HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 03, 2012, 11:35 AM
Have you seen my Cobra?
vespa's Avatar
Thousand Oaks, CA
Joined Mar 2004
2,576 Posts
Here's a good example of how solid you can expect a fully molded tail to look:
F3B Tail (3 min 4 sec)


Compare to a standard 2-piece V-tail:
V tail flutter (cam: Flycamone2) (0 min 42 sec)
vespa is online now Find More Posts by vespa
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 03, 2012, 02:22 PM
Build A Rocket Boys!
PDX Slope Pilot's Avatar
Portland, Oregon
Joined May 2002
4,009 Posts
Holy cow.
PDX Slope Pilot is offline Find More Posts by PDX Slope Pilot
Reply With Quote
Old Apr 03, 2012, 02:35 PM
Registered User
so. cal.
Joined Jan 2006
2,689 Posts
My morbid curiosity got the better of me and I watched the V-tail, yikes!
s2000 is online now Find More Posts by s2000
Reply With Quote
Old Apr 04, 2012, 01:24 AM
Registered User
Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
2,422 Posts
Quote:
Originally Posted by PDX Slope Pilot View Post
Holy cow.
Just what I thought

But this particular v-tail is not 2 piece. The Brisk series has one style 1-piece tails. So structurally not much in common with Perfection rudder fin.

But the video in interesting. If you look carefully, at 5-7 seconds, the flutter seems to start from fuselage twisting. Then it escalates to flying surfaces, them bending dramatically, and also up/down bend of fuselage. Looks really bad

Years back I had a v-tail F3J plane (Snake) that repeatedly generated tail flutter in very fast high wind launches. It went probably much like in this video, fuselage was quite flexible. Looking from the ground it was not very spectacular. The most visible result of the flutter was plane loosing elevator control for a moment and plane slowing down quickly, spooling the zoom.

BTW Later I sold this particular plane to a friend. He entered a F3B contest with it, destroying it in top of a launch (remember the higher speed given by long line). Whole tail unit came off... Was this due to stress of repeated flutters? Or initially too weak structure?
Tuomo is offline Find More Posts by Tuomo
Reply With Quote
Old Apr 04, 2012, 08:50 AM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,599 Posts
The Brisk is a very early molded model.
I'd be more interested in seeing what a current design like fS 3 or Ceres looks like.
I'm sure it would not look like that.
target is offline Find More Posts by target
Reply With Quote
Old Apr 04, 2012, 02:27 PM
Have you seen my Cobra?
vespa's Avatar
Thousand Oaks, CA
Joined Mar 2004
2,576 Posts
Well, the v-tail video was meant as a joke, hence the There's some bad flutter going on there but what you see is mostly an illusion generated by the camera. My point was that standard v-tail models have loose tails that flop around wildly and it doesn't cause any trouble at F3B or F5B speeds, and furthermore, the molded tail video I posted shows just as much movement as the Pike anyway.
vespa is online now Find More Posts by vespa
Reply With Quote
Old Apr 04, 2012, 02:42 PM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,454 Posts
Quote:
Originally Posted by s2000 View Post
So I guess the moral of the story is, I need to just go have fun with my airplanes and not worry about what a camera shows, and please, nobody stick a camera pointing at the tail of a V-tail! I don't want to know!
I am beginning to be sad I post that video. ALL F3J models will have tails moving when you throw sideways and need to correct unless you buy some bullet proof model. To be fair there were other models fluttering and destroyed on the same line (it was just staked to the ground 150m line) in beetween my launches. And that model was not from this company....
Dont worry guys. In North Cyprus we had 8-10m/s winds 90 degree from the side in some of the rounds. I launched "F3B style" and went around and into the wind in all my launches and that is very hard on a tail.
The video also had some bad throws and also includes some video stabilizing so it looks worse than it is.
Here is a video I made in 2004 with a straight tow not even going to the side
Pike Superior launch ice Norway 2004 Jojoen.no (1 min 7 sec)
jojoen is offline Find More Posts by jojoen
Reply With Quote
Old Apr 04, 2012, 02:47 PM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,454 Posts
Quote:
Originally Posted by target View Post
The Brisk is a very early molded model.
I'd be more interested in seeing what a current design like fS 3 or Ceres looks like.
I'm sure it would not look like that.
You cant be serious. You want to compare a V-tail F3B model with the light F3J models?
Well ok
A quick search around youtube:
Ceres
Ceres F3B Maiden winching (3 min 42 sec)

Supersonic is a world class F3B model as you probably know
Supersonic F3B Launch (0 min 52 sec)

supra
Supra launch (0 min 10 sec)
jojoen is offline Find More Posts by jojoen
Last edited by jojoen; Apr 04, 2012 at 02:57 PM.
Reply With Quote
Old Apr 04, 2012, 11:49 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,599 Posts
Quote:
Originally Posted by jojoen View Post
You cant be serious. You want to compare a V-tail F3B model with the light F3J models?
Well ok
A quick search around youtube:
Ceres
http://www.youtube.com/watch?v=d7MDrsD7yjs
Supersonic is a world class F3B model as you probably know
http://www.youtube.com/watch?v=x_EUZksAu6o
supra
http://www.youtube.com/watch?v=hnjBU...eature=channel
Oh, I am serious....
I'm seriously disappointed with how quickly you have misunderstood me, JoJo.:-(
I was suggesting only that the example V-tailed plane was a very old design.
Technology in composites has come a long way since then.
One would hope that a more current design is stiffer.
Nor did I make mention of direct comarison between a 3m 77oz plane and a 3.6m plane that weighs close to 60oz.... I never would think to compare them directly. That's apples and oranges.
target is offline Find More Posts by target
Reply With Quote
Old Apr 05, 2012, 01:16 AM
Registered User
Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
2,422 Posts
Never seen x-tail rudder fins come off in F3J launch. However, aileron flutters, control problems due to wing twisting torsionally, elevators breaking, spars folding etc. happen every now and then.

Current tecnolygy is better than what we had just a few years ago. With st80 we can have safe allround plane for under 2kg- not bad! Would be my choise, if I decide to buy Perfection. It is very nice lamination that covers 90% of F3J flying.
Tuomo is offline Find More Posts by Tuomo
Reply With Quote
Old Apr 05, 2012, 05:39 AM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,454 Posts
Quote:
Originally Posted by target View Post
Oh, I am serious....
I'm seriously disappointed with how quickly you have misunderstood me, JoJo.:-(
I was suggesting only that the example V-tailed plane was a very old design.
Technology in composites has come a long way since then.
One would hope that a more current design is stiffer.
Nor did I make mention of direct comarison between a 3m 77oz plane and a 3.6m plane that weighs close to 60oz.... I never would think to compare them directly. That's apples and oranges.
Yes you are right we have come a loooong way. But we still walk on the edge and make use of the new technology to make them lighter yet stiff enough to handle what they are designed for. You see that in the Ceres video. It shows one of the absolutely best F3B/F models around yet it does wobble sideways in a launch. But it is strong enough for the use it is intended.
The real problem today is commercial. When I put together a video I might make a very bad commercial for a product if the video contains "on the edge" use and potential customers starts questioning. I might have instead limped up the line and made use of those videos instead. But it was only straight line (no bungee or winch). It was blowing 6-8m/s with turbulence from the tents and I had a huge GoPro camera on the top making turbulence for the rudder and a keychain camera placed around the model.
So what you might question is instead how bad my throws were

We had a funny problem with customers in a country..
They wanted lighter models and especially fuses. So Samba made the honeycomb technology that took the weight of the fuses much lower and got stiffer. The downside was that they could snap in a landing sideways. Pilots started snapping some fuses and said they were not strong enough. Well when they want lighter stuff it will suffer in other areas. But if a customer wants a model that can fly in all conditions and land sideways he should not order a light model that is on the edge. So many orders a SL (superlight) and thinks it will be good in all conditions. All that sells a SL should say that it is light because it is made for light flying. The honeycomb fuses can take ALL conditions in the air but crooked landings it will snap.
BTW the Pike Perfection fuses are made with almost pure carbon and seems to be taking a lot of beating even in the SL fuses (they are virtually the same in the current layup Samba delivers)

Had a wonderful day out yesterday in conditions that I expect to see at WC in South Africa this year. High altitude flying with strong thermals and strong sink were you need to fly aggressive
jojoen is offline Find More Posts by jojoen
Reply With Quote
Old Apr 05, 2012, 05:57 AM
Registered User
maghed's Avatar
Sweden, Stockholm County, Stockholm
Joined Jul 2007
11 Posts
With this kind of fixed stab and moving elevator ala Prestige/Perfection
what is the spec for the elevator servo. Does it have to be very strong,
or is it ok to go for speed?
/Maghed
maghed is offline Find More Posts by maghed
Reply With Quote
Old Apr 05, 2012, 06:02 AM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,454 Posts
Quote:
Originally Posted by maghed View Post
With this kind of fixed stab and moving elevator ala Prestige/Perfection
what is the spec for the elevator servo. Does it have to be very strong,
or is it ok to go for speed?
/Maghed
No it can be very small. In my first test I used a 1,5kg 12g servo in 8-12m/s winds. But I changed to a bigger one because of bad neutral on my testservo after some use. I would go for a smaller one again next time.
jojoen is offline Find More Posts by jojoen
Reply With Quote
Old Apr 05, 2012, 12:32 PM
Registered User
Nederland, ZE, Zierikzee
Joined Dec 2010
54 Posts
Hi JoJo

What can you tel me about the difference in strenght between the fuse of a perfect SL and a perfection SL???



Adrie
Adrie1966 is online now Find More Posts by Adrie1966
Reply With Quote
Old Apr 05, 2012, 01:28 PM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,454 Posts
Quote:
Originally Posted by Adrie1966 View Post
Hi JoJo

What can you tel me about the difference in strenght between the fuse of a perfect SL and a perfection SL???



Adrie
Completely different building technique. Stiffer and stronger. About the same weight.
jojoen is offline Find More Posts by jojoen
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold T-Rex 550FBL 3GX V2 "PERFECTION" (SOLD) rapyd Aircraft - Electric - Helis (FS/W) 7 Jul 25, 2011 06:44 AM
Wanted Pike, Pike Plus, Pike P or Pike WR Wing Center Section Lancer263 Aircraft - Sailplanes (FS/W) 0 Nov 11, 2010 11:07 PM