JimmyDeQuinn

On takeoff my Tower Trainer 40 MKII stalled and took a nose dive into the grass from about 20 feet up. Luckily the damage was minimal and should be pretty simple to repair with a few pieces of balsa and minor cosmetic stuff. My Question is. . . Where can I find the piece of wood that the engine mount screws into and the gas tank cradle? Or will I have to have these pieces specially cut. I have a few pics of the damage. I am new to the hobby and could use all the advise you have for the rebuild. Take a look at the pictures and tell me how you think Should go about the repairs.

Thanks

Jimmy

michael wood

My Feedback: (1)

well the first thing I would do is clean up the the inside of the fuselage and the engine fire wall. sand the in side of the fuselage. then I would go to the hobby shop and get some tri stock and some 30 min epoxy and what ever the thickness the top and bottom of the fusselage is and glue the fire wall and tri stock to the fuselage clamp it and let it dry.then glue the bottom piece on the fuselage as far as the cradle I would cut it out of the left over pice of balsa glue it in mount the tank and glue the top part on the fuselage and cover and reblance and go fly michael

gboulton

My Feedback: (15)

That's nuttin! 

Were it me, I'd tack that firewall in (might even leave the motor on it, depending on how "in the way" it was) with a few dots of CA...just enough to hold it in place.  It looks like the firewall's intact, and has enough 'stuff" at the edges that it should fit in nicely like a puzzle piece.  Tacked in, it'll serve to keep everything nice and square and true.

Do what sheeting you need top and bottom, then permanently attach the firewall using tri-stock and good epoxy as suggested above, recover, and go fly.

JimmyDeQuinn

Thanks for the advice. The firewall is slightly bent and has a small crack in the wood on the top right corner. Can I purchase a new one? and What about the Gas Tank Cradle?

Thanks Again

gboulton

My Feedback: (15)

I'll take your word on the damage to the firewall, of course.

However, judging from those pics, where I can't even SEE such a crack, i'd say it's absolutely minor.  If the firewall can be "straightened" back to a flat piece of ply, just soak it in some CA and it'll be fine.  (I've done exactly that on MUCH larger airplanes with MUCH worse cracks)  if you want some extra comfort, just lay a small piece of say 1/16" ply covering any crack, and epoxy that in place as a patch.

As for the tank tray, that can be pretty much anything you want it to be, so long as it's reasonably "stiff" to hold that tank.  I wouldn't use something easily broken like balsa, but any thin piece of lite ply should do just fine.  Just cut it to shape, CA it in, and it should be fine.  You can drill some lightening holes in there if you want.

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One thing to keep in mind here is this...

Things don't HAVE to be "exactly like before" or "original parts" or what have you.  You can comfortably use a bit of your own judgment, and say "Ya know what?  The tank has to sit on something here."  Put a "something" there that's the right shape, and it'll be fine.

What's most important is that the firewall go back in the plane "correctly", and true, and that it be solidly re-mounted.  That will ensure that thrust angles remain close to the same, providing you with an airplane that doesn't need a whole bunch of trimming.  That will also serve as a "key" for keeping the rest of the airplane aligned and straight.

===========

One 'trick" I've picked up over the years (and believe me, if you fly like I do, you win up rebuilding a few *lol*) is to start at one end of the damage, and work your way toward the other end.

Any time you can begin at some point where you know things are "correct"...either an undamaged portion of the airplane, or perhaps some damage that's easily reset back in shape, then you have a "known good" starting point.  From there, simply piecing things back together carefully almost HAS to result in a straight airframe, and that's the single biggest factor to a successful rebuild.

JimmyDeQuinn

One last "Newbie" question.... What is CA???

gboulton

My Feedback: (15)

Hope not! Hopefully you'll feel free to ask lots more!

CA or cyanoacrylate adhesive. Available at any hobby store, or online at Tower, Great Planes, etc.

http://www3.towerhobbies.com/cgi-bin...&I=LXK282&P=ML is just one example.

P-Y

My Feedback: (1)

CA stands for CyanoAcrylate glue.

JimmyDeQuinn

So when you say soak the firewall in CA after it's straightened, does that mean literally soaking it or just being liberal with the amount used?

gboulton

My Feedback: (15)

Just be liberal.   Which, with CA, still ain't much. 

As a few examples:

When I talk about "tacking" the firewall in place, we want it to be fairly easily removed later, for the permanent fix.  We just want it "in place" as a key, of sorts, for keeping everything nicely aligned.

CA (especially thin CA) dries quite quickly (just a few seconds).  So, for that instance, just put the firewall back in place, making sure everything's nice and flush, and then maybe just a tiny drop or two at a corner or two.  VERY little...just enough so that it'll stay there when you handle the airplane.

On the other extreme, when we're talking about repairing, say, a crack in a plywood firewall, then we're after something that approaches "wet".  Bend the ply back into shape (we want the crack to go back together nicely, with smooth surfaces) and then run a "line" of ca into the crack.  Let it soak in quite well, and hold/clamp the piece for a good 2-3 minutes.  The result should be stronger than the original wood, actually, IF we've got a nice, flush tight fit.

For simply bonding two pieces of wood together (say, perhaps, gluing a stringer or maybe that tank tray back into place) then the technique is somewhere in the middle.  We want the surfaces, where they meet, to be covered with CA, but nowhere approaching "wet".  Frequently, the method is to hold/clamp, place the two pieces in contact with each other, and then run some thin CA down into the "joint" right at the edge, where the two pieces meet.  The CA will wick into the joint, again forming a very strong connection.

Since I'm sure you're not confused ENOUGH yet, there's quite a bit more to know about CA as you move along.  *heh*

There are medium and thick CAs, which take longer to cure (Thin can go off in as little as a few seconds, thick can take as much as 30 minutes), but tend to do a better job with harder woods (the longer cure time gives them more time to penetrate the wood), and some thicker CAs are used to fill small gaps in joints as well.  Many folks will move to the medium CA for bonding things TO plywood, but the thin works nicely for the repair we're describing above.

There's also "Foam Safe" CA...CA made specifically for foam applications.   Regular CA will attack foam, foam-safe will not.

Finally, know that CA is at its best with a good, tight, flush bond between pieces of wood, especially lighter/softer wood like balsa.  It's nearly useless for bonding plastic or metal, as its strength relies on the CA soaking into the materials being bonded.

Last but not least, CA is typically not used for areas where HIGH stress is expected, such as installing your firewall in this case.  While, with proper reinforcement with tri-stock, etc, it'd probably be fine, conventional wisdom usually suggests epoxy for such critical applications as firewall mounts, wing joints, stab joints, etc.  30 Minute epoxy is suitable for nearly any high stress joint you'll need until you get to the much larger airplanes, and even 5-6 minute epoxy would be fine for any joint in smaller glow airplanes like trainers.

=============

There's all kinds of other adhesives out there that many folks find uses for, or indeed prefer.  It all comes down to a combination of strength, flexibility, suitability for the material, and working time.  Don't be overwhelmed.  in THIS case, you'll be just fine with some CA for the bulk of the repairs, and some epoxy for the major work of reinstalling the firewall.

Just practice a little on some scrap wood, get used to the flow of the glue, etc.  Be careful, CA can AND WILL bond fingers to wood! (Unless you're one of the oddballs like me *heh*) Acetone (finger nail polish remover) will remedy that situation.

Best thing you can do is probably talk to the folks at your LHS, if you have one.  They can give you a rundown of what brands they sell, the various accessories (tips, bottles, accelerators, etc)  they offer, and how to use em.

JimmyDeQuinn

Thanks a million gboulton. I think I've got it [sm=confused_smile.gif]. I will post pics of the repair as I go along and hopefully I can get back in the air this weekend.

Thanks Again

gboulton

My Feedback: (15)

By all means, take pics as you go along, yes!  Would love to see your progress, and would be happy to offer insight along the way if you wish.

For a bit of inspiration,  hit http://www.rcuniverse.com/forum/fb.asp?m=9535127  to see what's possible with a little CA, Epoxy, and patience.

Good luck, I'll be following this one closely!

JimmyDeQuinn

The link doesn't work.

AERORICH73

Jimmey: Having done this repair before, and with aircraft mechanic's training, I would only add a bit more to the very good information already posted. You might want to remove the engine from the firewall, and use it as a pattern to make a new one out of 1/4" 5 ply plywood. The nutplates on the original firewall can be removed by installing the engine mount bolts back into the nutplates so they protrude a thread or two, and then supporting the firewall between two wood blocks, a quick hammer blow on the bolt heads usually removes them. Clamping the new firewall to the old one, the nutplates can be installed in the same location on the new firewall. It would be a good idea to install new triangler blocks to the front of the new firewall. I prefer to use slow drying epoxy when making repairs of this type of damage to the firewall. CA does work well in the rest of the repair.

Would really like to know what was the reason for the nose dive after takeoff. Sure would not like you to have the same problem again at the next takeoff. Keep asking questions as we really like to help in returning a plane back to flight status.

AERORICH73

mustange1

My Feedback: (11)

BEST TO JUST BUY A NEW FUSELAGE !!!!!!

willig10

VERYSIMPLEFIX. Here is what I would do.

1. Remove engine from firewall.
2. If firewall is cracked put a weight on it to ensure it is flat and use thin super glue to fill / fix the cracks and use acceleratorr.
3. Re-attach the firewall using either 15 or 30 minute epoxy and ensure you use clamps. Make sure the firewall is straight (use a square).

(fix any covering that may be torn. Now is a good time to use some epoxy and mixed with denatured alcohol to fuel proof the firewall wood area.)

4. Allow epoxy to cure for 24 hours.
5. Put foam pad under the fuel tank and re-install.
6. Re-install engine on the firewall.
7. Hook back up the throttle and fuel tubing.
8. Start the engine and perform static tests.
9. Go fly with your instructor.

The airplane is definetly fixable and dont go buy another fuselage. That is pure non-sense.

skater_719

My Feedback: (4)

Why would you want to buy something that is easily fixed in probably less then an hour? You should see some of the planes I and many others on this site have managed to fix.

Steve Landron

IMO, you don't need a new fuselage, it is totally repairable. Just use the suggestions previously outlined in the thread. Your fuse sides don't even look cracked; your plane is very rebuildable.

Take your time and post some rebuild pics. You have a wealth of knowledge here on RCU. This is what this hobby is all about!

Steve
[8D]

rtivel

Hi, Jimmy,

I recently rebuilt my trainer and learned a lot doing it. If you can, I strongly advise you to do the same as you, too, will learn a lot that will help you with your future RC aircraft. I wrote the following article chronicling the rebuild I did: http://www.selectdigitals.com/articles/fix.html. I am just learning to fly and am still on the buddy box. The tower trainer 40 is a great plane to learn with.

Royce

52larry52

My Feedback: (1)

DO NOT buy a replacement fuselage! The money you save by repairing it is chump change, but the lessons you will learn in the repair process are priceless. With this simple repair you will get a chance to cut wood, sand to fit, glue parts, patch covering, and have the satifaction of doing it yourself. Repairing ARF's will give you the chance to develop skills that will allow you to advance in this hobby over time. After doing some repairs like this you will be able to modify existing aircraft, kitbash new ARF's as you assemble them, and then stick build from kits. All of the previous advice on to do the repair is good correct information. Follow thier directions and enjoy the learning experience.

aerofly0610

The kit is on sale right now for $70 so if you are going to put more than that into the fix,,, buy a new one IMHO.  However, what a GREAT opportunity to learn how to fix crashes!  Its part of the hobby right?

I have one of these and its a 'nice' kit.  I recovered mine only to be horrified by how bad all the joints were.  I puttied and re-glued a lot of stuff before recovering.  It hasnt crashed so far but if/when I do....  I would put in a new firewall with a different engine mount.  I cant stand the stock engine mount.  I would convert the front deck into a hatch for easier access to the fuel tank.  If I was feeling creative I might even turn the front into cowling.

Hope you can get her back up in the air.  Please post pics of your restoration.

RCER88

My Feedback: (25)

Buying a new plane at this point is a total waste of MONEY! That can be repaired in an evening easily with minimal investment. What the gentleman have said about doing the repairs is absolutely correct. Gives you some experience.

But I have seen it many times. Type II pilots. Buy an ARF fly it, crash it, throw it away and buy a new one. (must be nice to have that kind of money cause I sure don't).

The Type I would repair it. Make it stronger and be proud to put it back in the air. It is a trainer and a trainer that is not had some damage has not been flown!!!! Besides you will bang it up again that is part of the learning expereince. But the repair done properly to the nose it will not break again unless it is a really bad crash.

Good luck and enjoy!!

banger1973

Jimmy I don't know about you but I picked up alot of heplful info on everything. It's really interesting how everyone in this hobby are willing to help one another. It's inspiring and thanks for the info you never know when any of the information you read on site is going to come in handy for your use.

JimmyDeQuinn

Thanks everyone for the advice. One thing is for sure, I wont be buying a new fuselage. That would be a complete waste of money and kind of defeats the purpose of the hobby I think. Im excited about rebuilding the plane, and look forward to gaining a little more knowledge about how it works. When I do get it back in the air I will feel a definite sense of accomplishment knowing that I was able to restore it.
To answer this question is really simple. I was over anxious to fly by myself so I took off got the plane in the air and freaked out because I was "Really Flying". It took off so fast and instead of my leaving the throttle open until I established a good altitude, I cut the throttle down as soon as it took off. The engine stalled and Bang!

But I have learned my lesson and once I become a seasoned pilot and able to teach someone new, the first thing I will tell them is "Its not as EASY as it looks".

I do have one other question. I definitely want to spend the least amount of money on the repairs, so where do you suggest I get the materials from. Should I get the wood, balsa, glue etc. from the hobby shop or should I order online?

gboulton

My Feedback: (15)

PRESUMING you have an LHS near by, and that it's locally owned :

IMO, absolutely support the LHS, at least until they give you strong reason (lack of knowledge, unwillingness to support you, etc) not to.

Keeping your hard earned money in your community, supporting local folks that will be around to answer your questions, offer advice, and support the products you buy...all of those things matter, imo, a great deal.

Of course, you might have a nameless/faceless chain store with random flunky of the week behind the county, in which case...meh...most of your money's leaving town anyway, and they offer no real value to you, so hey...go wherever it's cheapest.

For the record, if youDO order on line, I've always gotten top notch product from National Balsa.