pocatosaras

Well......

I decided to go out today to test the newly beefed up landing gear on my CMPro Super Chipmunk (see Thread -- http://www.rcuniverse.com/forum/m_34...tm.htm#3468695).

The day was beautiful post Wilma here in the Sunshine State. When I got to the field I noticed that we once again had a crosswind from the north sporting steadily at about 15 - 18 mph. Not too bad as I've flown in this condition before. Today the temperature was down to a chilly 65 degrees though and the last time I flew it was 20 degrees warmer.

A quick range check and she's started and ready to fly. A takeoff across the runway and she's airborne. A flew fly-bys at half throttle as I trim out the airplane then throttle up to gain altitude and.... oh no a dead stick from my OS .46 FXi. I've got it though.. not to panic. I've had several successful landings with a dead stick. Today however the crosswind is giving me a fit and I'm down wind. I line her up to the runway coming back upwind at about 15 feet off the deck. I'm still a little too far from the runway when she stalls. She's still horizontal to the ground coming down but the landing gear sinks easily in the soft ground (Wilma dumped a lot of rain) as it hits the short grass west of the landing field.

Noses over and breaks the prop. Ripped the gear right off the wing... ouch! Fortunately the plane sustains no colateral damage.

Back to the bench for more LG repairs. (sigh)

rjm1982

Not busting your chops, but did you have enough epoxy on that gear?

I've never built a in-wing gear setup...so i'm speaking out of my realm of knowledge, and im not accusing, just wondering for personall knowledge...

Usually the landing gear blocks and firewalls are the messiest looking parts of the plane from all of the epoxy....

Interesting

shag555

The way I understand it, these type built-in wing LG's are notorous for failures like this. Get to your LHS and buy a set of aluminum gear. You'll be better off with extra clearance and won't damage the ribs / sheeting anymore.

MPB

pocatosaras

Triple5 -- I was thinking in the same realm as you with aluminum LG and spoke about it at the field with a few of the guys and got mixed feedback. Some say rebuild the wing, some say aluminum gear (AG). Take a look at the pics below. I had an old AG setup and put it on just to see what it might look like. This is a mock up only, in fact the fuse is just resting on the AG. The one concern I have is gear height (about 3 1/4") -- do you think that's high enough?

rjm -- Plenty of epoxy. The problem is I epoxied to the balsa without much hardwood support underneath. My bad and a lesson learned.

I appreciate continued observations and feedback.

CGCOMM3RET

Not that I know much about building planes (my trainer is still sitting on the shelf waiting for $$$ to get more stuff for it [8D]), but the AG looks good on that plane to me. I hope u weren't using that STAR WARS book for plans when u repaired it .

Either way, nice looking plane. Glad there doesn't appear to be much damage.

Larry

pocatosaras

LOL, yeah... apparently the wrong FORCE was with me (my 3 yo's book for the record that made its way to the table!!).

308jockey

An aluminum gear would be butt ugly and this is an easy repair. Put some triangle stock on each side of all three ribs so that when you put the block back in it will be touching the triangle stock. Make it long enough to be attached to each rib for at least 3/8" on either side of the block so it has plenty of rib to use for support. Epoxy or yellow glue all of it together and the only way it will come apart will be to destroy the wing. This is maybe an hour's work if you watch television for half of that time.

Rick H.

rjm1982

im with the "fix it" crowd...it looks silly with the AG on it...maybe when you put it back together...glass the area...

nitro wing

My Feedback: (1)

Fix it.the AG is ugly on that bird.Double check the alignment and forward angle of the gears and wheels before gluing everything solidly.

Sukhoi_Madness

Exactly!!!

The AG looks crap... I followed you other build threads on breaking the gear the original time and them fixing it...

The fix was not the right thing to do obvisously... (Good thinking though)...

But now you have the chance to build in a proper landing gear plate (as described above) on each wing and keep the Airplanes good looks so go for it...

Matt

Sukhoi_Madness

Just incase you wanted to use the AG... The one in the picture is not big enough in my opinion...

Matt

forestroke

pocatosas - well i hate to be right in this case. IMHO, the original blocks didn't have enough epoxy on them anyway! they came out very "clean" instead of bringing some balsa and ply along with them. in fact, i'm willing to bet that even with the original setup, with the exact same landing, the blocks would've ripped out anyway. so don't be too hard on yourself!!!

as for the aluminum gear, i'd rather see a chippie with the original gear.

shag555

I'd agree with Matt. The gear you show is too short. If you go with AG, get another 1 - 1.5 inches clearance. Make sure you have something to bolt it to in the fuse, too.

These guys are probably right, you could repair the gear you have the right way now. I just hate winged gear, and the fuse mounted gear would be an easy fix if that's what you're looking for.

MPB

pocatosaras

Ok, I'm convinced. You guys are awesome and I appreciate the candid responses.

I'm doing it. I'm going to fix it right and use triangular stock and rework the internal hardware to make this right. All I need now is a good TV..........

I'll keep you posted with progress. Thanks to everyone.

forestroke

when you rework it. the important thing is to make sure that the block around the vertical part of the gear covers it completely and touches all sides of the reinforced rib.

if i were you. i'd be inclined to send these pictures to CMP to see if they'd replace it with a new wing. i mean from the pictures, there doesn't seem to be ANYTHING holding it together! if there were, your first problem wouldn't have arisen. looks like the ply was just hanging in air, unsupported by the sides of the rib. that allowed the ply keeping the gear vertical to break. if it had been properly glued, that wouldn't have happened IMHO.

i don't know... here in taiwan, and equally so in hong kong, you don't get much customer service... but in the states... i'm led to believe you can probably get them to do something. what do you think?

308jockey

The downside to that is that if he gets a new wing it may be no better built than the one he already has. At least now he can install the gear blocks properly and do any other repairs so it will actually be better than new.

Rick H.

pocatosaras

Good food for thought forestroke.. the gear stock was poorly built. It looks as though there was very little of anything holding the assembly in place originally. I'm inclined to agree with 308 though... I can rebuild it better than new now. CMPro is out of China with a Canadian distributor (Jet-Hobbies). Though I've not asked them I don't know what they'd do for me.

Tomorrow I'm off to the LHS to get the parts I need (Disney World visit today with the little one -- one of the many joys of living in Florida). I have to work for the next four days but I'll get it started.

I'll post pics as the progress moves forward.

poca

forestroke

never a downside to a free wing :-) you can easily open it up and go over everything with epoxy.

but you're right... maybe less work just to repair it given that nothing other than the balsa skin seems to be damaged. good luck on your repair!!!

i'd take off all the balsa from the wood blocks so that you can mount it in the original location rather than on the extra block you had. add a few more layers of ply around where the wire sticks through the wood, resheet with balsa and cover. it's not going to be fun, but it'll be better. triangle stock may not be necessary but always a nice touch.

had there been enough epoxy, the block should've taken a lot more of the main spar with it... lucky? or not :-)

cmulder

If the joint would had hold the wire of the landing gear most likely would have bent and absorbed the force.
From what i can see in the pics it looks strong enough to me so i would sugest to just glue it propely this time. if you want to "play save" you can always glue a block of spruce vertical to/against the spar so that you need to drill al hole in the center to absorb the force of the end of the wire that goes into the wing.
A size bigger wheels also helps.

Btw when you are working on the plane why not mount the airlon servo on its side in the wing instead of this ugly cover?

pocatosaras

Quick update -- not a lot of time the last couple of days. I reenforced the ribs with triangular stock and installed a 3/4" oak dowel as suggested by Geistware and MinnFlyer in an earlier thread. I used wood glue here and after it's completely dry I'll hit the joints with CA. (Picture 1)

I've got a template ready to go (Picture 3) to insert in the wing structure made out of 2.5mm aircraft ply (Picture 2). I'll cover that with 5mm aircraft ply and rout a gear track for the LG. A 5/32" hole will join the two aircraft plys and the 3/4" dowel for the LG to insert into. This should really secure everything. Cover it with 3/32" balsa and it's ready for a new cover. I'm going to tear off the blue and white and recover completely with Monokote.

A good learning experience for me.

forestroke

okay... i didn't think that's what you mean by using triangle stock but :-) works!

there shouldn't be a gap between oak dowel and the main spar, you should try to get that joint as strong as possible since right now it looks like you've glued it to the balsa skin on the other side. make sure you glue that dowel firmly to the block. but otherwise the fix looks fine.

remember, you don't want to make it too strong... i know that sounds counter-intuitive... but if you make it too strong, next time you have a very bad landing, you could take out the entire wing. what you've done is just good enough! just make sure that it gets enough epoxy this time!

pocatosaras

I know it's hard to see but there is glue between the dowel and the rib. I'll be sure to add a little more for good measure.

pocatosaras

I'm pleased with the progress and feel this fix will be pretty solid. As you can see, I've finished adding the 2.5mm and 5 mm pieces and lated a track in the 5mm. The gear hole goes through both and into the oak dowel. The left wing has been covered with balsa and short of sanding is ready for covering. I'll get the right wing done shortly and the next post will show the finished project.

I considered cmulder's comments on changing the orientation of the servo but dismissed it after looking at the ribs in that area and not wanting to alter the original design. Thanks for the suggestion anyway.

As for 308jockey.... I feel like an idiot since this has taken me much more than an hour and I haven't even watched any TV!! ..lol

Villa

Hi pocatosaras....I noticed in your original post you state that it was 20 degrees cooler that day than the last time you flew. That means the engine would be running leaner on the cooler day, the day it quit on you. Did you run the usual checks to adjust the mixture prior to takeoff?

pocatosaras

Villa -- Good catch. I was wondering when someone was going to call me to the carpet on that one. Chalk it up to ever increasing experience based on trial and error. In short - I DID NOT!! Frankly, the thought didn't even occur to me, you can bet it will from now on. I did my usual inspections and range check and started it up on the table. I let the engine warm up a bit and did a few throttle ups on the table and it seemed to me to be running alright. To be honest, I was probably thinking more about testing out the landing gear than anything else. I made no mixture adjustments.

I don't really understand the whole temperature/mixture thing too well. Can you give me a quick lesson?

As for the next time............ my brain will be working a little sharper and I'll be a little slower to get off the ground to make sure everything is alright.

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