Well, the end of another winter draws near so back into the basement I forage for something to do....Mid-season last summer I pancaked my Hangar 9 Arrow into the center of the runway. The impact dropped the engine and firewall out the bottom, bent the throttle control rod and basically messed up the front 1/4 of my plane. ((Note: When doing high speed loops always remember that a trainer type airplane usually has a lower exit than entrance altitude....even though it might not look like it when its waaaaaay up in the air...try it closer to the ground if you don't believe me.)) So into the shop I go. Cleaned all the broken pieces off, and started with the rebuild. I have a pretty good idea of how its going to go but chime in with any thoughts you have. I think what I'm going to do is glue the balsa sides to the ply sides(wood glue) and firewall(epoxy), then glue that assembly to the existing fuse. The 'good' remaining bits will have about six inches of fresh balsa glued to them. I may also put a couple of doublers over the joints but I'm not sure that will be necessary. Then of course tops and bottom and such. I'm going to go taildragger as I'm tired of getting nose wheels and hardware and stuff. Do ya'll think I should mount just in front of the leading edge or just behind it? (location of the second former after the firewall.)

Here are the ply and balsa sides and the new firewall and formers.

I puzzled the new ply to fit into the fuse on both sides, may cut holes for weight but I doubt it as I'd rather have the surface area glued for strength.

Here it is with the firewall and formers mocked up. One thing popped up that has me a bit baffled. In the first picture you can see the original fuse ply on the right hand side just above the clamp jaw. I'm going to have to remove this corner of the original fuse to have the firewall sit flush against the side as you can see on the left hand side. I don't understand why this is...where was the original firewall???? Seems like the notch I have to make wasn't there originally....

This was the third crash of significance in the life of this airplane. The first one was straight into the ground and took the fuse out to behind the wing saddle. The rebuild of that airframe will be caught up in another crash and rebuild thread that I started last winter. The second one was a nearly pulled up in time that seperated the firewall a bit, and was easily repaired. This crash left the engine hanging off the front end as mentioned, I glided it post impact about 30 yards into some tall grass where it came to rest. I had full control of it as I watched the guts hang in horror. The receiver has a couple of cracks on it. I'm not sure if these were from this crash or from the first one. After the first big crash I range tested everything while running and never had any kind of glitch problems at all. I pulled the board out tonight and looked it over. There don't appear to be any cracks on it and there is no sign of any damage to the innerds... Would you think that doing a range check running, perhaps for a half tank or so would show any potential issues? If not, does anyone know of a reliable place to get this sort of stuff checked out in Canada?

whether you're going with wire or aluminum for landing gear, it looks like you can put your landing gear block just forward of the bulkhead at the leading edge. If balance is a problem on the ground you can always sweep the wire forward or find alum lg made with a forward sweep. Keep in mind you'll need to check your CG for flight too. Hope I understood your question and it looks like you have very little left to do...

On my Arrow, the firewall has four "tabs" about 1/2" long, one at each corner of the firewall, that fit into corresponding notches on the side of the fuselage. So where your notch went is an interesting question. For some reason (and it may be the camera angle) the distance between formers seems a bit short. By some chance, could you have lost a piece of the original fuselage that had the notch?

In the end, it probably won't matter, especially since you've already expoxied things together. I assume you're going to reinforce the firewall/fuse joint with some triangle stock? Another thing I did when I rebuilt from a similar crash was to put a piece of 1/16 ply on the inside of each fuselage "cheek" in front of the firewall. That way I made sure the firewall wasn't going to pull out of the plane, and added some rigidity to the cheeks as well.

I'd be very careful with your receiver. I've had them check out in the shop, and even with a running engine, but when I put the plane on the ground a did a control check, nada! That looks like a JR receiver... usually you can send them back to Horizon and they'll check them out for you. It would be a shame to get the fuse rebuilt, recovered, and then lose it to a radio glitch.

Yeah, yeah, yeah...measure twice, cut...awww crap. Wasn't the camera angle. Good eye FallDown, and thanks. Somehow I managed to get the firewall back about a half inch or so too far....****ty drawings...lol...Always make me wonder why they don't include a cheap set of plans with an ARF, for the just-in-cases like me. Fortunately nothing has been glued yet so modifying is a nothing job now....glad I didn't get everything glued before someone noticed... You might like my other thread here... http://www.rcuniverse.com/forum/m_7164146/tm.htm . This is the modifying rebuild of the first Arrow.

Glad you caught the 1/2" before you glued, that would have made setting the CG interesting. Once upon a time I called Horizon to see if they had plans for the Arrow, and the answer was a polite "no". Apparently they build ARF's with parts cut from computer controlled machines, assembled in jigs so that everything lines up perfectly, so there's no need for plans. I've often thought I should draw a profile of an ARF and put in firewall and former locations, just to simplify the rebuild process. But that's kinda like planning to fail... or putting a garbage bag in the fuselage to pick up the remains.

One other thing: did you put some side/down thust into the firewall?

So did you ever get the low-wing arrow to fly?

Fred

I actually did trace out the whole plane....well...at least back to where the tail feathers meet...nothing gets broken behind there anyways...lol. I kind of suspected that this plane wouldn't last in one piece and that I'd like it to be around for a while. I really enjoy how the plane flys and I'm hoping that the low-wing version gets just a bit more of the aerobatic tendancies that the high-wing has, slightly more stable knife edge and I really hope it has a more axial roll centre. I love doing classic aerobatic manouvers, slow rolls, nice spiralling barrel rolls, hammer heads.

The down thrust was drawn into my plans, I don't recall there being any side thrust. If you can find a way to measure your firewall to see if there's anything built in that would be great but I dont suspect so. If there is I don't think it would be very much at all, washers behind the motor mount would likely be enough if I need it.

As far as the low-wing Arrow...Dart, as it will affectionately be known in its next incarnation, it sits exactly as the thread left it. Once flying season got going last year the rebuild died and then life got in the way, got married, fixin the house up, visits from family. I only actually made it out to the field about three times last season. I'm hoping that between the four planes I now own I'll be able to get at least two of them flying in time to open the season this year...still very winter here.

Looked at the Arrow this morning... there doesn't appear to be any right thrust build into the firewall. And my engine installation looks pretty much straight.

I smoothed out the rolling performance on mine by shifting the CG back a little bit, maybe 1/8" in back of the wing spar. Or maybe my thumbs got better.

Thanks, I didn't remember seeing any thrust built in...maybe an eigth of an inch if anything. I think if you measure from the firewall to the first cutout on the 'cowl', its a bit different from one side to the other, but very little. I got the two formers glued in last night and the ply sides glued to the balsa. Then found a wicked twist in the front end when it had dried today....has to be in the first former up front. Broke it out, cleaned all the glue off and figured out how to line it up tight and straight. I'll glue that back in tomorrow. Got the sides and the firewall all lined up (straight and true) and epoxied them together. Does epoxy have a shelf life? My 15 minute is starting to get a bit thick. Won't come out the tiny little hole in the end of the spout but it poured out of the open bottle fine. When it mixed up it looked and smelled right. I think its about two years old...maybe not that long.

I don't really know about the shelf life of epoxy. I'm using some 30 minute that's easily a couple of years old, and what I've noticed is that if I mix and apply it in small amounts, it seems to cure as expected. But I end up mixing a fair amount (say 1-1.5oz), then it "kicks" in 10 to 15 minutes, and the heat generated from the reaction can melt a plastic mixing cup. Ditto with some fiberglass finishing resin that's getting a little long in the tooth.

So I use new expoxy on critical joints, and use the old stuff to mix with micro-balloons for filler, or for fuel proofing. Could be that the old stuff is fine, but why take a chance on the firewall failing in flight?

One thing I'd try with yours is to use acetone to clean out the nozzles on your epoxy tubes. You may have inadvertantly mixed some hardener with the epoxy and it formed a small blockage in the tip of the tube. I can't imagine another reason that it would flow easily out of an open bottle, but not come out of the end of the spout.

Well, I got the firewall epoxied to the sides...set up real straight. Fit the sides to the fuse, a little sanding here and there to get it just right. Drilled and glued it on. The drilling was for locating pins that I put on, 9 in total. Good strong bamboo toothpick reinforcement.... I also got that twisted former put in straight this time. Holes drilled for the throttle cable, fuel tank opennings checked for fit, little sanding there too... Guess we'll see tomorrow how straight everything is. What did I forget? Anyone???Anyone?????

Since you've pinned the firewall to the fuse sides it's probably not necessary, but I'd still consider epoxying a couple pieces of 1/4-3/8" triange stock between the back of the firewall and the fuse side. It might be overkill, but it's additional safety for minimum weight gain.

Are you going to put foam around the tank? If so, make sure the hole in the former is big enough so you can stuff it through, or glue the foam in place before you put the top/bottom on the fuselage. Will you cut notches in the bottom of the fuse for the landing gear block?

I didn't pin the firewall, I notched it the same as original so it has 3/8 inch high 1/8th inch deep tabs on all four corners into the ply sides. I did use the triangular stock on the last one but don't really think there was any need for it. I still might...who knows. The Arrow never had any foam around the tank, it slides through the formers and into the hole in the firewall. It is held in with the ply that covers the receiver and battery and seems pretty stable there. I've never had any issues that I would relate to an uninsulated tank so I'll go with that.....I figure keep the RPM maxed out and the vibration won't be anough to whip anything into a frenzy....lol...

As far as the landing gear goes I just picked up a GP aluminum gear. I'm going to epoxy maple blocks to/on either side of the former under the leading edge of the wing. I think this will give me enough support for the gear, as much as I think I'll need when I coming crashing into the runway anyways... I'll have enough room for a bit of ply support up the sides if i think thats necessary as well. I think I'm going to bolt the gear directly to the bottom of the fuse, no notching or setting in or anything like that....The glue has dried on the sides and I'm surprised at how rigid the assembly is, actually feels stronger than the rear section of the plane that is still original. A hair thicker balsa (standard as opposed to metric perhaps) and plenty of Elmers wood glue seem to have shored everything up pretty well...

Almost there....Couple of things. I forgot to fuel proof my fuel tank compartment before putting the top and bottom on the fuselage, not a big deal as in the two crashes this plane has had the tank has stood up very well, fittings are of good quality and I make sure to silicone the tank to the firewall. I also didn't mount the front landing gear block ahead of the leading edge former as I had planned. I could still do it if I wanted to though it would be a bit of a pain....Oops. What kind and how many fasteners are necessary to hold the gear onto the bottom of the plane. I'd like to use the block as I have it mocked up. I think it'll be positioned okay and I can beef up the fuse a bit at the front of the compartment if I have to. Can I just use two screws???? to hold it on?

Thanks for your input guys....

Ryan

Almost done.... Got some minor repairs done at the tail end including adding some light ply to attach the tail wheel to. Prepped the front end for covering and cleaned well. Also removed that yellow patch from a previous repair. Started at teh bottom with the blue and worked my way up, next with the white and then some silver windows.... Just have to seal the firewall, mount my landing gear and put the electronics and the powerhouse back on and we're good to go...should be flying by the end of the weekend I hope.

I use two 1/4-20x1.25" steel machine screws run through a 1/2 plywood block with a pair of T-nuts to hold on my main gear.

Your repairs look good. As long as you're modifying things, just a thought...

I got sick of changing rubber bands every couple of weeks last year, so over the winter I modified the wing to use hold down bolts. Two in the front, and two in the back. I epoxied 1/2 ply blocks to the sides of the fuselage. I opened up the front of the wing and glued in 1/4 ply plates, then added enough balsa so I could sand everything down to the original sheeting line, then drilled/tapped 1/4 holes for the bolts. The rear of the wing is solid balsa in the hold down area, so I just added some 1/16 ply plates to the top of the wing then drilled holes for the bolts.

I thought about the bolt on wing idea, really hard actually. But I really wanted to get something flying this year and the wing didn't need any significant tear down so I'll just stick with rubber bands for now. This is the only plane out of the four in the hanger that uses rubber bands and I bought a bag from Staples last year and have most of it left so no biggy really... I'll get the windsheild trim done and the firewall sealed up and the landing gear mounted and should be ready to mount the engine and fly by tomorrow sometime....oh...and balance...can't forget to balance. I'm curious to see how nose heavy my repairs and mods are. I did manage to get the landing gear block epoxied in front of the firewall as well so I can mount my mains as far forward as I'd planned....

Well, all the final prep is done. I got it balanced mostly...wow... After all that worrying and I'm acutally a bit tail heavy. The CG is called for at 3 and an eighth inches and it balanced perfectly level at about 3 and a quarter. I'll move the battery forward and the receiver back to get a bit more weight up front. I'm really surprised that it came out weighing a bit less than before the crash. Weather permitting I should have a flight report tomorrow....

Done, done and done. I didn't check the CG again after hard mounting the innerds but everything was perfect. Got four flights in and about 14 ground loops. Lots of fun trying to control a taildragger with no tail wheel control. We have an asphalt runway that is still spotted with big puddles here and ther so ground control is interesting to say the least...especially with a 5 mile/hour tailwind getting out to the runway threshold, and around and around and around...... I changed up to a cable for the throttle becaus eI had some here and I thought it might be a little less bound through the travel. The original rod got kinda hung up on the motor mount screw and the cable allowed me to bend the throttle arm away from the engine a bit. And it also makes getting the adjustment just right a whole lot easier. Is the any place anyone would recommend against using cables with the set up I have on the servo arm?

All I'm missing now is the beak as my five year old says. Good flying airplane all around. I highly recommend this plane for a first plane.