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Old Jun 27, 2010, 01:27 AM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,673 Posts
Flutter!!!

Well this has been a big bump in the road of my quest to go fast.

Plenty of CF, balsa elevons painted with epoxy, strong control arms/rods with no play at all. I should also note that the elevons have been taped, top and bottom.

The flutter seems to be coming from both wings, near the rear in front of the elevons.

My only theory is that the 5mm cf tubes I am using are not doing the trick.

A buddy is using CF strips, really thick ones. They are basically rectangle rods not tubes.

His Stryker has no flutter whatsoever. Those rectangular cf rods can't bend sideways.

Any other suggestions? This is driving me crazy. I have two motors that can push this thing but I don't have the airframe solid yet.
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Old Jun 27, 2010, 02:55 AM
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Peter M's Avatar
Newcastle, New South Wales, Australia
Joined Sep 2007
2,366 Posts
Johnny,
I suggest you spend 10 minutes taping the underside with packing or bi filament tape. Packing tapes often adhere better if you prime the surface with "spray on" adhesive first while the bi filaments seem to stick to anything straight off the roll! Start at the trailing edge and work forward trying to have the tape continuous from wing tip/leading edge to wingtip/trailing edge. Over lap each run by a few millimetres.

I'd also suggest that on you next rebuild that you try and have your cf tubes actually intersect each other where possible and try and have a good mechanical/glue joint to transfer the load directly rather than rely on the flimsy/springy foam.

All stuff I should have heeded from reading earlier Stryker threads but of course I had to learn it the hard way.....

Good luck with it!

And thank you, your earlier posts are how I became interested in Strykers originally!

Peter
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Old Jun 27, 2010, 03:10 AM
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Peter M's Avatar
Newcastle, New South Wales, Australia
Joined Sep 2007
2,366 Posts
Gryphon,
Thank you, thank you, thank you!

My Mega 16/40/1.5SC turned up unexpectly a few days ago, before I had finished my fully glassed current build so I cobbled it into my well used cf'ed & taped Stryker as I couldn't wait to try it!

Even though I was limited to 4 cells and a 7 inch prop it was magnificent and everything you said it would!

The more rearward CG made flying inverted fun and I found it was also supremely easy to launch - something I had been needlessly anxious about! - again just like you said it would.

Thanks again!

Regards
Peter

PS: Using a APC Sport 7 x 6 prop on 4 cell 4000mAh it only pulled 83 amps or 1236 watts. Sorry wasn't able to get a tach reading. Can't wait to try it on 5 cells and higher currents!
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Old Jun 27, 2010, 07:57 AM
Why so serious?
2500GENE's Avatar
United States, FL, Cape Coral
Joined Dec 2007
5,972 Posts
Quote:
Originally Posted by novastar View Post
OK, what do you guys think? This is a weird one. Then again, I am little off myself to begin with

I got the APC (mad pitch) props in from Tower Hobbies this week, the 7x6, 7x8 and even APC 7x9 Sport Gas props. I use a HobbyCity 4mm "collet-style" prop adapter with a machined aluminum spinner to hold my props on the Turnigy 2836-2350 K/V 4mm shaft outrunner motor. BUT, as my bad luck would have it, the stupid prop adapter has a shiny, smooth backplate such that, these gas props only slip around it and I cannot tighten it down...at all! I spent a lot of time last night fiddling with the thing. My last ditch effort was to use (don't laugh) a piece of ~320 grit sandpaper cut into a neat rectangle and folded over between the prop adapter's backplate and the APC 7x9 gas prop's front face, since it is a tractor prop. It tightened down immediately! It appears to be holding VERY well and in fact, I have performed static WOT tests and I didn't see any slipping.
Novastar,
I use alot of those HC collet prop adapters on several planes. With the 4mm one with an APC prop I noticed it slipping. The problem was the spinner (nose) would bottom out on the threaded part before the prop was tight enough. They seem to be made for a GWS prop that has a deeper hub. Adding a washer between the prop and spinner
then tightening kept it from bottoming out and held the prop properly.
Just my 2 cents.

Q
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Old Jun 27, 2010, 08:36 AM
Victim of C.D.O.
murdnunoc's Avatar
United States, TX, Lubbock
Joined Oct 2007
4,081 Posts
Quote:
Originally Posted by Switch2403 View Post
I'm needing a little help and opinions from you guys.

I finally was able to maiden my 4s stryker this weekend and i wasn't happy with the controls. I am using the midwestern elevons, 2-56 control rods, metal clevises, and Kids tape hinge. With the throttle down the stryker was flying straight and level but under WOT it wants to fly straight up and roll to the right. I am sure this has got to do with my thrust lines but how do I shim the customRC mount and which direction? When at WOT I was having to fly with my elevators all the way down to keep it flying level but my ailerons was very sensitive.
I will adjust my rods and get more throw from my elevators and turn down my ailerons with my controller but I am still worried about it wanting to climb straight up and roll right at WOT. Any more suggestions?
Switch,
What's your CG look like? Stykers with more than stock power like to run with the center of gravity forward of the CG dimples located in the fuselage hand grips. They'll fly with the CG pretty much as far forward as you put it, but controls become mushier as you move it foward. 3/8" - 1/2" forward of the factory location should be a good location for your CG. You can shift batteries (cut some foam if it's in the way) to achieve your target CG.

Once CG is nailed down, if you still have issues with the plane climbing under WOT, you can adjust the thrust angle like you suspected you needed to. If it's climbing under power, the motor needs to be tilted back a little more so that the thrustline is pointed farther up. To do this on the CustomRC mount, you can add a 3mm washer to each of the front two mounting screws between the top fuselage bracket and the motor mount piece.

Another thing to look at is whether your fuselage has developed a "banana" shape with use. I forget how old your airframe is and whether you have a carbon rod going front to back. Old airframes tend to curl up around the nose/battery area and this will lead to climbing with increased airspeed. If yours is curled, you can put it over your knee and bend it back, and install a carbon tube going straight down the center of the fuselage to straighten it up and hold it there.
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Old Jun 27, 2010, 10:01 AM
4000 posts?!
micro_builder's Avatar
United States, TX, Fort Worth
Joined Jan 2005
4,038 Posts
I got some doppler passes checked on my 16" F-27C, 69.7mph!!! I had no clue it was going that fast. Yet another video from yesterday, slowing it down, inverted slow and low, and some low altitude high speed rolls (and the obligatory crash into a tree ). Time to finish up the big F-27C to match the little ones...

micro Stryker F-27 3S - &%#!$ TREES! (3 min 29 sec)


Nick
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Old Jun 27, 2010, 10:05 AM
helter skelter
NOTAR 600's Avatar
Central Ohio
Joined Nov 2007
1,384 Posts
Medusa 28-40-1700 V2
hobbywing 100 amp 6S esc
hyperion 3S 2100mah 25C
spektrum AR6110e receiver
customRCparts mount
HS-82mg servos

I am running 6S using two hyperion 3S lipos in series.

I used a 60 amp esc first, and now a 100 amp esc and still have this same problem. When I give it more than two thirds throttle the motor makes a chirping sound and cuts out. If I lower the throttle stick it runs and flies just fine and goes pretty fast. I have the throttle trim set to center. I am sure the AR6110e receiver is not the best and I am trying not to fly very far out. I have never experienced a problem with this model of receiver on my other 4S stryker in about 50 flights.

What might be the problem here? Have I just run up against the limit of the setup? Does this normally happen on 6S? It really doesn't seem right.
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Old Jun 27, 2010, 10:27 AM
helter skelter
NOTAR 600's Avatar
Central Ohio
Joined Nov 2007
1,384 Posts
Microbuilder, very cool plane! What battery are you using?
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Old Jun 27, 2010, 10:30 AM
Registered User
Dreadan's Avatar
USA, WI, Argonne
Joined Jul 2008
59 Posts
Quote:
Originally Posted by NOTAR 600 View Post
Medusa 28-40-1700 V2
hobbywing 100 amp 6S esc
hyperion 3S 2100mah 25C
spektrum AR6110e receiver
customRCparts mount
HS-82mg servos

I am running 6S using two hyperion 3S lipos in series.

I used a 60 amp esc first, and now a 100 amp esc and still have this same problem. When I give it more than two thirds throttle the motor makes a chirping sound and cuts out. If I lower the throttle stick it runs and flies just fine and goes pretty fast. I have the throttle trim set to center. I am sure the AR6110e receiver is not the best and I am trying not to fly very far out. I have never experienced a problem with this model of receiver on my other 4S stryker in about 50 flights.

What might be the problem here? Have I just run up against the limit of the setup? Does this normally happen on 6S? It really doesn't seem right.
Your batteries can't handle the load and are dropping past LVC. I'm having the same issue with mine.
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Old Jun 27, 2010, 12:10 PM
helter skelter
NOTAR 600's Avatar
Central Ohio
Joined Nov 2007
1,384 Posts
Thanks Dreadan, have you been able to correct yours by using higher (C) output lipos??
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Old Jun 27, 2010, 12:27 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,673 Posts
Quote:
Originally Posted by Peter M View Post
Johnny,
I suggest you spend 10 minutes taping the underside with packing or bi filament tape. Packing tapes often adhere better if you prime the surface with "spray on" adhesive first while the bi filaments seem to stick to anything straight off the roll! Start at the trailing edge and work forward trying to have the tape continuous from wing tip/leading edge to wingtip/trailing edge. Over lap each run by a few millimetres.

I'd also suggest that on you next rebuild that you try and have your cf tubes actually intersect each other where possible and try and have a good mechanical/glue joint to transfer the load directly rather than rely on the flimsy/springy foam.

All stuff I should have heeded from reading earlier Stryker threads but of course I had to learn it the hard way.....

Good luck with it!

And thank you, your earlier posts are how I became interested in Strykers originally!

Peter
I have heavy duty strapping tape, but I never considered it would do much in comparison to cf. I might try it. I am also going to put some of this in.

http://www.myatomic.com/catalog/view...strip_092x_220

I've seen this work in person for a buddy. No movement at all.

I am done with the cf tubes.
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Old Jun 27, 2010, 02:02 PM
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GryphonRCU's Avatar
United States, CA, SF
Joined Mar 2008
3,818 Posts
johnnyrocco123,

C.F. has worked out for everyone in past….so that is not the problem. Please don’t mention say bad things about it because some other readers might get the wrong idea.
Having said that, I too prefer flat C.F. strips (solid rectangular cross section).
Problem with strips is that they do not come longer than 24” from Midwest products.
So when I go to fly-in events I try to buy as many of the no brand name ones as I can which come 40" or longer.
Consider making a bulk purchase of your desired C.F. with your friends to justify the shipping charges and ask the company to cut them down to 37” and include the ends in the package to avoid “OVER SIZE” package shipping charges.
If my friends and I do a big purchase you would be welcome to get in on it.

__________________

As it has been mentioned it looks like you have not extended your C.F. to meet other C.F.

***Go ahead and connect them by running some shorter C.F.
Do some sketches and post before doing it for feedback …..maybe some of the guys can post a sketch of their suggestions for you.

____________________

Since you might do the previous step, I was wondering if you have replaced the stock plastic rods with C.F. , if not you might consider doing it because it can help you in this case.
It will also be an anchor point to help stabilize other C.F.

***I have a pic showing how I removed the stock ones very nicely using dental floss. Let me know if you want that pic posted…I might just do it anyway when I have time later.

___________________________________

***It looks like your main C.F. in rear running left to right by motor mount may not be installed deep enough.
If that is in the airflow it will lead to some flutter.
You might see a post by couple of guys on this thread …..they might raise their hand and say they had same issue….I will not name names, if they are shy they can PM you instead.

________________________________

***Back to your elevons, your 4th picture still appears that they might be hanging a bit low and in the way or airflow….I think last time you said that was optical illusion and they are fine…..O.k.
__________________________________

***** Question regarding your 3rd pic with orange paint on top of fuse.
I’m not so sure what I’m looking at.
The color of wing does not match your current build. Your control horns look to be different.
Regardless of that: Why is there shaded hinge looking dark line which almost looks like a hinge line between T.E. and foam? …….that area needs to be smooth and nothing disturbing the airflow.

What is that in the stock hinge locations? Kind of looks raised above foam????

________________________________________

Have you figured out how to use the data logging feature of you Castle Creations Phoenix ICE 100A ESC?


Good luck in your high speed attempts.

Gryphon
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Old Jun 27, 2010, 02:20 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,673 Posts
[QUOTE=GryphonRCU;15415211]johnnyrocco123,


***** Question regarding your 3rd pic with orange paint on top of fuse.
Im not so sure what Im looking at.
The color of wing does not match your current build. Your control horns look to be different.
Regardless of that: Why is there shaded hinge looking dark line which almost looks like a hinge line between T.E. and foam? .that area needs to be smooth and nothing disturbing the airflow.

What is that in the stock hinge locations? Kind of looks raised above foam????

________________________________________

In the third pic, that is the basswood between the elevon and the T.E. of the wing. The basswood is lower than the top of the T.E. of the wing. I figured it wouldn't be a problem as long as it wasn't above the T.E. of the wing.

That is a different Stryker, but the same hinging and elevons as the "rainbow stryker".

The CF is as deep as I can go without coming through the other side of the foam. It is all 5mm+ CF. I replace the stock spars too. Down the middle of the fuse, that is the stock 6mm FG spar that comes with the Funjet.

I would love to see pics of removing those stock spars with floss

Those are a pain to get out without chunking foam.

I'm putting some of the strips in today in front of the T.E. of wing as well as some strapping tape. Hope to try it this evening.

Thanks for input.
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Old Jun 27, 2010, 03:03 PM
4000 posts?!
micro_builder's Avatar
United States, TX, Fort Worth
Joined Jan 2005
4,038 Posts
Quote:
Originally Posted by NOTAR 600 View Post
Microbuilder, very cool plane! What battery are you using?
Thanks Lipo is a 250mah 20C 3S...its on the small side, starts getting a little warm at the end of the run, but it gives me over 6 minutes of screaming around, which is pleanty for my thumbs!

Nick
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Old Jun 27, 2010, 04:36 PM
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Peter M's Avatar
Newcastle, New South Wales, Australia
Joined Sep 2007
2,366 Posts
[QUOTE=NOTAR 600;15413917]..... When I give it more than two thirds throttle the motor makes a chirping sound and cuts out.....QUOTE]

Notar,
I suspect this issue is related to timing and not because the batteries are sagging under load and tripping the LVC. (If it was the LVC you wouldn't get the chirping noise). Consequently before you spend any money, I suggest you try different timing settings on your ESC to see if that will rectify the problem first.

Regards
Peter
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