Prop Specs ?

[Rob_P]

My afternoons sailing came to an end when I snagged my prop on a submerged powercord for a floating fountain. I think my mistake was then trying reverse,,,,
Anyway, I recovered the boat with a tennis ball tied to a piece of string minus the prop which I now have to try and replace. The prop came with my boat and I'm not sure I have sufficient information to replace with exactly the same.
What I do know is its a brass three blade, 3" diameter, M4 thread.

How do I determine if it was RH or LH and with this type is the pitch pretty standard ?

Fortunately I took a couple of pics prior to losing it.

So what do I ask for & and any recommended suppliers?

Rob

[toesup]

My afternoons sailing came to an end when I snagged my prop on a submerged powercord for a floating fountain. I think my mistake was then trying reverse,

What I do know is its a brass three blade, 3" diameter, M4 thread.

How do I determine if it was RH or LH and with this type is the pitch pretty standard ?

So what do I ask for & and any recommended suppliers?



Yes, but was the cable damaged? :confused::confused::confused:... :p

Try harbour models..
http://www.harbormodels.com/site08/main_pages/propellers_rivabo.htm
They stock a 3 blade, 3" brass prop witha 4mm thread.
The brass props they stock are fairly standard pitch i think..

Rotation is determined by looking at the propeller from the rear of the boat. A right hand propeller will turn clockwise therefore moving down to the right hand side. Contrary, a left hand propeller will rotate counterclockwise or down to the left while looking at the propeller from the rear of the vessel.
It looks like you have.. or had... a 'left hand' prop...

[mfr02]

Assuming that you can get to the motor terminals, the wrong rotation should not be a problem. If it wants to go backward with the new one, reverse the motor connections, job done.

[Kmot]

Rotation ("Hand")
There are right-hand rotating (RH) and left-hand rotating (LH) propellers (Figure 4-12). Most outboard and stern drive propellers are right-hand rotation.

To recognize a right-hand propeller, observe the prop from a position shown in Figure 4-12 (resting on either end of the hub is OK) and note that the right-hand propeller blade slants from lower left to upper right. A left-hand propeller will have the opposite slant-from lower right to upper left. The blade slopes or climbs up in the direction of rotation. A right-hand rotation propeller has the same basic blade slope as the threads on a common right-hand screw.

http://sites.mercurymarine.com/pls/portal/docs/102/3592.JPG

Based on the above, you have a left hand prop.

[Umi_Ryuzuki]

That image is almost confusing,


If you are looking from the stern or behind the boat they would look like this...

:p

[Rob_P]

Thanks guys, I know what to order now !

Rob

[CG Bob]

Lay the prop flat on a flat surface, with one blade up in the 12:00 position. If the right edge of the blade is touching the table, it is a right hand prop. The left edge will touch the table on a left hand prop.

[patmat2350]

Good pix! Now linked in the Scale sticky FAQ.

PM

[Rob_P]

OK, in speaking to Harbor models, they don't have a 3 blade LH but can offer either a 3 blade RH or a 4 blade LH.

What are the pros & cons of each.

To my mind with a RH, I'll always be running the risk of the prop un-screwing by virtue of the water resistance opposing the props rotation, so to me thats a big red flag.

What happens when you go from a 3 blade to a 4 blade of the same diameter?
What is likely to happen to -
a.) The speed of the boat ?
b.) The current draw ?

Should I just try and find an alternative supplier?

Rob

[CG Bob]

To my mind with a RH, I'll always be running the risk of the prop un-screwing by virtue of the water resistance opposing the props rotation, so to me thats a big red flag. Depending on how the prop is made you will either:
a) Use a jam nut on the shaft next to the prop - with a thread locking compound. The two props I show above have jam nuts.
b) The prop will have a set screw in the side of the hub, between the blades. Replace the mild steel set screw with a stainless steel one and use thread locking compound.
c) The prop will need a drive dog ahead of the prop and a nut (or two) aft of the prop. This is usually seen on the race boats.

What happens when you go from a 3 blade to a 4 blade of the same diameter?
What is likely to happen to -
a.) The speed of the boat ?
b.) The current draw ?
Assuming that the 4 blade prop has more blade surface area than the 3 blade unit, the motor will run a little hotter. There may not be any noticable difference in the boat speed, at least to the naked eye. The boat will most likely run a little faster. The current draw will increase slightly, accounting for the warmer motor. You may have to go with a gear or belt reduction drive when you change to a prop with more blades. If you already have a gear drive, you will have to increase the gear ratio, say from 3:1 to 4:1.

[tim slocum]

CGbob, who sells the two outside props in the left picture in your post?

[CG Bob]

Those three props are from the Tian Jie S-100 (http://www.loyalhannadockyard.com/TJSCHNELLBOOT.htm) kit. I provided the photos for Don at Loyalhana Dockyard.

[tim slocum]

Thanks!

[rlboats2003]

How deep is the fountian and can you walk out to the light. How clear is the water. Just a thought.
Rich

[Rob_P]

My motor is a direct drive Torpedo 850 and it already gets too hot to touch so I'm not keen to risk it getting any warmer.

The water must be pretty deep as there are fish in it and seeing how cold it gets in winter round here it must deep to allow the fish to survive. Its also too green to see the bottom. I had thought about dragging it but any "equipment" that I use will also risk catching on the fountain wire.

When I first put this assembly together being an engineer I thought thread Loctite would have been the way to go but was advised against it in a previous posting.

Maybe I should either find an alternate supplier or come down fractionally on the diameter and stay with LH thread.

Rob

[Rob_P]

OK, this is what I have done & I hope I will not be too disapointed.

I have stayed with a 3 blade brass prop but dropped from 75mm dia to 65mm dia.

My thinking being I'd maybe have less thrust to initially get on a plane but after sufficient time the overall speed may not be too different.

Also with my original prop after 15 mins of running the motor was getting too hot to touch. Hopefully my current consumption and heat will be less now.

I'll let you know what happens.

Rob