dragonpilot

My Feedback: (38)

BirdofPray,

First, Sorry to see this loss,the Rafale seemed to be flying great!
Would you be able to shed some light on how you installed the hinges. It seems like that was the consensus on the failure of a hinge point.
I'm neurotic about aligning them and I know that sometimes if one of them is not perfectly 90 degrees to the wing, it can work against the others and possibly work out the end of the pin from the plastic and then release itself. A great jet pilot that I know always suggests to everyone and is surprised that this is rarely done is to get an inline amp/volt meter to test each control surface up to full deflections to measure the amp drawn from the servos, if it is high, this can tell you there is a binding problem.

With anyone who has already installed 3 hinge points has anyone applied hinge tape as a secondary means of support commonly seen in pylon racers as a viable option?

john agnew

dragonpilot

You are correct about being fussy with your hinge installation. I am currently building a Feibao MB 339. When it arrived I found that the hinges had been glued into the control surfaces at the factory. I suppose they thought they were saving the builder some work! Unfortunately they were not glued into the hinge pocket in the correct location, they were 2/3mm too far forward with the result that the control surface started to bind on the flying surface trailing edge shroud as soon as the control surface was deflected.

I had no option but to cut the hinges behind the pin and drill out the remainder of the plastic pin. I did this by using progressively larger drill bits starting with a 2mm pilot hole as close to the centre of the pin as I could get (I filed the pin flush with the hinge pocket first) on a couple of the pins they rotated with the drill bit on the biggest drill and pulled out some of the balsa hinge block. To repair these I pumped in Hysol using a nozzle until I was sure the hole was filled, I also did this on the rest of the holes. When the Hysol had set I drilled new hinge holes, again using a 2mm pilot drill first. Finally I opened up the hole at the front to allow the thicker part of the pin to seat in the correct location relative to the pivot axis of the control surface. The Robart hinges were then glued in with Hysol after being roughened with coarse sandpaper and having coated the hinge with silicone grease.

I reported my findings to Sandor at Digitech who supplied my kit and he has given the factory feedback on this matter and I understand that hinges will not be glued at the factory in future. The mesage appears to have gotten through as my Feibao Velox arrived with the hinges loose! I did have to do a little work on the pin holes to allow the hinges to seat in the correct location but, I would much rather do that than go through the process of drilling them out!

John

BirdofpraY

My Feedback: (31)

dragonpilot, I am pretty fickle about how I install hinge points. I pre fitted the hinges first and on this jet, this is something that must be done due to the missile rails. then I get a measurement of distance so that the surface does not bind on the rail or the fuselage then I hysol the hinge points to the movable surface first and check the 90 degree then once cured I work them in to the wing and recheck fit and the alignment on the control surface. Then I pull it back out and hysol them in. When I glue the hinges I apply hysol to the hinge and I shoot it up in the hole.

I had a similar incident with a Skymaster Hawk. On the rudder the bulk head support failed and through the rudder into a violent flutter. I had 4 hinge points installed there and although the it fluttered like hell it never ripped and hinges. Todd knows this, as he was piloting the jet when it happened.

Also guys I did cut down the control horn just above the last set of holes and I redrilled holes in the top.

jetnuno

Hi Birdof Pra

Eventhough if you lookk at picture the control horn goes all the way thru the depth of the surface. In your opinion what do think it was the main reason?

Regards

Nuno

BirdofpraY

My Feedback: (31)

In my opinion I don’t think depth intrusion made the surface area of the horn any weaker to cause total failure here, if anything it added for more area of adhesive to the part. I feel one of the hinges gave way, most likely the inside hinge and flexed the control surface to crack open and the horn pulled out at a lateral angle. that is why you see the glue points still there and from that it cause a domino effect of failures. If there were more than three hinges I believe there would have been flutter all the way to the ground, but this is not the case. There was not any redundancy at all and I feel now that if there were 5 hinges and two horns with a ball socket between the horns there would have been some added strength, and all the forces would be evenly divided.

Ehab

My Feedback: (44)

The IMAC guys install two hinges about 1/2" apart at both ends of the moving surfaces and then lots of hinges in between at equal spaces!!! I may do that on my next jet.

Vincent

My Feedback: (61)

I few years back i had an AD Mirage elevon flutter (same as the Rafale) and crash. It appeared to me there was flutter that started from the inboard section of the elevon that was unsupported. I built another but modified the elevon so that the inboard and out board sections were fixed so there would be no air turbulance at the tips. Worked well and never had a problem in 150flights.The pic is the modified elevon configuration.
V..

BirdofpraY

My Feedback: (31)

Vincent, I remember that you pointed that out after I built my Mirage back then. but I had mine already finished, I do remember using 6 hinge points on that jet. I will have to look for my build pictures on that jet that I did...

extra 300

My Feedback: (3)

BirdofpraY,

Just out of curiosity, did you have the wing tip missile rails installed on the fatal flight?

Thanks. Dany

Shaun Evans

Amen. Nice to see some clarity and honesty amidst all the subterfuge in here...

BirdofpraY

My Feedback: (31)

Yes they were on there from day one, and there was not any contact between the rail and elevator surfaces .

BirdofpraY

My Feedback: (31)

Yellowaircraft what are you digging at here? I guess I should call it a Dreamworksrc Rafale then since I bought it from Dreamworksrc. I still think it does not matter who I bought the kit from....

maverick5269

Hi Guys

I've also bought a Feibao Rafale, but it hasn't flown yet, because it has just been finished and I'm waiting for good weather conditions for its first flight....
Don't you think, Birdofpray, it's an excessive roll rate the cause of your crash? Too much aerodynamic pressure on the surfaces?
What about your settings for elevator and roll course? Normally, between 15 and 20 mm, as described by Digitech.

So sorry for this loss.....[]

BirdofpraY

My Feedback: (31)

mavrick5269, the roll rate was set to TAMs demo plane at Florida jets, which like mine. I solely believe it was a failed hinge. I have looked at the video over and over. I have the one elevon here and have looked at it over and over. There are two hinges where the ends are ripped off and there is one hinge that is still in tacked. It's like if the pin popped out. When I start building my Rafale, there will be more hinges used. You just never know when a possible bad hinge might get away and installed in your plane. With more hinges, and them positioned in the right places you divided the amount of load and forces applied, which creates a stronger workable surface to control. What do you think?

BirdofpraY

My Feedback: (31)

Well I got my parts in today and put my turbine back together. All I need now is a ECU and RPM sensor board. Thanks again Tony for the parts and quick service.

maverick5269

Yes, sure if you increase the hinges number, you'll divided the load.
But the flutter is an aerodynamic problem and will destroy all the extra hinges you'll added in this case...

My hinges are already glued, how can I add 2 more hinges without damaging my elevons?

Before having glued them with epoxy, I've scratched them with sand paper and dry-cleaned them with acetone...
Did you prepared them like this?

Glad to see your turbine repaired...

BirdofpraY

My Feedback: (31)

Also adding extra hinges adds alittle more redundancy to equation of force and load tolerance. So with a abrupt change in aerodynamics the amount of force and load will be greater, so in my case since there are only three hinges and one with a failure point the weakest part will fail due to the abrupt change in aerodynamics. Now add more hinges you are changing the load on each hinge and adding redundancy to where if one fails there are 4 more to shift the load to. Back to my case when one fails the load was shifted to two hinges and they could not take it.

Now to remove pin hinges use an xacto knife and heat the tip, then cut at the pivot point of the hinge. Next start with a very fine drill bit in your dermal and progressively inlarge the bit as you drill them out.

lov2flyrc

My Feedback: (24)

Easier way of removing pin hinges is to cut some teeth in an appropriate size brass tube, chuck it up in a drill and use it as a hole saw to cut the hinge out.
Todd

Woketman

My Feedback: (6)

Why not just cut them off flush, Dremel down the stubs and leave them in? Just mount the new ones a bit to the left or right?

SinCityJets

I have uncovered some never before seen video of this crash.....I think it is pretty clear what happened!

[link=http://www.youtube.com/watch?v=07OSy_favls]Rafale Flutter[/link]

BOP, sorry for your loss. Crap like that keeps me up at night.

josecilurzo

Ok guys,
we lost our BABY BOOMERANG, in 5ΒΊ flight, with eletronic problem in TX ou RX, but, the turbine survived !!
A guy our friend use "tape" in all the surfaces to try to prevent the fluter.
Sorry for your RAFALE.

JR

digitech

My Feedback: (10)

a ok.

rcjetmodels

Hi Jose Ricardo and birdofpray,

Sorry for your losses []

Shok

My Feedback: (28)

Here's an X-treme Rafale going in this weekend

http://www.voy-tech.net/friendsrides...afalecrash.wmv

Looked like wing flutter to me

i3dm

My Feedback: (51)

Shok thats definitely wing flutter ! what did X-treme have to say about it ?

On a different note, Fei bao jets are exploding all over the place.

there were two here in Israel (Hawk and Sabre) that crashed for reasons other than pilots error as well. [>:]