Gazzer

I like RCJI magazine and learn a lot, as well as getting some great reports.

Last few issues though has seen many of the review models coming to severe grief and ending in disaster, the Lightening, The Thorpe Hawk and latterly the Ziroli Panther although less damage.

Is there a trend developing, or is it mere coincidence? Is it a lesson for all of us and a good reminder, that experience and knowledge still doesn't take the risks out of modelling, or are editorial deadlines having a less than positive influence[:-]

Discuss!!!!!

Gazzer

Shok

My Feedback: (28)

Dont forget the mig that took a year to review

Gordon Mc

My Feedback: (11)

Not sure what the cause is, but at least it's good to see that the "came to grief" stories get published too - i.e it's not all just swept under the rug in order to ensure there's absolutely no chance of upsetting a manufacturer etc.

Gordon

David Gladwin

Well, the BVM F4 I reviewed about 6 years ago is still flying, as is the StarJet, as is the BoBcat with almost 200 flights on it (as well as its XL version with 100 flights on it ) as is the Savex L39, now waiting for a MW44 Gold after 70 flights with the original MW44, as is the Skymaster Hawk, as is the FC Mig 29 as is the BVM Sabre turbine conversion.

However, the BVM T33 JPX turbine conversion went through a hangar roof at Wroughton after yet another spin (the wing aerodynamics of the original model were truly awful, dont worry Gazzer it has been improved on the AFS version ) so perhaps the Lightning was just bad luck, happens to us all !

Regards,

David Gladwin.

Gazzer

I re read my post.

Apologies to some as it might be taken the wrong way.

My reasoning was to get things into perspective. With some much electronics, and gizmos, composite structures and complex assembly...... there is one hell of a lot of things to go wrong, in use but also in preparation. Seeing how some very accomplished and capable people can suffer from some problems, and given how many models have now been reviewed, it is no surprise to me, that we have seen a few issues translate into crashes or serious failures.

Thus given this as a situation, its to RCJI's credit that they have followed the review through, complete with post mortem so that people like me can heed the warnings and learn. I doubt if anyone on this planet who either knows Tom Wilkinson or knows him by nature would think he would allow deadlines to compromise safety, but would the reveiwers unwittingly fall into a trap? Or do these more sophisticated modles need a new method to assess their build methods?

What it does show is that fallibility happens around us all, and that despite some critiscisms heading towards the manufacturer, the magazine holds fast in the review and in my view delivers a good balanced read, and has been having a run of bad luck with its review models.

Just in case anyone thought I was having a pop, I wasn't but my post did not make it overly clear where I was heading or coming from......

Too many canopy tint fumes in my brain methinks!

David,

My T-33 is so far from completion still it is more danger of rotting than crashing!!!!

Gazzer

David Gladwin

I certainly did not think there was an "agenda" in your post, far from it !

I have always tried to be absolutely frank in my reviews, doesnt always go down well with one or two manufacturers, but to do otherwise is treating our readers with contempt. That said all of the mods./ improvements I have suggested have worked in machines that are still flying !

Hope my big AW Hawks have uneventful lives !

Regards,

David Gladwin.

erbroens

Losing a lot of time, money and effort in a expensive r/c plane crash is still a lot better than losing the life in popular hobbies like motorcycling/jetski/ultralight aircraft/etc... at the same time, the adrenaline levels on r/c are as high or higher than in those activities so we are kept busy and satisfied with this model planes..(at least, this works to me)

so let the "disasters" trend continue... in our sport, crashes teaches us a lot and we get
wiser...as well as the reviewers!

Enrique

rhklenke

My Feedback: (24)

Well in the case of the Panther, the reviewer admits he's a beginner (we all were at one time). However, on reading the article, you could have deduced that by a) he used HiTech servos (and a hard-over failure almost cost him the jet completely), b) he had someone hold the model while the turbine spooled up, and 3) when the model was released and it headed RAPIDLY towards the weeds (why you don't have someone hold a turbine, you let it run a bit to get the steering straightened out before it builds a lot of speed, right?), he didn't know how to use rudder to correct it and it hit a landing light...

It might have been better to have someone more experienced do the first flight, but I like the fact that it was all out there for us to read and make of it what we will.

Bob

EASYTIGER

My Feedback: (119)

I think part of it, also, is that the big US mags will NEVER talk about a crash, even though the review model may have been totalled. For real. Seen it firsthand.
RCJI shoots straight. Each crash had a seperate cause, it's just coincidence...and honesty.

john agnew

Gazzer

If you re-read the articles the reason for the Panther and Thorjet crashes are readily apparent. The Panther, as described above was the victim of an inexperienced pilot in a cross wind takeoff situation, the Hawk, in my opinion was overweight and overpowered for the small airframe size. It never ceases to amaze me how some people think putting in the biggest possible turbine , which by definition needs more fuel,and ending up with a heavily loaded wing and still expect the model to fly well.

Eight or nine years ago JPX's, which on a good day were producing between 10 and 12 lbs of thrust flew relatively large airframes, you only need a thrust / weight ratio of 2:3 for a model to fly well, many early full size jets had thrust ratios considerably less than this, ask David Gladwin!

I do think that the suggestion that the Hitec sevo was a primary cause of failure was a little unfair, they are no worse than any other brand, I have never had a Hitec fail in the air and only one on test before installing in a model.You do need to select the correct servo for the application of course.

Colin's Lightning was a catalogue of minor disasters which may just have been bad luck as he is a very experienced builder and flyer, rest assured they happen to all of us sooner of later!

So my answer is no, it's not a trend ,just statistics!

John

TREADSTONE

I think Johns spot on with this .... the trouble is with scale Jets is the wing is on the smallish side by definition ....then when you start with some of the great detail ..(more weight ) that goes into these models + retracts and all the support gear thats onboard, if your not careful you soon have a wing loading thas very high indeed...

TS...

David Gladwin

John I was going to jump up and down because you think I am so old that I know a bit about early jets, after all, I don't go back earlier than the Vampire, Meteor and Canberra, but them I realized you're right , there WAS nothing earlier than the Vampire Canberra and Meteor so you are off the hook ! If you want to see low performance from pathetic T/W ratios try a Jet Provost 3 (There are still some around) on a very hot day with the constant thrust, variable noise Viper doing its very best to, eventually, get you airborne or a Victor Mk 1 tanker out of Akrotiri on a med. summer day. 185,000 pounds of aeroplane and fuel all on little more than the thrust of just ONE engine of a B757. We must have been crazy , but how I enjoyed every second of it , and at least no one was shooting at you ! On the other hand, want to see real performace, try an empty B767 on full power with CF6C2 engines (6o,ooo pounds of thrust on each engine . Sadly we can no longer experience the ultimate ride, a Concorde on a positioning flight from say Man to LHR on a full reheat takeoff ! Halcyon days !

Regards, David.

rhklenke

My Feedback: (24)

Just to correct this one thing, no one said that the HiTech servo failure was the cause of the crash at all. However, the author did have one fail hard-over in the model. He took it out and it did the same thing on the bench, so he replaced it. I know of several people who have lost jets and giant scale airplanes to this failure mode in HiTech servos. They were the correct servos for the application in each case, and yes, that is a higher failure rate than *I* have seen in any other brand...

No, I do not want to restart the HiTech servos vs. others debate in this thread...

Bob

rorywquin

[quote]ORIGINAL: David Gladwin

Well, the BVM F4 I reviewed about 6 years ago is still flying, as is the StarJet, as is the BoBcat with almost 200 flights on it (as well as its XL version with 100 flights on it ) as is the Savex L39, now waiting for a MW44 Gold after 70 flights with the original MW44, as is the Skymaster Hawk, as is the FC Mig 29 as is the BVM Sabre turbine conversion.

/quote]

When do you get the time to work?

Glorfindel

Quote : No, I do not want to restart the HiTech servos vs. others debate in this thread...

You dont want to, but youre doing pretty good to restart it lol!!

More servos on the market = more failure....But in % it's not the case.....

Eric Banner

Hi John,
Please excuse my snip of your original text...

There’s no doubt my Thorjet Hawk was at the top end of the stated weight range, at 17lb wet. This came about because I glassed the wings and statically balanced the elevator with 4oz of lead.

The extra weight in the elevator of course required additional weight up front. So I increased the capacity of the two Rx batteries and moved them as far forward as possible.

The MW54 turbine used was to the kit manufacturers recommendation.

The MW44 is a very good match for the AMD Hawk but I doubt its suitability for the Thorjet Hawk unless severe attention is given to weight reduction. Such as no static balancing of the tail, single lower capacity Rx battery and manual start turbine and the wings covered with film. The suitability of some of these weight reductions might be questioned in a jet.

Interestingly the wingspan of the AMD Hawk at 55.1 inches is greater than the Thorjets at 54 inches. While the Thorjet Hawk is nearly 5 inches longer at 61 inches than the AMD Hawk at 56.25 inches! They are two very differently shaped aircraft.

Having said all that, the Thorjet Hawk was a delight to fly at the above weight. Solid as a rock without feeling at all heavy. Agile when requested and the glide on landing with “take off� flap, was embarrassingly long! Not at all the flight characteristics, I would think, go with an overly high wing loading. I only wish I’d achieved more than 7 or 8 mins total flight time!

You will be pleased to hear that all three pilots survived, more or less, intact!

Best Regards,
Eric (Jet Rookie)

rhklenke

My Feedback: (24)

The statement that HiTech has the largest market share in servos is wrong, but I don't want to start that debate here, so I won't comment on it...

Bob

TREADSTONE

... Excuse my ignorance here[:@]....what does statically balancing the elevator entail, why is it necessary and how do yo go about it..?

....also what was the wing loading on the Thorjet..?

David Gladwin

8.30 till 10am on Wednesdays , vacuuming before our help comes in, plus mowing the lawn as required (twice a week at the moment ) and writing for RCJI !. However I did work from 1962 to 2001 doing 12-14 hour days, 5 sometimes 6 days a week for the last 15 of the those years, flying for an airline and running my Concorde business. I think I may possibly have earned my early retirement ! Work, the curse of the drinking classes, cheers !!
Regards,
David.

Dave Wilshere

David

Good job you never worked in the Model business with such short working hours...damm guess I was ready to retire about 2 years ago!

Dave Wilshere

john agnew

The two Davids

What a double act! We all feel so sorry for both of you. David G having to build all day and suffer that sunny weather and David W having to run a model buisness and fly jets every weekend. We did not realise how lucky we were, please accept my deepest sympathy

John

Dave Wilshere

John

The cold must really be affecting you!
HT servos as good as anything else!! and I fly jets once a month as we only get access to an airfield then (plus a few jet meetings during the year)
I'm lucky to fly three times a month out side, I do fly indoors every two weeks

Regards

Dave

EASYTIGER

My Feedback: (119)

That's so bizarre. My wife does the same thing. Wednesday mornings. She VACCUMS before the HOUSEKEEPER comes. I don't understand it, but she insists on cleaning the place up before the cleaner arrives.

E.Banner

_____________________________
Hi Treadstone22,

There are others on this forum who are qualified to answer this question, I’m not. However, having got the disclaimer out of the way, lets have a go…:-)

Static balancing of the tail surfaces is the process of ensuring that the turning couples forward and aft of the tail surface pivot point are in equilibrium when not subjected to any other force or influence other than gravity.

Or more simply, add weight to the leading edge of each tail surface such that the tail surfaces stay horizontal, rather than rotate, when released When disconnected from the servo of course!

Why is it necessary? There are those who say it’s only benefit is to reduce the load on the servo when the plane is at rest. I believe (hope!) most will agree that it is a flutter prevention measure.

I don’t have the wing surface area figure with me (I’m at work) so can’t immediately respond to the wing loading question. Not sure I have the figures at home either, I’ll try to get the figure from Peter Thorpe.

HTH
Eric

rhklenke

My Feedback: (24)

Simply stated, flutter is a resonance of the mass of the moving surface about its piviot point and a"spring" that is the stiffness (or lack thereof) of the control linkage. If the linkage lacks stiffness or the rotational mass of the control surface is large, then the resonant frequency will be lower and therefore, more prone to be excited by aerodynamic forces at normal aircraft speeds. Mass balancing the control surface about the piviot point effectively increases the resonance frequency so that it is less likely to be excited by aerodynamic forces. It also decreases the magnitude of the resonance if it occurs. It is not a definitive cure or preventative measure, but it does decrease the likelyhood of the onset of flutter at normal aircraft speeds and potentially decreases the magnitude of the flutter should it occur and thus decreases the likelyhood of surface or control linkage damage should the surface flutter...

Bob