HUNTERANDJEFF

Hey, I know what you mean Bob.
My son Hunter (now 13) had a terrible wreck on his dirtbike 2 weeks ago. He broke his femur 1" below the ball and socket. He cannot put any weight on it for 8 weeks so he is wheelchair bound and no boats or float flying for a while. He had surgery and the whole nine yards. I have a new super cub with custom floats that I want to maiden but cannot get him into the boat! Poor guy, he is healing well, but all of our hobbies are put on hold for this year.
Hope your knee gets better soon,
Jeff

Tsutomu Mabuchi

My Feedback: (1)

OK, I will.
I went to the flying site( Lake Saiko) to test the engine some days ago.
But I didn't fly the airplane since I was alone there that day and the wind was
too strong for Seawind to fly.
I also hope to fly my Seawind as soon as possible and see how the C.G change affects.
I understand what you feel, please take care.

Tsutomu Mabuchi

Bob93447

Jeff,

Put your son to work building for you while he is wheelchair bound. One airplane you may want to look into is the Polaris from Model Aero. There is a big thread on it over on RCGroups. I'm going to build a Polaris followed by an e-powered Northstar (basically they are the same aircraft, the Polaris in foam and the Northstar, much bigger, in balsa).

Bob

Bob93447

Guys,

With my enforced "downtime" I am spending a bit of time on RCU and RCG researching the setup of other seaplanes. One of the key issues I've found in threads involving the " ARROW" (a delta wing seaplane very similiar to the Northstar but without the elevator) and the Polaris (a small, foam version of the Northstar) is the relationship of performance to the angle of incidence of the motor (and horizonal stabilizer) to the wing. One "Arrow" was nearly unflyable until 5 deg. of downthrust was dialed in for the motor. In the case of the Polaris, the design setup calls for both the motor and the horizonal stabilizer to be mounted with a negative 2 deg. incidence with respect to the wing. Videos of takeoffs of a properly set up Polaris are uneventful; no propoising.

I have done a preliminary assessment of the Seawind; with mine the stabilizer is mounted with a positive 3 deg. incidence with respect to the wing. I have not yet found a good way to measure the incidence of the motor with respect to the wing but I can guess as to positive or negative with repect to the pylon. In my last takeoff attempt with my Seawind, I had dialed in a large amount of downthrust, but I was not able to get it off the water due to the amount of chop. It seemed to be behaving better, i.e. no porpoising, but I won't consider the data conclusive until I get it off the water.

So to all you Seawind flyers out there, If you get a chance to measure the angle of incidence of the motor and/or the horizontal stabilizer with respect to the wing, post it along with your performance data and lets see what we have.

Bob

[email protected]

Hi Seawind Dudes,

I want to backup ALO 111's comment. I had a lot of trouble with my GP Seawind porpoising on take off(search my posts: www.rcuniverse.com/forum/fb.asp?.m=6076754...). Now I follow ALO 111's recipe: go to 50% flaps, full elevator, increase the throttle slowly. Full elevator keeps the stern(tail) in the water which damps the porpoising. As the plane builds up speed the ailerons and rudder start to bite, then level the wings and the Seawind usually just rises off the water. Two- three years ago jrf posted in this thread ( he seems to be the designer) - he said think of the Seawind as a hydroplane, with the 2 sides of the step and the tail always in contact with the water before takeoff.

Different issue: I typically get one flight before the speciall collar that connects the water rudder to the air rudder breaks. Has anyone experienced this and have a solution?

Tony Loomis
[quote]ORIGINAL: ALO 111

To solve the bouncing on take off try this. Give full up elevator and slowly increase throttle till she planes,now keep building up speed while keeping plenty up elevator. As speed builds release up elevator and let her build up plenty of speed while keeping wings level. when you have enough speed pull back till she climbs gently. This works for me. Good luck
[/quote

Bob93447

Do you normally take off from relatively smooth water? What is the worst chop that you will attempt?

Bob

jrf

My Feedback: (551)

Tony:

Thanks for remembering. No, I am not the designer, but I did write a product review on the Seawind for Model Aviation a couple of years ago and I didn't write it until I figured out how to take off and land without porpoising. (Landing is harder than taking off, by the way.)

The review model was 100% stock out of the box, with an OS 61FX engine and no landing gear. Since then I have flown a lot of Seawinds and they all require the same technique. Take off directly into the wind, with 1/2 flaps and accelerate slowly. (Tony, I only use up elevator on smooth water. With a little chop, the Seawind will take off by itself when it is ready.)

The number one reason the Seawind porpoises is because of too much throttle too quickly. The pylon mounted engine wants to push the nose down into the water. Then the nose pops back up like a beach ball pushed into the water. Then the engine pushes it down again. By accelerating slowly, you give the airplane enough power to build speed on the water without the extra power that is wasted, pushing the nose down. The Seawind doesn't need a lot of power to take off. With my 61 2-stroke it usually came off the water at 3/4 throttle.

Landing is tougher because you have to get the angle just right so that the step and the tail touch down at same time. Get it right and it is an absolute greaser. Get the angle of the flare too high or too low and it will bounce.

I watch this thread sometimes and I am glad to see that several others have figured the Seawind out as well.

Bob:

I have taken the Seawind off several times in 2 inch chop. I once tried a 4 inch chop and failed completely.

Jim

Bob93447

Jim,

My problem is that with limited opportunities to get a friend to take me out in a boat to fly the Seawind, I have been too aggressive in attempting to negotiate rought water conditions. Like you, I have had success in 2" chop; anything much more than that results in an aborted takeoff. This was compounded by using a prop with far too much pitch resulting in a substantial increase in thrust at liftoff which substantially magnified the porpoising issue.

Fortuneately I found a shoreline site last year that will allows me to wade several hundred feet into the lake with only neck deep water. Another guy and I flew there last fall with Seawind EPs and I am getting familiar enough with the issues that I will be able to fly there in the fall when the lake falls to a more reasonable depth. The big advantage is that I can go out early am during the midweek and get the water and wind conditions I need for successful takeoff.

Have you ever measured the angle of incidence between the wing and the horizontal stab of your Seawind? Mine show a positive 3 deg. incidence of the horizontal stab vs. the wing which may explain why most successful Seawind takeoffs require a substantial amount of up elevator. I have sealed the hingeline on mine to increase elevator effectiveness. I have also installed a higher KV electric motor so that I can get the same performance with a lower pitch pitch prop.

As a point of interest, the Seawind EP seems to be able to handle a lot more chop; probably because it is so light and gets off the water very quickly.

Bob

jrf

My Feedback: (551)

Bob:

I'm sure this issue has been covered and recovered, but your electric version probably has a much more nose heavy condition at take off than a glow version with a full fuel tank would.

I think I would try moving the CG back in increments. Each increment will reduce the amount of elevator required for takeoff and at the same time it will make the elevator more effective. Move it back until you start to notice the elevator being a little to sensitive on landing.

Then let us all know where your CG wound up.

Jim

Bob93447

Jim,

Yes, CG with the electric version has been one of my key issues with the electric version since I started putting it together. Early on, I contacted Great Planes and asked for a CG recommendation. They came back with the stock answer of 26mm. I decided that didn't make sense so I balanced it there, then strapped on a 12 oz can of coke to see where the cg would be on a nitro version slightly after takeoff. I came out with something like 2" so being somewhat conservative I did my first test, off of snow, at 1.5". Since then I have moved it progressively to the rear to nearly 2". Recently I have run across some posts by Mike McDougal on RCG, who did the review of the electrified Seawind, with CG's ranging from 2.125 all the way back to 2.5". And yes, things seem to be getting better as I move it back. Since it still requires substantial down elevator for inverted flight, I am sure that I can go back quite a bit more.

I also think that there is a combination of alignment parameters including wing vs. horizontal stab incidence, thrustline, etc. which all have an impact on performance.It's probable that the wide range of manufacturing tolerances found in this airplance added up to the wide variety of flight performance found in the discussions of this airframe.

Bob
i

Cyntec

Hi Guys!

Sorry to bud in here but the Great Planes Seawind has been my dream plane for years now but I've been waiting until I got good enough to fly it. Now that I feel I'm ready they've discontinued it!!! Does anyone know where I can still get my hands on one, preferably a new one in the box (I like building them myself)? I've tried posting a wanted ad but for some reason it keeps making it a selling ad.

Tsutomu Mabuchi

My Feedback: (1)

Maiden flight for another Seawind.
The C.G Location is 2"(50mm) instead of 1 5/8"(40mm) of original one.
The engine is OS FSa110/P, MA13x6 3 blade prop.
I slowly increased the throttle while the elevator was full up, stopped increasing the power
at 2/3 throttle position and concentrated to control the airplane for straight planing, as the
speed got high the airplane became airborne soon with very stable movement( much controlable).
I reduced the elevator a bit right after airborne not to stall, so the airplane touched the
water once but it ascended again as I put the elevator up again.
The flight characteristics of this Seawind( C.G is 50mm) especially on take off and landing
is definitely better than original( C.G is 40mm).
I found that the take off of partial power is much easier than full thrust take off because
nose down tendency is less than that of full thrust. And the C.G of 50mm is no ploblem at
all or much better than 40mm(1 5/8").
I flew this airplane at the river of 30min drive distance, not at the lake I usually fly.
The water surface was quiet with headwind of around 5 knots.
The landings were not good, the first one was done with flap 1/2 and the next was with full
flap. Both bounced once on landing, I have to practice more. May be it requires slower speed
for smooth touch down. I am very glad that this one flys better than the previous one.
The first take off was with flaps up and the second one was with 1/2 flaps, I could not recognize
the difference of two.

Tsutomu Mabuchi

Bob93447

Tsutomu,

Congratulations on the maiden of you new Seawind. It sounds like that will all of your careful setup and preparations that things went at there were supposed to go.

If you want to play around with takeoffs and landings, you might want to consider buying the Realflight 5.5 simulator. If you are not careful, the simulator will porpoise on takeoff and bounce on landing; the only way, on the simulator, to not bounce on landing is to get it down close to the water than hold it off as long as possible. I know that on mine that if I bounce too hard on landing that I knock out the covering over the wheelwells.


Any idea what RPM you are getting with your 3-blade prop? Is it really a 13x6? That does not seem like much pitch with a 4-stroke.


Congrats again,

Bob

Tsutomu Mabuchi

My Feedback: (1)

Bob,

Sorry, the prop was a MA 13x8 3 blade, not 13x6.
I didn't measure the RPM, but it sounded below 10000rpm with a bit rich side setting
since the engine is new.
FSa110/13x8 3 blade pulls the airplane more than enough even it is being broken in.
The loop was a complete circle, flew most of the flight with 60-70% of the thrust.
I don't like an airplane flying with full throttle since it is noisy and doesn't look scale.

Tsutomu Mabuchi

Bob93447

Tsutomu,

Thank you for the prop info. I have a 13x8x3 MA to try on my Seawind when I get mobile; from what I can tell I will get into the same RPM range with my electric setup. Did you balance the prop statically or are you relying on the "Dynamic" balance from MA?

From all the posts I have read and videos I have seen on the Seawind, 3-blade props seem to work better. It seems like it must have something to do with the amount of thrust produced at a particular pitch speed. The only problem with a 3-blade comes when the prop stops its like hitting a brick wall because of the increaed resistance of the prop disk. I ran into some problems with my little Seawind EP when I switched to a 3-blade; normally I cut power totally a few feet above the water. With a two blade prop it drops the nose as you land, with a 3-blade prop it stalls because of the extra air resistance. The only way you would run into that problem would be if your engine flames out.

It looks like you have come up with a very nice setup for your Seawind. I hope you have many, many enjoyable flights with it.

Bob

Tsutomu Mabuchi

My Feedback: (1)

Bob,

I don't balance the prop in most cases, use props as it is from the shop especially
when the engine is smaller than 1.20 since I use props so as to get 10000rpm or lower.
I will balance a prop when I use a large engine with high rpm or there is an unusual vibration.
I didn't know 3 blade prop has such resistance compared to 2 blade prop, but it makes sence.
Yes, I am much satisfied with my setup this time, thank you for your help.
I will fly Seawind as many times as possible to see it's beauty in the sky.

Tsutomu Mabuchi

biggles256

Dear enthusiasts,

Some time ago I posted how my wing tip floats made for routine Seawind take-offs. My friend took these great shots which I just want to share with you all. The lake is at Colwick in England, and yes the sky was blue.
I have upgraded from the original OS 90FS to the new alpha 110FS. My first take off was worse than normal due to too much power with the new engine. The prop is a 13 X 8 three blade. I now have a 13.5 x 8 ready to try. The three blade prop is really the only option due to the limited clearance available.

Tsutomu Mabuchi

My Feedback: (1)

Yes, I added a similar wing tip, too. It works geat.
It makes the flyer free from fear of wing tip sinking to the water.

Tsutomu Mabuchi

Bob93447

I am trying to gather some Seawind data. Specifically, what is the angle of incidence of your stabilizer relative to the wing. Add to that whether or not you experience severe porpoising with your setup.
In my case, the stabilizer came out at +3 deg. relative to the wing as measured with a Robart incidence meter. And yes, I experience severe porpoising.

On another site, a model called the Polaris is set up with the stab and motor set up at -2 deg and it lifts off the water with no porpoising complaints.

Thanks in advance,

Bob

jrf

My Feedback: (551)

Bob:

As many of us have finally figured out, the porpoising is caused by advancing the throttle too fast. With high throttle at slow speed that high thrustline tries to push the nose into the water, the nose bounces up and the engine pushes it back down again. Repeat, repeat...

No-porpoise takeoffs are easy if you advance the throttle slowly (2 or 3 seconds for idle to full) until the Seawind has enough speed to resist the down force of the high thrustline. I found that mine would take off by itself at 3/4 throttle (OS 61 FX) with no elevator input if there is a little chop on the water. Smooth water takes a little up elevator once you reach flying speed.

OBTW, the more engine power you have, the more likely it is to porpoise.

Jim

Bob93447

Jim,

Mine behaves a bit differently. As I advance the throttle relatively slowly, it actually takes off, goes a few feet into the air, hits the water jumping into the air a bit higher, hits the water again and jumps high enough that if I throttle back a bit and then readvance the throttle slowly I can keep it in the air. Makes for a bit of an exciting takeoff. I'm just trying to figure out if some of the incidence angles are sufficiently different from plane to plane to explain the differences in takeoff behavior.

Bob

greggK

Bob,
Its been a while... I haven't flown mine in several years. I wanted to make several mods before I fly it again. I was using an overpowered (and heavy) set up on 8S and a 4 blade 13x13 prop. When it got of the water (some easy and some hairy) it was very fast. I think you are on to something with the down-thrust and I'm going to try it. Additionally, I fiber-glassed a piece of 2" balsa aileron stock and I'm going to add it just behind the step with the thinner end facing forward thus adding a secondary step. This method is utilized extensively on deep-v boats.

Bob93447

Gregg,

Jeff, posting under HUNTERANDJEFF, implemented a setup similiar to what you are proposing in post #829 with a picture in Post #832. He claimed that it worked very well. I'm not so sure of the downthrust any more. A guy flying the SWEP is claiming to have better results with upthrust, which does not make any sense unless the propwash on the tail is having a major effect. Waiting for him to make some water takeoffs.

If all else fails I am going to put the SW on a diet.

jrf

My Feedback: (551)

Bob:

It sounds like your Seawind is taking off before it reaches flying speed. Are you holding up elevator on the takeoff run? Perhaps you should try just letting it run on the water with no elevator input until you are sure you have enough speed to keep it in the air.

If it was an incidence problem you would have to hold or trim the elevator in flight to compensate for it. How is your elevator trim? It should be level.

Jim

Bob93447

Jim,


Although I will admit to holding some up elevator to dampen takeoff occillations, its certainly not comming off the water in a mushy, stall mode. And it does require up elevator trim for straight and level flight.

I think I have two problems. The first is that the stabilizer is at a +3 deg incidence to the wing (measured with a robart incidence meter). That in itself is bad because it will drive the nose down, and that tendency is reflected in the requirement for up elevator trim. That's why I have been asking if anyone else has measured the stabilizer incidence relative to the wing. Second, I think that I have been using a prop with too much pitch, a 13x11. Its partially stalled at the point of takeoff but becomes unstalled as the plane leaves the water. The rapid acceleration as the plane becomes airborne forces the nose down as I am not quick enough on the elevator to compensate. But this part of the issue is supported by the fact that if I decrease the throttle just as the plane becomes airborne I can usually stabilize to a level attitude and slowly add power to achieve a successful takeoff. I've changed props to a 13x8x3 which should eliminate the second problem.

Bob