RE: GP Cap 232
 

My GP Cap 232 27% Experience……………

I was in the market for my first large scale model and settled on purchasing the GP Cap 232 27%. GP have a good reputation in the market place and with spare parts readily available through tower hobbies, I thought it would be a good option. I also wanted to run a 50cc engine and reading this thread, there are numerous references to people running a DA, or DL50 engine with this model without a problem even though the ceiling is 43cc according to GP’s documentation. I decided to run a DL50 engine in mine.

The set up I was running was;

Servos: JR9411 for all control surfaces and 8231 for the throttle
Receiver JR921
Engine DL50
Prop Bolly 20x10

While I am no expert in relation to building larger scale models, during construction, I was somewhat surprised by the size of the joiner that is used to join the two wing sections together. For a 27% model that will run a 43cc engine, it appeared rather thin to me and was constructed from hardwood (approx 6mm thick). GP on there website make specific reference to this to keep the weight down rather than using an aluminium or carbon joiner.

The model went to the field yesterday for its maiden and I had arranged for the club instructor to take it up for its first flight. The machine powered into the air with no trouble what so ever. It had completed probably three circuits of the field in near level flight between half and 3/4 throttle while the instructor adjusted all the trims. All of a sudden there was an almighty crack and immediately it became apparent that something had let go in the wing at the join.

I thought for sure the model would be lost. Through an amazing piece of flying, the instructor managed to nurse the machine down onto the ground using rudder and elevator only. The wings had folded upwards about 6/7 inches at each tip. Our immediate thought was that the glue joint had given way but on inspection it appeared to be quite different. The glue joint was in tact however the timber ribbing on each side of the wing had sheared, the spar was broken, and the plate that holds the wing bolts was split in half.

The only thing that was holding the wing together was a cable tie that I had wrapped through the aileron lead holes which I was using to stop the cables from falling back inside the wing, the dowels at the front which appeared to be in tack, and the wing bolts held the back of the wing together. When we got the model back to the pits, the wing bolts were removed that wing fell in half and was held together with the cable tie only. I am incredibly lucky to still have this model, The fuse is in perfect condition however the wings will need replacing as I believe it would be risky to repair them given the potential value of the loss should they fail again in flight.

If this machine was performing any sort of aerobatics at the time of the failure, there is no question I would have been taking home a pile of tooth picks as I am sure the stress on the wing from the recovery would have broken the wing off entirely.

I have attached the photos for you guys to look at. You can see that little cable tie that I referred too. I would welcome your views although I am of the opinion it was a product failure. I do believe that the experience raises questions as to whether the wing joining method is appropriate for a 27% model running 50cc engines. Especially this is promoted as a performance model.

On a side note, the wing failed with a DL50 running at 50% to 75% capacity in near level flight. I would suggest at a 43cc engine running in full aerobatic mode would have created a similar occurance but with a catastrophic outcome.

I intend to get this fixed however I am inclined to change the joiner to carbon or aluminium and remove the DL50 for its next flight

Has anyone else had a similar issue with this model?

RE: GP Cap 232
 

Sorry about your mishap. Glad it came down in one piece so to speak. That being said, I built a GP Cap in 2007, flew and abused the heck out of it with a DA 50 in it with many many flights. Was a blast to fly, I wasnt nice to this plane at all.:D I sold it last year to a guy in our club and he put a DL 50 in it and is flying the heck out of it with no problems. I dont think its a design problem, as many people have put 50cc engines in these birds. Rather it might have been a bad wing joiner? Was the wing fully seated in the wing pocket (fuse). I'm interested in what caused this problem, like I said I dont think its a design fault.

RE: GP Cap 232
 

One question.............Did you use Gorilla Glue to join the wings together?

RE: GP Cap 232
 

Although mine remains to be built, I've always wondered about that particular issue. Joining a wing this size with what amounts to a thin plywood brace is perhaps not enough.

However, I suspect that your brace Jolly might have not been fully bonded (back, front and ends) to the wing panels as it appears that the piece came detached in flight locating the load onto the root rib joint. The bond is actually tricky to acomplish since the insertion of the brace essentially removes much of the adhesive.

My inclination would probably be to peel back the covering around the center joint, join the wing as directed and then glass the entire root area with two layers of glass cloth (6 oz followed by 2 oz) in increasing widths. The strength of this joint would be considerably higher and would distribute the stresses over the entire glassed surface as opposed to concentrating it on the brace joiner. I'd go 4" wide with the 6 oz cloth followed by 8" wide with 2 oz cloth (the edge of the fuse sides + 1").

Of course, all the other models in this series used plug-in wings. Aside from the "surfboard" wing syndrome of the CAP, perhaps the above is one reason to have gone toward alum/CF tubes and wing panels on the later designs.

David.

RE: GP Cap 232
 

Wow .. What a story... I agree.. faulty wing joiner..
I'm in the habit now of drilling small holes along the with wing ribs for the epoxy to bond to. I'm not a big fan of the 1 piece wing as the newer designs have wing tubes and the wings are so much easer ti transport. A similar story is that I have a small Reactor that had a glueable wing joint. I wasn't doing very radical manuvers and I noticed quite a dihedral when I was flying .. brought her down and the glue joint failed.
I think you should call GP and ask for a new wing. They will prolly give you one. his shouldn't have happened to you yet.

So .. so far .. Wing failues, Gear issues .. (I can't stand the way this was designed .. ie.. gear attached to engine box) , Tail heavy issues..

With that said.. I'm starting my rebuild this week of the CAP.. I'll try another season with her. But she has alot of company and compatition with all my other large scale planes I own.. so she better behave or she's a hangar queen.

One nice thing to say is that it sure is perrty sittin in the pitts..

Later Guys,

Dan

RE: GP Cap 232
 

Yup!

All CAP's do look purty in the pitts.

Speaking of CAP's some of you might be interested in a project of a CAP 21 that I've been working on. Although there must be myriads of CAP's out there by different manufacturers, I wanted to do one according to my design objectives. The goal is basically a 1980 TOC size version (90 glow in the day) with a 9.5 lb max weight. In order to achieve this, I decided to start from scratch.

I'm at the stage of prototyping the design in a 30 size version. The idea is to confirm the design, structure and laser cut on a smaller version so that I can proceed with the TOC version with whatever modifications may be necessary to insure a successful model.

Here's a link to a thread on the development:

http://www.rcuniverse.com/forum/m_9429991/tm.htm

David.

RE: GP Cap 232
 

I used the Great Planes epoxy adhesive on the brace and wing as described in the instruction manual. I am not sure what the Gorilla glue is that you mentioned. I assume its a product available in the states. I was careful in how i went about glueing the halves together

I certainly recall using alot of adhesive. It would take a post mortum on the wing to check out the bonding issue you mentioned Doxilia.

i have raise the issue with product distributors in Australia in relation to what has happened. i will let things run their course and report back on this forum to let you know how things play out.

Do you guys really think that the brace in this wing is up to scratch?

RE: GP Cap 232
 

I've had one for about a year now with no problems, 40cc gas. I'm sort of aggressive with it. Not sure what that brand of epoxy has to do with it either! From the pictures it looks like you did a good job with the epoxy! Have you contacted G.P.? Had a problem with fueling valves a while back and they stepped up and replaced them all.

RE: GP Cap 232
 

Do not use Gorilla Glue on wing halves.. It's too porious and will not hold.

The wing failure could also be attributed to a poor glue job by the manufact on the wing rib. It's not the first time it's happened to me. I had a H9 showtime last season that the wing decided to pop off in mid air from the wing root.

Call GP ... See what they say..


4 inches of snow today ... No flying. Blahhhhhhhh

RE: GP Cap 232
 

That's good to know. I've never used it, but have heard of it. No snow here! Got a few flights in this morning.

RE: GP Cap 232
 

All this talk about the GP Cap, makes me want mine back! It was a blast to fly with a DA 50!

RE: GP Cap 232
 

Jolly,

Dan's idea of drilling holes into the bracket helps to retain the adhesive and forms an epoxy bond across the bracket between the lite-ply plates on either side of the bracket in the wing. It is still beyond me how a 2m wing is supposed to be supported by a short bracket like this but so be it. Actually the height of the bracket is the key here as that is what supports the load but if the bracket detaches... well, we know the result.

The above will just help insure that the bracket is bonded across the wing rather than in a less reliable plate-to-plate laminating fashion. However, it is still a high stress point to locate the load over that single bracket even if it spread out by the bond to the adjoining ply in the wing panels. As mentioned, I would still glass the section under the fuse. If it's glassed, you could probably just insert the bracket without glue and there is no way those panels will come apart (using the right glass) - not that I would ever do that... :)

David.

RE: GP Cap 232
 

I am still waiting on a reply from the Aussie distributor in relation to the wing failure.

I did some research on GP's Performance Series models. There are five mono wing models of similar scale to the Cap 232 that are part of GP's performance series. They are listed below along with the approx release date (which i have picked up from the instruction manuals - could be out abit) along with the wing joining method for each model.

1) Cap 232 (rel 2005) Single large fixed wing with single hardwood joiner
2) Yak54 (rel 2006) 2 piece wing with carbon joiner (bolt on)
3) Extra 300s (rel 2007) 2 piece with carbon joiner (bolt on)
4) SU31 (rel 2007) Single fixed wing with 2 x timber joiners + 2 x aluminium support joiners all laminated together into a single joiner arrangement. Uses an anti rotation pin in the wing join.
5) Edge 540 (rel 2008) Single large fixed wing with hardwood joiner + 1 aluminium joiners fixed each side (2 aluminium plates in total) all laminated together.

It is interesting to note that the three models that utilise a single large wing have over time used an upgraded spar/brace arrangement with the Cap232 being by far the weakest to my mind.

I suppose you would expect design development and improvement over time. I am surprised though that there havent been more failures with the joining method on the cap.

RE: GP Cap 232
 

I really dont think its a design problem....As I told you in my last post, others including myself have put 50cc engines on this Cap with no problems at all....I flew the heck out of mine and its still in service at this time....The only thing I did was pin the firewall which doesnt have anything to do with your wing failure. I'm not 100% sure why your wing failed, but I'm thinking the wing joiner (weak) or maybe the root.........Whatever it is I hope GP takes care of you and please let us know the out come.

RE: GP Cap 232
 

Saying the root is weak is an understatement. We're talking a layer of 1/8" lite-ply capped with a 1/8" balsa root rib - not to mention that it is bored out. Adhesive on the root is simply to keep the panels aligned but supports virtually zero stress on a model of this scale. Actually I'm not sure why there is a balsa cap there other than it being more porous than ply. However, a ply-to-ply joint would already be stronger - under stress, the balsa root caps will simply split from each other at the joint with the ply rib as shown in Jolly's pictures.

No one who has had some experience building model airplanes would consider a simple root joint to be sufficient on a model of practically any scale. I'm currently building a 48" span model that has almost the same wing panel joining configuration as the CAP: 1/8 ply brace across and interlocked between ribs (therefore already stronger), and mated bonded root ribs. Even though this wing weighs in the vicinity of 10 oz when finished (therefore almost laughable compared to the CAP), the model will be subjected to the same sort of stresses as the 27% CAP. I wouldn't consider for an instant simply joining these panels and covering the wing. The roots must be glassed unless a loud crack is what I'm looking for during the first snap. The key here is to distribute the stress across the entire wing root area surface - top and bottom - not just at a truss point in the wing structure.

Although I can't put the blame on us for the failure of an ARF when assembled properly and according to instructions, taking oneself out of the ARF mentality when we assemble "production line" airplanes goes a long way. For the same reason that most everyone seems to pin firewalls in large scale ARF's (after all there shouldn't be any need if designed properly), we should also consider, keep in mind and augment strength in other key areas where the manufacturer has omitted to do so.

Frankly this sort of phenomenon only happens because these are ARF's. One would most likely never encounter this kind of failure if building from a kit or from plans - the same mentality that comes with ARF assembly just doesn't apply.

Still, a $350-$400 already built model should hold up in level flight if following the manufacturers recommendations and assembly procedures.

David.

RE: GP Cap 232
 

Seems to be your a ARF hater...........Which is fine David...................But something to remember is that the GP Cap was not designed for a 50cc engine.....So mods must be done......Take a look at the GP Ultimate thread if you want to see some mods that these guys had to do to make it "fly" with a 50cc engine.

RE: GP Cap 232
 

I wouldn't put it that way. I'm not much of a hater of anything (except some human behavior traits).

Actually, my comments are just to highlight that some building experience helps in assessing the air worthiness of a pre-built model. For the same reasons that many mods are made to ARF's to equip them with power plants for which they weren't designed, I'm suggesting that the same logic can apply to other areas of the aircraft. If we put a 50cc engine into the CAP (beyond the manufacturers recommendations) and then find that the wing snapped, well, it calls into question more than the factory design of the model.

Actually, based on what I've learned from this thread (which I've followed from the beginning), my CAP will never have a 50cc engine in it (too heavy). In light of the latest news, it might never have any engine in it. The design strikes me as a lightening project (if desired) for ~3000W (4 horses) of electric power. A 12 lb CAP would have a wing loading of 23-1/2" oz/sq ft - not bad.

David.

RE: GP Cap 232
 

I have one of the Edge 540's also. Your research is correct. The joiner on the Edge has 2 aluminum joiner pieces that are epoxied to the wood joiners.

RE: GP Cap 232
 

Im not sure I would say that a 50cc is too "heavy" in the Cap. Its still floats like you wouldnt believe and the 3D capabilities are outstanding. Was it designed for a 50cc, no. On the other hand I had a OS 160 in my Cap when I first assembled it, it came in around 12 lbs. Yes, it was still a blast to fly, but I'm a horsepower freak. More is always good, right? Maybe not so in some planes. I just hope Jolly gets his problem taking care of. I for one would really like to know what caused this problem.

RE: GP Cap 232
 

David,
The Cap will hold up to the 50cc engine just fine if assembled correctly with no modifications. I have one and my friend Chris has one. Ours both came in less than 15lbs. We abused the airplane with full throttle blenders, high speed snap etc. on a regular basis.

RE: GP Cap 232
 

I totally agree.....With all this talk about the Cap....I really wish I wouldnt of sold mine, might just have to order another.:D

RE: GP Cap 232
 

Are you a TH discount member? I have a code for $60 off $300 or more if you are!

RE: GP Cap 232
 

Don't know about you guys, but I buy GP for the airframe only. Landing gear and hardware get thrown away. The airframes are solid and fly well. Some guys don't like one piece wings, doesn't really bother me! I have a few pictures of my GP Edge, my cap is done the same way. CF gear, ball links and aluminum control horns.

RE: GP Cap 232
 

How do you like the GP Edge? What engine do you have in it?...I've always like the Edge

RE: GP Cap 232
 

Yes! I am a member, Thanks!