Pic of small changes to uniform stringer stock...

Pic of small changes to uniform stringer stock...

I know old school boat construction has the rudder behind the prop. so if i was going to use a dual prop would i need a dual rudder or just use a single centered rudder?

i posted a pic of the rudder i found below

On an R/C boat it is always more convenient to allow the flex
shaft(s) to be pulled without having to remove the rudder.

The rudder from HOR is a good choice. Once the rudder stuffing
box and support bracket is installed, it is easy to make any
other actual size of rudder blade your boat might prefer. A short
length of SS rod brazed to a piece of SS sheet is all the
rudder itself really is.

Which ever rudder you select, it's a good idea to keep a
complete spare rudder on hand. It just takes one unsuspecting
turtle or one of those submerged sticks (tree branch) to really
do a number on a hull mounted rudder.

Those brass rudders that come in three sizes with the plastic
stuffing box - forget 'em. They bend too easy to be used on
most gas boats. I tried them on my first R/C and have already
replicated them in SS.

_____________________________________________________

Just curious, I'll bet you already have a copy of:

Boatbuilding With Plywood
Glen L. Witt, Naval Architect
copyright 1989
ISBN: 0-939070-07-3

LOL i believe thats the only book i dont have yet...

i have

The New Cold-Molded Boatbuilding: From Lofting to Launching

and
the gouneon brothers on boat construction 5th edition...

good point on having an extra fin. check...

Do you think that the rudder i uploaded a pic of would be enough to turn a 19" (at widest point) x 65"L twin prop wood rc boat?

does anyone have any idea whatsoever about the amount of water it takes to cool a rcmk K600s engine?

found a neat mini pump that i thought was better than the old exhaust pump driven coolers....


Input
Voltage 12v
(V) Current
Draw 0.5
(A) Power
Usage 6
(W) Pressure
Head 3500
(mm) Pressure
(mBar)345
Free Flow
Rate 2800
(ml/min) Weight
(g) 33
Operating
Temp -20 to 100

Smokeater2005 wrote:

> Do you think the rudder I posted a pic of would be enough to turn
> a 19" (at widest point) X 65"L twin prop wood rc boat?

That's why I brought up the fact that you will be able to fit other
sizes of blades. The rudder from HOR is most commonly used in FSR-V
competition boats (usually much shorter than 65 in.). This rudder size
issue is one of the important design aspects that you will be testing
for. Stay with something to scale and I would start out with one of the
larger 1/4 scale servos for steering. Just big enough to do the job
with ease but also conserve battery power.

Engine cooling: When a high performance engine is operated with
submerged prop then the cooling requirements are different when
compared to the surface drive configuration most boaters use. The prop
blades have water resistance applied to all surfaces all the time. Your
boat will turn high RPMs spinning a relatively smaller prop (than it
would if it was surface drive) but the difference in heat production due
to increased resistance on the prop will need to be compensated for.

I'm going to guess that the minimum cooling requirements will be
something like:
- Twin impulse driven cooling pumps - the Pro Boat (PRB2651) should work
- Exhaust manifolds with four barbs on each (double coolant circuits)
- Cooling caps with four barbs - water inlets low on the caps and
outlets up high on the caps
- Hull pickups (twins) with a positive scoop shape that will ram the
coolant thru the system at higher speed.
- If the exhaust will exit the transom using thru-hulls in a wood
hull, then it may be safer to use coolant flow to take off some heat
from the pipe stingers just before the exhaust pipe comes in close
proximity to the transom.

Sidebar: A cooling system like this has a lot of water lines going
here, there, and everywhere. Plan for this with cutouts in the
station frames, stringers, etc in order to avoid the spaghetti look.

____________________________

The reason I brought up Glen Witt's book is it has more diagrams then
any other book I have seen. Witt spends a lot of time using the text
to explain the diagrams. It really is a must have for every boatwright.
Be sure and get Santa to drop off a copy - you deserve one.

Yep, thats what i thought they used those rudders for. But, i still cant help seeing it on my scale woody. "pun intended"... Now with a bigger rudder will come more drag so my concern would be if the rudder body and mounting flanges can handle a biggie sized rudder? Even though it would not be optimal, would it be possible to run twin (stock) hor rudders with twin 1/4:servos (rud=servo=servo=rud) mechanicaly and electronicaly ganged... Inline with the twin prop design purposed? of course far enough aft the prop to make possible maintenance without rudder removal... my WAG on the props would be twin 3 blade 47mm-ish and play with pitch until proper speed/engine loading can be found...

As for cooling you are so very correct to point out the differences in surface drives versus submerged ones. And yes i would most likley be using water cooled exhaust flanges, water cooled exhuast pipe rings, and the water cooled engine head jackets, of which some heated cooling water would exit direct threw hull and one into the end of the exhaust system just before trasom exit for the scale wet exhaust look, and cooler pipe temps on the wood transom. The exhaust system, A single exhaust muffler (the 55cc-60cc long length aircraft tuned pipe) and a custom 2-into-1 header design i have put together from my original 54" bonsisport build exhaust prototyping that i had to scrap for a single cylinder motor, because i couldnt find a short enough 50-60cc muffler that would fit without cutting a beercan size hole in the boat. Anyway, i digressed a bit sorry...
As for water pickups i was planing on using some like on the 54" build... x4 in number and placed on the scale "Cavitation Plates"...

I hope that i will be able to hide as much of the cooling lines as possible using some scale flooring off of the oringinal designs... fingers crossed...

The FSR-V rudders are generally well built and tough. There should be no problem with the body handling a larger rudder more the proper mounting of it. You can always bracket the top of the body to give extra support.

Using a rudder of the same size as the one shown my 27cc boat uses a Savox 1258TG.

I got froggy today and cut out frame 7 "where the seating is near the back" it looks fairly nice now just to get started on all the other ones...LOL