[hpv-boats] V15 Shaft

[Rick Willoughby]

Vic
I tried the 6mm sleeve I had on a 1/4" spring steel shaft.  I was  
disappointed because it did not make measurable increase in the  
torsional rigidity.  It is an effective way to protect the shaft.   
When I tested it the epoxy was only a couple of days old so not fully  
cured.  I will do a more precise side-by-side comparison with  
unsleeved rod at some point.

As Mark Drela commented it would have been smarter to use thicker  
tube.  It is much easier to reduce the diameter of the tube by  
pulling it tight than it is to increase the diameter when it is  
loose.  The fibes in the sleeve are running more like 20 to 30  
degrees than 45.

The new shaft is a combination 12mm aluminium rod through a HDPE pipe  
in the hull and 8mm spring steel beyond the tube.  The steel portion  
slots into the aluminium.  That connection is epoxy glued and I have  
wrapped a few layers of glass tape over the joint.  I made a small  
sleeve from UHMWPE for the bearing at the bottom of the shaft tube.   
The tube exits just behind the gearbox so it does not need to be sealed.

The folding prop sheds most weed so I do not need access to it.  It  
is possible to get a bit of weed wrapped around the hub but that will  
usually dislodge by reversing.  Most floating weed gets pushed aside  
by the hull.

Having the prop right out the stern reduced the tendency to ventilate  
in waves.  This improves as I go faster because the boat sits bow up  
a little and the prop goes deeper.  In the 1 to 2 ft waves yesterday  
the prop only ventilated a couple of times.  The side mounted prop  
would have ventilated more often in waves like that.

Rick

On anothe note, wonder if you ever got the time to test out the idea  
of a
carbon fiber sleeve reinforcement on your flex shaft?
http://www.cstsales.com/carbon_braid.html  I haven't had free time to
explore this yet.

Regards,

Vic