Quick tips on replacing engine bearers.

I was working the bottoms off on my pattern today, now I need to add a little bit. Unfortumately, I'll need to add a little bit to the engine bearers on my arf Nobler as well. Another foot and we wouldn't be having this discussion, but thats moot now.

My bearers broke across the rear bolt holes, whadda I do now? If I'm to cut those suckers out all the way back, what do I use to cut them free?

Kinda hoping they used that funky hot melt glue that is easier to remove than wood or epoxy.

Now I've got to get this done cuzz I stink and I need all the practice I can get before Wichita's contest weekend after next. Other than the gear being folded back a bit, I don't have any other damage that I've been able to see, squeeze or smell.

LAST EDITED ON Jul-28-04 AT 02:31 PM (CDT)
 
Bill,

Sorry to read of your misfortune. And I, unfortunately, am in a position to relay a few details of the igNoblarf motor mount replacement strategy....

My motor mounts broke thru the rear engine bolt holes. The nose was otherwise intact, although the cowling was pretty well shredded. Sound familiar? The adhesive appears to be (and smelled like) an epoxy, perhaps with a filler, hence the milky white color.

I removed the detachable parts (muffler, needle valve, engine, tank, gear) and degreased everything that I could. I sawed the mount stubs off flush with the fuselage sides. Next I used a round burr (about 1/4" diameter, I think) in a Dremel moto-tool to grind away the mounts flush to the inside of the fuselage. It isn't apparent until you start cutting that the mounts are keyed into the fuse sides. If you grind the mounts flush to the inside of the fuselage, some of the mount remains. I went back to about the front edge of the landing gear mount and left a butt joint with a large fillet radius. This whole exercise took me about an hour and a half, but it came out smoother than I expected, and I had no trouble fitting new mounts. I made the new mounts out of maple. I stepped them at the forward edge of the fuselage (I didn't make the holes in the firewall any bigger) so the portion forward of the sides is full-sized, the portion pushed thru the firewall is relieved on the outsides. I used 1/2" cross-grain balsa between the two mounts to complete the engine crutch. (I did this when I first built the plane and it worked fine.) I also put 1/2" vertical gussets in front of the firewall. Now I am working on a new cowling made from balsa. I am going to put the parting line thru the muffler and needle valve so I don't have to screw around with the stock (mickey mouse) disassembly procedure.

Hope this helps!

Dave
LA_Flyer

PS-I may have hit the ground, but I can say I got my first three vertical eights in before it happened....

Sigh! Grinding. I was toying with using an RC Radial mount, but I have the equipment to do this.

I actually hit on the prop on the gear, so there is a crack in the cowl, but I think after degreassing, a spot of ca and then a thin layer of fiberglass all will be well. The soft gear actually came in handy taking most of the rather fast and steep landing force and deforming. Didn't dent the bottom wing sheeting. I expected it to be broken as well.

Off to cutting out the tank plate and starting the grinding process. I needed to start some laundry and clean the litter box anyways.

Well, got one in, now to wait on hour. Wish I would have remembered to pick up some fiberglass filler from Melvin Saturday. I could swear my motor mounts were walnut!

Bill,

Once I got over the disgust of having to do this exercise at all and got started, it went pretty fast. I must have hit the ground harder than you. My rear fuselage partially split in two places between the wing TE and the first lightening hole. The covering split so it was easy to identify. Be sure you squeeze/twist this area carefully to see if you have any latent damage. The other wood was sound, and I was impressed with the construction details and the wood selection.

Because I wanted to be sure to find all of the cracks, I stripped the covering off the aft fuselage. Since it came off easily and because I noticed some oil soaking on the bottom just behind the wing, I stripped the whole fuse. I'm glad I did, because there was oil in the nose from the cowl screws, in the belly pan from who knows where, and in the aft fuse probably from the flap horn hole. I took Mr. Umland's advice and used paper towels and a Monokote iron to get rid of most of it. Getting the oil out took longer than repairing the mounts. I'll give it a wipedown with lacquer thinner before I recover it. I'm wondering if the Monokote scrap box has any yellow. Maybe I can make a "reverse PT-19" color scheme.

Some of the talk about the Nobler speculated that the motor mounts were oak. They certainly looked like oak, but they did not smell like oak when I started grinding on them. I would assume they are some kind of ring-porous tropical hardwood. I wore a dust mask because some of those woods can cause an allergic reaction....

You must get really excited about laundry and kitty litter if that was your excuse to replace only one mount and then take a break!

Regards,

LAST EDITED ON Jul-28-04 AT 04:58 PM (CDT)
 
I don't know if this will help, but I have had two nasty crashes with my ARF Nobler and actually broke the thing in 3 pcs. both times.
1} Nose section including cowl, engine and broken engine mounts.
2) Forward fuse including wing
3) Rear fuse and the rest of plane.

Now to the point, I used a Dave Brown radial engine mount and it works great. I just cut the broken hard wood mounts off at the forward former, added a 3/16 plywood firewall and mounted the radial mount. I did have to shave the mount down on the sides a bit to get it to fit under the hood. But I will tell you that it worked very well and I can't tell any performance difference between the hard wood mounts and the radial mount. If you go this route make sure that when you install your firewall that it is straight, not canted outboard or inward, the first time I did this I had mine canted inboard just a little bit, BAD THING. I added a couple of washers behind the mount and corrected the problem and it has worked well ever since ( the second crash was my fault as well ) and had nothing to do with the performance of the plane. I was able to rebuild my 3 pc Nobler in about 3 hours using this method. Hope this helps, Dave Markley

I mounted the engine before coming to work this morning to check alignement and see if the cowl was in the right place. I all looks good so this afternoon (late morning really) when I get home I'll shove the tank in and glue the bottom plate on and hopefully an hour later I'll be cleaning off the bench. I had one split on the inboard side of the fuse where you mentioned, the outboard was solid. Dribbled a little CA on the crack and let it setup, a quick wipe with WD40 took care of the fogging. I had originally set this plane up to be an removable wing, so all the area in the wingmount and just behind has a light coat of thinned epoxy on it to fuel proof it. Last time I had it off before I put it on solid, there was minimal seepage of fuel, what little there was wiped off. Gluing the wing on sealed the holes where it came in. Wish I had some touchup paint and a little time to fill and sand the cowl, but I'll likely just smash it again anyways. 'Sides, this is a practice plane, even though I'll be using it in the upcoming contest.

Bill,

Glad to hear that you Noblarf is nearly back together! That was quick work even with the laundry break. I think you were very wise to fuel proof prior to assembly. I wish I had done more. (Like the belly pan.) And thanks for the WD-40 tip. I wondered how you guys solved that problem....

I'd check the fuel tank over pretty carefully before you reinstall it. Mine plastic tank (stock) split at the neck along a mold line after about a dozen flights. I think that is where most of my "fuel soaking" came from. And I learned that you can't fly many inverted laps on an empty tank....but you can practice inverted landings.

Good luck practicing and at the contest!

In the car waiting on this little obstacle called 'Work' to get out of the way. I am using a sullivan 6 ounce tank in mine, it survived the crash with no problems. My friend put the stock tank in and it split almost immeadiatly. He fabricated a 4 ounce metal tank and put it in. He only flies the beginner pattern anyways, so short tanking is in the works for him.

Bill,

After my stock igNoblarf tank split, I replaced it with a Pylon RST-6 / Sullivan tank. This one has the hole facing forward. Was working great with a stock OS.40LA running pressure to the tube at the top of the tank (into the bump.) I had to cut away (bevel) a bit of the landing gear mount so the tank would just tuck under it. The fuselage cavity was plenty long, just not quite deep enough without, sigh, grinding. Sounds like you did something similar. I was surprised when I searched here at SSW, no one had listed the alternative tanks....

Squeezed a little more oil out the balsa last night with the iron. Mebbe I can recover it this weekend (while some guys are flying!)

Best wishes,

Thats the tank, using 4.75 ounces in the Brodak 40 on an 11x4 APC at 10.0-.1k, 58' eye to eye starting with 5.1's and going to 4.9sumptin at the end of the flight. Flights today were really nice and I think that I have just a tad more weight in the nose thanks to the mod, it flys really nice. 3 flights and I had to run my daughter to the Ortho. Just a wee bit grinding on the gear mount, a little shaving on the mounts and stick the tank in, there is about 3/16 of a inch between my piece of balsa going across the bottom of the tank mount and the tank, with foam rubber shoved in between, my lap times are same same upright and inverted.

Flying tomorrow, the circle at the RC field finally has enough cover on it to fly off of and it was kinda nice. I plan on a long day of CL and maybe some RC flying with some guys I haven't seen in a while. Wish I had an RC combat plane ready.