BJ29 prop washers?

[helidan]

Searching through various forums it seems to be almost universally agreed that prop washers are not needed on the type of drivetrain that the BJ29 uses.

I was just wondering why Proboat included them.

Out of interest is the endfloat on the motor shaft (which is a good few mm) sufficient to allow for flex shrinkage if there's no gap between the dog and strut?

[tlandauer]

Well, the washer is useless if one observes the gap rule. In the event that practice is over looked, the washer can be an item that offers some minimum assurance that it can be worn down and thus at least gives way to cable shrinkage.
Better to allow the gap than to "rely" on motor shaft "end float" as you put it. This opens up a whole new discussion, thrust bearing, reverse force when the cable is pulling the motor due to shrinkage......

[helidan]

Is it acceptable to allow the motor to take the full thrust of the propeller or should a small amount be taken by the strut? I did think a helicopter blade grip thrust bearing between the collet and motor can might be useful.

[tlandauer]

Good question, have read:http://forums.offshoreelectrics.com/...at-s-your-take
My opinion is that leave a gap and run the boat as is. I have not used any thrust bearing, it is an area with two distinct thoughts. it's a long thread, but if you haven't read it, it offers some very interesting discussions.
Cheers!

[helidan]

An interesting read!!

My head is now hurting from trying to absorb everything that people are saying but the key point appears to be that as long as there is room for the flex to shrink a bit you should be ok. I noticed someone else mentioned the motor end float being used to allow the flex to shrink.

I think for now I'll forget about installing thrust bearings, the boat I've purchased is only going to be used for a bit of fun/sport, nothing serious.

Interestingly the BJv3 manual does state to leave a bit of a gap between the dog and strut but then they go and fit thrust washers down there.

[tlandauer]

HA HA !

As a new member, first of all, Welcome!
I thought there is nothing better than an initiation for you by having you read through this particular thread. Sorry......
I think you have come to the right conclusion, I agree that for this boat and for sport running, all one has to do is to leave a gap....
My own speculation is that Proboat is really targeting the average consumer and therefore by providing the white washer it is just giving a little insurance (however small it might be) to the situation.
I don't remember how the previous version BL manual was printed, but it is possible that they now have included this provision for more serious boaters while at the same time kept the washer for the aforementioned purpose.
Again, just my personal speculation.......

[helidan]

No worries!

To be fair there's some quite interesting theories in that thread. Who'd have thought getting a little prop to reliably spin in the water could be so involved!!