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Author Topic: Another Approach to Embryo  (Read 2974 times)
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kittyfritters
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« on: April 20, 2015, 11:49:47 PM »

Here is a bones shot of the embryo that I am building for the O.F.F.C Bostonian/Embryo contest next week.  The working title for this opus is "Just The Right Amount Of Wrong".  Yes, it does meet the rules.
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Hepcat
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« Reply #1 on: April 21, 2015, 06:36:06 AM »

Is the tailplane too small or is that just the way the photograph makes it appear? (It is pretty by the way, but is that an insult on a Bostonian!)
John
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kittyfritters
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« Reply #2 on: April 21, 2015, 10:05:13 AM »

The apparent size of the tailplane is just the perspective.  The Bostonianish look of it is because I put the 3 inch dimension of the imaginary box vertical to get enough gap between the wings. 
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kittyfritters
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« Reply #3 on: April 22, 2015, 12:48:58 AM »

Trying to get it done, or at least flyable for the O.F.F.C. meeting tomorrow (Contest is next week) so I can at least find out how it flies.  Doing one of my typical 3-tone tissue jobs.  The wings and tail surfaces are yellow and the fuselage is blue on top and bottom and white on the sides.  While I was covering it I didn't notice that I had cracked the two lower longerons just ahead of the landing gear struts. When the tissue shrank it became obvious.  I had to cut the tissue and sister in some new strip stock.  Great,  I haven't even got it off the bench and it has hangar rash...sheesh! Angry
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kittyfritters
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« Reply #4 on: April 22, 2015, 08:37:46 PM »

Here's what it looks like covered.  I don't have the wheel pants or exhaust pipe on it but it's flyable.  It balanced, as calculated, with no ballast.  (Now how many times do those calculations actually work out?)  First, I had to establish the turn so that I could fly it in that room. It took considerable left thrust and drag tabs on both left wingtips.

Then I had to find out if it would actually R.O.G. so I put a few hundred winds on it and launched.  It would not quite get up, so I went up a size on the rubber and it tested fine.

https://www.youtube.com/watch?v=id-lxmEMQSQ

All I had to do now was find out how many winds I could put on it and still keep it out of the lights hanging from the ceiling.  I over estimated it a bit on this flight and had it scraping the ceiling.  Despite bounding between the lights like a pin ball and the collision with the back stop no damage was done during all the test flying. 

https://www.youtube.com/watch?v=zG2bnfAd63s

A little more down thrust, plus the drag of the wheel pants, should tone down the climb a bit and allow enough winds during the contest for a good showing.  This thing looks to be a lot of fun as an outdoor embryo too.
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kittyfritters
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« Reply #5 on: June 17, 2015, 03:20:02 PM »

I flew the Wright Amount of Wrong (Official name) in the O.F.F.C. Predicted Time/Spot Landing contest this morning.  This was the first time I've had the opportunity to fly the design outdoors.  I took off the drag tab on the lower wingtip, one of two used to keep the circle tight indoors, and took out the down thrust that suppresses the climb indoors.  I wound it to what my indoor experience would have given a 50 second flight, predicted 50 seconds, and both to my embarrassment and delight got 83 seconds.

I put the drag tab back on and reestablished the down thrust but still finished out of the money being 4.1 seconds off my best predicted flight.  (I finished 8th!) However, there is no doubt that this design is a real flier and as soon as I have finalized it there is a kit in the offing!
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« Reply #6 on: August 06, 2015, 11:38:47 AM »

OK!  I think that I would like to build your little lovely.  Cute and a great flyer, how can ya go wrong.  snort3
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Maxout
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« Reply #7 on: August 07, 2015, 07:41:03 AM »

A little more down thrust, plus the drag of the wheel pants, should tone down the climb a bit and allow enough winds during the contest for a good showing.  This thing looks to be a lot of fun as an outdoor embryo too.

First off, a very nice flying airplane. Looks like it could easily do 2+ minutes outdoors.

Now, your strategy for increasing flight times there is incorrect. Flattening the pitch attitude like that will make the aircraft climb slightly faster (that mush on your videoed flight actually reduces the climb somewhat) and unloads the prop so that the turns burn off faster.

The best way to increase flight times on an indoor embryo is to fly it right/right with as little downthrust as possible so that the model practically hangs on the prop. Trim the model using a trim tab on the right wing to hold said wing up and a touch of right rudder as needed. Use right thrust to drag the nose around to the right and prevent a full stall. You can turn extremely tightly this way. Also, if flying to embryo rules, an 8-8 1/2" prop will improve performance further. If flying to Bostonian rules, the Tern Aero prop re-pitched to P/D 1.5-1.6 will give good performance. For Cat I and low Cat II sites, aim to have 100 turns left when your embryo lands. You'll want to start with a motor taking around 2000 turns, and expect to back off 200-300 turns to get down to launch torque.
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Bredehoft
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« Reply #8 on: August 07, 2015, 10:04:20 AM »


The best way to increase flight times on an indoor embryo is to fly it right/right with as little downthrust as possible so that the model practically hangs on the prop. Trim the model using a trim tab on the right wing to hold said wing up and a touch of right rudder as needed. Use right thrust to drag the nose around to the right and prevent a full stall. You can turn extremely tightly this way. Also, if flying to embryo rules, an 8-8 1/2" prop will improve performance further. If flying to Bostonian rules, the Tern Aero prop re-pitched to P/D 1.5-1.6 will give good performance. For Cat I and low Cat II sites, aim to have 100 turns left when your embryo lands. You'll want to start with a motor taking around 2000 turns, and expect to back off 200-300 turns to get down to launch torque.

I need to start copying these nuggets down into a personal flight manual.  I know about a year ago you posted how to diagnose outdoor NoCal flights and counter the poor flight with either down thrust or side thrust - but I can't find that nugget back!  (I think it was counter stall with side thrust and counter wallowing turns with down thrust, but I don't trust my memory.)

--george
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Maxout
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« Reply #9 on: August 07, 2015, 12:40:02 PM »

I need to start copying these nuggets down into a personal flight manual.  I know about a year ago you posted how to diagnose outdoor NoCal flights and counter the poor flight with either down thrust or side thrust - but I can't find that nugget back!  (I think it was counter stall with side thrust and counter wallowing turns with down thrust, but I don't trust my memory.)

George, you're far, far too kind. That said, you've got my method correct, except that it was primarily in regards to regular models. Would work on Nocals as well, though, especially those flown to the right.

One thing that should be put together some place is the repository of Phantom Flash trimming strategies.  Wink
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kittyfritters
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« Reply #10 on: July 15, 2016, 03:53:37 PM »

After developing my (mostly) self-aligning box fuselage structure for my Bostillation, Bostonian, I decided to apply this to the Right Amount of Wrong when I kitted it.  The fuselage structure was more conventional with verticals since the Warren truss structure of the prototype was light, and certainly strong enough for flying, but the long, unsupported lengths of 1/16" longeron made simply handling it, without breaking something, require too much effort.  I also changed the nose contours to include the 30 degree windshield for the extra points and made fuselage the minimum width. (The imaginary box stands on end to get sufficient wing gap.)  Now, viewed from the front quarter, it looks even longer. 

That was version 2, but I was not satisfied so I redrew it again making the center section of the fuselage of sheet parts with the same keying system that I use in my No-Cal designs.  I also added a wing saddle for the lower wing to allow the wings to be removable, and added lightening holes in the wing ribs and center fuselage cross members as in the Bostillation.  (When you have a laser cutter, why not?)  Versions 1 and 2 had a Comet type attachment for the lower wing, the spars going through holes in a flat fuselage side plate and the wing halves being glued to it.

When I built version 3 it certainly aligned easily enough, but I discovered that it had serious structural issues when I took it off the board.  I had forgotten that the parts layout and keying method that I developed for my No-Cals works because the structure has a motor stick glued to one side of it!  I've re-engineered the center section of the fuselage, and while it can be done, I don't want to add the weight of the extra stock required to solve this issue with the laser cut parts in this particular design.   The final version will revert to the version 2 structure adding the wing saddle for the lower wing.

The version 3  fuselage in the photo is sitting on a working plan section for version 2.

Another Saga continues!
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kittyfritters
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« Reply #11 on: August 05, 2016, 03:03:54 PM »

Here's what it looks like now.  I was intending to supply the kit with the 8 inch, Peck prop shown in the photo, but it does not fly well with that prop.  The best plastic prop I have found for it is the 7 inch, North Pacific prop which is, unfortunately, out of production. 

Unless I can find a supplier that has a large stash of these propellers I will have to delay kitting this until I can find a suitable replacement.  I realize that you serious competitors are quite capable of making your own props, but I do have to find something that works well out of the box.
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kittyfritters
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« Reply #12 on: August 18, 2016, 05:38:46 PM »

The clothes dryer stopped working.   What does that have to do with this model? 

We had a repair tech come out and he fixed it, actually did something like a 100 hour on it, and it works fine.  Unfortunately, he did not get the vent pipe completely hooked up.  My wife did the laundry and it got quite hot an humid in the garage...where my shop is located.  The only model that was on the bench at the time was my version 3 prototype.  My wife complained that the garage was like a Turkish bath which caused me to check the dryer vent and discover the leak.  I had to pull out the washer to get access to the back of the dryer, which I did and fixed the problem.  The following day we left on a one week trip (50th anniversary!)

I came back from the trip and went to the O.F.F.C. meeting for some more test flights.  The Wright amount of wrong prototype was flying in a manner I could only call bizarre and was untrimmable.  I took a good look at it and realized that the steam bath from the week before had warped the wings.  I will attempt to steam it out and try some outdoor testing on Friday morning. 

Oh well, I've redrawn it again and I will have to build another one anyway.
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kittyfritters
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« Reply #13 on: August 20, 2016, 12:38:48 AM »

Now this is why you don't just draw a plan and put it out there as a kit without testing it!

I took my version 3 prototype of the Wright Amount of Wrong to the Grassy Knoll this morning for some outdoor testing.  It was a bit humid since the sprinklers had run just before I got there but otherwise great flying conditions.  Except that it wouldn't fly!

https://youtu.be/zBjBqPyasGk

I had steamed the warps out of the wings the night before so I knew that wasn't it.  Aerodynamically it should be exactly the same airplane as the earlier versions except for a slightly different fuselage profile.  I put the same motor in the original version, used the same number of turns and got something completely different.

https://youtu.be/VWzmNvu_fZA

There was not even a grams difference in weight between the two models.  I sat down in my camp chair (You do bring a camp chair to the flying field, don't you?) and studied the two models closely.  A disturbing clue was that the Version 3 model needed some nose weight.  There had to be something different about the moments.  I held the models belly to belly and the cause was readily apparent.  When I redrew the plans, somehow (And, you really have to wonder how I did this on a computer.), I moved the lower wing forward by 1/2 inch!

I had some testing to do on the Bostillation this morning but after I finished that I cut the lower wing off the saddle, slid it back as far as I could, changing the incidence, and glued it back on.  This made it fly a little better (No video, the camera had run out of battery by then.) but still not as good as the earlier versions.  Well, I knew I had some re-drawing to do anyway.  There will definitely be another prototype before the kit!

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kittyfritters
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« Reply #14 on: November 09, 2016, 07:03:53 PM »

So, after sorting out the stagger and incidence errors in the Mk3 prototype I was still having some problems with it flying.  It occurred to me that sometimes you build a model that just wants to fly the other way.  I have been trimming "right/right" lately so I decided to see if it wanted to fly left.

Voila! the flying characteristics became very close to the original prototype.  It seemed to be behaving itself very well, indoors, so i decided to see what times I could really get out of it.

As soon at it left the floor I realized I had put too many winds in the motor.  It started climbing like it was outdoors.  It bounced off the 24 foot ceiling several times but recovered like a light stick model.  It circled between the lights several times before it hit one, but recovered nicely and climbed back up to the ceiling. It  hit three more lights and the guy wires for one of the basketball back stops but managed to recover nicely each time.  I thought I would get a very good time despite all the collisions but the last one put it in direct line with the flat wall over the seating area.  It hit the wall and slid straight down the wall, inverted, nose down, which would not have been a problem if the wall went all the way to the floor, but this one stops 12 feet up and it picked up velocity without enough room to pull out and went straight into the floor.

Oh well, it's a prototype and I learned a lot from it.  (And, it is rebuildable!)  The next one may be the production version.
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« Reply #15 on: January 19, 2017, 02:33:43 PM »

Now this is why you don't just draw a plan and put it out there as a kit without testing it!

I honestly think you're doing a lot more testing than many manufacturers do, and you may be giving yourself too hard of a time. Tissue covered models tend to be unreliable on humid days. You don't want to show up to the field and just start putting up official flights unless the model is several years old, the tissue has stabilized, and you're very confident of the trim based on many flying sessions. Embryos are a prime example of this because of their light construction. The only scenario in which you can get around this is by using a Warren truss fuselage and geodetic ribs on your wing, stab, and rudder. That is the only way to ensure that from the point of construction, the model will never, ever change its warps or alignment in any way, and even then you need to be sure you've used waterproof glue in construction and that your tissue is attached with dope or some other water resistant adhesive so that the balsa itself doesn't go floppy. I've taken some of those measures on my recent builds, and it has reduced the number of flying sessions and cure time necessary to bring a model up to complete reliability, but it hasn't eliminated it entirely. Doesn't matter how well you trim your high performance model in its first session, your going to have to adjust the trim next time out. And the time after that, and so on for at least 6 months, and possibly 18 months.

I say all that to say this: it may be time to go ahead and kit the model. It's an embryo, and there's only so many changes you can make to prevent it from being vulnerable to moisture.
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kittyfritters
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« Reply #16 on: January 19, 2017, 04:06:07 PM »

Now this is why you don't just draw a plan and put it out there as a kit without testing it!

I honestly think you're doing a lot more testing than many manufacturers do, and you may be giving yourself too hard of a time...

...I say all that to say this: it may be time to go ahead and kit the model...

Now that you mention it, I have the production version ready for kitting.  There are a few tweeks to the parts sheets and the plans but I expect to have it on my website next week.

Here's a video of the production version flying.  I couldn't get another flight in because I had to leave the rec center for a doctor's appointment, but while this is not the greatest flight it gives you some idea of it's capabilities. Oh, the color scheme reflects my original intention to have it out before Christmas.

https://youtu.be/W56GG2fSMPQ
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« Reply #17 on: January 20, 2017, 08:19:16 AM »

That's a nice flying airplane. Recovers well from major hits...always a plus. What does it weigh? From the flying speed it must be reasonably light...

You kit it and I'll start recommending it to people. It looks to be an excellent model and a definite competitive option for Embryo.
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kittyfritters
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« Reply #18 on: January 31, 2017, 04:18:41 PM »

Here's a photo of the production version of the Wright Amount of Wrong.  It will be available on my web site Thursday, 2/02/17.  (Yes, there are wheel pants in the kit.)


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kittyfritters
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« Reply #19 on: August 30, 2017, 08:28:09 PM »

Here's another video of the Wright Amount of Wrong flying, just to prove that I can keep it away from the walls and all the other obstacles at Stonehurst.

https://youtu.be/24Zxn94idmM
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