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Author Topic: Shrimp and Swan  (Read 120 times)

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Online Deerslayer

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Shrimp and Swan
« on: December 17, 2019, 07:18:29 AM »
Here are the results of one of my current adventures. I came across a cheap and cute little machine called the Jupiter Swan, a somewhat replica of Canada's entry for the 1930 Schneider Trophy. The link to the location follows, below.

I built one, pretty close to the drawing but with a couple of significant differences. If anyone else is interest in this, let me know and I can provide more information. One visual deviation from the original full scale and everyone else's models is that I gave up on mounting the engine pod with skewers and made a pylon from some trailing edge stock. Not only did this work out much better, it simply slides into place and requires only a smidgen of hot glue to secure it. The overall result is a plane that has a very Spitfire-ish wing planform with a slight resemblance to a Seamaster. This one uses a KFm2 airfoil (flat, top layer extending 40 to 50 percent average chord length), no dihedral nor spar.

Now, my Shrimp flies pretty well but exhibited one nasty characteristic - it wanted to pitch over as soon as I gave it power. Handlaunching, holding it by the motor pod and simply letting it loose, went fine. I did get sort of used to the difficult takeoff from snow, impossible on bare grass. Meanwhile, I decided to evolve the design a bit, slightly enlarge it and see how that goes.

I enlarged the basic Shrimp somewhat, along with a couple of other changes which included using a KFm4 airfoil (both top and bottom layer with step back the same distance on the chord as with my Shrimp. I think this one looks nicer, a bit more sleek than the Shrimp, so I called it the Swan. This time, unlike with the Shrimp, I found a Lemon Stabilizer+ receiver in my stash.

As with the Shrimp, the ground takeoff was still a problem, despite the change of forward hull shape and lengthened tail moment. However, in the air, she is a real beauty! It flies better than the Shrimp and the stabilizer makes it pretty much perfect in the wind and at crawl speeds.

I decided that something had to be done about the nosing over situation. When I checked both planes, I found that the thrust angle of the motor was almost parallel to the fuselage. The original drawing had shown a 6 degree upthrust, overall, and I had somehow screwed up! (Not a totally unheard of situation down here in the Cave). So, I set in some upthrust on both planes, a combination of measuring and TLAR, which probably ended up at about 6 to 8 degrees. I would fly then and eventually measure it if things went well so that I could create and save a final set of paper templates.

Takeoff problem solved! Landing problem solved!

I much prefer my Swan to the original Shrimp and will probably build another variation very soon. Dwayne commented upon the Shrimp  as if he may consider building one. I told him that, if he decides to do so, to hold off and I will give him the improved design.

This plane (the Swan, or whatever it morphs into) may also be suitable for indoor flying. As soon as I get a chance, I want to try water takeoffs. Lake Ontario is too cold to take a chance on having to retrieve a plane from my bay! Any reasonably large puddle should suffice. Another approach is to do as was shown for the Seamaster: run a small tube, across and through the fuselage just ahead of the step such that an axle could be pushed through for light wheels. Instant conversion for land to/from sea.

The Swan is a great plane. Simple and quick and cheap to build. Everyone should have one!

https://www.rcgroups.com/forums/showthread.php?2914672-Jupiter-Shrimp
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Online Bill H

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Re: Shrimp and Swan
« Reply #1 on: December 17, 2019, 06:23:16 PM »
The Thrust Angle makes the difference, I have heard that before, can’t quite recall where

Online Deerslayer

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Re: Shrimp and Swan
« Reply #2 on: December 18, 2019, 06:57:04 AM »
The Thrust Angle makes the difference, I have heard that before, can’t quite recall where
Hmm ...
No, never mind :)
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Offline Terry

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Re: Shrimp and Swan
« Reply #3 on: December 18, 2019, 03:34:45 PM »
I here the same thing from my wife

Online Deerslayer

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Re: Shrimp and Swan
« Reply #4 on: December 18, 2019, 04:59:29 PM »
Now, it has started! (at last).
Blame Bill!!!!
Kill Bill (it's just a movie, folks, nothing to do with this mess)

My dirty little mind has been just boiling with all of the clever retorts I could have come up with after that guy started into it. You got there first, Tree D.

Next thing we know, you will warp my report about  my "Shrimp" into something nasty, right? Bring it on!

Meet you at the Toyground at high noon Friday, if you don't chicken out. The NTF will be congregating then and we will probably talk about you, unless you arr there to defend yourself. Just warning you, because of our bigly friendship.
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Online Bill H

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Re: Shrimp and Swan
« Reply #5 on: December 20, 2019, 02:53:13 PM »
Now, it has started! (at last).
Blame Bill!!!!
Kill Bill (it's just a movie, folks, nothing to do with this mess)

My dirty little mind has been just boiling with all of the clever retorts I could have come up with after that guy started into it. You got there first, Tree D.

Next thing we know, you will warp my report about  my "Shrimp" into something nasty, right? Bring it on!

Meet you at the Toyground at high noon Friday, if you don't chicken out. The NTF will be congregating then and we will probably talk about you, unless you arr there to defend yourself. Just warning you, because of our bigly friendship.

I was there today, you were not, I did not chicken out.
Bruce and I cleared the walkways so you should have no trouble getting into the warm clubhouse tomorrow.
Once again, I will be there, don’t wimp out again Droppo.
Can’t have you talking about me without me there.
High Noon or sooner, sooner for me as I have a direct route without relying on a Shrimp Boat to ferry me over.

Online Bill H

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Re: Shrimp and Swan
« Reply #6 on: December 20, 2019, 06:32:08 PM »
Hope I didn’t scare Gary off, It would not be a good day if I could not see the master fly.
Hey...did I just say that out loud?
We might still have a beef to settle, I am just not sure what it is.
Maybe we could have a good old fashion dog fight, my AT-6 against your Shrimp, that might be fun