Hydrofoil - Shaft Speed Guidance

[abracadabra]

Preamble
=======

I am still trying to figure a way to get the propulsion
in place for my hydrofoil without it being bow-heavy.
I've looked at a number of ideas, but I haven't come
across anything better than what I see at the links
below.

http://www.sdp-si.com/D125/HTML/D125P5008.HTML
http://www.sdp-si.com/D125/HTML/D125P5008.HTML

However, their rated speed is 600 RPM !!!

Everything I've seen so far, gas/electric, seems to be
up in the 6000+ RPM range.

QUESTION
========

So here is my question ? What is the usual propeller speed
and motor speed for the model hydrofoils that have been
built/sold before ? Please indicate the boat's length and weight.

RPMp RPMm LENGTH WEIGHT

Keeping in mind that I would like to build the FHE-400,

http://boatdesign.net/gallery/showphoto.php/photo/1062
http://www.corrosion-doctors.org/Cases/BRAS-DOR.htm

I am thinking of fitting the above-mentionned gear-boxes
in the main foil fairings for foil-based props, like the original.

Thank you,

Eric

[William]

"abracadabra" <marceau504@rogers.com> wrote in message
news:AN6dnbCml7GBJKXfRVn-1Q@rogers.com...
> Preamble
> =======
>
> I am still trying to figure a way to get the propulsion
> in place for my hydrofoil without it being bow-heavy.
> I've looked at a number of ideas, but I haven't come
> across anything better than what I see at the links
> below.
>
> http://www.sdp-si.com/D125/HTML/D125P5008.HTML
> http://www.sdp-si.com/D125/HTML/D125P5008.HTML
>
> However, their rated speed is 600 RPM !!!

Yeah, they're not really designed for the kind of work you
want. You might have more luck putting together some
custom gear boxes using R/C car differential parts.
All you really need is a pair of miter gears of the same size
for a 1:1 ratio. Use ball bearings, and a good gear grease
and they'd probably do a better job. You can get "dogbone"
shafts and fittings, too, to give you a nice universal joint
arrangement.

A toothed belt drive might be even easier - use as many
idler rollers as needed to thread the belts from shaft to shaft
without rubbing on anything. Less vibration and cheaper.
(You'd might need some kind of access cover at the
bottom to facilitate belt replacement depending on how tight
things are.) -Wm

[abracadabra]

Thank you. I will look into that.

Eric

"William" <all_replies@news.group.please> wrote in message
news:OVN_d.25046$8D.11542@tornado.texas.rr.com...
>
> Yeah, they're not really designed for the kind of work you
> want. You might have more luck putting together some
> custom gear boxes using R/C car differential parts.
> All you really need is a pair of miter gears of the same size
> for a 1:1 ratio. Use ball bearings, and a good gear grease
> and they'd probably do a better job. You can get "dogbone"
> shafts and fittings, too, to give you a nice universal joint
> arrangement.
>
> A toothed belt drive might be even easier - use as many
> idler rollers as needed to thread the belts from shaft to shaft
> without rubbing on anything. Less vibration and cheaper.
> (You'd might need some kind of access cover at the
> bottom to facilitate belt replacement depending on how tight
> things are.) -Wm
>
>
>
>

[aeronavale]

Eric,

If one day you get you project of building the FHE-400 underway, remember that the ship was not sold for metal and is still opened to public visits in the "musee maritime du Quebec", (Quebec maritime museum).

This is the museum site :http://www.mmq.qc.ca/parc.html where you will find all the informations if one day you wish to see the real thing.

[abracadabra]

I was at the museum in summer of 1987, by myself, for
4 bed+breakfast days, going thru their material on the ship.
There was not much preserved in the way of documentation
because most of it (original construction drawings) was
left inattended upon first delivery, with leaking mechanical
parts packed on top of non-protected cardboard boxes
containing the drawings, all in a crate (as told to me by the
"handy-man" of the place. They sat like that for close to a
year before anyone paid attention to the stuff, and by the
time they did, there wasn't much left.

I tried contacting the RCN afterwards, and they told me that
anything they had was transferred to the museum. (I couldn't
believe it when I read it.) IF this is true, and I suspect it cannot
be true, then only foreigners possess the "cream" of the
research information thru sharing under the multi-national
research project.

The only thing that I did manage to locate was a copy of the
bulkhead section dimensions in table form in the clip bound
ledgers. I am going to have to do guesswork based on the
information in "The Flying 400" book, which I bought many
years ago.

My visit was a LONG time before the current setup which allows
visits into the ship using a steel stairway leading into a opening
that was cut directly into the hull. (another bad decision; it could
have been refloated later with a change of foil systems.) The
photos I took back then were deliberately slides, because of
the better resolution for reprints and better colour control.

So ... there you have it. If you happened to be working with
one of the cooperating research groups, and are able to obtain
some of the photographic records of the foil system testing
done down in the US, I would like to get my hands on it.

As it stands, I am still trying to work out the most difficult part,
in my mind, which is the foil-borne propulsion system (props
in 2 nacelles at foil system joints). Using the traditional
modelling route of mounting the engine near the bow in order
to get a long shaft deep enough into the water will put the
weight of the center of the main lifting foil, putting too much
stress on the bow foil system. (Should only be 10% of ship
weight borne at bow foil. I toying with many different
concepts just now:
- 90deg gear boxes
- miniature hydraulic motors
- drive pumps

I had hoped to build it no longer than 1m, but I may end up
with a 1.3m long ship to have enough size for scaling the
mechanical drive, if it requires a powertrain going from hull
to foil nacelle. I've also toyed with mounting the motors
in the actual nacelle, although this raises concerns for me
about exposure to leakage ... unless I implement a pressurized
air system to blow into the nacelle and exit around the shaft in a
way that it does not cause excessive cavitation at the props.

I also hope to be able to have a scale speed so that the
foil's wake will have the realistic look of the full-size ship
under way.

These are all interesting challenges that I now have some time
to devote to.

Si vous le désirez, on peut aussi correspondre en Français
de façon direct par courriel.


Eric Marceau, 49

[William]

"abracadabra" <marceau504@rogers.com> wrote in message
news:KpudnWNPY-w13frfRVn-uA@rogers.com...
>
> I had hoped to build it no longer than 1m, but I may end up
> with a 1.3m long ship to have enough size for scaling the
> mechanical drive, if it requires a powertrain going from hull
> to foil nacelle. I've also toyed with mounting the motors
> in the actual nacelle, although this raises concerns for me
> about exposure to leakage ... unless I implement a pressurized
> air system to blow into the nacelle and exit around the shaft in a
> way that it does not cause excessive cavitation at the props.

If you do a decent job of sealing the shaft, the amount of
leaking air should be small and probably won't cause excessive
cavitation - keep the pressure just a little higher than the water
pressure at the bottom of the nacelle. Vent the excess pressure
inside the hull. You might need the airflow just to cool the motor
anyway. (A weighted or spring-loaded flap valve would do as a
pressure regulator.) -Wm

[abracadabra]

"William" <all_replies@news.group.please> wrote in message
news:FYZ9e.17014$h6.6833@tornado.texas.rr.com...
> "abracadabra" <marceau504@rogers.com> wrote in message
> news:KpudnWNPY-w13frfRVn-uA@rogers.com...
> >
> > I had hoped to build it no longer than 1m, but I may end up
> > with a 1.3m long ship to have enough size for scaling the
> > mechanical drive, if it requires a powertrain going from hull
> > to foil nacelle. I've also toyed with mounting the motors
> > in the actual nacelle, although this raises concerns for me
> > about exposure to leakage ... unless I implement a pressurized
> > air system to blow into the nacelle and exit around the shaft in a
> > way that it does not cause excessive cavitation at the props.
>
> If you do a decent job of sealing the shaft, the amount of
> leaking air should be small and probably won't cause excessive
> cavitation - keep the pressure just a little higher than the water
> pressure at the bottom of the nacelle. Vent the excess pressure
> inside the hull. You might need the airflow just to cool the motor
> anyway. (A weighted or spring-loaded flap valve would do as a
> pressure regulator.) -Wm

Darn! I had forgotten about the cooling of the motors if nacelle
mounted. Another challenge to ponder. Now where was that
aluminum slide rule of mine ...

Thank you for the heads up.

Eric

[William]

"abracadabra" <marceau504@rogers.com> wrote in message
news:K56dnft8E4TnGvXfRVn-2w@rogers.com...
>
>
> Darn! I had forgotten about the cooling of the motors if nacelle
> mounted. Another challenge to ponder. Now where was that
> aluminum slide rule of mine ...

Well, there're always heat pipes...

Or put a water scoop on each nacelle and make a cooling
jacket for the motor.

This is starting to sound like engineering :-) -Wm

[abracadabra]

"William" <all_replies@news.group.please> wrote in message
news:Wniae.19674$AE6.19119@tornado.texas.rr.com...
> This is starting to sound like engineering :-) -Wm

Yeah, baby ! Now you're talkin'.

Eric

[William]

"abracadabra" <marceau504@rogers.com> wrote in message
news:KpudnWNPY-w13frfRVn-uA@rogers.com...
>
> As it stands, I am still trying to work out the most difficult part,
> in my mind, which is the foil-borne propulsion system (props
> in 2 nacelles at foil system joints).

This little item just occurred to me:
http://www.micro-tools.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=MT&Product_Code=DREM-575

I bet it wouldn't be hard to modify to fit your needs and it's speed
and power specs are probably plenty for your purporses considering
how fast a Dremel tool turns and that it's often under a decent load.
Compact size too. -Wm

[abracadabra]

"William" <all_replies@news.group.please> wrote in message
news:TSebe.26067$AE6.12996@tornado.texas.rr.com...
>
> This little item just occurred to me:
>
http://www.micro-tools.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=MT&Product_Code=DREM-575
>
> I bet it wouldn't be hard to modify to fit your needs and it's speed
> and power specs are probably plenty for your purporses considering
> how fast a Dremel tool turns and that it's often under a decent load.
> Compact size too. -Wm

Excellent call ! I will look into it.

Thank you muchly ! (it's ok, I get creative with language sometimes too
:-) )


Eric

[Umi_Ryuzuki]

Pods work, Ron Swart built his PHM using motor pods.
A simple stuffing tube would keep the water out.

http://home.wanadoo.nl/~hydrofoils1/phm.htm