RE: COMP-ARF A-4 BUILD
 

cosmetics started! cut off the embossed air louvers and have done new ones with plastic stock (4 have to be done)
equipament tray done as well

RE: COMP-ARF A-4 BUILD
 

by pass and tailpiped done.
had to work a little on the back of air intakes(came misaligned)
made custom wood support for the tailpipe to hold it on the back fuselage on 2 points, later will attacj it to the bypass as well via 2 x 4 mm bolts on the underside of the bypass cover

RE: COMP-ARF A-4 BUILD
 

a few more pictures od the main equipment tray and tailpipe supports

RE: COMP-ARF A-4 BUILD
 

Today started out to be a great day. Install completed, everything functioning properly. Now is the time for the turbine run-up and taxi testing prior to first flights at BITW in 3 weeks.

Turbine and fuel systems test: A-OK

Radio Range Check: Static A-OK; Turbine running: A-OK

Control Surfaces Check: All surfaces functioning, proper directions, no binding: A-OK

Taxi test: What an absolute, abject, POS FAIL![:'(]

The weakness in this jet, and the primary reason Comp ARF factory are still the only people to successfully fly one of these, is that their nose steering system simply doesn't work! I can't tell you how many hours I have put into trying to get this system to function properly. Finally when I hit upon a combination that worked well on the test bench, I find it simply doesn't have enough power to move the nose wheel under load![:@][:@][:'(]

So now I've got a beautiful jet that looks like it should fly very well, but which I can't get safely off the ground! And other than to blame Intairco for faulty cylinders, Comp ARF has been less than useful in providing a solution to the problem.:eek:[:'(]

So now with three weeks left before BITW, my 2 year sojourn into the abyss, has to start over at square one, with the messy job of trying to develop an hydraulic steering set-up that will work under load. I know it can be done, I've seen Andreas fly theirs at Buttonwillow on numerous occasions, but when I've asked Andreas to send me photos of exactly how they accomplished it, my response from him is: "I don't have pictures of the steering. I just know that it indeed is critical and we have not gotten the manufacturer (Intairco) of the gear to admit that something needs to be done about the cylinders he is providing. "

BOLLOX!

David S

RE: COMP-ARF A-4 BUILD
 

David !

Good to see that you are closer to the final flight !

Mine also needs some thoughts with respect to the nose steering .-(

Join the club of the worst customer satisfaction index from my point off view.

This jet cost a fortune and after you paid for it - they **** you bigtime.

No help no nothing - Motors & Rotors has helped so much but still need backup from Carf.

I am still looking from official setup - nothing, nothing nothing.

Mine will be a hangar queen until someones actually fly theirs !

Peter B

RE: COMP-ARF A-4 BUILD
 

David,

Your findings and the problems we too have had along with others concern me greatly. I to have the kit and am trying to build this jet for the JWM -2013. We NEED ANSWERS COMP ARF on how to fix this issue!!!!!!!!!

On another note, I found that the gear that I have doesn't even fit the wing properly in the older kit that I bought. I bought one of the original kits and it did not come with the gear. I had to order the gear and Low and behold, they redesigned the main gear and shortened it causing all kinds of creative modifications to get them to fit properly. Moreover, they changed the suspension to an air system that is prone to leaks and isn't even remotely scale. I have found a set of springs that does the same thing and am hopeful that they will work.

I never thought that after spending so much money on a kit that it would be fraught with so many problems and issues.

Andy

RE: COMP-ARF A-4 BUILD
 

double post..

RE: COMP-ARF A-4 BUILD
 

I have two kits. both on back burner for now. I thought I had steering figured out but that was on the bench. you get it all loaded down and ready to fly and theres a ton of weight on nose.
Scott

RE: COMP-ARF A-4 BUILD
 

Gentlemen !

So what do we do !!

Peter B

RE: COMP-ARF A-4 BUILD
 

We figure out a way to fix it on our own. The factory won't help.

RE: COMP-ARF A-4 BUILD
 

Perhaps you could have a look at the Skymaster A-4 nose gear? Their version is a bit smaller but roughly the same weight according to their site.

RE: COMP-ARF A-4 BUILD
 

Long-shot I know, but has anyone ever tried using independent braking to steer?

RE: COMP-ARF A-4 BUILD
 

fellas, any chance to modify the strut by poopcanning the hydraulics and simply mounting a steering servo to the strut? (non-scale perhaps but functional) Maybe Matrix gear could lend a helping hand.

RE: COMP-ARF A-4 BUILD
 

I've not tried it on a model but that is how you steer the full size Hawk.

RE: COMP-ARF A-4 BUILD
 

Ali,

That is my next plan of action. I'll make the nose gear completely castoring and then use two proportional brake valves, one for each wheel, mixed with rudder for steering and combined for brake application. In theory it should work, my fear is if one of them locks up, ugly things will happen.

I do find it thoroughly annoying though, that Comp ARF has found a method to make this steering work, as evidenced by the multiple successful flights I have witnessed at CA JETS, and yet Andreas refuses to make the effort to share their method with the rest of us who have invested thousands in his product![:@][:'(]

David S

RE: COMP-ARF A-4 BUILD
 

Well if you need a hand at all at BITW.. I know a decent pilot who is available, and if Tam says no, then I am always around :D

I have watched Andreas and Wolfgang fly the factory one and it is almost as if the nose is castoring on the take off and landing roll as they are banging in huge rudder inputs to keep on track. Go with is like that and maybe just have the brake operated steering for slow speed manoeuvring??

Regards Al

RE: COMP-ARF A-4 BUILD
 

As you probably know castoring nose gears that rely on differential braking may require a non-scale trailing link type strut. Might work with adequate shimmy dampening.

RE: COMP-ARF A-4 BUILD
 

It might be worth having a different mix for take off. In the Hawk you only use the brake on take-off if you really have to. The idea is to line up properly and then if you find yourself going off line during take off you use (up to) full rudder and hold it. If that isn't enough then you use the smallest dab of brake possible to bring the aircraft into line. After a little bit of airspeed has built up (way before rotate speed) you don't need to touch the brakes any more. As you say, a lock up here would be nasty.

RE: COMP-ARF A-4 BUILD
 

Hello again !

A pity for the Comp ARF team I couldn't join the Jetpower 2012 this year for a little chat !

I do not modify or redesign anything - for that amount off money I have paid I will get a sollution from CARF - period !

Othervise all of you have to design a EDF ramp too .-)


Peter B

RE: COMP-ARF A-4 BUILD
 

What is funny is that they still sell this kit even though it is quite evident that they gave up on refining it and fixing known issues with it a long time ago. It's several years out now and they still don't have a manual. You get a bunch of bagged parts and there is no way to know what their intent is with half of them. I ended up making my own parts and tossing the bagged ones in many cases.

RE: COMP-ARF A-4 BUILD
 

Man this is just like the MiG 29 gear all over again. Sorry for your pain.

RE: COMP-ARF A-4 BUILD
 

Has anyone tried to find out if its the cylinders on the steering side (the ones on the gear itself) or the drive side (the ones at the servo) that are the problem?

If you purge all of the air out of the system and clamp the lines right where they come out of the steering cylinders, does the gear hold its position with sufficient force? Maybe try that with the nose gear straight and then off to one side or the other and see if you can taxi in a straight line or constant circle. If so, then the problem is on the drive side.

On the drive side, maybe you need larger cylinders to provide more force to the steering cylinders? Maybe the tube between the drive cylinders and the steering cylinders is expanding with the pressure too much and you are loosing steering effectiveness that way?

Bob

RE: COMP-ARF A-4 BUILD
 

My viewing of CARF's models would say they only have enough steering power when the model is moving too. I don't remember seeing the nose wheel work standing still and as Ali says they use full movement each way as they are doing any manoeuvring.
The other option I thought of would be a worm drive cylinder on the steering. Whether that would act fact enough I don't know, but someone would have to design a circuit to power the drive in each direction.
The steering cylinder from memory is quite small, so maybe just not possible?

Dw

RE: COMP-ARF A-4 BUILD
 

Andy Andrews I believe is in the process of building the Comp Arf A-4.

RE: COMP-ARF A-4 BUILD
 

Gentlemen,
Although it does not provide a solution to your problem, it is a bit of history that is quite relevant to the A4. As a Naval Aviation and Gulf War vet, I knew an officer back in the late 80's early 90's, I believe he was a Commander at the time who was in our sister Reserve unit out of North Island assigned to the USS Ranger, we were attached to the USS Constellation. We often did our drill weekends with each others' units when we had to reschedule a weekend for one reason or another. Anyway he was an old A4 pilot who I spoke with on occassion, I had always noticed that he had suffered some pretty extensive burns at one time or another but I never asked or assumed what had caused them. Well anyhow one weekend he started talking about his ordeal and even brought some photos that he had of the accident which caused his injury. Essentially. the nose gear steering on his A4 went haywire when he was on his takeoff roll. The plane veered off the runway and he ejected. The plane continued on then hit some sort of pumping equipment or the like mounted between the runways. The plane exploded and he had the misfortune of coming down directly into the fire. Well all of this eventually ended up as a lawsuit years later, which he won, and if memory serves his accident led to the removal of all the nose steering units on A4's. So it is always interesting to me how models can imitate their fullsize counterparts. Hope you enjoyed this story.
Cheers, Dave