Tiny might propeller to rudder distance

Designs for inboard or outboard power

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JhlFin
Posts: 5
Joined: Tue Sep 11, 2012 12:43 pm

Tiny might propeller to rudder distance

Post by JhlFin » Fri Jul 05, 2019 5:09 am

Hi, First sorry for my bad englis :) im building tiny might (tiny shite because my lack of skill) and now im having problems with prop being way too close to rudder. Now propeller tip to rudder is about 1/2 inch, little clearance, big problem :lol: Some things changed after first mockup. Book says clearance should be 4" or whats needed to get propeller off whitout removing rudder. What is the absolute miniun clearance? I can move prop forward maybe 1,5". Could 2" clearance work? I can handle removing rudder in order to remove prop. All help and ideas are welcome

Greetings from Finland!

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Mr Hot Rod
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Location: Chelsea, Quebec, Canada
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Re: Tiny might propeller to rudder distance

Post by Mr Hot Rod » Fri Jul 05, 2019 9:14 pm

Welcome to the Forum !

Stuffing a driveline into a 12' boat is tough. A 10% stretch will make your installation a lot easier !

Can you provide us with details about your inboard installation e.g. engine specs, transmission (if used), strut drop, shaft angle, propeller specs etc.

The clearance specs should be followed as stated in the book. Refer to the Tiny Might Design Notes for more details.
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Any details concerning your mockup ?

Related Links

Support Knowledge Base - Shaft angles & layout diagrams

Support Knowledge Base - Cracker Box Design

Calculate shaft angle from strut drop and transmission output flange location

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You'll find more info and calculators on our website's Transmission Page.

Here's a direct link to the shaft layout section : Shaft Angles & Layouts - Drilling the Shaft Hole

Hope this helps !
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kens
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Joined: Wed Nov 12, 2003 5:25 pm
Location: Coastal Georgia

Re: Tiny might propeller to rudder distance

Post by kens » Sat Jul 06, 2019 4:28 am

JhlFin wrote:
Fri Jul 05, 2019 5:09 am
Hi, First sorry for my bad englis :) im building tiny might (tiny shite because my lack of skill) and now im having problems with prop being way too close to rudder. Now propeller tip to rudder is about 1/2 inch, little clearance, big problem :lol: Some things changed after first mockup. Book says clearance should be 4" or whats needed to get propeller off whitout removing rudder. What is the absolute miniun clearance? I can move prop forward maybe 1,5". Could 2" clearance work? I can handle removing rudder in order to remove prop. All help and ideas are welcome

Greetings from Finland!
Greetings,
You mentioned you can move the prop forward. How far along are you with the build?
Have you already mounted the strut?
Have you drilled the shaft hole?
Have you drilled the rudder port?
These 3 dimensions will determine what you can do to make a correction.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

JhlFin
Posts: 5
Joined: Tue Sep 11, 2012 12:43 pm

Re: Tiny might propeller to rudder distance

Post by JhlFin » Sat Jul 06, 2019 10:12 am

Hi, im messing up a lot and forgetting things and maybe rushig a bit . Maybe also too eager :lol:
About ten years ago when i ordered plans, i was going to stretch, but somewhere i just kinda forgot. Was bit of a hassle to convert inches to metric :)

Hull is completed and epoxied, no decking yet.
I had a mock up jig for engine, shaft, prop and rudder and all seemed to fit just fine. I think at some point messed up with engine location and thats why nothing lines up.
One thing is also that my mockup prop was 10x10 and now im using 11x15, orginally i planned that 11" prop would be cut to 10", but rather not if not necesary.
I dont have proper strut yet, none available here in finland so i have to make one .Now im using adjustable strut.
Shaft and rudder holes are drilled already... Yeah i know im bit stupid :shock:
I
Strut was not properly mounted yet, i moved it and now i have 2" from hull to prop and 2" from prop tip to rudder, i really hope thats enough. If that wont work only option is outboard rudder.

Engine is 2100cc from volvo 240( im volvo guy :D ) and marinized with penta parts, no transmission. Same engines are used in boats with stern drive, volvo penta aq series.
I used bellhousing from car, main shaft from car gearbox with flange bearing behind it. I will try using car clutch, but i dont have high hopes for it to work :)
Shaft angle is 15 degrees, or thats what im aiming for.

JhlFin
Posts: 5
Joined: Tue Sep 11, 2012 12:43 pm

Re: Tiny might propeller to rudder distance

Post by JhlFin » Tue Sep 10, 2019 9:57 am

Hi, now i have test drived the boat, lot of little problems still, engine not running properly etc. I managed to get 5-6000rpms shorty on test drive, did not have speedo, but with questimated speed prop slip was about 50% 😲
I know few issues that could cause problems. Prop strut is adjustable type (just for now) and propably causes lot of drag and maybe not clean water to prop? Other issue is prop tip being only 2" from rudder, should be 4". Can this mess up water somehow and cause extreme slip?

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