Carbon Fibre Undercarriage

[Mastercrashman]

Hello Forum

My club recently moved to a new flying site and the grass surface is still slightly bumpy. I have just started to fly an Acrowot, so I purchased a carbon fibre undercarriage thinking this would help with landings. My landings were bumpy at times but not severe. The undercarriage started to crumble at the junction of the fuselage but was still physically sound. However it has now failed at the same point. I am more than a little disappointed and did expect more from the carbon fibre.

I would appreciate your views regarding a replacement. Generally speaking and from experience which type would you select with regards to toughness. Dural Aluminium, Fibreglass or good old fashioned Piano wire.

Regards

MC

[Richard Wood]

Hi MC,

The fibreglass U/C fitted to the Wot 4 is certainly very tough & is available

for the Acrowot.

Mount it to the fuselage with two nylon bolts & captive nuts.

Nylon bolts will shear in a heavy landing, saving the model or U/C

from damage but are strong enough for normal landing loads.

[Peter Miller]

I would be tempted to return your Carbon Fibre undercarriage as it is obviously not fit for purpose.

I have used CF U/Cs and they have taken an awful lot of punishment without any damaage at all.

[ken anderson.]

hello MC......you've been fleeced-- as the carbon undercarts under normal use(inc bumpy) landings will normally stand up well----- only failing in high impact crashes.....return it for a replacement or your dosh back ....

ken anderson ne..1. ...c/fibre dept.

[Ernie]

Hi MC, Yup, My carbon undercarriages take a huge amount of abuse..Sometimes, after a few years, they start to delaminate, but I can fix that

ernie

[Mastercrashman]

Thank you for your replies.

I sent a picture of the surface crumbling to the company before it failed completely and received an acknowledgement which said, "Thank you for you email. I will pass it on to the relevant person for him to take a look at and get to you ASAP." That was on the 27th April and the relevant person hasn't come back to me as yet. I will contact them again.

I did ask other club members if they thought my landings were "extraordinary" but none thought they should have warranted the damage.

I also have an unmade Acrowot kit which has a fibreglass U/C in the box that I could use but I am now sufficiently paranoid about my landings to look for the toughest system possible. So based upon the punishment my Tutor 2 trainer used to take, I have, this morning ordered a wire bender and will try and make a double leg U/C of similar shape and size out of piano wire.

Thank you again for the input and advice and I will let you know if I have any joy with the carbon fibre U/C supplier.

MC

[ken anderson.]

MC...the piano wire u/c wont last more than a couple of flights......it'll be prone to bending ....

ken anderson ne..1 ...landing dept....

[Mastercrashman]

Ken, I totally agree but I am prepared for this and will carry a couple of heavy pliers / grips with me to bend them back into shape. Not very subtle, I know, but it was a habit formed with the Tutor 2 - difficult to break now.

Thanks for the input.

MC ..... Undercarriage Reforming Dept.(basement)

[Richard Wood]

Hi MC,

TBH If you already have a fibreglass undercart in another Acro you'd

be better off using that as it's much better than wire. They're easy to fit with nylon

bolts & T- nuts & easily transferrable between models if necessary.

Anyway good luck whatever method you decide to use.

 

 

 

Edited By Richard Wood on 03/04/2012 15:10:02

[fly boy3]

Stange thing, but over the years I have seen many u/c ripped off in Acrowot landings compared with other models. of course this could well be, that as they are so popular there are more Acrowots around than other models, and these landings were on a tarmarced surface. Cheers.

[Martyn K]

Posted by Mastercrashman on 03/04/2012 14:15:10:

Ken, I totally agree but I am prepared for this and will carry a couple of heavy pliers / grips with me to bend them back into shape. Not very subtle, I know, but it was a habit formed with the Tutor 2 - difficult to break now.

Thanks for the input.

MC ..... Undercarriage Reforming Dept.(basement)

I had the same problem with my Tutor II. It was resolved by replacing the plasticene wire that came with the kit with some decent 8swg piano wire. The problem then was that it was simply too bouncy - think Zebedee on Amphetamines. I tamed it by soldering a 16swg piano wire brace between the legs, about 1/3 of the way down to the axles.

 

Martyn

Edited By Martyn K on 03/04/2012 15:48:38

[Mastercrashman]

Richard - Still thinking about the fibreglass and my club training guru tends to agree with you.

FB3 - Its a grass surface with a plentyful supply of sheep droppings.

Martyn - My wife likes your idea because she knows I've just paid £35.00 for the wire bender. Until recently I hadn't soldered piano wire since school days - Bakers Fluid etc. I made a long saddle bracket out of brass for the front wheel of the Tutor because a fixed wheel was less of a liability on take off (for me anyway). I used plumber's solder, flux and propane gun. Although it worked out OK I wondered whether it would have been better and more secure with silver solder. How did you solder the brace to the main legs? What solder? Flux? Solder Gun? Did you wire tie or make a bracket?

Oh, and I really know what you mean by Zebedee on Amphetamines.

MC

[Peter Miller]

Don't silver solder piano wire, it may heeat it too much and lose the springyness.

Soft solder is fine, where joining wires bind with wire, Even the galvanised garden wire will solder and work well to bind the job.

[Mastercrashman]

Thanks for that Peter.

MC

[Ben B]

But the fact remains that a CF u/c shouldn't fail except in such a bad landing that it re-kits the rest of the plane..... be intersting to hear what happens and name+shame the company if they don't sort it!

[Mastercrashman]

Ben, I feel that its a very subjective issue. What constitutes a bad landing? The Acrowot is fine. The U/C bolts are fine. Yes it bounced but not badly (I believe) and other club members agreed with me on that point but I can't prove it to the company either way. The plane is not heavy, its powered by an irvine 46.

Only one other club member has a carbon fibre U/C (from the same company) and he hasn't had any problems but he has a pattern ship and quite happily lands it like a cruise missile so fast that it refuses to bounce so he hasn't really put much stress on the U/C.

I suppose I am disappointed, however, that I haven't been contacted by the company even if it was to tell me to go away. I have now waited 7 days and will contact them again and perhaps return it as suggested earlier.

Thank you for posting

MC

[Mastercrashman]

Photos of the transverse fracture. I have found some delamination on the other leg which may be due to heavy landing or taking the stress from the fractured leg.

I have sent a new email to the company.

MC

[Hogster]

I total destroyed a travel air that was fitted with c/f u/c and apart from the radio gear it was all that survived. I`ve now fitted it onto my new travel air

[Keith Berriman]

Hi There I had s similar delamintaion on a CF U/C on a Wot 4. My solution was to make an alluminium support same width as the U/C which went across the fixing holes and about 1" down the curved section of the U/C and then I fixed the out side section with a 4mm Nut and bolt this also took some of the bounce out of the U/C. I am assuming you have a vice to bend the alli Good Luck KTB

[Mastercrashman]

I have received a reply from the makers of the carbon fibre U/C.

They have been very gracious and will send me a replacement unit on receipt of the fractured U/C.

Hogster - you give me hope.

Keith - your aluminium support sounds interesting. I had already thought of putting a tie rod across the new U/C but didn't want to provide a weakness with the holes. I assume the U/C in your system didn't deteriorate in the region of the 4mm holes??

I do have a new wire bender on the way so I may still make an U/C and put some time in with that before I fit the carbon fibre unit.

MC

[ken anderson.]

hello again MC.......good news about a free replacement...that looks like a funny type of C/F construction.....more like a C/F sandwich...with some other material in the middle.......hence why it is failing on you......maybe the light/photo angle......but to me it looks like it's not a solid C/F under cart ? ....

ken anderson ne..1 C/F doubt dept....

[Mastercrashman]

Hello Ken

Yes I know what you mean, that was my first impression but if I flex the U/C the laminates open up. Whether they are all carbon fibre I couldn't say. They seem light in colour but that could just be the resin bond.

MC

[ken anderson.]

i'm afraid it doesn't look like true C/Fibre as i know it(my opinion) ...hence the problem you are having...if it was it would take a fair bit of punishment etc...without any harm comming to it...double check the replacement one...

ken anderson ne.1 C/F doubt dept.

[will -0]

Doesn't look like carbon all the way through to me either. In fact if this is a well known company that makes reproduction parts I was in communication with them some years ago about this and they confirmed that they're mainly glass with a layer of carbon on either side. They assured me that it was impossible to make a U/C out of just carbon laminations, although I do have one I got from Westons that is carbon all the way through.

Does explain why their undercarts are so heavy!

Personally, I think it is highly cheeky to sell something as "carbon composite" when they really mean "glass composite with carbon wrap"

[Ben B]

Yes- that's "composite" in the true sense of the word. A thin coating of CF with an inner core of something different. Might even be core mat Not really surprising it broke. It wouldn't be so bad if they'd wrapped the edges to make a box section but two thin sheets of CF with something soft in the middle ? chocolate teapot time.