john josey

I have read quite a lot of this being the case,but i have to say that the three main retract cylinders i have are all completly leak free. They loose almost nothing in a 24 hour period,

lozza1965

Well its taken near on three years to get this model finnished so i was mighty pleased to see it get airbourne yesterday for the first time, decided for the first few flights to put it in the hands of Geoff White, who's experience really shown through on the day, flying with an 18 pound turbine provided a good deal of power, took a bit of trimming but by flight four Goeff was really giving it the beans, undercarriage worked a treat though right side gear door kept opening on high speed runs, so stronger rams are going to be fitted, havn't flown a turbine since last October so decided not to fly it yesterday, but learn't loads watching Geoff at the controls, after yesterdays flight the decesion was made to take out the borrowed turbine and order a brand new Jetcat P100, reason being this turbine it will be shared with the Typhoon and the extra power 22.6 pounds will be ideal for it, so now have to await the release of the engine which personally i don't think will be till mid summer, but well chuffed the model flew well, had another great turbine outing today flying my Phoenix 97 flights on this model now.


1

2

3 Going tech just before rotate on maiden run, thankgod it wasn't a few seconds later :shock:

4

5

6

7

8

9


lozza

Countryboy

My Feedback: (25)

Laurie,

Congrats on the maiden... great looking F-16 and as usual, great photos !

SJN

Check out htese guys destroying the F-14 [X(]


[youtube]http://www.youtube.com/watch?v=7cC9WqQKifw&feature=player_embedded#at=27[/youtube]

bigbaggy

How much weight was used to produce this faiiure?

FenderBean

thats a lot of weight im not even sure if a flying jet would produce that much.

Billy

My Feedback: (15)

Unless he planned on flying it like a dang Kingcat, that was a waste of time. Obviously tooooo much weight was added. And if you are going to "test" your wings, why take the time to install stuff like batteries and other electronics. Seems like a hugh over kill that only proved one thing........you need to order new wings.

Fly it like it should be flown and you will not have a problem.

Billy

causeitflies

132.277 lbs.

siclick33

It's not a waste of time if it's a certification requirement in your country

Assuming a take off weight of 30Kg then 60Kg per wing on a more conventional model would not be that much (4g?). I'm not sure how that translates to a model such as the Tomcat that creates a lot of it's lift from the fuselage though.

causeitflies

That's only about 3 g's at empty weight.

rcjets_63

My Feedback: (4)

Hmm,

The video said that the wing failed when 60 Kg of load was applied to the each wing. So that would be a total of 120Kg which is 262 lbs
60Kg = 132 lbs

I checked the FEJ website but they didn't have a weight listed for the plane. I think it would be reasonable to assume that the plane weighs about 60 lbs (if not more)

So 262/60 = 4.3 G's

They loaded the wing with a linear distribution that was biased inboard. This is a bit conservative as the outer portion of the wing also generates lift and therefore should have been loaded too (which would have lead to an earlier failure). The test setup (the fuselage is supported at each wing pivot) doesn't account for lift being generated by the fuselage

Assuming that the fuselage generates half the lift, that would mean a the wing would have failed at 8.6 G's which is certainly possible.

It wasn't the most thorough test but, all in all, it wasn't too bad and certainly showed the possibility of the wing failing during maneuvering.

Regards,

Jim

Edit: calculations updated based on 60 Kg applied to each wing and using aircraft weight of 60 lbs

siclick33

The big bag on the right wing (as you look at it) says 25Kg. There are 2 of these bags on the left wing so I think it is 60Kg per wing (not total).

EagleJC

My Feedback: (2)

From what I heard, these guys put over 90kg on that wing to cause fail, seemed trying to test 6 g's or over, not sure exactly.

If they want, company can make a special set of wings ( I-beam bar of wings) for them if they want to test that much weight on.

Thanks
James

rcjets_63

My Feedback: (4)

Siclick33,

Fair enough, I'll edit my original post.

In the thread [link=http://www.rcuniverse.com/forum/m_9515483/anchors_10568527/mpage_4/anchor/tm.htm#10568527]RE: FEJ_F14_Black_Bunny_by_enrico63[/link] in post #86, he lists the values for the weight, wing, and fuselage area and states his assumption that 50% of the lift is generated by the fuselage.

Based on these values, he comes up with a value of 62Kg per wing to simulate an 8G load. He then includes an additional security (safety) factor of 1.3 which means he needs to load each wing with 80.6 Kg. The calculation seems reasonable and well thought out.

So, getting back to the video SJN posted (#2084) in this thread, the wing had a catastrophic failure at a load which could certainly be achieved in flight. No good!!!

Regards,

Jim

bigbaggy

It is a difficult analysis. The fuselage generates lift. Say 4gs at 50lbs gross, the combination of wings and fuse would have to generate 200lbs of lift plus what ever force the stabs generate to produce the nose up pitching moment.
The design of the wing pivot point is a big deal. They need a system that transfers the loads to the top and bottom skins and the main spar.
It is hard to tell how they secured it.

rcjets_63

My Feedback: (4)

Bags,

Good point about the H-stab loads (which so far have been neglected in the calculation). Indeed it is a difficult analysis. I was simply trying to show that the loading of the model was conservative (not excessive) and well within what could be expected in flight.

Quite right that the loads need to be transfered to the wingskin. Of course, the spar structure surrounding the pivot needs to not only withstand the loads but to transfer them to the wingskin. The failure point appeared to be the spars (at the junction with the pivot block).
So, all in all, I'd say that the test was conservative yet resulted in a catastrophic failure. Not good []

Regards,

Jim

Edit: added clarification "(at the junction with the pivot block)"

Shaun Evans

Hi,

Has anyone seen the spar itself? I wonder what it looks like and what it's made of. I can't tell from the video, but how is the wing spar structure mated to the pivot? When the fellows in the vid are pointing out the absence of glue, what exactly are they talking about? What's not glued that should be?

FenderBean

So what are we saying here, which scale is this and there is so much unknown about the test. Your all just assuming are you not?

VF84sluggo

My Feedback: (55)

Hey Bags, perhaps they need a titanium box beam

rcjets_63

My Feedback: (4)

Not really, it sure looked like the 1/7.5 scale version. There didn't seem to be much that was unknown about the test which seemed to have a pretty conservative setup. A less conservative setup would have produced a failure at a lower weight.

If someone doesn't like the answer, that doesn't mean that they can just throw out the calculation and the results. The math doesn't lie.

Well, the calculations show pretty clearly that it can.

Regards,

Jim

molo_30

So what actually failed on the wing?

VF84sluggo

My Feedback: (55)

Just a guess here, but my observation is that we generally put some heavy 'g' loads on our planes, even when flying a scale model "scale", so to speak, as compared to the full-size bird with a human pilot onboard. I would bet that 6 to 8 g's happen on a regular basis, especially in the last quarter of a loop if speed and altitude get a bit mismanaged.

And Bags' point about the horizontal stab loads. In a hard, high speed, high g pull, it would be worth considering the potential for them to fail in a downward direction. The resulting abrupt lawn-dart would be something to see, with the wings then possibly failing under excessive negative g due to the huge unbalanced nose-down pitching moment.

rcjets_63

My Feedback: (4)

Per post #120 on the FEJ Black Bunny thread:

siddus74

Hi fella's,

Picked up a unflown 3rd hand FEJ 1/8th F16 today for a good price, ive read back to page 64 (phew) loads of good info ... I have an Mk3 Wren 54 which I plan to stick in the tail, I know its not going to be massively impressive but im so bored of my boomerang intro .... I have tarmac so a long take off and landing will not be an issue ...

I plan to leave out any think thats not require to keep it as light as possible.

Looks like CG is best at 155 - 160 and may have to strip and mod the retract cylinders .. mine are the white non pro version ...

I want to fly it on taileron like my F15, can any body comment on this configuration? I dont have the instruction so I could do with some settings or guide to the throws etc, the PDF from FEJ website seem to be corrupted on download, does anybody have a soft instruction manual?

Thanks in advance for any imput ...

Scott.

lookilook

I used to have an Mk3 Wren 54in the mid section and despite my f16 came to 9.3kg as i loaded it with stuff i was very happy with wren. ok no unlimited verticals but i was flying and enjoying it. Asking around in this forum a lot of jet experts told me its better to fly the f16 as is , i.e ailerons and elevators so i did.
Yes the pdf does not work but you can have online all the pictures, this is what i did and put the laptop next to me!!