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Old Feb 28, 2012, 12:58 PM
Mariner BC Canada
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Quote:
Originally Posted by Umi_Ryuzuki View Post
It's starting to look like Takahashi san's Hayate.
http://www.rcgroups.com/forums/showthread.php?t=1505228

http://www.youtube.com/watch?v=eECYB...2&feature=plcp

.

The high tower bridge will cause stabilty issues by raising the cg.
The single and inverted "T" hydrofoil designs are inherently unstable, and
will require a bit of effort, that may include gyro sensors to make the boat perform.
While they may excel in speed and agility, hydrofoils are typically less than stable.

Hi Umi,

Thanks for your response.

The tower bridge (wheel house) is 19 grams compared to 7500 grams total displacement, with over half of that in the keel (pod). That's <0.3 % so, it wont be contributing anything significant to instability. I think it's visual impact on the end view may have mislead your thinking. Understandable, as it is a very narrow beam. I wouldn't include the tower at all but it is part of the competition and I'd loose points without it. Also, (not shown) the top view is oval (elliptical) for weight savings, ergonomics and reduced wind effect at sea. The height is necessary but it's not any higher than a conventional ships bridge.

The inverted "T" has no inherent stability or instability, it is neutral. I am considering a "V"-tail but haven't looked closely at it yet. The tail pivots with the rudder.

There will be no gyros on this vessel. The auto leveling strut sensors will keep an even keel but will need much initial tuning.

I'll dig up another hydrofoil video of Japanese origin for you as the one you posted is really not that similar to what I'm proposing.

Thanks again for your input, I really appreciate your feedback.

-Tom

P.S. Here is the video link:
HYDROFOIL -- The Amazing Boats of Kotaro Horiuchi. Video posted by Ray Vellinga (9 min 28 sec)
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Old Feb 28, 2012, 01:24 PM
Mariner BC Canada
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Quote:
Originally Posted by pompebled View Post
Hi Tom,

Dragging a wing that size through water will create massive drag, no doubt about it. It'll generate lift, due to the shape, but I sincerely doubt if the lift will outweigh the drag involved.
Just look at the size of the 'wings' on underwater crafts (submarines) where those wings (diveplanes) are as small as possible to reduce drag.

No, I'm not aware of the competition, do you have a link, so I may better understand the 'need' for such unconventional / unpractical designs?

Regards, Jan
Hi Jan,

Thanks again for responding.

The wing will not create massive drag, if it did, the hydro foil would not lift the surface hull out of the water. The aspect ratio and a number of other factors insure this. Submarines use small control surfaces because they do not require any lift to maintain buoyancy. Much like hot air balloons don't require wings at all!
I didn't think the hydrofoil would work either, but was pleasantly surprised when I did the lift, thrust, drag calculations to find it's possible. I am an aeronautical engineering technologist so you may have some faith in my unconventional considerations.

There is no link for the competition, besides, it would be too much information. I'm not looking for help designing my entry, I'm looking for feedback on stability, maneuverability and speed potential of my design as these are the major components of the competition. Small boats behave and respond differently to full scale boats (which I have experience with), so I came to the "small boat experts" here at RC Groups hoping to find some insight.

Jan, thinking outside the box is how innovation and progress works, it's how competitions are won. I'm wondering if you'd consider working with me instead of against me here. Think of it as brainstorming rather than nay-saying.
If not, I understand and thank you once again for your input, I appreciate your efforts.

Regards, Tom
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Old Mar 01, 2012, 12:49 AM
Model trains, Rc Boats, Rc air
United States, CA, SF
Joined Mar 2009
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Little off topic but look up sea breacher on YouTube. It is a very stable boat.
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Old Mar 01, 2012, 12:08 PM
Mariner BC Canada
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Quite a bit off topic but what a great ride 'eh!!

I've followed this one for some time. Too positively buoyant for my liking.

I have a micro submersible in the planning stage that will do 15 knots.

Think of it like a submarine you wear. Very sporty, very fun and very simple.

Thanks for your response 6789b.

-Tom
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Old Mar 01, 2012, 03:46 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Quote:
Originally Posted by BluenosePacific View Post
Hi Jan,
Thinking outside the box is how innovation and progress works, it's how competitions are won. I'm wondering if you'd consider working with me instead of against me here. Think of it as brainstorming rather than nay-saying.
Regards, Tom
Hi Tom,

Offcourse I'd like to work with you, instead of...

You are right in that small boats react differently to design alterations than the 1:1 boats, it's the (not scaled down) water that makes that difference.

If the information on the contest is too much information, not relevant to your questions here, could you 'dumm it down' for us "small boat experts"?

Because, frankly I've seen a number of unconventional designs over the years, that sometimes worked surprisingly well, but mostly were very to catastrofically unsuccesful.

Rule of thumb to keep things running stable in small boats that don't exceed hull speed is a sufficiently low center of gravity.

If the hull is rounded under water, adding stabiliser fins (either active, or coupled to the rudder) will add dynamic stability and the amount of lead can often be reduced.
Most likely this isn't relevant to your design, but it is to a scale model with a high superstructure, where more lead isn't an option as the waterline is already reached...

Regards, Jan.
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Old Mar 02, 2012, 02:00 PM
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Terrific Jan, good to know you're onside!

Excuse my ignorance, but shall I give you the Norwegian competition rules or the translated English ones?

For the record, I don't speak, or even understand, most French even though it is one of my two national languages.

-Tom
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Old Mar 06, 2012, 12:29 PM
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Here we go, THIS is exactly the concept I had in mind.

HYDROFOIL -- High flying torpedo or low flying aircraft? Ray Vellinga edited video (5 min 59 sec)


-Tom
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Old Mar 08, 2012, 02:10 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Hi Tom,

As I don't speak or read Norwegian, the translated version would be best.

The Hyswas has been around for about 17 Years, I guess, that miniaturisation has come far enough to allow you to build a model and have the foils/riding attitude controlled by a microprocessor.

Presuming the rules allow the use of a microprocessor...

Regards, Jan.
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Old Mar 08, 2012, 06:43 PM
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Hi Jan,

Much longer than that actually.

More importantly, the rules don't disallow it, but I would try surface spatulas first.

KISS!

-Tom
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Old Mar 10, 2012, 11:30 AM
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No, I wasn't sending you a kiss Jan, that's Keep It Simple Stupid, or as I like to say Keep It Stupid Simple. Less offensive, yet still effective.

Why you want to see the rules I still don't understand but if you think it will help with feedback on stability, maneuverability and speed then I shall post them below. Now for some reason maneuverability didn't show as one of the test criteria in the rules...

-Tom
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Old Mar 15, 2012, 03:27 PM
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Jan,

Would you expand on your ideas around "having the foils/riding attitude controlled by microprocessor"?

How would I do that? What microprocessor would I use?

Thanks.
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Old Mar 15, 2012, 05:13 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Hi Tom,

I'll dig into that and report back to you.

Regards, Jan.
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Old Mar 16, 2012, 04:41 AM
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Take the tip of a screwdriver, and balance it on the end of your finger....
Don't let the screwdriver fall. That is what a boat is inherently trying to do on
an inverted "T" foil. That is why they use computers and gyros to make them stable.

In a model the simplest way to attempt this is to use some of the solid state gyros
that are sold for RC helicopters and aircraft. On the other end, you could consider
doing some programming for an Arduino board/chip.

If you want to "KISS" then a mono, or catamaran hull would be the simplest design.
If you want to "KISS" a hydrofoil, then the propeller driven "V" foils are the "simple" designs.

As soon as you try to balance the weight of the boat, rising out of the water, on the
center of the wing, will introduce a huge tipping moment. Especially in a turn. The good
performing "T" foils, and "SWATH" designs all rely on well coordinated "flight" control.
Something that can be done mechanically, but s often gyro/computer controlled, by either
directly controlling aileron and elevators, or some by pumping high pressure air over the
foils to decrease lift on the inside foils to bank the boat when turning.

A "V" foil maintains the boat's roll stability due to it's shape. As the boat tips, the
low side will dip more "wing" into the water increasing lift, while the high side loses
lift as the "wing" comes out of the water. The self correcting feature of the "V" foil is
why you still see hydrofoil on the IJ, in Amsterdam, or on Sydney Harbor in Australia.
While it is still possible to find some of the old Boeing Jetfoils still in service, most of
the high performance "T" foils and jet driven military ships are retired.

Building a model of a hydrofoil is not impossible. However, depending on the
type of design, it can be technically difficult.



.
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Old Mar 16, 2012, 11:43 AM
Mariner BC Canada
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Quote:
Originally Posted by Umi_Ryuzuki View Post
Take the tip of a screwdriver, and balance it on the end of your finger....
Don't let the screwdriver fall. That is what a boat is inherently trying to do on
an inverted "T" foil. That is why they use computers and gyros to make them stable.

No Umi, they use gyros to make them easier to control. A leveler would control my roll.

In a model the simplest way to attempt this is to use some of the solid state gyros
that are sold for RC helicopters and aircraft. On the other end, you could consider
doing some programming for an Arduino board/chip.

What is an Arduino board chip?

If you want to "KISS" then a mono, or catamaran hull would be the simplest design.
If you want to "KISS" a hydrofoil, then the propeller driven "V" foils are the "simple" designs.

These options are not open to me.

As soon as you try to balance the weight of the boat, rising out of the water, on the
center of the wing, will introduce a huge tipping moment. Especially in a turn. The good
performing "T" foils, and "SWATH" designs all rely on well coordinated "flight" control.
Something that can be done mechanically, but s often gyro/computer controlled, by either
directly controlling aileron and elevators, or some by pumping high pressure air over the
foils to decrease lift on the inside foils to bank the boat when turning.

A "V" foil maintains the boat's roll stability due to it's shape. As the boat tips, the
low side will dip more "wing" into the water increasing lift, while the high side loses
lift as the "wing" comes out of the water. The self correcting feature of the "V" foil is
why you still see hydrofoil on the IJ, in Amsterdam, or on Sydney Harbor in Australia.
While it is still possible to find some of the old Boeing Jetfoils still in service, most of
the high performance "T" foils and jet driven military ships are retired.

Not necessary as I have roll control surfaces. I'm looking for something to control them.

Building a model of a hydrofoil is not impossible. However, depending on the
type of design, it can be technically difficult.

You are most correct and I thank you for your input but don't confuse wing design stability and over-all craft stability.



.
Replies embedded above.

Thanks again Umi
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Old Mar 16, 2012, 01:11 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
5,122 Posts
Hi Tom,

In addition to Umi's reply, you should look into the so called 'Lage-Regler' for submarines to control your control surfaces.
Maybe one to counteract porpoising and a second at 90 to control the roll.
Lageregler U-Boot Uboot (0 min 15 sec)


http://www.modelluboot.de/
http://www.engel-modellbau.de/catalo...roducts_id=621

Regards, Jan.
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