New heel bearing, glassed rudder, hydrodynamic side support build

Comment

Comment by bob mitchell on December 1, 2017 at 7:37pm

Hi Jim,

       This shot is better viewed full size to get rid of distortion. Also, the prop shaft may not been in position because the couple is not bolted together. However, if it would be helpful I could put the shaft right up to the coupling, although I did install a new (rebuilt) engine.  I could retake this picture with a tape measure or two in the shot, if that would be helpful.

           One thing I wonder about. The original prop has really good torque at low end, like docking - and would a feathering prop be able to supply that. And finally, how much extra top sailing speed and efficiency would the feathering prop supply to a heavy displacement boat like a Newporter. I do not know the answers to these questions, but do know that of my 6 sailboats, the Newporter is by far the biggest, and yet handled the best at low rpms in tight quarters. Incidentally, for a lot more photos and information on Newporter rudders just enter "rudder" in the upper right hand corner site search engine.

Comment by bob mitchell on April 21, 2017 at 8:22pm

Hi Jim,

          Removed all the posts because I was still on a learning curve - will do a final post on taper in a couple of days. BUT, when I went to the boat this morning I measured the chart given taper length (for 1.25 shaft) of 3.5" back from the shoulder and the shaft diameter was 1.25", giving the expected 1 in 16.  - as you expected.

        My confusion was thinking the length of the Propeller hub was the taper length  - an impression I got from www.propellerpages.com web site.  And of course, as I so astutely pointed out, the shaft diameter was still 1.25" at the end of the hub as well!   So now  I think I understand the statement  "All dimensions for S.A.E. taper standards are based on the SMALL end of the taper. The reason for this is so propellers with different hub lengths (i.e. different diameters at the large end of the taper bore) will fit the same shaft diameter and have the nut face in the same position on the shaft"  

   It is still not clear to me whether the taper is cut all the way in the hub or is cut for the standard distance and then the diameter is left constant at the max.

Comment by bob mitchell on April 18, 2017 at 8:50pm

www.propellerpages.com , in their technical information section, has a brief section on measuring taper, as well as charts for the standard tapers. There is one for a 1.25 shaft, but the length of the hub is different. They also mention

S.A.E. Specification J755
The most widely followed dimensions for tapers is the internationally accepted standard S.A.E. taper dimensions which is 1 in 16 up to and including 5 1/2" diameter. Above this diameter the taper is 1 in 12. This standard is incorporated in the American Boat and Yacht Council (A.B.Y.C.) rules which are commonly used in Australia. All dimensions for S.A.E. taper standards are based on the SMALL end of the taper. The reason for this is so propellers with different hub lengths (i.e. different diameters at the large end of the taper bore) will fit the same shaft diameter and have the nut face in the same position on the shaft.

The chart itself exceeds what is allowed on site, but is worth looking at. Let me know what you think. I am going to go check the length once more. Hasn't grown a bit - still 4.25 inches. Also, the depth of the keyway into the hub is one half of the 5/16 inch key.

Comment by bob mitchell on April 18, 2017 at 8:00pm

Hi Jim,

    After taking some measurements of the shaft at the boat, I could not get that consistent because it was a little hard to tell where the taper ended. I am using a pretty nice digital caliper. When I got home I worked off the propeller, in millimeters, and there was some variation, but I noticed the small end inside diameter was very close to 25.4 mm, a measurement I know as an inch. I switched to inches, and it appears after repeated measurements that the large diameter is 1 1/4 inch, and the smaller diameter is 1 inch, and the length of the hub is 4 1/4 inches, giving a taper of 1 in 17.

           The keyway extended the full length of the hub, open at each end, and was 5/16 inch by 5/16 inch     (.31 inches).  If you are not in a hurry, I will check the shaft and hub again tomorrow to be sure. friend bob

Comment by bob mitchell on April 18, 2017 at 4:14am

         OK! The method props.com describes  is the same as the one I described. I will get a battery for my caliper today and take the measurements from the shaft as well as the hub of the prop. They should agree. It will be interesting to see if we get a standard SAE ratio.

Comment by Jim Benbow on April 17, 2017 at 6:36am

Bob,
Seems the most likely way to describe the taper is using the SAE ratio
I think this is how you determine this,
Subtract the small diameter from the shaft diameter then divide the result by the taper length, you will get a number like .06259 Then go 1 divided by ( the result e.g..06259) and you will get a number like 16 ( or very close to it) the SAE taper is 16 to 1
There is an example on an Aussie website www.props.com.au click on products and then prop tools software then taper tools shows it pretty good
Been a bit quiet on the boating front the last couple of years for various reasons
Hopefully all about to change over the next few months, I currently have the rig out of Sultana for a much needed service, some rot in the top of the mizzenmast but the main mast looks good considering it may have been 18 years since it was last out, some of the stays and shrouds will be replaced to bring it back up to an offshore standard, a couple of modifications including looking at a high field lever arrangement for the staysail stay to make tacking the genoa much easier while sailing locally in the bay,
Then the big desicion do we head to the tropics next year?

Comment by bob mitchell on April 16, 2017 at 7:54pm

Thinking about it, the prop is in the basement. Would the taper be the difference between the diameter at the forward end minus the diameter at the aft end, divided by the length?   See www.propellerpages.com 

Comment by bob mitchell on April 16, 2017 at 7:52pm

Would be glad to. I think mine is 1 1/4 as well, but will check tomorrow. It is amazing that you posted, because YESTERDAY I thought about emailing you to see if you were still around. First time in years for that thought!!!!! global telepathy??????!!!!!. Anyway, I will contact you tomorrow and we will work out the methodology. friend bob

Comment by Jim Benbow on April 16, 2017 at 5:35am

Hi Bob,
That looks like a very solid job you are doing there, should give you no problems for a long time.
A thought sprung to mind, I have been in discussion with a company in the U.K. about a new prop for Sultana, the present one is well past its use by date, presumably your prop shaft should be the same and something I would like to know is what the taper and key way dimensions are? Sultana's
is I am pretty sure 1 1/4" diameter, the only way I can check the taper is to slip her, can you help on this please?
Thanks Jim