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Wot4 foam-e wing failures

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John Lee05/06/2017 11:11:52
644 forum posts
47 photos

The wing of the Wot4 foam-e mainly consists of two large full span foam mouldings forming the top & bottom skins. These are bonded together and contain some carbon reinforcements and the servos.

Yesterday at the field a club mate was performing some mild aerobatics when there was a loud 'pop' and the wing separated from the fuselage. The wing fluttered down in two parts, being the separate top & bottom skins which had delaminated. The fuselage plummeted vertically of course & upon recovery was found to have a small part of the trailing edge (about 5cmx15cm) still attached by the wing bolt.

The wing parts were also recovered and it was obvious upon inspection that the 'glue' holding the top & bottom skins had failed allowing them to delaminate, the air then entered the wing causing the catastrophic failure. The 'glue' was a rubbery compound which could easily be picked from the surfaces & had clearly failed in its job.

This is the second such failure I've witnessed recently. Two weeks ago at the RC Hotel a model lost the underside of one wing panel in flight, fortunately on that occasion it was able to land successfully & the wing was repaired with cyno.

Both models were new, it was the second outing for my club mate's model whilst those at the RC Hotel tend not to grow old!

My club mate will be taking it up with the Retailer &/or Ripmax &/or the credit card company for recompense.

Has anyone else experienced such a failure?

If you have a newish WOT4 I'd suggest a careful inspection and perhaps a precautionary wicking of cyno around the joint of the two skins.

Bob Cotsford05/06/2017 11:37:14
7880 forum posts
433 photos

Certainly the older version with the blue and white scheme could take a lot of stick, including unplanned impacts, and though I've seen the foam living hinges fail the wings have hung together. I had thought about retiring mine and replacing it with a nice new orange trimmed one but maybe not...

Neil6705/06/2017 11:47:04
181 forum posts
3 photos

Although I haven't experienced the specific problem with wing construction I have had to re-glue several parts and I, like many others I suspect, have been disappointed with the poor quality and design of these models.

Don't get me wrong, they are great flyers and I have several, but I often wonder how Chris Foss feels about the comments about the obvious shortcomings inherent in these versions (which have been covered many times in this forum).

Buying a model and then having to ditch or changing bits you have just paid for seems crazy to me but I fully appreciate why and I have done it myself. Has Chris Foss signed away his design input? I cant believe he has passed some of the clear design issues!

Yes these are made at a price, but good design doesn't have to be expensive.

John I do hope your mate succeeds in his quest for reimbursement of some kind.

Nightflyer05/06/2017 12:42:02
178 forum posts

I also fly a Foam E and have done since early March without any problem, as have others in my local club for some time. From what you describe it could well be a bonding issue of the adhesive used. The use of cyano on foam - I trust you mean a foam friendly one as there are some around which people might use one that attacks the foam.

The models are light in comparison to the full size wood and foam wing Wot 4's but would have expected a good development programme before the model went into production.

Hope you mate gets his issue sorted out.

John Lee05/06/2017 13:13:46
644 forum posts
47 photos

I don't think there is anything wrong with the design, like Bob I got the blue one years ago plus an Acrowot and a Wots-wot and all have been trouble free over hundreds of flights.

The problems I witnessed with the new orange trim batch is specific to the glue used in constructing the wing.

Nightflyer - no I don't mean foam friendly cyno. Conventional cyno works perfectly well on the EPO foam used on the Wots. I reserve foam friendly for depron & the likes.

ChrisB05/06/2017 13:35:20
1219 forum posts
34 photos
I've thrashed my old blue one to near extinction several times without any failure on the part of the aircraft. Mine looks a right heap of junk but keeps on going. I rekon you were just unlucky. Like Bob I've been tempted to replace mine...I might hang on until the tail meets the spinner again.

Edited By ChrisB on 05/06/2017 13:36:28

Simon Chambers05/06/2017 19:24:26
789 forum posts
42 photos
I had a blue one many years ago that I flew until I smashed it in. This was repaired and crashed many a time. The replacement was flown until one day I misjudged a fence trying the flying under it at ever increasing speeds! Again repaired over and over. All those times I never debonded the wing. I've had to glue massive cracks straight along them and heat up to pop out big dents, but the glue never went. I threw that one out a year or so ago when it was looking very worse for wear.

To get back into flying I purchased another this year - the revised model. I've not had debonding issues but I might have a good look at the wing to double check. Maybe they've changed the glue used? The old one was some white, rubbery sealant type glue.

I have noticed the decals have a lot less stick than the old ones. They keep on curling up and trying to depart company with the surface.

Edited By Simon Chambers on 05/06/2017 19:25:07

og05/06/2017 20:07:13
61 forum posts
5 photos

john - what did spiros say about it

John Lee05/06/2017 20:56:35
644 forum posts
47 photos

It was just repaired at the RCHotel and was regarded a one-off. The second incident yesterday made me wonder if there is a problem batch, hence the question as to whether anyone else has suffered such a failure with a new model.

Glyn4405/06/2017 21:48:50
696 forum posts
92 photos

Simon, I totally agree re the decals. The nds just come unstuck and then look really tatty. CA no use for re sticking either.

John Lee05/06/2017 22:05:43
644 forum posts
47 photos

I use UHU por to stick down any lifting decals

Guvnor05/06/2017 22:16:27
117 forum posts

I dare anyone here to ring Foss and see what he thinks... secret

ChrisB06/06/2017 00:31:36
1219 forum posts
34 photos

I'd contact Ripmax or best off going back to the retailer who can take it up with Ripmax themselves

Andrew Ray06/06/2017 08:29:14
699 forum posts
19 photos

I am not impressed with Ripmax products any more as I have had significant quality issues with 3 out of 4 purchases over the last 4 years. 3 out of the 4 had Chris Foss' name on them and 2 had faults (not limited to clevises that pulled off the threaded rods on an Acro Wot XL and a Wot's Wot wing joiner that I snapped in half because it had a large knot all the way through) had I not spotted them during the build they surely would have resulted in crashes and potential risk of injury to someone.

And now this. John, I really hope you pursue this with Ripmax, second flight on a new model this should not happen to this type of model even during extreme aerobatics and IMHO points to poor quality control and a product that is not fit for purpose. In hind sight I should have made a bigger fuss about the wing joiner but it was easier for me to make a new one. Please keep us posted.

Edit. Also meant to say the designs themselves are rock solid coming with a great pedigree. Chris Foss has probably made as big an impact on model flying as anyone. 

Edited By Andrew Ray on 06/06/2017 08:43:04

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