August Issue Feedback

[David Ashby - Moderator]

Thanks Peter, you've made your point now ;-)

David

[Chris Dickens]

Graham's editorial has hit the nail on the head regarding ARTF undercarriages, for years I have been telling people to learn to land rather than moan about weak U/C mountings and I have never had a problem, but the two of the last three small electric models I have built for review (you'll have to read the opposition to see them)have both had ridiculouly weak areas around the legs and the last one completly pulled out on a greaser of a landing on the first flight. All I can think is that the manufacturers must carry out all their test flying on billiard table smooth runways or, more woryingly, don't test production models.

[Graham Ashby 123]

I don't know about you Chris but some of the undercarriage installations I've seen recently seem more of an afterthought then anything. When you consider how fundamental it is to have a decent u/c on a model it's pretty poor when they can't even survive a greaser on a stretch of mown turf. Let's face it, faffing around with a weak undercarriage is as detrimental to a good days flying as a dodgy engine. Most annoying.

[Chris Dickens]

I sometimes think that a prototype has been built then somebody thinks that they will play around with the fancy CAD program and put in lots of lightning hole to make it look nice, forgeting that they are also taking away strength. It might be OK in a kit when the builder uses plenty of epoxy but when there is also a lack of decent glue then it is a recipe for disaster.
You can leave the U/C off a sports model, but a Yak or Extra has got to have it on to look right.
As Grahsm says, most annoying

[Mike Rolls]

An example from a recent model - 4 lb AUW, 60" span and the U/C was screwed to an 1/8" ply plate jut glued to the fus sides of 1/8" balsa with a doubler of either balsa or lite-ply (can't remember which and the bits have been binned after 'modifications' had to be carried out).
So the whole landing impact was being taken by two glue joints about 2" long by 1//4" wide.

Mike

[Peter Miller]

I feel that the very weak undercarriage mountings on ARTFs (and I have seen quite a few in the club) are further proof that the people who engineer ARTFs know nothing about models.
I say this because any real, experienced modeller will know that a heavy landing can bend 8SWG piano wire quite easily and that it then takes a vice and heavy hammer to get it back to its original shape.
That is an indication of the load imposed.
When you add in the factor that the ARTF undercarriages are normally dural with no rearward flexing it is no wonder that they just rip out the pathetic mountings.

[David Ashby - Moderator]

Absolutely Peter.

It's funny how we tend assume that the folks who design these ARTF's must have a superior knowledge of model flying? I'm rapidly coming to the conclusion that they may be, in many cases, pretty raw beginners with limited, or non-existent flying experience.

The good ARTF distributors do have a hand in the design and production process and will reject poor models - Hangar 9 and J.Perkins with their Seagull range are good examples. Clearly some other distributors never go near the factory and just buy whatever leaves the factory gates.

David.

[nasa_steve]

well from experience i reinforce every ARTF undercarriage mount i have i've been doing it for a few years now and i've been lucky since then i've not lost any. i use 30min epoxy and a patch of carbon fibre cloth works every time
regards
nasa

[Peter Miller]

One of the secrets of strength without excessive weight is this.
Spread the load and taper the strength off the further away from the maximum load areas.
This was something that I was taught on my Airframe Fitters course in the R.A.F. about 51 years ago
A suddent change of section is always a weak point and stress area.
For example spars should be thick at the root and thin at the tip.

[Bill Courtney]

Im not surprised that the right undercarriage leg ripped out of the F5E Tigre on landing as from both of the flying shots it appears that the nose leg has a great twist to the left. Upon touch down the aircraft would have veered to the left placing the weight of the model sideways on the right leg. Perhaps a field repair to the nose leg was not such a good idea. A proper repair in the workshop may have enabled the leg to be put on straight and the plane may have survived for more than one arrival.(maybe at least three). Beats me how it took off in the first place.

[Slopetrashuk]

From memory - the nose leg collapsed on the taxi to the first take off run. It came about from a total delamination of the 'plywood' making up the bulkhead that the nosewheel was mounted to. As this bulkhead is built in to the fuselage and way behind the motor bulkhead or in front of the wing mounting bulkhead it is totally inaccessible without sawing off the complete nose of the model.
It held together for a take off and was still in the air with the model riding on the mains when the right hand main leg ripped out from the mounting. (wanna see the pics?) Had the wood just given way the damage may not have been so bad but the leg tookre the plastic retract moulding with it along with much of the bottom wing skin. Not a blob of excessive adhesive in sight!
The grass was fairly short and the runway quite smooth. The landing a greaser in every sense of the word. Just crap building I'm afraid. Inspecting the replacement wing gave us no reason to believe that this would perform any differently.
Google it up - There is loads of stuff about the VMAR range of prop jets and their instant retracting non retracts.

As an aside Bill, wouldn't you expect a decent undercarriage to be able to handle any slight shift to the side or bumpy run along the floor without collapsing? It sounds as if you're trying to excuse shoddy products though I'm sure you're not.

Andy

[Peter Miller]

The BMFA has a reporting system for ARTF faults. I suggest that everyone uses that.
They do get on to the manufactures/importers. I know because I reported a major U/C failure on a Baby Boomerang owned by a club member. The retratcs started to rip out on take off.
There was not glue holding the retract bearers to the spars.
When the owner started to repair it he was able to removed the entire bottom skin without any problem, again, no glue.
It hasn't failed since inspite of numerous landings and take offs from grass strips.

[Bill Courtney]

Andy. I am certainly not trying to excuse shoddy products, it was just an observation which would not have helped an already weak structure. It was good that MacGregor were kind enough to send a replacement wing(did they know that it was for a review). When I wanted a replacement canopy for my VMAR Chipmunk I was told that no spare parts were available for any of their range, forcing me to construct a new one from ply and clear plastic sheet. The plane flies so well however that it was worth the effort. I have also owned a VMAR CAP 232 which again flew very well until an incorrect rudder input during knife edge resulted in a meeting with terra firma. If I was flying my Acro Wot at the time im sure that the damage would have been repairable, however because of the brittle wood construction, the plane was just a pile of splinters. My favorite ARTF at the moment is a Ripmax Bossanova which is just superb with a JEN 56 in the front. The build quality is very good and all for a very reasoable price.

[Dead-stick]

Hmm, can't say the same about my Ripmax Citabria Pro, Bill, the undercart has been re-attached 3 times now as the mounting block has very little to adhere to. And before any bright spark says learn to land, I am a well practised and gentle lander (is there such a word????), but I do fly off a couple of f**tb**l pitches!

[Mike Rolls]

I think one of the mistakes they make is the over relaince upon a rigid U/C - CF, GF or alloy, with no consideration of the degree of flex it can (or can't) exhibit in relation to the likely landing stresses. Torsion bar wire U/Cs are much more forgiving in this respect. I usually use them in my own designs - once mde the mistake of re-usinf a CF U/C from a time expired model weighing a bit over 4 lbs in one weighing just on 3 - much to rigid - lands like a kangaroo in a hurry!
Mike

[scott cuppello]

I was quite pleased to see a "harder" and more "critical" stance than Iv'e seen since I started buying mag's again.

One or two that Iv'e read in the past from various sources severely dented any faith I was likeley to have in magazine tests, as they were obviously garbage, based on my own problems with the same aircraft. [one example simply didn't fly!].

I must admit, a few keep going on about "too much electric" [the only stalls mad busy at Cosford were the EF ones, I couldn't get near them!], and "too many ARTF's"....well, can we please, please, please see an end to the 'Super Ace' articles? I'm bored stupid with it, I saw plenty of scale aircraft at Cosford that were worthy of more than a photo....why not feature one scratch built, privatly owned scale aircraft per month? Couple of pages should do it....and more jets!

[David Ashby - Moderator]

Scott

The last Super Ace article has passed. Jet article next month.

David.

[Peter Miller]

I have just been asked where to get the canopy for my CAP 21.
I did put all the addresses and telephone numbers etc for the various items at the end of the text of the article
Please ask the editor why they were not included in the article in the magazine.
Anyway, Here they are again folks.

Photosets from Practical Scale: Check out This website for sets of pictures:
http://www.toni-clark.com/english/modelle/cap21/cap_foto.htm
or Email [email protected]:

Canopy from Vortex-Vacform at:
http://www.vortex-vacforms.co.uk
or phone 01162 207080 after 6 pm

Vinyl lettering:
Email: Nick Attridge on
[email protected]
or check out eBay as they may be listed there after the plan comes out.