1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

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1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby HO229 » Sat Jan 22, 2011 12:34 am

Have been in the design phase of this project for some time now, it gets more exciting every day!

I have gathered and researched allot of data for this exciting project; met and made friends with allot of kind and very generous people who made this project possible through very generous contributions of time and source data.
This project will be slow to progress but is an active topic when I am not in the shop working on the Goose.

The P173 was a proposal put forth in the height of the cold war when tension between the free world and the former Soviet Union was at its greatest.
The Princess was to be refitted with different engines, the for-body extended, after-body extended, vertical fin enlarged.
The under-wings were to carry two Saunders Roe SR.53 XD151 fighter interceptors to fend off the soviet threat.

Image

FLIGHT SURFACES

Image

THE LOFT (A WORK IN PROGRESS)
Last edited by HO229 on Sun Jan 23, 2011 4:07 pm, edited 4 times in total.
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby seawings » Sat Jan 22, 2011 9:55 am

Hi Dave,

Princess drawings, do you want the real thing?

I have a set of the only existing factory drawings - big'uns - that I can send you for total accuracy? Got a hellova lot of measurements on them.......

Let me know,

Cheers,
Best Regards,

Bryan Ribbans
Owner of:

The Flying Boat Forum
SEAWINGS - The Website

"I put the sweat of my life into this project, and if it's a failure, I'll leave the country and never come back".
Howard Hughes, re: the HK-1 Hughes Flying Boat, aka the 'Spruce Goose,' 1946.
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby HO229 » Sat Jan 22, 2011 11:20 am

Bryan,
Please do.

Thank you,
Dave
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby Kuni » Sat Jan 22, 2011 2:29 pm

Hi,

Dave, do you intend to use contra-rotating drivesets at your bird? This would really be cool. If interested I can help with the prop alignment...

Bryan, I have a set of Princess-plans; especially a general arrangement drawing. What would be welcome is a stations-/formers plan. Do you have such a thing?
BTW your CD arrived yesterday. Thanks alot; that will certainly help.

Regards,
Rene
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby HO229 » Sat Jan 22, 2011 3:59 pm

Rene,
I have a GA drawing of the Princess and all the ARC reports, plus a coarse resolution 3 view drawing of the P173 configuration. I would welcome any data. The formers would be very helpful as I am using the ARC formers and fairing them in along with some dimensional data in the GA drawing.
This GA drawing showed up on RCG (see link) it sparked my original interest in the aircraft. I wish I could read what is annotated on it as it is a bit different than the GA drawing I have (Maybe something useful on it)?
http://www.rcgroups.com/forums/attachme ... id=1294881

I have been in contact with Mr. Bob Wealthy of Solent Aeromarine; he has been very kind and helpful with data. I also contacted the Publisher of the book “stuck on the Drawing Board” Mr. Richard Payne has also agreed to help (exciting).
The 3 view of the P173 removed the counter rotating screws and illustrates an above the wing mounted nacelle configuration. My ambitious goal is to design the wing plug in such a way as to install removable segments so as to be able to cast the original wing configuration and the P173 configuration (all subject to change.
I have a few other ambitious projects that require the counter rotating screws so I will be jumping off the deep end and procuring power-plants for these projects.
I have a gearbox assembly that I have designed that utilizes commercial off the shelf parts (COTS) one motor to drive both driveshafts; while this configuration sounds attractive it comes at the cost of efficiency. Engineering data for this style of gearbox penalizes the design with a 30% loss in efficiency! The gear train design is basically an automotive differential based design with an inner and outer shaft (beveled gears).
I have the parts to fabricate the prototype gearbox, I will give it a go and see if the losses are as high as the referenced engineering documentation says they will be.
Off to the Library, my favorite librarian has the book “Luftwaffe Secret Projects: Fighters 1939-1945” and “Saunders and Saro aircraft since 1917” for me to read
Kind regards,
Dave
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby Kuni » Sat Jan 22, 2011 5:52 pm

Hi Dave,

the drawing you mention is exactly the one I have. I can copy her in paper or digital form if you need her.
Do you intend to make moulds of the Princess? Here is one who would like to have a model from :D
What other projects do you have with contra-rotating motors? A friend and me are thinking about some japanese floatplanes: the Kawanishi E15K Shiun or the Kawanishi N1K-1. Another long-time project of mine is the Supermarine Seagull ASR; the one reason why I didn't begin the model until now is I have no idea of how to make the main landing gear. But the engine is nearly finished: a 2x1,5KW brushless contrarotating motor.

Regards,
Rene
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby Adventureguy » Sat Jan 22, 2011 6:02 pm

Dave,

Please let me make a suggestion or two about the contra-rotating props. I wouldn't want to see you waste your valuable craftsmanship.

First, you might be better off getting gears from a transmission instead of a differential. There are a couple of challenges in using transmission gears, namely weight and hooking up the shafts to the gears, but differential gears have their problems. Differentials use small, crudely cut gears and essentially no bearings, because their running speeds are actually very low, in the 10's of revs. Even in the tightest, fastest turn you can manage, left and right wheel speeds for the differential are not very different, which is what causes the bevel gears to turn. The exception is on ice, but the gears aren't designed for more than a few seconds of running like that. Most automatic transmissions use planetary (epicyclic) gears, some of which can be used for contra-drives. If I recall correctly from my university days, the gear set from a small GM 4-speed transaxle may work efficiently and give a closes speed match for front and rear props. That gear set has two groups of rotating parts and two separate gears that all turn around the same axis: one group for the engine, the other group for the gear case, one gear for the front prop, and one gear for the rear.

All that said, though, I think you would be best served by simply putting dummy rear props on and simply letting them windmill in the wash from the front props. Contra-props are misapplied when used on multi-engine aircraft, because operating in the wake of one prop is NOT worthwhile when everything is considered. In my humble opinion, that was a design mistake on the part of the designers of the Princess. The amount of energy gained by using the trailing vortex of the front prop is just not enough to offset all of the other trade-offs. Operating contra-props are tricky, too--the constant-speed versions almost killed Howard Hughes--so a set of four big operating contra-props would be another very impressive achievement in an already very impressive project plan.

Alan

PS -- Wouldn't it be even more fun to build a scale model of the Princess big enough not to require servos?
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby HO229 » Sun Jan 23, 2011 4:04 pm

Rene,

“Do you intend to make moulds of the Princess?”
Yes… this will be a molded Princess

“What other projects do you have with contra-rotating motors?”
R3Y/XP5Y Tradewind
Blackburn B-49B Clydesman

The kawanishi e15k shiun norm is a VERY interesting subject

The Supermarine Seagull ASR has some really nice lines and would be very exciting!

The Kawanishi N1K-1 appears to be a land based aircraft adapted to a sea plane usage. The gear looks to be a very simplistic type that I believe could be simulated with a standard retract or a simple One Off build/MFR.

Concerning the Princess GA DWG, I am very curious about what is written in the large notes in the upper left and mid right hand side. The GA I have seems to contain the same data less the large notes.




Alan (Adventure Guy),

PS -- Wouldn't it be even more fun to build a scale model of the Princess big enough not to require servos?That would be a large undertaking and a few trips to the FAA for an experimental certificate.


“Please let me make a suggestion or two about the contra-rotating props. I wouldn't want to see you waste your valuable craftsmanship.

First, you might be better off getting gears from a transmission instead of a differential.”
I have attached the prototype sketch that I sent to the machine shop for quote; the concept is very simple the input shaft is slaved to and drives the drive gear the spider gears transfer counter motion to the FWD drive gear.
The design is not new; contained within the ARC database is an example of a similar design that they used to power the tow tank models.


You obviously understand some of the issues at work here:
1. The gears must be cut in such a way as to keep constant rotational linier motion, crude cut gears do not create linier motion (the gear set I purchased could hardly be classified as precision).
2. Allot of the losses are due to the force vector caused by the bevel gear set, I was in discussions with “Timken” a bearing manufactures to find a suitable thrust washer in an effort to mitigate the high thrust forces caused by the bevel gears.
3. The tiny spider gears must be problematic, just because they are spinning at a much higher rotational speed than the driven gear and they are just plain tinny.
4. The forward prop is chopping through nice clean air; the aft prop is seeing something that cannot be classified as clean air.
a. I must admit I do not fully understand the dynamic environment the second prop is operating in… There is an exhaustively long counter rotating prop thread in RCG and the data these fellows came up with is very impressive.

RC Counter-rotating motor/ESC Background:
The two motors operate independent of each other with independent speed controls
The motors operated on concentric shafts
The motors were of the same size
The FWD motor & prop achieved higher current draws and RPMs than the aft motor & prop
The two motor speed controls are receiving the same Pulse width modulation signal (commanded RPM + or - tolerance).

My opinions:
The methods of metering torque is flawed in my simple mind(that’s because there is none); the two motor/speed control combinations need some torque metering scheme or the first motor will be doing the lion’s share of the work. The RCG data supports my opinion.
Prop no. 2 (aft prop) is seeing incoming air at a higher relative speed when compared to the first prop, I believe the 2nd prop requires a different torque meter profile (more aggressive).
I believe the form drag table highlights some of the issues that prop no.2 must operate in and be tailored to

Please feel free to correct any of my simple observations and opinions.

A simple transmission is the best approach I believe?
I agree, some method of metering torque I believe is also in order but the nostalgia of the counter rotating power plant is very impressive.
It would seem that designers were trying to make the scheme work during the mid to late 40’s until the late 50’s at some time they figured out that the design was a bit problematic.

I never fully digested what fully transpired with the Hughes mishap as it relates to the prop combination, I do know that drag goes WAY up when one prop stops spinning especially when it cannot achieve feather.

A tangent:
I commented at a meeting that a new 8 bladed T56 prop would have dire consequences if it pitch locked and could not achieve feather during an engine out scenario… Hmmm… I will let you fill in the blanks on what transpired in the years that followed… In the wonderfully written book by author Daniel Raymer “Aircraft design a conceptual approach” the author speaks to this very topic.

Image

Image

Dave
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby Kuni » Sun Jan 23, 2011 7:32 pm

Hi Dave,

I can make pictures of the areas you want, and send them if you let me your e-mail-adress.

Regards contra-rotating motors: I build the two-motors-with-hollowed-shaft-version. I have built 2 different sizes from 2x250W up to 2x800W and all are working without trouble. The third size with 2x1,5KW is in work. There is no black art in the motor part; you have 2 ESC, both driven from the same receiver signal. So they turn both motors to the same acceleartion.
The props are a different issue: some say the rear prop must be the same size as the front one, some say it has to be bigger in diameter... I have found out that the rear prop works at the best efficiency regards rpm versus current if it is a little smaller in diameter but has more pitch. I have written why in the extra long thread at RCG...

There are some systems at the market that work well: http://www.maxxprod.com/mpi/mpi-266.html

I always would work with 2 motors; the only solution with gear would be a modified planetary gear where the outer case rotates too. This would require a very fast running motor, as the gear translation doubles to the prop.

The N1K-1 was at the first a floatplane, but was converted to a landplane later.

Regards,
Rene
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Re: 1/10TH SCALE SAUNDERS-ROE PRINCESS (P173)

Postby HO229 » Sun Jan 23, 2011 10:52 pm

Kuni,
I'll PM you with my E-mail data, any Princess data would be welcome

Of the several mechanical configurations for the counter rotating system which one did you use?
The COTS stuff seems a bit expensive to me.

Did not wish to muddy any water with my thoughts/readings concerning counter rotating systems, just some observations that I came away with after reading and digesting all that data...
I believe much like you that text book data/theory is no substitute for practical real world experience. The RCG thread was a bit long and tiring but many interesting facts came from it.

The start of a 1/10th scale SAUNDERS-ROE SR-53 can be seen on the bench; this blank will be put away for a minimum of two weeks so the wood can stabilize. The whole fuselage can be shaped in a few days with the draw knife, spokes and planes.

Image

Cheers,
Dave
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