drive shaft systems

[pistonbroke]

My first post. New to this game ,so be gentle with me!
Browsing the site shows lots of surface drives (ie. props some
distance behind the transom ,half out the water and rudder offset).
I have lashed together a bare WILDTHING hull from plan downloads here
and I thought of using the traditional offshore layout of rudder hung
centrally, at or near the transom, and a prop ahead of the rudder .
What are the pros and cons and where can I find info about driveshaft
angles, Distance from transom to prop and rudder dimensions and so
forth. I will use a standard Homelite motor for now.
Second question! Is there a convenient source of rubber engine mounts
for such a motor ( eg. is a suitable size commonly available as a
mounting in some or other automotive or similar application?)


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pistonbroke
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[John]

pistonbroke;395 Wrote:
> My first post. New to this game ,so be gentle with me!
> Browsing the site shows lots of surface drives (ie. props some
> distance behind the transom ,half out the water and rudder offset).
> I have lashed together a bare WILDTHING hull from plan downloads here
> and I thought of using the traditional offshore layout of rudder hung
> centrally, at or near the transom, and a prop ahead of the rudder .
> What are the pros and cons and where can I find info about driveshaft
> angles, Distance from transom to prop and rudder dimensions and so
> forth. I will use a standard Homelite motor for now.
> Second question! Is there a convenient source of rubber engine mounts
> for such a motor ( eg. is a suitable size commonly available as a
> mounting in some or other automotive or similar application?)

I don't think it will matter too much if you have the rudder offset or
directly to the rear of the prop with your boat. Are you planing on
making your own hardware or do you want to buy something pre-made?

As for the driveshaft angles, positive angle will lift the bow of the
boat and negative angle will lower the bow

[image: http://www.modelpowerboat.com/images/attitude/strut01.jpg]

Have a read of this page to learn how different setups impact on how
the boat rides http://www.modelpowerboat.com/RC_Boat_Hull_Attitude

You should be able to pick up the rubber engine mounts off ebay or a
local engineer spare parts shop. What country do you live in?


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[pistonbroke]

John, thanks for the help. Rereading my own post, I see I did not make
myself clear. I meant putting the prop AHEAD of the transom, with the
driveshaft at an angle steep enough to accommodate a prop of a suitable
diameter. The rudder would in the old days, then be hung behind the
prop, but either at ,or somewhat ahead of the transom.
In short, the sort of arrangement that prevailed before surface drives
became everyday.
I am in Durban, South Africa and I would prefer to make my own running
gear.
I have lathe and milling equipment , but perhaps not the degree of
skill that might be expected!! If you could point me to a site where I
can see what's for sale I would still appreciate that.
I found some rubber mounts, which leads me to more questions. I take
it that the lower one mounts the motor the better. So I have sawn off
the lower corners of the pullstart end of the Homelite block to drop it
to about 10mm off the hull and I must now make mounting brackets. Can I
use the original clutch, which takes a 5.5mm (7/32") sare cable end?
The clutch has no provision to lock the cable in place, does it need a
grub screw or is there some usual way of stopping the cable slipping out
towards the prop?


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[John]

pistonbroke;437 Wrote:
> John, thanks for the help. Rereading my own post, I see I did not make
> myself clear. I meant putting the prop AHEAD of the transom, with the
> driveshaft at an angle steep enough to accommodate a prop of a suitable
> diameter. The rudder would in the old days, then be hung behind the
> prop, but either at ,or somewhat ahead of the transom.
> In short, the sort of arrangement that prevailed before surface drives
> became everyday.
> I am in Durban, South Africa and I would prefer to make my own running
> gear.
> I have lathe and milling equipment , but perhaps not the degree of
> skill that might be expected!! If you could point me to a site where I
> can see what's for sale I would still appreciate that.
> I found some rubber mounts, which leads me to more questions. I take
> it that the lower one mounts the motor the better. So I have sawn off
> the lower corners of the pullstart end of the Homelite block to drop it
> to about 10mm off the hull and I must now make mounting brackets. Can I
> use the original clutch, which takes a 5.5mm (7/32") sare cable end?
> The clutch has no provision to lock the cable in place, does it need a
> grub screw or is there some usual way of stopping the cable slipping out
> towards the prop?

Yes you can set it up like that. Boats with the prop under the hull
are running submerged drives. FSR boats as they are known are fairly
big in Europe.

The idea of having the prop clear of the transom is so you can have a
surface drive. This is where part of the propeller is clear of the
water when the boat is running. having the propeller half in the water
and half clear provides less resistance and allow the engine to unload
more.

If you want to keep the clutch on your current engine then you need to
have a ferrule setup with the strut like in the picture I posted
before. The ferrule and the drive dog keeps everything in place. The
flex cable just sliding into the square output on the engine and is not
fixed in place.

Here is a store that sells gear for surface and FSR type boats in
England http://www.prestwich.ndirect.co.uk/


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[pistonbroke]

Thanks again. Looks like surface drive is the way to go.


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