Another Impact bites the dust
 

Well it lasted for the summer at least. Went to the flying field today for some much needed practice, on the first flight at the bottom of the outside loop when I started pushing for the way back up the tail started the death dance and before I knew it the tail was flapping in the wind only being draged along by the pull pull cables, I just throttled back and watched it plow in. NO MORE COMPBARFS FOR ME THANK YOU!!!!! This was the second failure I have had with an Impact and don't plan on another! What do you guys think for a replacement, OTOP or BRIO? Any opinions on either? Heres some pics of the corpse. At least it's not the middle of the season.

RE: Another Impact bites the dust
 

A few more

RE: Another Impact bites the dust
 

Brios are in and in stock; if your timing is right (which is now).

Don

RE: Another Impact bites the dust
 

Brian,

Very sorry for your lost.

From the pix, it looks like you have the ladder crutch installed, and it broke from right behind the canopy area?

I know it must be painful for you to talk about it now. But, if you don't mind my asking, did you use the stock rudder, and did you install a former in front of the fin area?

I have just finished mine with all of the modifications. But, if it still breaks right around the canopy area, I'll have to re-think everythiog.

Again, my condolences.

Adrian

RE: Another Impact bites the dust
 

Adrian,
I added a former, at an angle, that matched the canopy line a little. The second that I did that the structure stiffened up remarably. Even before I glued it! There is no way that I can see these things holding-up without some internal, logditudinal support that transfers the forces in an uninterupted manner. My two were flung around the sky with no respect and they are still holding up, (Fingers crosed of course :-))

The former is sandwiched between the long brace to the stab and the servo tray on the same line. On the second one I used 1/16" balsa sheet rear long/brace glued on two rails to save weight


Eric.

RE: Another Impact bites the dust
 

Adrian, yes stock rudder was used but had it hinged with ca hinges and the leading edge was replace with balsa. Rear former in front of fin was installed. This plane had quit a few flights on it and I figured it was going to hold fine with the mods but I guess I was wrong. Think Im ordering a BRIO! Here is a pic of the rear. Good luck with yours, some last and some don't!

RE: Another Impact bites the dust
 

Brian, the Abbra is an attractive ARF to add to your list, from what I hear. Though I did hear something about no chance of receiving one until next year.

RE: Another Impact bites the dust
 

Eric,

I did added a former made out of honeycomb similar to yours right behind the canopy. I've also installed a rear former, and ladder crutch along the fuse. Also, made a new rudder out of light balsa instead of using the stock one. The only thing I didn't do was to install a cross brace along the fin like one of yours.

I actually test flew it once with Derek Koopowitz about a month ago. However, it was late in the afternoon, and I only managed a short flight. All I did was the first three Sportsman manuvers to trim the plane out - straight flight out, half reverse cuban, and straight flight back. Needless to say, Derek was rolling on the ground laughing, and I've been hearing nothing but trash talk from him since. Anyway, now the season is over, I will be spending a lot more time with the plane.


Brian,

Thanks for your reply and picture.

Adrian

RE: Another Impact bites the dust
 

EEEYikes... Not a pretty sight. I have seen this happen 1st hand. I cant believe you lost one with the ladder assembly in place. Are you going to try to get them to make good on it?

RE: Another Impact bites the dust
 

No Mike, took me three months of whinning to get the first one replaced as I think it was one of the first to fail and they claimed it was the builders fault! I would not even build it if they gave it to me, I have had enough.

RE: Another Impact bites the dust
 

Having lost models through mechanical failure, I can sympathise. It is very disheartening. Just start planning the next model and things start to get better quickly.
Sounds like the model is named appropriately..........................
Gordie

RE: Another Impact bites the dust
 

Sounds like the model is named appropriately..........................

No kidding, should have known!!

RE: Another Impact bites the dust
 

Jeez Brian, that sucks!!!!!!!

Are you sure you really want another composite plane? [8D]

Seriously, I hope you can get something built and get back in the air quick. Drop me a line if I can be of any assistance. Ocala isn't all that far away from now!

-Mike

RE: Another Impact bites the dust
 

Sorry to hear about your misfortune Brian. My Impact (boy I really hate that name now) lasted me the season and was a great flyer. It's electric and have had no structural problems with it yet. I still wonder if IC engines are too much for this airframe, but that is no excuse. The lack of support from C-ARF is horrible, and for that reason I decided to go another direction for next year. Great flying airplane, but I don't have much faith in how long it's going to stay in one piece.

Good luck with your Brio.

RE: Another Impact bites the dust
 

Brian,

Central Hobbies is going to carry the OXAI models. These are great flying models. They are not cheap but are truly the top of the line. Everybody I know that has flown one loves it. They are not cheap by any means but they perform and are built right.

I look at this way. Buy a Kit, pay a professional builder to build it and you are nearly equal money! Combine this with the quality and way the model is built and its a great model. Not for everybody for sure at the price but a great model. It sucks because I can build...but the Oxai stuff comes to me as good or better than I can do it. Especially on the painted surfaces. I was originally nervous about this. But I think a Painted wing and tail is awesome now.

I build my own models and have never been really happy with anyone else's build. But the Pinnacles I have are built the way I would do it. They have everything well engineered and it amazing how easy they go together and are trimmed out. Wings and stabs are all set and adjusted out of the box. In the 4-5 OXAI models we have flown around here....They came off the board as close to right as any model I have ever had. In fact they all needed the same trim adjustments...a little positive ion the wing compared with stock! In fact my new one only has about 30 flights on it and it flies the same as the old one. So I flew the new one at the Nationals.

Just a thought since you are looking for a model. There are lots of models that fly well out there. I just prefer the stuff I have now. Probably with the best models I have ever flown.

I'm not pushing the OXAI stuff over other models and I pay for my models from them too. But I think they are the best out there! I choose these planes for the flying and quality in them. I don't think you will be disappointed at all.

Troy

RE: Another Impact bites the dust
 

Thanks for the tip Troy! Do you know what the selling price will be on the OXAI from central?
Also I was going to ask you if you know where I can get a ZN Caprise sheeted wing, stab, and rudder? I have a Majestic im thinking of converting to pattern until I can afford to buy what I want.

RE: Another Impact bites the dust
 

From your pictures it does not look like you have a former at the rear of the canopy installed and it also looks the crutch didn't come all the way up to the rear of the canopy. The failure looks like it occured where the crutch ended...

Mine is just about finished (not painted as of yet) and I've put in all the mods everyone has suggested (crutch, new rudder, former at the rear of the canopy, former at the base of the fin, and the additional brace that Eric H. put in as well) so I'm hoping it will last. Again, this will be an IC (160 DZ) powered - I've seen 1st hand the electric powered one that FokkerPilot has and it flys very, very well.

I've also seen an electric Abbra (Jerry Budd's) and it also flies very, very well. If I had my druthers... I'd go with the Abbra but you'll have a wait for one.

RE: Another Impact bites the dust
 

Brian,
Really sad to hear about this. That was one good looking and flying airplane. This has just not been your year!

Jon Lowe

RE: Another Impact bites the dust
 

Thanks Mike, John! I will be in Ocala With my Majestic, I think I will take my time and see how some of the new offerings are holding up!
Derek, Im sure yours will fine if set up Like Eric H., I should of carried the cruch up furter but at the time I was more worried about the tail but now I see I just move the stress to the next weakest point. We should not have to do anything to them for and reliable airframe!!! Oh well

RE: Another Impact bites the dust
 

Get an Xtreme Comp Astral XX its like $2500 and built out of this cool TAVS stuff. You might have heard it was made famous by this company in China. They built the model that won the US NATS in 2004 :eek:

Just in jest. I have an Impact too. I won't build it. Its a pile and not straight. I guess at my age $800 would have bought a wild night at a Vegas Strip club. Instead I have a right wing that is twisted a full degree from root to tip. The fuse is "bent" laying a straight edge down the side, right side fits the straight edge perfectly. But the left side is low in the middle and I mean low its about 1/4" low.

Then we can talk about the fin and built in right rudder/thrust compensator. Or the weight of the wing panels.

I'm not alone here and hate talk poorly about a product. You pays your money and you takes your chances! I won't go bargain basement again. My motor, servos, radio, and my time Why would I waste all this to fly a pile of crap than could cost me even more than it already has.

RE: Another Impact bites the dust
 

Brian,

Very sorry to hear No. 2 went in with such a catastrophic failure. I remember what it feels like from Flight 19 of my No 1 last year and wouldn't wish it on anyone.

While there aren't many positives, I sense the last couple of failures have eliminated some potential causes and draw us closer to the likely cause. A couple of observations:
-- The failures aren't associated with high stress antics, mine failed pushing through an outside radius into the down line of a triangle, Brians not dissimilar, and same for two others I have talked to people about.
-- The crutch treats the symptom, not the cause. One down in Oz failed at the rear, but was repairable. A crutch was added in the rear and 3/4 of the way up to the back of the canopy, but not all the way. It subsequently failed as Brian's did, ahead of the crutch and behind the canopy opening.
-- The structural materal subscribes to Peter P's egg shell theory. When intact it is fine, when is is compromised a tiny bit it can fail completely. It seems to fail first in compression, which you see in the minor buckling/wrinkling of the surface, and once that happens all strength is gone.
-- Brian has now (expensively) isolated the hinge issue -- even with the exposed Robarts with lever arm embedded in soft balsa construction replaced it has failed.

So my guess is it points to the mass balance issue on some of the stock rudders, and there is a combination of airspeed well within the flight envelope, and perhaps a vibration that kicks it off in IC ones, that starts the death flutter. I don't know a lot about flutter but I assume it is some undamped natural frquency based vibration. The pulsing of the flutter down the fuz finds any weakness and Bang!

The lessons (aside from an aversion to flying Composites!) may well be:
-- Replace the stock rudder ala Eric H and others, and hinge it traditionally.
-- The crutch has to be one structural piece from the stab tubes through to well into the canopy area, with formers to stop any deformation of the oval structure. And as we have seen, that includes tying the crutch tightly to the rear former and through to the servo tray/rear wing brace.


An expensive set of lessons.

David

RE: Another Impact bites the dust
 

I wonder if and when CompArf will admit that the Impact was a failure from an engineering stand point and refund said money to customers that have had failures. LOL ya right, who am I kidding.

RE: Another Impact bites the dust
 

I fully support what Troy wrote below about the Pinnacles. Also the after-sales service is very good. Even when I did not complain they fixed and replaced a wing problem for me.

The plane can be in the air in only a few evenings and the trimming session is so short you keep wondering what you missed. Mine(2) uses OS 1.60's and have left an "imprint" on Mark Atwood. Just say "Lasso Grande" when you see him and watch him smile....

Regards,

Eric.

RE: Another Impact bites the dust
 

This thread is making me very nervous indeed.

Sorry about the model Brian. I think enough is a enough and comp ARF better do something about it.

Doesnt help me at the moment as mine is ready to test fly. I have had a bit of a break from modelling over the last 4-5 months so that I could catch up with other duties.

Anyway I plan to test fly in the next couple of days. I have taken every precaution I can to avoid any problem but when you look at Brian B photos it really makes me wonder. The front of the fuse will probably fall of mine because I have taken care of the rest.

I think the TVCS or whatever it is is just not suitable for this application. It might be fine with their big stuff but those things have a significantly much larger cross sectional area to distribute the load. The electric debate is another interesting situation. I dont know of any electrics which have failed yet. Is it vibration or speed as thte electrics do fly a little slower.

Mine has a DZ160 in it - The worst of both worlds.

Lets hope I dont have to make another post to this thread


Fingers crossed.

RE: Another Impact bites the dust
 

Brian,
Your funny. I got the it was your fault.

RE: Another Impact bites the dust
 

Peter,
I think that it is "luck of the draw". If you get a thin one you lose.

I have watched George Asteris fly three new IMPACTS with no fuselage issues. He killed one with a turkey-vulture. RIP both of them. He killed the other with the terra-firma between the runway and his empty fuel-tank, way down wind, windy day.

Now hear this! He is using a 1.60 DZ, Hyde and nose ring. None of his planes have the ladder and extra formers that I used. None of his planes have shown any signs of the well known failure. I know and respectfully accept that this brings no comfort to those who have had failures, but I can see how C-ARF don't really know what to do. No approval intended by that last comment BTW.

Regards,

Eric.

P.S. I did learn that thin CA destroys the strength of the fuselage material. Medium is OK but only use epoxy. - E.

RE: Another Impact bites the dust
 

Wow Peter, Great looking plane, you did a great job making it your own!! Wish you the best of luck and with the way you have put it together I would be suprised if it fails. Best of luck!!

RE: Another Impact bites the dust
 

Hi Eric,

What CG point did you and George settle on in the end?


Regards,

Peter

RE: Another Impact bites the dust
 

Sorry to hear of your loss BB.

The IMPACT is just too variable. From the findings I made recently on your first one, it makes no sense that CARF is just burrying his head in the sand. His raw material variability appears to be too great for pattern. He should bump the thickness up at least 50% on the urethane foam, like the folks at Piedmont are doing with their TAVS material.

BB, for what it's worth, Dave L is getting ABBRAs rigged up. The BRIO also appears like a decent choice

I will be back home over the TG holiday. Let's hook up then.

Matt

RE: Another Impact bites the dust
 

I'm in the final stages of building an Impact that was started over a year ago (other planes and priorities in the way...). I need to make some exit openings for hot air -- cooling the engine and muffler. I think about all the mods/additions from the other Impact build/post mortem threads have been included, but seeing the break in BrianB's fuselage go (what looks like) right through the cutout for the muffler stinger makes me a little nervous about whacking holes in the bottom of the fuselage. Any pictures of Impact undersides with cooling vents would be appreciated -- words of advice are always welcome, too!

Thanks,
Tom

RE: Another Impact bites the dust
 

I thought I'd say something good about the Composite-Arf Impact. I went for the all white/red version and decided to paint the trim colors with Rustoleum spray cans. I found out all whites were not created equal so I bought some Composite-Arf white touch-up paint to cover the seams. The results couldn't be any better so if you don't like their paint schemes don't worry, because you can make it look great with your own custom paint scheme.

RE: Another Impact bites the dust
 

I've been reading about the Impact failures and find it interesting. I have not had a composite pattern plane, so I'm speaking only from what I've read here.

This reminds me a little of a failure state in the Army OH-58A & C helicopters. These are versions of the Bell Jetranger. The failure mode is called critical tailboom dynamic mode. The tailboom would buckle at a certain spot during vibrations in autorotations. Basically, a terrible vibration would be introduced at the rotor head and then cause the transmission to start oscillating in the pylon mounts. The vibrations would travel down the tailboom in a sine wave. Once they reached the end of the tail boom (with vertical fin and horizontal stabilizer) the vibration wave would start a return towards the nose. This would meet the next wave from the transmission, and the buckling would occur at that spot.

I'm wondering if vibrations aren't flexing the fuselage in a similar way. They do damage. We would look for 'oil canning' on the panels to find small buckles in the sheet metal. Someone mentioned a nose ring set up doing well, without problems.

Or, maybe the tail feathers are flexing the fuselage and causing stress failures.

RE: Another Impact bites the dust
 

Hey OhD --

The paints look good. If your Impact is IC powered, could you post a photo or two of what you have done for venting cooling air around the muffler exit? or anyplace else for that matter!

Thanks,
Tom

RE: Another Impact bites the dust
 

Tom,

This is how I vent the exhaust

Adrian

RE: Another Impact bites the dust
 

Sorry, let's try this again

Adrian

RE: Another Impact bites the dust
 

Adrian --

Thanks for the shots of what you did. Having some vents in the engine cowl as well as the belly back by the muffler exit seem like a good idea. Thanks again! Is your Impact holding up well? After reading all the good things people have said about the way it flies, I can't wait for the snow to melt and the temp to get flyable.

Thanks,
Tom

RE: Another Impact bites the dust
 

Tom,

Make sure you have enough ventilation, especially if you are using a DZ, it generates tremedous amount of heat.

I have about 60 flights on the plane now, and its holding up well, thanks to all who contributed their ideas on modification. The plane is flying well with very little mixing. However, I don't particularly like the way it snaps, still thinks the wing area is a bit on the large side.

Adrian

RE: Another Impact bites the dust
 

I do plan to use a 160 DZ -- and being aware of all the heat they can generate I wanted to get some Impact wisdom/experience from the "field" so I could get enough ventilation but not cause unecessary structural weakness. Your pictures will help a lot. I have followed the various Impact threads with great interest also and have incorporated all the items to help the fuselage maintain its integrity...

If you're "flying well with little mixing" you must have it set up pretty straight and have the CG in a good spot -- where do you balance in relation to the wing LE at the root?

You also mentioned not being impressed with the snaps -- what don't you like about them?

Thanks,
Tom

RE: Another Impact bites the dust
 

Tom,

Mine will be electric but I'm also interested in cooling exits. I looked at Jason S's but it's tough to estimate the total area of the holes from the photos. If anyone has a successful design, I'd be interested.

Jim O

RE: Another Impact bites the dust
 

CG is set per instruction with battery pack (yes, I'm still using Ni-Cad) as far forward as possible right behind the floor exhaust opening, I'm using two Futaba 9650 on the tail. Wing and stab incidence first set at zero/ zero, I ended up with very slight negative incidence. Might not be suitable for all, but that's the way I like it for both upright and inverted.

I have the following mixes, 3% on thr to down ele, 5% thr to left rudder, 2% left rudder to up ele, 1% right rudder to down ele. As for rudder to aileron mixes, 3% on one side and 2% on the other side.

I am using a condition on my elevator stick. I normally fly with very little elevator, but, when I give it full elevator, it increases aileron, but decreases rudder throw. With my Smaragd, both the snap and spin stops on a dime. But with this one, I still haven't quite master the snaps yet. Eventhough I had over 100 snaps, it stil looks real funky, guess I have to keep playng with the throws.