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Mountain Models ETana Build

Old 01-09-2009, 11:12 PM
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birdDog
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Default Mountain Models ETana Build

Well, Gonna try out a build thread. This won't be the most in-depth thread seeing as one of the other groups has about 60 pages on this bird.
Here I will post some of the tips I have read about and the mistakes (hopefully not many) I feel I have made. I bought this kit as i was looking for an airframe to accept the AXI2820/10 I have just gathering dust. Looks to be a decent match. I am not of the skill level to fully appreciate the 3D capabilities of this plane but I am looking for a really cool looking plane that I can tool around with at pretty good speeds! This looks like the one!

I ordered the plane early evening on Wednesday, Got a shipping notification in about a half hour and arrived home on Friday after work to find my package at the door. THAT is service!

So far it looks great. The balsa looks to be pretty select and the laser kerf is the finest I have seen in any kit to date. I am hoping this reflects the overall accuracy of the fits, and from what I have read elsewhere, It does. Mountain Models has taken alot of input on these planes since introduced in 2005 and has adjusted the design to come up with a grade A kit.

The hardware kit is the most complete I have seen, Wheels, t-nuts, magnets, velcro, shrink tubing, CA hinges etc.

The instructions look very straight forward and easy to read with lots of pix.

So far, my take on this kit is that it was designed and sold by a group with a real passion for model airplanes, not just a guy with some open time on his laser plotter.

Note the three inches of snow on the ground, some real building weather!
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Old 01-09-2009, 11:36 PM
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Looking forward to seeing this .
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Old 01-10-2009, 12:46 AM
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Sky Sharkster
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Default Mountain Models Club?

Hello Rob,
Great to hear you're building the Etana! I've seen a couple of these fly, they're fine aerobatic models.
Mountain Models are some of the best kits going.
We sent our latest snowstorm your way, but kept the cold and wind. I may finish several builds this winter!
Good luck, keep us posted,
Ron
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Old 01-10-2009, 04:50 AM
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Default Fuse Panels

Allright... allright..... I don't mean to keep gushing about this kit but here goes....
I have been a machinist and a pattern maker for almost 20 years. I know what a good fit is. After gluing the finger joints for the fuse together, I just gotta mention this.
These things go together so tightly that after sliding them together, the two panels are straight within about .005" or less at almost 34". THAT is pretty impressive. Makes me question my straight edge.
Lay the two pieces flat and slide them together. Don't try to join them by putting one on top and trying to pop it into the other one. Wax paper, ca, viola! Also, a straight edge doesn't hurt.
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Old 01-10-2009, 05:56 AM
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Watching and learning.
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Old 01-10-2009, 02:08 PM
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Rob, I've built just about every kit MM sells. You will enjoy building the Etana. It has an amazing amount of engineering.

In my experience, if/when you have parts that don't fit pretty much perfectly, it's usually due to one of two reasons. The first is the part is backwards. The second is that there is variation in the thickness of the wood. The milling of wood really does not go to three or four decimal places of accuracy. Generally a couple of swipes of 120 grit sandpaper will take care of the issue.

Enjoy the build! MM kits go together so quickly that it will seem to be over before you start!

Mark
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Old 01-10-2009, 06:16 PM
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Three inches more snow. Coffee and Etana day!
I installed the t-nuts in the LG mount but they protrude slightly from the bottom plate of the fuse. I removed them to keep things straight 'till I get the fuse glued up. I will reinstall them later since I already made the holes for the little "spurs". This is ok since the aluminum LG shoulders the nuts.

I am using the back of a x-acto blade to scrape the charcoal from the lite-ply. This does not remove wood like sandpaper would. Gives a better glue joint.

Definately dry fit all formers first. Although this kit has no full sized plan, the pieces are notched so that they can only fit in one location.
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Old 01-10-2009, 10:48 PM
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Got the fuse glued up real straight (a couple small waves but all in all, pretty darn straight). Nice snug fits.

Used a couple of drill bits wrapped with wax paper to bring them up to a snug diameter fit, to align the spar supports. I clamped them lightly. Gaps don't mix well with CA. Not to say that there was gaps, but just to be sure.

I am also filleting some of the main structural joints with thick ca.
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Old 01-11-2009, 01:39 AM
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Next, the tail wheel support. Pretty cut and dried. I did have a little trouble locating the support. It was in one of the drops from the plywood crutch. I also had a brain fart and glued the rear former in upside down.:o

Oh Yeah, was your hands after the tail wheel support, before working with the wet sheeting.

Turtle deck was a cake walk. Sand the top of the angled former at the read of the cockpit to follow the line made by the tops of the aft formers.

I wet the sheeting with a spray bottle of water and it was ready to go almost immediately. I like to roll the balsa with the wide side of a 12" ruler to keep the line straight across the formers. Let this dry, sand the top of the sheets to the top support and glue on the 3/32" top sheet. Sand to contour.
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Old 01-11-2009, 02:02 AM
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Birddog, your build thread is going good.

I'm just wonderin, how much balsa, how much ply to this point of construction? Are you putting the parts on a scale?
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Old 01-11-2009, 03:51 AM
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Dave, Thanks for the encouraging words.
Disclaimer: I am using a pretty liberal amount of CA.

The fuse at the point after sheeting turtle deck: 116.5g or 4.11oz
One wing, sans servo box and refining: 41.6g or 1.47oz

For Installing the t-nut into the wing, use a c-clamp followed by a block of wood with a hole to handle the protrusion. I pointed one of the spurs up and not in contact with the ply reinforcment figuring that a spur so close to the edge of the ply would sptil it anyways.

I used a drill bit again (10mm) to line up the ply reinforcments for glueing, although I did not seem to need it.

Sand the front of the wing ribs to match the sweep of the leading edge if necessary before applying LE strips.

Thats it for day one. Still snowing....
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Old 01-11-2009, 06:50 AM
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Its looking good Rob, I like the way that kit is made, that wing is very interesting and strong, much different from what I am used to, Keep up the great work, Chellie
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Old 01-12-2009, 02:01 AM
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Pretty decent day.
Built the second main wing in about 1/2 hour.

Ailerons. Straight edges come in really handy for joining the two leading edge strips.

Stabilizer. Pretty straight forward. Wet the sheeting a little for the bend and, I could be wrong, but I like to use the thick CA for sheeting around the sharper bends.

One Elevator half. I have begun using waxed paper to keep my fingers from sticking to the feather edges at the back of the ribs for a good glue joint.

After attaching the main wings I clamped the fuselage flat on the table. The dihedral is even to within 1/64" at the tips. The rear fuse looks to be dead square. Side lines look great. Nice kit.
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Old 01-13-2009, 03:17 AM
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Spent a couple hours after work. Got the secong half elevator done and glued to the other. Pretty simple. The dowel came out needing to be cut to exactly 6". Go figure. All I can say on this step is Eyeball, eyball and eyeball again. With the airfoil, there is really no flat areas that you can put to a surface plate. Not problem though.

Glued up the Vert stabilizer in about 5 minutes.

Rudder took somewhat longer. Follow the directions and it should come out straight. I had a slight bow in the trailing edge so I clamped it between to steel rules, misted it with the spraybottle and called it a night.

After looking at the control horns for a while I figured the two with the long horns are ailerons, the one with the short post is the elevator and the one with four holes is the rudder. The instructions were not very explicit on this so get the right ones in the right pockets before you glue any.

Blizzard warnings tonight!
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Old 01-17-2009, 03:36 AM
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Default Wheeee! Covering!!!!!!!

I needed a change of pace so I sanded, (they recomend tack-cloth to cleaan off the sanding dust, I used an air compressor CAREFULLY) hinged (use a small steel ruler on the control surface leading edges to keep your cut straight) and covered the main wings. This will split up the "too much fun" covering process and give me something to look at while I am working. I am using Coverite Microlite red and white and cutting blue 1/4" strips off a sheet of coverite vinyl. I might even go nuts and try printing "Goodrich" and cut that out in black vinyl. Unfortunately I blew my layout and forgot to have the blue stripe clear the aileron, Oh well. Later
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Old 01-18-2009, 12:37 AM
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Very nice covering job.
(bet you placed the motor at the back of the wing and had a thought)
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Old 01-18-2009, 12:44 AM
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Originally Posted by CarpenterDave View Post
Very nice covering job.
(bet you placed the motor at the back of the wing and had a thought)
Oh yeah! Got a fan fold of blu-cor foam in the corner. THAT'S gonna cover a whole bunch of thoughts! Thanks for the thumbs up on the covering. The biased lines with no support under them made me seek out the beer thread here last night.....

P.S. Thats my crappy heli pad, the one that got me into this whole RC mess, being use for a cutting board.

The Microlite realy goes down nice and seems to have a lot of shrink. Obviously
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Old 01-18-2009, 12:45 AM
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Rob, covering looks great! Can't wait to see more pics!
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Old 01-18-2009, 12:54 AM
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Rob,

Very nice build thread you have here. You are doing a great job on both.

Frank
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Old 01-18-2009, 03:15 AM
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Default Hinge Tip

Use pins to keep the hinges centered while you push them in. After inserting to the pins, remove them and push parts together fully.

Since this plane is so light, the hinges only need to be narrow, I used two pins to keep them straight. They also held two drops of thin CA per side.
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Old 01-18-2009, 04:01 AM
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Originally Posted by birdDog View Post
Use pins to keep the hinges centered while you push them in. After inserting to the pins, remove them and push parts together fully.

Since this plane is so light, the hinges only need to be narrow, I used two pins to keep them straight. They also held two drops of thin CA per side.
Rob,

Are you saying you install the hinges to the pins on both sides of the hinge (the stab AND the elevator, for example) at the same time, then slide them together?
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Old 01-18-2009, 05:20 AM
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Thats right. The pins will keep the CA hinge centered in the joint. Basicaly insures it is an equal distance into both balsa pieces. Without them you might just push the hinge all the way into the H. stabilizer and have very little in the elevator.
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Old 01-18-2009, 05:31 AM
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The hinges are red and the pins are yellow. Push the hinge into the H stab first. Then push the Elevator onto the hinges. Pull out the pins out, push together the last little bit and apply thin CA to upper and lower sides of hinge. Keep a little pressure holding the two part together and wiggle the control surface back and forth till the glue sets up.
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Old 01-18-2009, 06:08 PM
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Default Motor Mount

Remove as much carbon as you can from the mount pieces (no, this is not tedious). I recommend using a slower setting epoxy to give you more time to assemble all five plywood components at once. Also, the slower setting epoxy will sink deeper into the wood. Clamps

I added a hunk of lite ply on the inside of the motor plate. run the grain vertically to oppose the horizontal grain of the front plate.

The corner blocks are the biggest thing you can do to strengthen this assembly. Sand to get the joints as close as you can. Run the grain on a 45 degree (see black lines) to give you the most bang for your buck.

I am also gonna assemble the included stick mount to have on hand for some other project.
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Old 01-18-2009, 11:43 PM
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Default Cowl Construction

Cut the cowl out roughly staying away from the lines but getting the bulk of the flash off. Refine it by cutting closer to the lines. I recommend fitting the cowl to the fuselage by taping the two halves together, test fitting, re cutting and test fitting again. Mark some light lines on it and grab the plastic model glue. You don't need much. Try not to have it squeeze out on the outside.

I had to shave a little off the corners of the motor mount to get a good fit. This is probably because I can only find a giant collet adapter for the 5mm shaft. The output is a massive 5/16-24. I may take the prop base plate to work and turn some of the bulk off of it in a lathe. The nosecone is a turnigy and comes in at an even one ounce. I will hack a plastic Great Planes 1 1/2 cone after I reduce the size of the base plate. Looking good though.
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