The Learning curve Gone Circle (Orion, please be gentle)

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Voyeurger

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Oct 9, 2010
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612
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Northern Phoenix, Arizona, U.S.A.
OK. Here's the deal. Started out here in the group intending to add wings to a hovercraft to do ground effect flying. Cooler (smarter) heads convinced me the regimen was fraught with dangers to body and wallet. Went gaa-gaa over the Bearhawk (the plane IS fantastic by any measure), bought plans, several thousand dollars worth of aluminum and started banging out ribs. THEN, I started forming the 270 or so rib stiffener angles. After I knocked those out, and about halfway through attaching them to the ribs, it occurred to me that this business of grinding out work that someone ELSE had designed was in fact, work. As in factory line type work. The future became bleak. Lost the wind in my sails. Started hanging out with my wife who was delighted but suspicious. I have just discovered that it's the chance to build something unique, with a definite mission profile, and that might (probably will) succeed as intended, is what drives and delights me. I discovered this when I took the Bearhawk main spar sections I'd set aside and turned them into the main structural elements of my new flying boat project. To wit....

To build a small, sleek, flat bottomed trimaran (or outrigger) boat that can lift off the water's surface, and maintain steady level flight at an elevation equal to the length of the drivetrain on the outboard motor which will propel the first iteration. Drag reduction (water) will be enhanced by spring powered lever arms putting constant downward pressure on each of the pontoons serving to 1) get the boat up on plane very quickly and 2) lifting the main hull out of the water entirely at speed. The pontoons' collective wetted area equals that of the main hull, at less than 10% of the main hull weight. The entire flight regimen depends on glass flat lake water and still air for this attempt.

Construction: The aluminum structure of the boat is almost complete. I have configured the underside to allow the mechanical adhesion of foam/carbon fiber/epoxy resin matrix to the aluminum hull. I intend to turn the boat upside down and use the underside to build up a male plug for a clean hull mold conforming to the predetermined attachment points.
LOA: 10 feet
Main hull beam: 24"
Overal Beam: 84"
Power: 35 HP Johnson Evinrude Outboard Engine

The above is certain as I've built/acquired to this point as described above. So, once the CG, pontoon strut suspensions, buoyancy/flotation requirements are ironed out and implemented, I should have one very tiny, very fast boat. Now, about the wing. In watching the flight of pelicans (traveling, not hunting) in ground effect, I notice huge drooped wings with a slight dihedral to mid-span. To gain similar properties for my "minnow" I would like to combine a very high A/R wing of carbon fiber (think helicopter wing or blade) with a dacron "V" supported in part by CF rods in stitched pockets or somesuch. The main "hard" wing will have struts (aluminum tube) which tie into the pontoon suspension much like high wing planes' struts often tie into the landing gear hardware supports. The wing will, at the roots, be approximately 40 inches off the water. I am attaching photos of where I've got to so far and at this point would very much like to hear your thoughts on wing planform design. I'm not worried (yet) about NACA or reynolds numbers, or incidence or AOA (isn't AOA and incidence the same thing?). Once the bare boat is run through it's paces I'll have a much better idea of wing placement requirement particulars.

Any and all suggestions, thoughts, ideas will be much appreciated. (I pray no hilarity will ensue).
Gary (got to change that signature) SatterleeAirboat1.jpgAirboat2.jpgAirboat3.jpgAirboat4.jpgAirboat8.jpgAirboat9.jpg
 

fly2kads

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Jan 2, 2010
Messages
1,514
Location
Justin, TX
Well, Gary, looks like this craft's whole reason for being is hilarity on the water, so you'll have pardon us. You do think outside the box, don't you?

I'm not understanding the wing arrangement. Do you have a drawing to share?

I think this looks like a recipe for getting wet, in a whimsical, Flugtag kinda way. In Arizona in the summer time, this may be half the point.
 

WonderousMountain

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Apr 10, 2010
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1,853
Location
Clatsop, Or
Live free or die trying. I'm concerned with the structure being insufficient. The pontoons are bolted on to bent sheet metal arms? Also the boat appears to have no torsional ridgidity. The wing brace isn't so bad of an idea, and long AR helps with empannage control. The hull length is certainly minimalistic. One serious concern is with a thrust center several feet below your CG, Well, you'll likely do a backflip if the fishbird actually makes it into the air. A possible solution would be a propeller just below the surface and another "sustainer" engine placed more reasonably. A sad fact of this forum is the more you build, and the less you draw, the less sense it makes to us....

Can you do some dimensional drawings for us? I'd really like to run the numbers before you become a youtube star!

Blessings,
Mountain
 

Voyeurger

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Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
SWATH? (no idea what that means but, I don't like the "feel" of it). ACME? The project IS under construction you know. HAH! You know what they say? "Success is the best revenge". Thanks guys. You have just added fuel to my fire.
Fly2, you almost have it right. I'm only a few miles from Lake Pleasant. It does warm up a little around Phoenix in the summer. Hilarity? No. Fun? You bet. Wet? From spray rather than dunking ideally.
What could be more fun in the summer than what will essentially be a quick little foil test platform with a whole bunch of built in shade?
It will be water/stability testing in around thirty days. Good or ill, I'll post video.
So there!
Gary (gotta change that signature) Satterlee
 

Voyeurger

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Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
Hello Wonderous,
As to the longitudinal stability I have used three runs of 1/8" capstrips on both the top and bottom rails. The pontoon suspensions are going to be the most built up part of the structure. What you see now are 1/8" thick flex arms. The struts above these are attach points for springs and wing supports. These struts will be shortened and built up with more capstrip materials.
Here's a better view:
Airboat6.jpg
I WILL post a three view when I get home (next couple of days) and can do exact measurements.
I want to hear what you think then.
Thanks,
Gary
 

Voyeurger

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Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.

autoreply

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Jul 7, 2009
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Location
Rotterdam, Netherlands
Ah, thanks Orion. I am sorry Autoreply. I(assumed (wrongly) you were having me on (paranoid I guess).
I couldn't do that... not to you at least ;)
SWATH cannot attain speed on such a small platform to make it worthwhile. My "Minnow" will move over the FLAT water more like a skipping stone. An UNSINKABLE skipping stone. I did consider hydrofoils however.

Now, here's an interesting concept:http://en.wikipedia.org/wiki/M80_Stiletto
I've had the pleasure to ride on one of the SWATH's of the Dutch Pilots (the naval ones) and it's an amazing concept:

Even in fairly large waves (4-5') you go absolutely flat while the tenders:

Require the use of seatbelts in those conditions (25 kts and 4-5' waves). I think the SWATH is an interesting concept for amphibians too, but I might open another thread for that...

Sorry for derailing your thread, I must admit I still don't fully understand your design.
 

craig saxon

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Sep 26, 2010
Messages
549
Location
Canberra, ACT, Australia
Gary, planing hull design for aircraft is a fairly exacting science. Even for ground effects vehicles Most of the science was done by NACA in the 30's and can be found on line. You can also buy a cd of all the relevant NACA reports on ebay if you don't want to spend the time collecting them yourself on line here: http://www.ebay.com/itm/100-1920-50s-SEAPLANE-Flying-Boat-Studies-CD-/190468093432
Here are a few references that I have sent to the 'Seabuild' yahoo group.
http://groups.yahoo.com/group/seabuild/attachments/folder/334908326/item/list
http://groups.yahoo.com/group/seabuild/attachments/folder/480350227/item/list
If you are not already a member of this group, it would be worth joining it. I have recently obtained the 4 classic references on Seaplane Design, some of which I have been searching for for 25 years. You may be able to find copies by looking at the second hand book sites, Abebooks, Amazon etc. Some of these sites have 'wants' lists where you will be notified when a book seller lists a copy when it becomes available.
Titles you should look for:
Seaplane Float and Hull Design, Marcus Langley, Pitman, 1935
Seaplane Design, William Nelson, McGraw Hill, 1934
Marine Aircraft Design,William Munro, Pitman, 1933
How to Build Flying Boat Hulls and Seaplane Floats, J Streeter, Pitman, 1936.
Hope this helps.
Craigb
 
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Voyeurger

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Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
Hi auto,
I believe the SWATH concept is only practical for heavy, large displacement vessels. My concept is pretty simple. It's a very small, low drag boat that will cruise a foot or so above calm lake waters. Think of it as a simple airfoil test platform.
Quick and dirty drawing coming in a few minutes.
Gary
 

craig saxon

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Joined
Sep 26, 2010
Messages
549
Location
Canberra, ACT, Australia
SWATH doesn't work in planing mode so all that extra hydrodynamic drag has to be overcome before flight is possible. Therefore when talking about seaplanes and ground effect vehicles, Swath actually stands for 'So Why Alter The Hull', LOL
 

Voyeurger

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Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
Craig,
I've been racking my brain to come up with something like that ever since AR posted it and you beat me to it. Thanks very much for the references old buddy. I know taint simple. This foray is a simple, fun, exploration. I am configuring the main wing attach fittings for quick change ops and for AOA adjustments (unfortunately not on the fly). I'm going to mount the outboard on a thing called a kick-plate which "kicks" the engine out, away from the stern, and will be height (prop depth) adjustable. I'm going to play with all composite wing structure, then, assuming it may be helpful, add a dacron shroud trailing from the tips in a "V" shape to stern braced extensions going astern off the gunwales. These may then be used later to support a set of tail feathers should that be indicated. The hot Arizona sun, the cool waters of the lake, more than enough shade built in right overhead, and veritable herds of hot, half nekkid chicks. I'm not a dirty old man. I'm frikkin' filthy. THIS is a work environment I can live with. That reminds me, I need to put a binocular mount on my little fishy (hee hee).

Seriously, in about 30 days, I should have my "fishbird" (thanks Wonderous (shouldn't that be "Wondrous"?)) in the water minus anything above the gunwales. I will make certain she is well balanced with good buoyancy and trim and no ugly traits. She must JUMP on plane in the wink of an eye and have a little more power than I need. Then, and only then, will I build up wing structures. Herewith, as threatened, is a quick drawing I knocked out. Three view will have to wait until I'm back home.
Thanks again for the references Craig.
GaryFishplane.jpg
 

Voyeurger

Well-Known Member
Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
Gary,

David Thurstons book, 'Design for Flight', has a good chapter on basic Seaplane design also.

Here is another reference for you from Sport Aviation 12/06 by Neal Wilford
http://www.oshkosh365.org/saarchive/eaa_articles/2006_12_03.pdf


And more thanks to you Craig. BTW, one need not travel very far afield to find brilliant expositions on aircraft hull design. In the stickies on the top of this forum's headers, our own Orion has gifted us with a PDF file called "Hulls". Great stuff and understandable. You know, Orion may be older than dirt, but, he is one sharp cookie. A wonderful, dear, human being. He even has a sense of humor which bursts out on rare occasions.
I am taking his advice on chines and splash deflectors. As to stepping the hull, heck, all the little "minnow" is is a step.
Regards,
Gary
 

orion

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Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
Older than dirt? Really? OK, maybe some mornings feel that way after a bit too much "Uncle Jose" the night before, but feet nowhere near the grave yet. :grin:
 

BDD

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Joined
Apr 2, 2005
Messages
388
Location
WI
As I see it the advantage to "SWATH" is that it mostly eliminates wave drag from gravity waves. This is what provides an upper (and very low) speed limit for any displacement hull. Because of this, displacement hulls have very low top speeds that are proportional to waterline length. Battleships can move pretty fast even though they have to displace thousands of tons of water per second at a cost of $35,000 per mile (a pre-inflationary figure that I was told many moons ago). They can do this because of their considerable waterline length.

As long as the drag from the piercing foils is low swath should reduce drag even for light displacement hulls. There might be some stability issues though; the solution of which could increase drag. Submerged hulls though would be of no use whatsoever, I would think, as pontoons for an airplane. They would only be for boats.

The craft in this thread has a displacement hull (which could become planing at high speed but it has an unfavorable aspect ratio for that; with planing sponsons, which if placed further outboard, would have more of a stabilizing effect. If the planing hulls don't lift the boat, or until they do, the bow and stern wave created by the central hull could tend to swamp the hull. When displacing at high speed, the stern of the central hull will also tend to "squat" down in the water as the wave moves rearward with speed. There is not much freeboard to the hull to keep water out. It will need to be fully enclosed with a top and waterproof....beyond just the obviously necessary waterproof parts in contact with the water, to keep from being swamped. You could try a model and see what that does.

The parts which carry the sponsons appear to be very flexible.
 

WonderousMountain

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Joined
Apr 10, 2010
Messages
1,853
Location
Clatsop, Or
Wonderous is spelled phonetically, as per european standards. So you might call it old english. My current design is twin railed also Voyeuger.

The initial photo's didn't show the wing supports. I was under the impression the wing would be located directly behind you on the hull. The drawing shows a more sensible approach. Provided reasonably sized tubing, the whole thing looks quite workable. A little dune buggy even, or would that be wave buggy?

I mentioned empannage, but don't see any. Is this a flying wing? That would be really rad!
Curious about your motor weight. I am vying for inboard motor. Great to see you making progress, but I'm still not really seeing the whole picture. If you finish it before spring you can advertise quick build time!

Sincerely,

Mountain
 
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