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Old Jan 27, 2012, 11:26 AM
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I built FSW full fuse plane by someone on here. It was the nasa one, x-37 or something along those lines. He had a long thread about getting the CG and everything right as its hard with planes of this style. Also had some bad pitch tendencies depending on throttle. Think the way he solved it was by adding a cheap gyro to the elevators,and that helped it out a lot.That might also work for the guy having issues flying in the wind.
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Old Feb 22, 2012, 07:27 PM
Gusac
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Originally Posted by crxmanpat View Post
Success!

On one of passes it looked like I had a little wiggle in the wings, but didn't think much of it. So at the end of the second pass I turned in to the runway for a WOT pass. The wingtips fluttered and promptly departed the airframe! I forgot that forward swept wings need support all the way out.

Pat
Thanks mate
i am making one too, if you care to, here is the reason why it broke and have taken some effort to make the concept clear

wash out/ Wash-in Due to Flexure

Disclaimer (This discussion pertains to RC aeroplanes and esp foamies, therefore aeroelastic tailoring has been left out of the discussion)

When a swept back wing flexes due to less of torsional rigidity the incidence at the wing tip reduces , effective lift production is concentrated inboard of the wing (See image) wing tip therefore looses lift, the centre of pressure moves forward and aeroplanes pitches up, if the tip lift loss is high, she will pitch up and yet loose altitude

How does this happen (You need to have some imagination , easier way is to fold a paper and see)

When a swept back wing flexes under load, all chordwise points at right angles to the main spar are raised to the same degree, see image two, the points A and B rises through the same distance and the points C and D rise through the same distance but through a greater distance than A and B.Thus C rises further than A and there is a consequent loss in incidence at this section. This effect is termed, ‘washoutdue to flexure’, and is obviously greatest at the wing tips. It is most noticeable during high g manoeuvres when the loss of lift atthe tips and the consequent forward movement of the centre of pressure causes the aircraft to tighten up in the manoeuvre. (very applicable on faomies).

Now washout is structurally not dangerous, because wing tip is unloaded of high lift

Wash-in Due Flexure on a swept forward wings (Like su-47 berkut)

In a swept forward wings if you see the image above due to flexure the wing tips will produce more lift, this will overload wing tips and it will break away clean . (http://www.rcgroups.com/forums/showp...60&postcount=9), you can see how cleanly it has broken, it is due to wash in due to flexure





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Old Mar 21, 2012, 09:52 AM
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Inspired after SU37 Profile


Hi, Its a great thread and a lot of information about Su-47. I have flown F-16 then Su-37 and now working on Su-47.
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Old Mar 21, 2012, 09:57 AM
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I agree pusher jets Rule.
I am just curious if a 1800KV motor would be enough for it. I am making in 5mm depron, as this is the only size is available here. I have previously made F-16 & SU-37 out of it. I had 100% success rate even in windy flying conditions. But I has 3700KV motors on them. Since, these motors are already hooked on planes, the only available in my stock is 2209/1800kv (RC Timer brand). Kindly let me know.
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Old Mar 21, 2012, 05:03 PM
Pusher jets rule!
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Mesa, AZ
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That 2209 will work OK, but you can still only use a 6X4E prop (or maybe bump up to a 6X5E) due to the prop opening. The plane will fly, but not with authority.

Oh, and I now carry the motors and ESCs for these bad boys on my site. There's individual pricing for the motor and ESC, and then there's a combo as well. And I have APC style 6X4E props too.

Motor only

ESC only

Motor/ESC Combo

Pat
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Old Aug 11, 2013, 09:35 AM
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Looked great, crashed great..

I've had this plane for a while now, returning to it from time to time. Although I've never had it in the air more than a few minutes I have yet to completely give up on it. If I had to guess I'd say that my CoG is completely out of whack. I've tried putting the CoG where the plans call for it and then tried moving it forward but the plan still acts, I think, like it's overly tail heavy. When launched it noses high, starts to slide sideways and then will usually end up rolling over onto its back.

Anyway, after having the nose crumpled yet again I decided to take another swing at this and try something different. Functional canards.

I cut the old nose off, traced some new replacement pieces, toyed around with a few different sizes and shapes for the canards and set about putting my plan into action.

First thing I did was change the programing of the two existing servos to dual-aileron mode. Then I dropped in a spare 9g servo towards the nose for the canards. To make the canards I used some carbon fiber tubes, a spare control horn and a bunch of epoxy. Everything went together well and functioned correctly on the bench.

First flight - EXACT same thing. Nosed up, slide sideways, flipped onto its back and then nosed into the ground. Surprisingly no foam damage but the one side of the canard popped the epoxy from the carbon tube and was spinning freely so I couldn't reposition the battery forward to test a more forward CoG.

Frustrating... I really want to see this thing flying some patterns at my local field. Oh well, I've re-epoxied the canard and we'll try it again with a more aggressive forward CoG.
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Old Dec 23, 2013, 10:39 AM
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Hey Pat, Thanks for another beautiful bird. Got one on the table in the garage now. You may not remember me, been several years since I posted anything on here, Actually the last bird I built was your Sr71 Blackbird back in 2010, right before my wife and I made a trip to see her sister in Prescott. I got a job right after we got back and ended up getting hurt on a bad section of roof so haven't flown in over 3 years. This will be my first bird after I get a doctors release sometime in the next couple moths hopefully. Also, going to try to move out your way mid year maybe will be living in Prescott if so. I'll come down and fly with you when the weather is up around the hundred degree mark if your up for it. Also, will post pics when I get her built, and video once I take her out and fly her.
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Old Dec 24, 2013, 09:34 AM
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Building out of Fan Fold Foam.
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Old Dec 24, 2013, 01:51 PM
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So Blade, did you just lay the KF airfoils on at the back of the spar? That's kind of what it looks like.
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Old Dec 26, 2013, 10:38 AM
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So Blade, did you just lay the KF airfoils on at the back of the spar? That's kind of what it looks like.
Yep, just dropped them on top. Can't tell you how they work as I've been battling a severe CoG problem.
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Old Dec 28, 2013, 10:08 AM
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Originally Posted by BladeGrip View Post
Yep, just dropped them on top. Can't tell you how they work as I've been battling a severe CoG problem.

I understand, just a thought that entered my mind this morning as I drove to the flying field to maiden an F22 I built this week also. I wonder if anyone has tried doubling up the vertical fuse on one of these like the Yardbird RC F22. That might add some forward weight without having to use weights or such.
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Old Dec 29, 2013, 04:42 PM
Pusher jets rule!
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j4ck4,

Yes, I remember you doing the SR (that was actually eliworm's build, I sell a smaller version). Nice to see you getting back into the RC game.

One thing on your Su-47 build, you will need to get another piece of carbon on the fuse right behind where the current two rods come together. It may not be totally necessary, but I would add something there for extra support.

But otherwise it's looking good!

Pat
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Old Dec 29, 2013, 07:18 PM
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Originally Posted by crxmanpat View Post
j4ck4,

Yes, I remember you doing the SR (that was actually eliworm's build, I sell a smaller version). Nice to see you getting back into the RC game.

One thing on your Su-47 build, you will need to get another piece of carbon on the fuse right behind where the current two rods come together. It may not be totally necessary, but I would add something there for extra support.

But otherwise it's looking good!

Pat

Thank you sir, I'll look at adding that. And, you're right I got to looking and it was Eliworm's SR. I was chatting with you at the time and made the trip out to Prescott so got confused aver the years.
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Old Dec 29, 2013, 07:25 PM
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Well, his and mine are very similar, and I did do the beta build on his, so yeah, it can be confusing. And I still have his original hanging in my garage. It still flies now and then.

Pat
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Old Jan 04, 2014, 09:35 PM
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I added the spar behind the two wing spars stiffened her up right nicely. I was wondering if that floppiness was going to be an issue, the plans I had used didn't show anything but the wing spars. And, stupid me didn't read far enough in the thread to find out that you had discovered the need for them.
I guess it will be a while before I get to try a maiden since we are supposed to get snow tonight and tomorrow possibly, and the temp is supposed to be right at zero for several days. Oh well, I got to fly a freshly built F22 last Saturday and a freshly built Zagnutz Thursday and today so, all in all its been a good week.
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