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A wheeled cradle for a seaplane?
Over the winter, I have been building a few seaplanes of the flying boat variety most notably a Neptune and a Seawind. I would like to make the maiden flights for these birds off of land for a variety of reasons, but don’t want to muck up a perfectly good seaplane with wheels.
The area where I fly is a huge area where there was going to be a housing development, but the only thing that ever got built were the roads. I’ve seen videos where folks just fly seaplanes off of grass fields. Unfortunately the grass is not mowed low enough for takeoffs at my field, but would probably be okay for a landing. So here is my thought: Build a cradle for the seaplane to fit in and put wheels on it. Once the plane got airspeed, it would lift off the cradle and I would land in the grass. A major downside would be that I could not steer the plane in the cradle, so it would have to roll true. Thoughts? BTW- I considered posting in Seapalnes, but this section gets a lot more traffic and it's winter in most parts of the US right now... including Florida (brrr) |
RE: A wheeled cradle for a seaplane?
Back in the day I built a cradle, it had castors on the front and it would steer slightly with the air rudder. It was a basic rectangle shape, I think I used 4" rear tires and free swiviling 1 1/2" taildragger wheels in the front. The frame construction was 1/4" ply and was glued and screwed together.
For launching I built up speed slowly to minimize torque effect. |
RE: A wheeled cradle for a seaplane?
Fine idea. I tried one once..but had the balance out of whack and the seaplane just over-ran the cradle. If I did it again...I'd add some sort of steering using the plane's rudder connection. Just a slip on/slip off connection so when the plane lifted off...the steering gear would stay on the cradle. Rich
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RE: A wheeled cradle for a seaplane?
How high is the grass at your field?
I fly my Seamaster off of grass and snow with no trouble. Give it a try first before building a cradle, you may have to give it a push to get it started. If that doesn't work wait for the next snow fall. ha ha ha Tim |
RE: A wheeled cradle for a seaplane?
ORIGINAL: Wonder How high is the grass at your field? I fly my Seamaster off of grass and snow with no trouble. Give it a try first before building a cradle, you may have to give it a push to get it started. If that doesn't work wait for the next snow fall. ha ha ha Tim |
RE: A wheeled cradle for a seaplane?
I would use large wheels (8 inch variety), aka old school baby carriage, they come on their own axle already. I wouldn't bother with steering as it seems like it would add to complexity. just my opinion.
Mike |
RE: A wheeled cradle for a seaplane?
If the grass is 18" tall, will a cradle go through it?
I have never tried to hand launch a seaplane, but it might be an option. You would need a second person to do the launch, but I would check with the guys in the seaplane forum before trying it. Tim |
RE: A wheeled cradle for a seaplane?
Tim,
The roads are paved so I have an asphalt runway. I don't think I want to hand launch a 60 sized plane for a maiden flight. SS |
RE: A wheeled cradle for a seaplane?
Ok, 60 size plane and paved road, now I get it.
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RE: A wheeled cradle for a seaplane?
Thanks for the suggestions, guys! I'll post pics and results when I do my maiden!
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RE: A wheeled cradle for a seaplane?
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I have made lots of launch dollys in the past for controlline speed and more recently for aerotowing gliders off both land and water. The secrete is to use two vertical push dowels for the leading edge of the wing that are fairly long allowing for safe separation. On wheeled dollys I prefer the tricycle arrangement with a long wheel base and a fixed front wheel but with clevis adjustable steering for fine adjustment. Avoid free swiveling nose wheel this only presents takeoff problems and contrary to what you might think even with the fixed nosewheel you will get some degree of steering from the rudder as you accellerate.
John |
RE: A wheeled cradle for a seaplane?
John has the right idea. 3 wheels with the single wheel castering so it will respond to rudder input.
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RE: A wheeled cradle for a seaplane?
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The slotted boards allow for easy adjustment for desired pitch attitude of the aircraft. Generally gliders are launched at substancial pitch and powered aircraft would be closer to zero with some positive.
John |
RE: A wheeled cradle for a seaplane?
John..how does the pilot that is towing the glider up release the dolly after taking off....or does his plane never leave the ground
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RE: A wheeled cradle for a seaplane?
ORIGINAL: MetallicaJunkie John..how does the pilot that is towing the glider up release the dolly after taking off....or does his plane never leave the ground Now for my question, why not reverse the dolly and have the two fixed wheels up front, with a trailing castering wheel in the rear? This configuration would be more like a tail dragger. |
RE: A wheeled cradle for a seaplane?
ORIGINAL: SushiSeeker This configuration would be more like a tail dragger. This is exactly what you don,t want. That is deliberately introducing takeoff instability and free swiveling wheels front or rear is even worse. And yes Metalica Junkie SushiSeeker correctly described the takeoff sequence. My recommendation is based upon direct experiance remains the best takeoff dollys for your seaplane is a long wheelbase tricycle with a fixed but adjustable nosewheel. And remember the airplane must be cradled at near takeoff angle of attack or it will never acheve flight If it cannot rotate in its cradle. John |
RE: A wheeled cradle for a seaplane?
ORIGINAL: SushiSeeker ORIGINAL: MetallicaJunkie John..how does the pilot that is towing the glider up release the dolly after taking off....or does his plane never leave the ground Now for my question, why not reverse the dolly and have the two fixed wheels up front, with a trailing castering wheel in the rear? This configuration would be more like a tail dragger. that makes sense |
RE: A wheeled cradle for a seaplane?
Sushiseeker-
Put a seperate reciever, battery,servo setup(for steering) in your dolly. You could add a catch and a release mechanizm to drop the dolly after takeoff- if you have a spare channel on your TX. BW |
RE: A wheeled cradle for a seaplane?
ORIGINAL: Bonified Wingnut Sushiseeker- Put a seperate reciever, battery,servo setup(for steering) in your dolly. You could add a catch and a release mechanizm to drop the dolly after takeoff- if you have a spare channel on your TX. BW |
RE: A wheeled cradle for a seaplane?
Metal- Read the thread starting post -BW
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RE: A wheeled cradle for a seaplane?
The dynamics are the same it makes no differance if its a glider being towed from the nose or an airplane being propelled from the nose or in an overwing nacelle. If done properly it works very well. The aircraft will depart the dolly at takeoff and the dolly will stay on the ground to come to a stop or even tumble but usually not.
If the dolly is attached to be dropped after being airborn the result will be dolly damage, Ok I suppose if you want a one shot deal. A steering servo for the nosewheel is over kill likely to cause more problems than neccessary such as how are you gonna separate the servo harness at takeoff. A tricycle dolly making a straight takeoff can be steered to some degree with the air rudder before liftoff. This will not happen though if you free swivel the wheel. John |
RE: A wheeled cradle for a seaplane?
John I was suggesting an entire seperate reciever system in the dolly. Since it only has to steer the plane on takeoff, a lightweight inexpsensive reciever(unless you fly 2.4ghz) and servo could be used. And I am sure you could easily make one that could be dropped in the grass at the end of the runway without the sllightest damage.
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RE: A wheeled cradle for a seaplane?
One thing I think is being overlooked is the landing. Somewhere above sushi states that he is going to be landing in 18" deep grass. In my short experience I have winessed several planes perform emergency landings in approximately 18" tall grass in the hay fields around the club, and I do not recall any of them coming out unscathed. John your dolly seems to be a fantastic system, but would it not make since for him to shoten the wheel base a bit to aid in rotation on takeoff and temporarily attach the dolly to the plane simply by wrapping rubber bands up and over the wing so it stays attached with out any permanent mounts. You could add a servo for the steering, and use a Y harness to control it. I Dont know how heavy your setup is, but it does not appear that it would be too heavy to really affect the flying charecteristics too badly. You would need to check the balance of this prior to flight, but it could be built. Also make sure that the width of the rig would remains tight to the sides of the fuse to keep the rubber bands from interfering with the ailerons. It's not very pretty, but it could work.
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RE: A wheeled cradle for a seaplane?
ORIGINAL: Flyin Beagle One thing I think is being overlooked is the landing. Somewhere above sushi states that he is going to be landing in 18'' deep grass. In my short experience I have winessed several planes perform emergency landings in approximately 18'' tall grass in the hay fields around the club, and I do not recall any of them coming out unscathed. John your dolly seems to be a fantastic system, but would it not make since for him to shoten the wheel base a bit to aid in rotation on takeoff and temporarily attach the dolly to the plane simply by wrapping rubber bands up and over the wing so it stays attached with out any permanent mounts. You could add a servo for the steering, and use a Y harness to control it. I Dont know how heavy your setup is, but it does not appear that it would be too heavy to really affect the flying charecteristics too badly. You would need to check the balance of this prior to flight, but it could be built. Also make sure that the width of the rig would remains tight to the sides of the fuse to keep the rubber bands from interfering with the ailerons. It's not very pretty, but it could work. Absolutely Flyin if you throw landing on wheels into the equation then that is an entirely different mission. Actually thats not all that uncommon to fly single hull flying boats on some form of temporary wheels and lots of folks have come up with all manner of inovative temperary gear. Some years back I flew a Laker (Balsa USA if I remember correctly) with a four wheel strap on chassis. Sorry no pictures That was before the marvelous photo systems we have now. That one was fixed all four with two wheels approximately at the step with two smaller fixed wheels forward along side the hull. The rear wheels must allow elevator to rotate the aircraft to takeoff attitude so they must approximate the positioning of main gear with a normal tricycle setup. John |
RE: A wheeled cradle for a seaplane?
im going to build at takeoff sled for a few spad planes that im building, my only question about the above design is the dowels, do you just get to takeoff speed and give it full up elevator? how well does the plane break free of the mount? is it a big deal at all?
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