
When I changed the engine in our boat the length of the shaft between the joints needed adjusting. An engineering shop made a new splined shaft for it.

Regards,
Richard.

Porche 930 CVs are way over capacity for your use. And imagine having to buy one "somewhere" if all went bang,highly unlikely. I have used lots of these on Class 1 Offroad race cars, they are a beautiful peice of equipment. If I still had a couple I would like one as a display item in my shed.:

[Hoghead]

Originally Posted by a64pilot

Automotive shafts are usually specified to hold ridiculous amounts of torque, cause you can do things like race the engine up and dump the clutch, or be spinning on ice then suddenly hit dry pavement etc.
Boat drives rarely or almost never have such shocks

I of course would never do a drag race start.............

I assumed that, but all the same it would be nice to know the TQ rating to put my mind at ease and confirm that the much cheaper Type 2 CV joint will more than do the job