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Old Sep 19, 2007, 11:22 PM
tic
thunderscreech
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New Cumberland, PA. US
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silicone will NOT attack this foam, however do not try and use "goop"...it WILL attack the foam
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Old Sep 20, 2007, 03:14 PM
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USA, VA, Harrisonburg
Joined Jul 2005
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Got a few flights in on my Seawind last night just a great little plane to fly. Was wondering if anyone else noticed that when the power is reduced it kinda zooms up a bit? Mine also wants to float forever and I have a hard time planting a nice landing right in front of me. All up the Seawind EP is just plain fun to fly.

Pete
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Old Sep 20, 2007, 05:39 PM
Electric Coolhunter
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I see a faint hint of that bit of pitch up when throttle is reduced. It is a function of the high thrust line.

I did angle my motor up an extra degree or so and adjsuted the cowl to fit the added upthrust. Doing a bit of that will reduce the pitch down with abrupt adding of power at low speeds and resulting trim changes might help the slight nose up trend after power is reduced.

However, I don't mind it. It is a nice sort of "auto flare" when aproaching to land.
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Old Sep 21, 2007, 09:56 AM
Foam Floats Better
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The Big Country of TX.
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Quote:
Originally Posted by Thomas B
I see a faint hint of that bit of pitch up when throttle is reduced. It is a function of the high thrust line.

I did angle my motor up an extra degree or so and adjsuted the cowl to fit the added upthrust. Doing a bit of that will reduce the pitch down with abrupt adding of power at low speeds and resulting trim changes might help the slight nose up trend after power is reduced.

However, I don't mind it. It is a nice sort of "auto flare" when aproaching to land.
Actually, adding in upthrust to a high, rear mounted motor puts the thrust line even higher above the pitching moment of the wing.
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Old Sep 21, 2007, 11:56 AM
Electric Coolhunter
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United States, TX, Fort Worth
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Quote:
Originally Posted by UAVPilot
Actually, adding in upthrust to a high, rear mounted motor puts the thrust line even higher above the pitching moment of the wing.

While the thrust line does get angled up, the thrust vector applied to the aircraft changes. Some thrust is now vectored upwards and that helps to cancel out to nose down pitching moment.

I think one can argue the fact of the Seawind having a rear mounted motor...

Even though the Seawind has a "rear" mounted motor, the prop position (and the resulting thrust application to the aircraft) actually ends up very near where it would if the motor was mounted in a pylon on top of the wing with the prop in back, like the side view of a full scale Lake Buccaneer amphibian shown below. Note the noteable upthrust applied to the motor in the picture.

In fact, the Lake has the prop a little further aft relative to the wing than the model Seawind does.

Also attached is a three view of the actual foamie Seawind model. Note the prop position relative to the wing...very much the same as the Lake.

The prop on both aircraft are at about the same (close, above and just behind) postion relative to the pitching moment of the wing...and when it is that close to it, the upthrust is a proven solution that does help nose down pitching caused by power application at low airspeeds.
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Old Sep 21, 2007, 12:17 PM
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I wonder if this effect is less evident when you have a more forward CG as I'm flying mine with the spec CG and like it there, but am using a 2100 pack to get the CG, and I don't notice any pitch change with throttle application, I wonder as you move the cg back like people are doing if that makes it show up.

Frank


Quote:
Originally Posted by Thomas B
While the thrust line does get angled up, the thrust vector applied to the aircraft changes. Some thrust is now vectored upwards and that helps to cancel out to nose down pitching moment.

I think one can argue the fact of the Seawind having a rear mounted motor...

Even though the Seawind has a "rear" mounted motor, the prop position (and the resulting thrust application to the aircraft actually ends up very near where it would if the motor was mounted in a pylon on top of the wing with the prop in back, like the side view of a full scale Lake Buccaneer amphibian shown below. Note the noteable upthrust applied to the motor in the picture.

In fact, the Lake has the prop a little further aft relative to the wing than the model Seawind does.

Also attached is a three view of the actual foamie Seawind model. Note the prop position relative to the wing...very much the same as the Lake.

The prop on both aircraft are at about the same (close, above and just behind) postion relative to the pitching moment of the wing...and when it is that close to it, the upthrust is a proven solution that does help nose down pitching caused by power application at low airspeeds.
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Old Sep 21, 2007, 12:22 PM
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United States, TX, Fort Worth
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At speed, you get little effect from the thrust line...mine is most noticable at a hand launch and when first starting a grass take off....

Try going into very slow flight at altitude...the slap on a big throttle change to high power....it will show up then..

The high thrust acts to the pitching moment of the wing, not to the CG.

I would guess that the forward CG might actually make it a touch worse, at LOW speed and high throttle....then again, if you are carrying some up trim, the propwash deflected up by the elevator might help...hard to say.
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Old Sep 22, 2007, 04:22 AM
Ozzie Express wiggy pilot
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YANKALILLA , SOUTH AUSTRALIA.
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Quote:
Originally Posted by Thomas B
While the thrust line does get angled up, the thrust vector applied to the aircraft changes. Some thrust is now vectored upwards and that helps to cancel out to nose down pitching moment.

I think one can argue the fact of the Seawind having a rear mounted motor...

Even though the Seawind has a "rear" mounted motor, the prop position (and the resulting thrust application to the aircraft) actually ends up very near where it would if the motor was mounted in a pylon on top of the wing with the prop in back, like the side view of a full scale Lake Buccaneer amphibian shown below. Note the noteable upthrust applied to the motor in the picture.

In fact, the Lake has the prop a little further aft relative to the wing than the model Seawind does.

Also attached is a three view of the actual foamie Seawind model. Note the prop position relative to the wing...very much the same as the Lake.

The prop on both aircraft are at about the same (close, above and just behind) postion relative to the pitching moment of the wing...and when it is that close to it, the upthrust is a proven solution that does help nose down pitching caused by power application at low airspeeds.
The position of the stab also has an effect on the pitching , if you notice on the Lake , the prop-down wash on the stab helps to counteract this during power on
The pitching moment of the wing varies with changes to the angle of attack , and the resulting center of pressure travel , its really the center of drag that we are talking about with High thrustlines
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Old Sep 22, 2007, 02:40 PM
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Had a good time at the Weatherford, Tx float fly today! Perfect weather, if a liottle hot..up close to 95 and humid. Winds were light and variable and the water surface was great...almost a mirror.

Did have a couple of minor model problems, all self induced....

Ernie (UAVpilot) and I had Seawinds in attendance. We had both modified our tip floats for more clearance in the taxi and takeoff run. Ernie took off a constant 3/8" and I actually flatbottomed mine at a slight angle. I took off about 3/16" at the rear and about 3/8" at the point where the bottom of the tip float is the fattest and starts to curve up.

Now I don't have to hold full up through the takeoff run and carefully mind the ailerons. The wingtips tend to glance off the water if they touch with some speed, instead of digging in.

I highly recommend a tip float trim job.

Ernie found his trim REALLY helped on rougher water days.

I glanced away from my Seawind model during an approach to land... ...as another model crossed the landing area and did a minor dunk on my Seawind.

It took off fine, but the ESC or Rx turned off from water intrusion after the first turn. The power went to low and the little guy spiraled down in an a right hand dive from about 75 feet high....with zero damage... I need to better waterproof my RX and ESC installation!

Got in a few GP PBY flights...had a motor come loose on my PBY with some minor motor mount damage and prop rash on the hatch. My bad..I had modified the stock firewall too much and it split and needs to be replaced. Parked mine for the morning and we flew Richard Ng's PBY...got a really nice long flight in on his stock one with the BP brushless. The little PBY has simply faultless water handling and shows the best differentiation between low speed taxi and step taxi of any R/C flying boat I have seen. We did endless long slow scale takeoffs and landings.

Also got flights in on the Curtiss semi scale flying boat and the Skimmer parkie flying boat..those models are mentioned elsewhere in the waterplanes area. Was fun to have 4 electric seaplanes to chose from today! Other Ezone electric guys in attendance were Ernie (UAVpilot) and Richard Ng. About 30 pilots and over 100 models there, with about 11-12 electrics.

I will post a link to the event pictures later.

so...think about trimming those tip floats!....
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Old Sep 22, 2007, 02:50 PM
Electric Coolhunter
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Quote:
Originally Posted by SON OF PALEFACE
The position of the stab also has an effect on the pitching , if you notice on the Lake , the prop-down wash on the stab helps to counteract this during power on
The pitching moment of the wing varies with changes to the angle of attack , and the resulting center of pressure travel , its really the center of drag that we are talking about with High thrustlines
a good point on the stab getting some downwash. However, when you add a bit of upthrust to the Seawind, you also get a bit of the same effect.

On my small Skimmer Park flying boat, pictured below, I have a LOT of upthrust and a low mounted stab...likely getting only the least bit of impingment, but less that the Lake would. The upthrust does a great job of reducing and almost eliminating power pitching effects.

Actually, it is not the center of drag the model tends at lowest speeds...it is the center of mass (not just the longitudinal CG or center of drag) that the model tends to pitch about, until there is enough lift or control effectiveness to overcome the high thrust line effects. As speed builds a little, other effects come into play.

Whenever the prop is above the wing
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Old Sep 22, 2007, 02:54 PM
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PS......anyone notice that the factory photo threeview of the Seawind model that I posted above shows that the models fuse and horizontail tail is crooked?....
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Old Sep 24, 2007, 09:09 PM
We shall serve the Lord
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Thomas B, looking forward to your Weatherford pictures. Does Richard Ng post on RCGroups? I flew indoors with Richard in San Antonio a few years back and I'd like to get in touch with him again. Our club, the Highland Lakes Flyers, is hosting the San Antonio River City Club's annual float fly in Llano on October 20th and 21st. The SA Club has no water because the local flood control authority will be draining their lake to repair the dam in October. We were happy to have them come up and use our area on the Llano river for their 16th annual club event. Why don't you and Richard come on down and fly with us that weekend? PM me for more details if you're interested. I'd like to see how your tip mods work on the Seawind.
Mike McD
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Old Sep 24, 2007, 11:53 PM
Ozzie Express wiggy pilot
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Quote:
Originally Posted by Thomas B
a good point on the stab getting some downwash. However, when you add a bit of upthrust to the Seawind, you also get a bit of the same effect.

On my small Skimmer Park flying boat, pictured below, I have a LOT of upthrust and a low mounted stab...likely getting only the least bit of impingment, but less that the Lake would. The upthrust does a great job of reducing and almost eliminating power pitching effects.

Actually, it is not the center of drag the model tends at lowest speeds...it is the center of mass (not just the longitudinal CG or center of drag) that the model tends to pitch about, until there is enough lift or control effectiveness to overcome the high thrust line effects. As speed builds a little, other effects come into play.

Whenever the prop is above the wing
Well I am sorry , but it is the center of drag , the center of mass can be in a totally different place to the center of drag , like the difference between the center of mass between a PBY Catalina ...and a Seawind or a Coot or a Lake
These all have high thrustlines , but the center of mass and drag are in totally different places..
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Old Sep 25, 2007, 06:28 AM
tic
thunderscreech
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No-one has even MENTIONED the importance of checking the flay rod to be sure it hasn't gone askew on the treloff!
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Old Sep 25, 2007, 11:53 AM
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Millarville,Alberta,Canada
Joined Jun 2000
544 Posts
Question for Thomas

I just got my kit last night and Rimfire motor on backorder for 3 weeks. Then I saw you use BP A2212-13 outrunner Motor. How did you mount this. Did you mount on back of firewall with radial motor mount. Just need a little help of what I should do and a picture would be nice. I really like the price and they could ship to Canada.

Thanks
Wayne
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