Which hull design?

[Ozpulse]

Hello all, I have been into RC for a while now(planes etc.) and thought
I would give the boating side a go. I work with aircraft so getting
hold of materials is easy and I have good tooling to
use(lathe,mill,drill etc.) I am currently building the 72in. mono from
this site to be powered by a hotted up weedeater motor. I also build
and sell valveless pulse jet engines with quite a few different designs
to my credit. What I would like to do is run one of these on a boat hull
just for fun. Does anyone have suggestions on a hull design that would
be best suited to a thrust only type of situation? weight wont be a
problem as the motor setups weigh less than any weedeater motor. Just
thought I would pick the brains of the more experienced members for
some help.

Thanks in advance,
Chad..


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[dwr9]

Welcome to the site Chad. Wish I could help you, but I have no knowledge
of pulse jet engines and I wouldn't know what to suggest.
Please post some pics of your 72" boat and let us know how the build is
going.
Doug


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[Rex Reynolds]

hmmm, not having a prop would rule out a 3-point hydro...mayhap a racing
'cat
rex
"Ozpulse" <Ozpulse.3k83i0@no-mx.forums.yourdomain.com.au> wrote in message
news:Ozpulse.3k83i0@no-mx.forums.yourdomain.com.au...
>
> Hello all, I have been into RC for a while now(planes etc.) and thought
> I would give the boating side a go. I work with aircraft so getting
> hold of materials is easy and I have good tooling to
> use(lathe,mill,drill etc.) I am currently building the 72in. mono from
> this site to be powered by a hotted up weedeater motor. I also build
> and sell valveless pulse jet engines with quite a few different designs
> to my credit. What I would like to do is run one of these on a boat hull
> just for fun. Does anyone have suggestions on a hull design that would
> be best suited to a thrust only type of situation? weight wont be a
> problem as the motor setups weigh less than any weedeater motor. Just
> thought I would pick the brains of the more experienced members for
> some help.
>
> Thanks in advance,
> Chad..
>
>
> --
> Ozpulse
> ------------------------------------------------------------------------
> Ozpulse's Profile:
> http://www.modelpowerboat.com/forum/member.php?userid=6593
> View this thread: http://www.modelpowerboat.com/forum/showthread.php?t=934
>

[John]

I recall seeing a video of a jet engine installed in a cat hull a year
or so ago. I think it was from Norway or something like that.

I think a Cat or a Mono would be suitable.


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To get my nephew started in modeling, we have built several air boats
together. We also have a SuperVee 27 deep-Vee commercial model. They have
all been 20 to 27 inches long with outrunner motors swinging 8 or 9 inch
props (the center line of thrust is about 6.5 inches off the water). Speeds
have ranged from 20 to 40 MPH. While not the same, you are looking at a
boat with the CG higher than normal, so perhaps our experience will be of
value.

Our first hull design was a flat bottom mono with an aircraft type rudder -
slow and unstable until we added 2, 1/8" square strakes down half the length
of the bottom for directional stability. Next was a 3-point hydro - faster,
but more easily capsized. Our latest design is by far the fastest and most
stable. It is a stepped hull catamaran with the hulls a little further
apart than you see in commercial boats (10" x 24"). We moved the steps as
far forward as possible and made them 1/2" deep. This essentially resulted
in a 4-point hydro design with the 4 water contact points moved as far apart
as practical to enhance stability.

We have learned several things along the way. With mono-hull design, the CG
needed to be about 25% forward of the transom. The catamaran design's CG is
at 40% forward, but still behind the steps. Either non-trip chines or turn
fins are vital to keep the boat from capsizing in turns. I have built with
foam, balsa, and plywood, finding that the foam was heavier than the wood
designs and the wood is easier to finish. A final thought - consider
placing the fuel tank behind the CG to keep fuel burn-down from affecting
stability.

Good luck and keep us informed!
Randy


"Ozpulse" <Ozpulse.3k83i0@no-mx.forums.yourdomain.com.au> wrote in message
news:Ozpulse.3k83i0@no-mx.forums.yourdomain.com.au...
>
> Hello all, I have been into RC for a while now(planes etc.) and thought
> I would give the boating side a go. I work with aircraft so getting
> hold of materials is easy and I have good tooling to
> use(lathe,mill,drill etc.) I am currently building the 72in. mono from
> this site to be powered by a hotted up weedeater motor. I also build
> and sell valveless pulse jet engines with quite a few different designs
> to my credit. What I would like to do is run one of these on a boat hull
> just for fun. Does anyone have suggestions on a hull design that would
> be best suited to a thrust only type of situation? weight wont be a
> problem as the motor setups weigh less than any weedeater motor. Just
> thought I would pick the brains of the more experienced members for
> some help.
>
> Thanks in advance,
> Chad..
>
>
> --
> Ozpulse
> ------------------------------------------------------------------------
> Ozpulse's Profile:
> http://www.modelpowerboat.com/forum/member.php?userid=6593
> View this thread: http://www.modelpowerboat.com/forum/showthread.php?t=934
>

[Ozpulse]

Thanks for the warm welcome! I know this may be a strange project.lol To
me speed and jet engines seem to go together :eek: I will be able to
keep the motor mounting low with some heat sheilding so as to keep the
CG as low as possible. It will be more for high speed runs more than
turning anyway. I will try a flat bottom mono first maybe just for
engine setup testing. The engine runs off of a very small lpg bottle so
that can be mounted on the CG so it wont effect balance as it emptys. If
you are interested I should be able to add a link to one of the engine
runs! http://au.youtube.com/watch?v=YIUPiCLi5zQ


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