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Arrow High-Wing Glow Trainer and Cub Repair

Joker 53150

Mmmmmmm, balsa.
Mentor
#1
A buddy of mine picked up the Hangar 9 Cub in the background, and also owns the Hangar 9 Arrow trainer in front of it. Both are glow, the Arrow is 2 stroke and the Cub is 4 stroke. He got the Cub at a swap meet last weekend and fired it up for the first time today. It ran well, but then we couldn't get the fuel to siphon out completely once he was done testing. The seller said he ran it less than 3 weeks ago and it had about 1/2 tank of fuel when my buddy got it. That got me thinking, so I picked it up and tilted it forward and back, and I could hear a faint "clunk" from the nose. I figured the fuel clunk in the tank came off, which would be an easy fix. Since his time is pretty limited and he's still learning to fix his toys, I took it home with me to do a quick project for a friend.

Off came the prop nut, prop, cowl, and a crossbar glued in to keep the tank in place. The tank then slid out easily, and the clunk was indeed the problem. In fact, the fuel line holding the clunk broke in half! So new line was installed and everything put back in place - total time about 90 minutes. While I had it, I also tightened the wires on the tail stabilizers (the detail on this 80" span plane are very well done!), re-sealed a couple areas where the covering was coming loose, balanced the prop, fixed a couple pieces of wood around the top hatch, and put the battery on the charger to cycle it a few times. It didn't come with the connectors to attach the wing struts to the bottom of the fuselage, but that's all he needs to get it in the air. It should be a nice flying plane!

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The Arrow, on the other hand, will require a bit more work. Earlier this year it came in for a landing at a "slightly" too steep angle. :) Another guy started the repairs, but has too many other distractions right now so I told him I'd give it a shot. So far I think the only thing that it still needs is a new gas tank, which was ordered today. The one I've got for it right now is just too big to fit without some pretty major internal surgery, so we're going with a little smaller 8 ounce tank to feed the Evolution engine.

While the damage may look pretty severe, it should be a pretty easy fix. The left side of the fuselage is fine, so all I need to cut is a new right side, new bottom, and new firewall. The firewall is the most complex piece as it's got to have a number of holes cut in the right spots for the motor mount screws, the nose wheel, etc. Covering will also be re-done to match as much as possible, based on what colors I've got on-hand. The plane is a little rough so close-enough will be good-enough! :)

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Even though the engine took a direct ground hit, it doesn't appear to have any damage other than a broken prop. It still rotates smoothly, but I'll still do a bit of disassembly and inspection just to be sure.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#2
There was no plan to really start any work on the trainer yet, but I couldn't resist! :rolleyes: Starting with the firewall, I removed the motor mount, wheel mount, and all the captured nuts.

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The destroyed side is made from two pieces - 3/16" balsa on the outside and a 1/16" layer of ply on the inside. Both were cut to size and eventually glued together. A little extra bracing will be added inside to bridge the butt joints, and once the top & bottom are added it should be plenty strong.

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Back to the firewall, the original was used as a template so a new piece could be cut from 1/4" ply. The tabs on the sides lock into slots on the sides.

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To make sure all the holes line up properly I ran a couple screws through the original firewall and into the new one. The appropriate size drill bit was then installed in the drillpress and new holes drilled.

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With the holes drilled I could then re-use the original captured nuts, for a nice copy of the original. Um..... except I put the nuts on the wrong side and now the pushrod holes are backwards! :eek: Oh well, that'll be a quick & easy fix!

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Joker 53150

Mmmmmmm, balsa.
Mentor
#3
Careful measuring and making templates is worth the time and effort, as the new firewall and side fit very nicely! :) I went with epoxy for strength for these pieces, and will probably do the same for the bottom cover as it's light ply. The top is balsa and will get installed with TiteBond II. Not having the fuel tank for the next few days will slow me down a bit, as I want to install it with good padding around it before completely enclosing the nose. There is room to pull it out back by the wing saddle, but I can do a cleaner job with the easy access I currently have.

Once the epoxy cures I'll cut the top & bottom pieces, fuel-proof the firewall & new "cheek" with thinned out epoxy, and then look at getting the engine mount and steering assembly installed. A couple small braces will also be added inside, although I'm not fully convinced they'll be needed. The more I work on this one the more I like the design - it is supposed to be a good, stable platform to learn on, and isn't overly complex to re-build after a crash.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#4
I was checking out the design of this plane in a little more detail, and really like what Hangar 9 did with it. Not only is the fuselage (relatively) easy to fix, but they made the tail easy to fix/replace as well. The vertical stab is bolted to the horizontal stab with 2 bolts, and then 2 more bolts hold that assembly to the fuselage. So I simply unhooked the pushrods, removed 2 bolts, and the tail is now sitting safely off to the side. This is something I will look at adding to future builds.

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The bottom is now covered and all I need is the fuel tank so I can button it up, fuel-proof it, etc. There are a lot of spots on the original covering where it's coming loose and is a bit ragged, so I'm fairly sure I'm going to go ahead and just re-cover the fuselage for my buddy. He doesn't know it yet, but I'm sure he won't mind. :) Heck, he doesn't even know I've started working on the plane yet, and it'll be a nice surprise for him when he sees it.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#5
I didn't expect this to happen so soon, but I got a new fuel tank installed. it's larger than the stock one and took some surgery, but it now fits snugly with some padding. I wasn't going to use it until I did more disassembly and found the entire receiver tray could move and make plenty of room. So BOOM, there it is! All new fittings, new fuel line, new clunk, and new padding should have it in good shape for the next few years.

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A little padding was added to the top of the new tank before new sheeting was applied. It'll still need final sanding, which I'll do after stripping the covering off so it can be prepared for new covering. You can also see the original motor mount and new fuel lines are installed. All exposed balsa & ply around the fuel tank and especially forward of the firewall have been coated with thinned down epoxy for a fuel-proof finish.

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When the plane hit the ground early this year it didn't hit too incredibly hard and the engine was already stopped (dead stick), so it didn't ingest much dirt. Everything rotates smoothly, but since it's already out of the plane I'm taking the opportunity to open it up and check the general condition. It's actually pretty decent, although there are a few spots of age showing. I'll give it a good dose of lubricant before putting it all back together. The glow plug looks like it's seen better days, so I'll recommend a new one before throwing it back into the sky. Other than that, it appears to be good.

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Last, there is no picture of it yet but the covering on the tail was pretty saggy and rippled with age, but with a little quality time and a heat gun it's substantially better looking after a quick shrink. This covering is some pretty heavy material, perfect for a trainer that will see a rough life!
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#6
The glow engine doesn't appear to have any issues, so the piston, connecting rod, carb, and bearings were given a good dose of after-run oil and it was reassembled, along with a prop and spinner. The prop that was on it at the time of the crash is long gone, but it was a 3-bladed prop which was probably a bit more "beginner-friendly" than the new 2-blade. It'll be something to look at before sending the Arrow back up in the sky at least.

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After checking how much covering I've got on-hand in the right(ish) colors, I went ahead and stripped the old covering from the fuselage. It's a good thing I did, as it allowed me to find a couple broken glue joints that can now be fixed easily. The seams from the overlapped pieces of covering were OK on the left side of the fuselage, but all down the right side they were coming loose. Considering all the exhaust oil that's been blasted down those exposed seams I wasn't expecting the original covering to stick back down easily. I'm told the wing only has a minor tear from the crash, but I'll want to give that a good inspection as well, just in case. I'm guessing it will also need a little re-shrinking of the covering, but fingers are crossed that there is no hidden damage.

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#7
The bolt on empenage is definitely nice. I have a Great Planes Escapade with bolt on tail surfaces. It can make repairs and storage easier.

That alpha is going to look new! Nice work!
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#8
Thanks, the fuselage won't look as good as when it was new, but it'll certainly look a lot better than when I got it a few days ago! :)

For a while I was second-guessing tearing off all the covering, as it'd create a bunch of additional work for me, but I figured a patched job with mis-matched colors would look pretty lame, so off it came. The fuselage was sanded to prep it for covering, and here's where tearing off the covering really paid off - this is the tail, just forward of where the tail surfaces mount, where there absolutely will be lots of stress...! :eek: That crack goes down one side and all the way across the bottom. The only thing NOT broken was the left side of the fuselage! It would have been darn-near impossible to find this with the old covering still on.

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I also found some damage at the trailing edge of the wing saddle, although not quite as severe as the tail damage. Both areas got fixed up, sanded, and then blown off with compressed air to be ready for covering.

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...And the covering has started. Like the original design, blue is going on first for the bottom, and the rest of the fuselage will then be covered with white. The red and yellow stripes will then be done. The original film was some pretty heavy stuff, and is being replaced with (I think?) Monokote. Not as heavy, but it should still look decent. Pardon the mess on the bench. And on the floor. And on the shelves. It'll be cleaned one day, I promise!

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Joker 53150

Mmmmmmm, balsa.
Mentor
#9
I'm taking some "creative license" with the final design of the re-covering. It'll have the flavor and colors of the original, but isn't a direct copy.

The windows are made from Silver SoLite, trimmed with 1/16" black pinstripe. Some additional work needs to be done around the nose, but overall I'm happy with how it's turning out. I also found that 1/2 of the horizontal stabilizer is missing it's yellow and red stripes, so I'll match those as best I can.

The goal is to have the Arrow finished up either tomorrow night or Saturday morning, so I can hand it back to Mike. At this time he only knows I'm working on it and that I was able to use the bigger fuel tank, and I don't think he's expecting it back so soon. Oh, how I miss the old days where Friday nights were for going out and having fun, and Saturday mornings were made for regretting Friday night! :)

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Joker 53150

Mmmmmmm, balsa.
Mentor
#11
That repair job looks great! I’m sure the owner will be very pleased.
Thanks, I think he'll be pretty happy. He's said a few times how much he enjoyed flying the Arrow and missed having it available. He still doesn't know how far the work has progressed or even that it's been re-covered, as I'm keeping it all a surprise. All he knows so far is that I'm working on it, the bigger fuel tank fits, and that the side is repaired. I think it's still on track to be finished up tonight.

When (IF?) Flite Test eventually moves into the world of balsa, hopefully this kind of build thread will be helpful so people can see it's really not as difficult as they'd think to fix crash damage. It's obviously more work than a foamie, or simply buying a new fuselage, but it's not rocket surgery! :)
 
#12
I think the fear of a total loss is what keeps people away. Once you realize how much fun you can have building or even repairing that feeling goes away. At least for me it did. I would absolutely love to see FT branch out into balsa. I honestly think it would completely revitalize the hobby.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#13
It would absolutely put a dent in the current trend of foam and immediate gratification, not to mention how it would help boost business for some of the surviving balsa companies like Balsa USA, National Balsa, and other kit designers/suppliers. The more I build, the more I like it. When the weather starts getting cold I attack the balsa with gusto, and by Spring I'm ready to attack the skies, so it's kind of like having 2 hobbies at once! :) Recently I've been on a tear trying to get as many balsa projects finished up, and the sense of accomplishment in getting one built and in the sky is far better than I've gotten from any ARF.
 

agentkbl

Illegal Squid Fighting?
#14
I think the perfect thing for Flite Test to do to get into balsa would be to buy mountain models. mm has the exact right reputation for Flite Test, and it would set an example for Flite Test to follow with every model they designed.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#16
.....aaaaaaaand, it'd done! Well, other than making sure the battery takes a charge and checking all the throws with Mike's transmitter. Overall, I like how it turned out, although I'm not sure how the glow fuel exhaust will react with the trim around the windows, but it's worth a shot. I also added a little extra thinned out epoxy around the edges of the covering around the engine to make sure it won't peel up. The glow engine stuff is new to me so I'm learning as I go! :)

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This is the area with the worst damage, and the repairs are now completely hidden under the new covering. This is one of my favorite things about working with balsa - as you get better at covering you can completely hide repaired crash damage to the point that it becomes invisible.

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While the tail was undamaged from the crash, it was missing all the trim on top, so I cut some pieces and got it fixed up. While not necessary to the overall repairs, it's a little extra gravy on top of the bacon-wrapped cupcake.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#17
Oops, I just looked at some stock pictures of a new Arrow, and the trim color covering was never applied to the right horizontal stabilizer from the factory. Sorry Mike! :p
 
#19
I've had pretty good luck with pin striping on covering in glow applications. As long as it's adhered well to start off, it generally stays on. The plane looks great, really nice work!
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#20
Well, the work isn't done yet after all! :) I knew there was a tear in the covering so I had Mike drop the wing off. The tear is pretty minimal and is an easy fix.

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However, there was a really soft spot in the leading edge at one spot, and I could feel a little extra damage under the covering so I decided to dig in and get it fixed up. At first blush it's about what I was expecting.

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But after digging a little further the damage was more extensive than expected. All the broken pieces were removed so the repairs could be planned. It may look pretty bad, but should be a fairly easy repair. The covering was removed with care to hopefully allow me to re-use it, but I'm not betting too much on that happening!

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