I too am so sorry to see the failure.

I keep looking at all of the photos and all of the fixes for clues why some are failing and some are not. There is not a large amount of data to work with.

I fitted logitudinal formers before I flew both of mine. My buddy did not. None have failed and we have been snapping them in FAI ubknowns etc, to our hearts content.

I have postulated that the rudder "death dance" could be a culprit. That made me put on two new lightweight rudders. He did the same.

I noted that in mine the logitudinal former is glued to the former in front of the stab. Thus making continuous force transference to the stab tubes etc. Could or would this make the difference? I don't know.

I did note that all of the ones that I know are using at least the lighter rudders. Could it simply be that the mass of the somewhat heavy stabs and the heavy rudder could be too much for the narrow neck just before the fin? This would be even heavier if rear elevator servos were used.

In any event, if I were building another IMPACT I would put a former lengthways from a balsa sternpost, glue it with sub-formers to the stab-tubes, and extend it past the narrow part of the fusealge.

I would, and have, run another former at an angle from 2/3 of the way up the sternpost, again, through the narrow section.

I would run 1/4" square strips all the way from the front to the sternpost and crossgrain sheet between them with 1/16" balsa. (I did this on #2)

Regards,

Eric.

P.S. I flew both of mine in a competition this weekend and they handled the P-05 snap stuff just fine. All they need now is a better pilot.

Eric.

Eric all that is fine and good stuff. Don't you think that C-Arf should be incorporating those mods into the new stuff that they want to sell? I would think that they open themselves up to serious product liability by ignoring the situation. After all an out of control pattern plane can do someone serious harm. Mike

I agree with Mike.

Comp ARF should take the steps necessary to fix known problems that will make their product SAFER and more RELIABLE.
I recently ran across a thread here on Rcuniverse for the Quique Somenzini Yak-54 102 in. and was extremely impresed when Quique himself join the post to answer user questions and to warn every one that they had found and issue with the wings that might cause a flight failure. He went on to suggest a fix for the problem and assured everyone that new wings would be shipped to everyone that owns the model. No one to date that I know of has had the wings fail on this Yak, except for one of their factory pilots Andrew Jesky, and if you've seen the ending of the XCF 2005 video, no wonder he was able to break these wings. The point here is that Quique didn't have to come forward and make his customers aware of this, and chances are that even if one or two incidents occurred they could have kept things to themselves and saved a lot of money. But here is a guy that cares about and is proud of his product.

Quique just got himself a new customer...... I've got my 102 in. Yak arriving tomorrow.

Don’t expect CARF to help out with broken planes. With mine I knew that it was partially my fault because of the rough landing (Stall from about 3 feet trying to miss a barbed wire fence.). The chin cowl just touched the earth with pretty much no speed and the tail wrapped around the plane right where others are breaking in flight. No other damage to the plane except for the damaged chin cowl. I had asked them if they would meet me half way on the parts to get the plane back up and flying. My plane was one of the first to hit the states. There were no stiffeners, no formers and no directions on how to setup. There is a know issue with the plane, CARF knows they have an issue since they now add a tail former and a depron fuselage stiffener from the tail to the wing. I would need a fuse, chin cowl, and hardware pack to get the plane flying again. CARF first said no, when I pointed out there known problems they came back and said that they would pay for the hardware pack. I don’t believe they care about pattern or pattern flyers. They have more then enough business with there scale aerobats. If they lost all sales of the impact it wouldn’t hurt them in the least. I’m not going to buy replacement parts, there are just to many good planes out there with people that will back there product.

Hello:

I purchased an Impact early in the year. I have not touched it. I am pretty pissed off that I paid almost 1k for a !QUOT!piece of crap!QUOT!. There are enough documented failures for me. I feel I got screwed and do not feel WARM about selling it to anyone else.
Gentleman what are my options. Does anyone know about a class action suit with CARF. Is it logistically impossible because they are out if country?

--john lees

GreggG

I am not denying that C-ARF have a problem but the model is certainly capable without the mods David S made. Lets not forget that Jason S won the US Nats in FAI just last year with the exact same model in stock form.

Jason could probably win the nats with my 4 year old Phase One. I plan on using gas/glow engine not electric. I believe electric would be much smooooooother as it lacks the pressure pulse from the piston firing.

Lets see about the mods. make new rudder -- replace rudder, don't put servos in stab. I bought 2 $80 mini digital SA's. Replace wings and somehow strengthen the fuse so it doesn't break. The factory fix just moves the breaking point forward a couple of inches.

I love the new instructions explaining how hard it is to manufacture, and how lucky I am that they went to all the difficult manufacturing processes for me the consumer. The fact that it is an inferior product with a potential safety risk is a side effect. --john

My current goal is figure out the problem and help folks fix it. The more we can help each other the more of us that will have sucess with this plane.

I am not a Composite-ARF rep. or connected to them in any way. I am not a person that would back away if I had a case or a campaign to run. But so far, as an individual, I can only represent my own problems and I have not had any. I. like many others, have benfitted from this topic of discussion and taken preventative steps.

I we were sure why some break and some don't I would then know what to really do.

If mine break I will act as I see fit. Untill then I am passing on all that I know so that may or will prevent the "breaking fuselage" problem.

Regards,

Eric.

Hi Mike,

Take a look at the Liabilities section of CARF's website, I think line 1a sums it up!

I too will be spending my hard earned sterling elsewhere in the future, even though my Impact is still flying and I'm really enjoying it. A really sorry state of affairs for an otherwise totally capable company.
It would seem that Queque's approach would be the ultimate answer to the purchasers problem with this one, just a shame that certain people can't find it within themselves to put there hands up and sort it out in a gentlemanly way.

Andy.

Andy, written wavers don't do any good for a flyer that injures someone else or the innocent victims. It's just poor business and moral ethics to have a safety problem and not address it in a responsible manner. I would have a problem with trusting the soundness if I owned one of these planes. I say this because my friend and fellow flyer Bill Brit has lost 2 of the C-Arf planes and I have been witness to it. He is a very capable builder and flys as calmly as could be expected with the plane. To those who havn't experienced an issue with the plane to date I can only say that it doesn't mean that you won't. Safety starts at home boys.
Eric I hope you didn't think that I was implying anything to you personally. It just seemed to me that the modifiacations that you were refering too were a way to fix C-ARF's problem when I think it's something that they should have already done themselves. Thanks for letting me view my opinions, Mike

Mike,
I am very comfortable with the way this discussion has gone and I have no problem with anyone expressing how they feel about this plane and its failures. I only wanted to state where I was coming from.

I would say that it is more effective to go straight at the vendor rather than try and put them in a corner in a forum. Having said that I do agree that a more pro-active response is needed in this case.

The problem is that we know it is happening but;

a) We don't know why.

b) We don't know for sure what will prevent a failure from happening.

If it were my product I would be trying to make it happen with tests on models and recall the failed ones for analysis etc. I used to be a QA manager for software and basically resigned and took a job with another conmpany when I was given the blatant order to "Ship now, fix later". [I later attended the meeting when their products died]

Regards,

Eric.

> The problem is that we know it is happening but;

> a) We don't know why.

Eric,

I don't have an impact, but I have seen CARF products. They are unique among other plane manufacturers in that they use a polyurethane foam shell for the entire fuselage. Other manufacturers use different materials. I speculate that the CARF formula works fine for larger models because they use a thicker wall, but that it becomes very weak and vulnerable to failure as the foam wall becomes thinner. This again is pure speculation. The cause may be more towards what you are thinking -- like an aerodynamic problem, perhaps a heavy, aft-balanced rudder. I think it is bad material choice/poor engineering.

Any thoughts on this idea?

David

In my line of business, I review various machinery vibration analysis reports. From my observations, most of the failures seem to be in front of the stab in the narrow fuselage section. There are a lot of factors that can affect fuselage failures. Resonance is one issue to be investigated. We know the YS four stroke engines have a different vibration pattern then the two stroke engines. The electrics seem to have relatively low vibration amplitudes. It would be nice to survey the failed planes and see if there is a common arrangement. Just my $0.02 worth.

Steve K.

Hi Mike,

I'm sorry if my last post left you feeling that I agree with the disclaimer, fact is I don't. I simply highlighted the info to hopefully shed a little light on the possible causes for the manufacturers being less than favourable when we the purchasers contact them regarding issues of this nature with one of their products. One of my e-mails to CARF actually called for a global announcement with regards to the safety aspect of these failiures in their product, their reply was that they had carried out extensive testing with their factory test models and could find no conclusive evidence to the problem. Strangley enough, within a few weeks an announcement was placed on their website outlining the possibility of a failiure of this nature with this product and suggested a possible fix which was the horizontal fuselage brace!
Kind of a smack in the face, don't you think?!!
As a so called "end user" I am constantly pro-active with regards safety in aeromodelling and do feel that the extra strength that I have added to my fuselage has, if nothing else, raised the safe operation of the model to a level that I'm more comfortable with, only time will tell.

Eric, I agree. Seemingly cornering the manufacturer via a forum is not the answer and I don't feel that that has happend. I do however, feel that customers of any nature deserve a certain level of product support, but when it comes to safety it should be un-conditional!
Imagine if these models were automobiles falling appart as you drove them down the street............................ their both capable of mass destruction. Just my opinion.

As I've said before, a real dissapointment when the product/model has such great potential.

Andy.

Hi Andy I was cool with what you had stated. I was just venting a little. Sorry if it seemed otherwise, Mike

(Post #661)

Hello BillB.

It appears to me from the way you are describing your fuselage reinforcement, that you may have created a significant stress riser (stress concentration) just at the rear former, where the foam plate ends. In my opinion, (as a structural/mechanical engineer) it is very important that the plate/shear web is continued all the way back to the sternpost, or at least to the stab tube. Think of the fuselage as a beam in bending, where the fuselage sides are the flanges, and the foam plate is the shear web. If the shear web was to suddenly stop, then you would have a very high stress concentration at this point, and local buckling would be likely to occur.

Eric Henderson wrote in post "676:
I just looked at CARF's Impact Instruction Manual Update, and this is the way they (now) recommend that the fuselages are reinforced, and is also the way new kits are being supplied. The longitudinal former behind the bulkhead prevents a sudden stress concentration. (Assuming that the foam plate is in place)

It would be interesting to categorize the failures uccurred so far, i.e.
- No modification at all
- Modified with what I call stress risers
- Modified with continuous plate/shear web
- Any other modification

Any reports of failures with the recommended fix? (I have not read all 691 posts in this thread, sorry.)

Just my observations and opinion, I could be wrong.

Magne

Hello Magne,

I had installed a rear former and a horizontal plate, just as is recommended in CARFs update on their website. I also had installed a bulkhead directly behind the canopy. From that bulkhead to the rear former I installed a 1" thick piece of foam horizontally. It was glued to the sides of the fuse and to the former . The break in the fuse was right at the former. The glue joint between the former and the foam stiffner had not broken all the way through. I had my elevator servo mounted between the wing. Except for using a bellcrank in the tail with pull pull cables back to the servo, and real Robart hinge points, the tail assembly was stock.

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Hi Bill,

Was the horizontal foam former you installed laminated with anything ( balsa - glass cloth)?

Mystified

Regards,

Andy.

Hey Mike, no problem!

Magne,

My fuselage failed on it's third flight. I had at this point only flown the model in very soft trimming flights. After landing on the third flight I noticed a vertical crease on the right hand side (viewed from rear) around 4" (100mm) in front of the fin base former, there were no unusual sounds from the plane as it was being flown ie: flutter noise or similar.

I have repaired the fuselage with 4" glass cloth all the way around the inside of the fuselage at the failure point and then I have installed a horizontal 3/8" square balsa ladder from the wing dowels to the finbase former. I have also installed a 45 degree former from the finbase former rear, to the rudder stern post (notched in). I have removed the false hollow leading edge on the original rudder and replaced it with a balsa bevel edge. I have also installed 5 Robart hinge pins
instead of 4. I decided to change the latter because I felt that far too much play at the hinge points could be an issue.

Since carrying out the changes to my Impact, I have had many flights all of which included snaps and spins and so far so good.

The model is YS 140 powered.

Regards,

Andy.

Still no reports of failures with an electric?

JAS,
Hows your Impact holding out, any chance of some post flight info regarding your E-Powered version?


Andy.

Anyone know of any failures with the new crutch as installed from the factory?
Thanks
Stuart

Hi fishgod!

How is your Mintor 3M 170 coming along? Is that the right engine for the Impact? Can you recommend this engine?
Greetings
Roman

Last time I looked at this post there were maybe 16 pages of complaints. I am amazed that there are 28 whole pages of shtuff relating to this problem now. Questions and answers are no different now than they were 28 pages ago. Since I wrote quite a bit on the problem and fixes a year ago, I realize that I wasted my time. CARF obviously doesn't listen well.

The best answer for this particular plane may be "don't play with it", no matter how low the price gets. CARF will be forced to either fix it, or pull it from the market.

On the other hand, it seems that something positive has come from CARF's pricing. It has kept other manufacturers' pricing fairly low.

MattK


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