SushiHunter

Sloppy engineering tolerances. Increase in the tolerance levels means increase in time/cost but resulting in better quality.....another trade-off.

Airplanes400

My Feedback: (349)

Yeah ... And far be it that FEJ would trade off their high profits for better quality & higher production costs.

But seriously, putting glue in the proper places would not increase their production costs ... unless they want to cut their costs by not using glue.

They seem to lack the capability of making a better product, while possessing the arrogance to not care about their customers.

invertmast

My Feedback: (23)

Is it worth it... Personally, for the price you pay for a FEJ model, no its not worth the expense of the original model and then having to cut into it to redesign all of th structure.
It would be easier to just use their model as a plug and splash a set of molds from it.

Does anyone else load test their models... In Europe, any model over a certain weight is requires to be load tested, it doesnt matter who or what manufacturer or plans it came from.

Here in the US, im not aware of anyone other than myself who is doing static load testings publicly. My F14 wing design is expected to withstand 10G's at 65lb wet weight, if it doesnt, it will go back for round three of structural changes.

smaze17

My Feedback: (60)

Seriously? Have you any idea how many extremely skilled builders have had issues with FEJ planes? Obviously not or you wouldn't have had the audacity to make such an absurd statement.

KENTUCKY123

Airplanes400,
I will answer that question now with one simple word, NO, but i repeat again, i am only going by the successful flights i have had with my 3 FEJ models, btw I had another 5 successful flights with my FEJ Phantom yesterday and i must admit, after reading all the negative statements here, my heart was in my mouth prior to every flight but after every successful flight, i examined the plane thoroughly looking in all the possible places for any sort of indication of failure and i could find nothing to worry me so after the 5th flight, i said to myself, by god i must be a lucky sob. Now having said that, i have only 12 flights on this plane so maybe by the 25th as you mention, i may be in trouble. I will point out that this kit is a late made kit so maybe just maybe, FEJ are improving the quality because slowly but slowly, they have been taking on board all the feedback from the guys you mention above and Dubd mentions 2 were FEJ reps, i bet that was embarassing for them and as the Chinese dont like to lose face, maybe they have slowly and quietly improved without wanting to admit that they had to improve. , I know this forum has free speech and every body is free to say what they think and pass on their experience and knowledge and i dont normally get involved in discussions here, i only started this one simply because of the way a few comments were made to philjac94 when he said he would do a build thread on the sport jet, i thought he would be doing everybody a favour by writing it but when some people started calling him a knucklehead and other insulting remarks, i took that as a personal attack on him so i retaliated in his defence and as RCKen says above, thats not on.
So now that i have said my 10 cents worth and learned a lot more from the various posts here, i will continue to fly my FEJ jets, i will watch in interest, the build thread by Phil and be very interested in his flying report.

AndyAndrews

My F-16 blew apart in the air at about the 50th flight if I recall.

KENTUCKY123

well maybe and only maybe, you could suggest fatigue or poor maintenance after 50 flights. I do a thorough maintenance check after 10 flights, i remove things to check underneath where you may not see cracks or stress without removing things, i take our the engine, i remove the tail pipe, i remove servos and anything else that moves or holds moving parts should be thoroughly checked on a regular basis, a full size aircraft goes through a very stringent maintenance check on regular basis and our model jets should be treated no differently. Just a suggestion, thats all.

dubd

Kentucky, are you flying your FEJ jets like fighters or Piper Cubs? The more like a Cub they are flown, the longer it'll last. My F-14 was fun and trouble free for 25 flights.

Damo260

I've been building model planes and flying for last 29 years so I think have bit of experience in the hobby

Damo

KENTUCKY123

Ha ha, i have never flown a piper cub so i dont know how they fly but i fly my jets like fighter jets, it has been suggested to me (jokingly) that i dont need a throttle stick, i only need and on / off switch.
I wring them out and i mentioned that my FEJ Phantom has 2 x JM 140's in it so i can assure you, it is no Piper Cub.

dubd

I have not heard any bad things about the FEJ F-4. Good luck with it.

smaze17

My Feedback: (60)

My point was that several of the guys who've had problems are world class builders. That's all I was really getting at. IMO, many of the airframe failures had zero to do with how the plane was assembled since they were obviously assemble with great care. Insinuating that the failures had to have been due to poor assembly by the owners sounds like something Johnny Wang would say

AndyAndrews

I do check my jets routinely. A jet shouldn't be fatigued to the point where the wings blow off after 50 flights. My BVM F86 was built in 2006, I am the 6th owner and it flys flawlessly without ever having to have any structural issues what so ever. I plan on flying it again at Top Gun this year and will probably end up selling it for quite a lot of money. Try doing that with an FEJ jet. I don't think there are many out there that get flown that regularly that have survived.

Just sayin...

philjac94

To be honest, I wish ARF kits would take a step back and be supplied like a lot of the older BVM or Yellow A/C kits were. At least then the builder can not only see the structure but enhance what he thought needed to.
But obviously in a time where people want to buy today and fly tomorrow this will never be the case.

AndyAndrews

This is something I can agree with. You are right. BV does everything in his power to make sure that folks build his kits properly. He gives you full scale drawings, in depth instructions, issues notams, flight envelopes, etc. Some of these new kits, even german ones don't even have a manual.

number27

let the guy get on with his build thread instead of a FEJ bash thread again. We are all tired of the FEJ bash thing. Lets see a build thread.

Jgwright

Andy

At last we are getting somewhere with this discussion. The whole issue is size. I had one of the first 1:8 scale FEJ Rafales. This is still flying and has been flown with a Jetcat p60 and more recently with a Kingtech 80. It still has the original jet pipe and retracts and the only thing that has been changed is the door rams. It is a great little plane, very little to criticise with it. Almost as soon as it came out FEJ stepped up in size. They started by making the planes as larger versions of the small designs but quickly found customers wanting lighter planes as they could not meet the weight for Large Model rules within various countries. There was a suggestion made to them to use HoneyComb. This they did and sure the planes were lighter but also more fragile. As we know the bulkheads should have been made of good quality birch ply and were not. All manufacturers had to follow suit making ever larger planes that were light and all have had problems with airframes breaking up. FEJ are definitely not alone.

Also the planes common being modelled have all flying tailplanes, and this too has given rise to problems.

The pivot position is critical (as is the construction within the stab) and not enough thought and testing has been given in using them on our larger models. There is only one person who appears to understand the forces to get this right and I know he has given advice in a number of cases. It would be very helpful to everyone who has bought a large model jet if the correct stab position could be entered in a database to enable anyone to check.

The best advice I have seen was on anther group where an Australian guy posted about how he found the correct pivot point. This was by making a test rig set up on his car. He could feel/measure the forces required to move the stab. With the pivot in the correct position the force is very little. We now commonly see hugely powerful servos grouped together to control the stab.

I have owned several small AMD Hawks. They were powered by engines ranging from a MW44 gold to a Super Sport. They were not flown gently! The pivots were 1/4" anodised aluminium rod with some knurling at the end in the stab. The planes were sold without the rods glued in the stabs. The stabs were solid balsa sheet with monocote covering. The rods were simply glued into the stabs with epoxy. I never had one of these rods bend in use and never had one come loose. These planes used just one analogue servo of about 10 KgCm. I make this point that designing for a smaller airframe is so much easier. If the stab is in the right position it gives the tail at least a chance of avoiding flutter. BVM has never made large aircraft like those being made now so a comparison with his nicely designed and made planes and the large ones does not move us forward.

Many of the problems we now have is of our own making we have asked the manufacturers to make ever larger lighter models. I too wish we could get back to smaller models, but I fear kits are a thing of the past. Many now seem to struggle to screw the servos into an ARTF airframe. There is no way we will go back to making kits.

One other thing that is constantly mentioned is that the airframes cannot get better and just want FEJ to go away. Well manufacturers do make things better given advice. I have just been converting the latest Falcon 120/navycat into a flying wing. This is just so much better than the first aircraft they produced. I had one of the first ones which were really bad in comparison. The doom-mongerers kept saying they would fall apart yet they have been proven to be one the most popular club planes.

Not all FEJ planes are constructed to the same standards. Some are really well made and fly great. I personally have not seen a FEJ plane self destruct, but from the video on youtube I can see it does happen. Some have ply formers and some honeycomb. Would I buy one now. Well personally I prefer to make unflown designs from scratch and am about to start my next one. If I was to buy a FEJ one I would look for one of the early pre honeycomb ones to a slightly smaller scale and make careful checks of the stab position and probably peel off the underside skin and check the stab anti rotation pins. I suspect the latest models are a lot better as shown by F-16 pair flying of the Bishops.

Are other manufacturers making mistakes. Well yes. I can speak first hand of one I saw that was a large ARTF jet 1:4 scale and where the pivots in the tailplane were in completely the wrong place. It crashed on its maiden despite having all the correct gear and powerful servos. After being rebuilt and with the tailplanes being redesigned it flew well. I also recall that even BVM had problems with the Ultrabandit nose detaching itself. All manufacturers prefer to keep things quiet and replace planes that have self destructed and make changes to the new ones being made. Jumping onto the Internet to tell everyone is a sure way of upsetting the manufacturer. It is less likely to produce results than quiet diplomacy.

Perhaps we can let this build thread continue in peace.

John

http://www.jgwright.co.uk

molo_30

Servos used are here. These are 30kg torque. One would think they are sufficient. No flutter on the aileron. Have a look at the angle the elevator is on before breakup. The elevator torque rod installation design is flawed. Phil it would be prudent to check these thoroughly.

philjac94

Hi Mark
Not really following you here, the Sport jet is a conventional hori stab and elevator.
I assume you talking about the F16, if so going by the small section of bend in the remaining pushrod, you would have to say that when it hit whatever was hanging from it was solid, pointing to a possible aerodynamic issue in flight.

Airplanes400

My Feedback: (349)

I think we are tired if FEJ, as well as hearing about them. FEJ is an unpleasant subject.

Airplanes400

My Feedback: (349)

First off, this is a bad design. Raising the height of the servo will put more twisting pressure on the plywood brace, the glue joint, and the structure that the plywood is glued to. Over time, the smallest bit of flexing will weaken the glue joint and allow flutter.
As a servo is raised off its mount, it allows more leverage to the arm linkage to produce a different angle of torque and pressure to the plywood brace. The torque on the plywood is no longer "in-line" with the plywood brace; it is at more of an angle to the brace.

The closer the servo and the arm are to the plywood brace, the more direct the torque is to the length (direction) of the brace. Thus, eliminating any twisting pressure to the brace and spreading the resistance to the entire brace and glued sections.

Secondly, it doesn't look like there was nearly enough glue around the plywood brace to secure it to the fuselage.

SushiHunter

Very good information to know!

Damo260

I total agree with you. I would have put some Carbon fiber cloth on top that to secure it to the fuselage better.. When I build and ARF kit such as my FEJ Hawk I go over it and do mod's and beef thing up..

One more thing I don't use any of the hardware that come with any ARF kit.. I up grade to SWB Titanium turnbuckles or AirPower Titanium Pro-links and AirPower 4-40 / 3mm Titanium rod links.

Damo

Desertlakesflying

My Feedback: (28)

AND...............Bring on the holier than thou trolls.

philjac94

With the engine rails out for painting I thought I may as well strengthen the fear main bulkhead, Not really convinced it was necessary but happy I did it now.
As standard the spar is carried in a heavily wound carbon fiber spar tube and supported at each wing root by the 6mm ply root rib and another 6mm square ply plate doubler.

The mod: 6mm ply former bonded to the existing honeycomb former and spar tube, tied in with 50mm carbon fiber tape.