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Mountain Models EVA Bi-Plane, Balsa Build Along Build Thread

Joker 53150

Mmmmmmm, balsa.
Mentor
#1
Game on! This build thread is part of the 2016 Balsa Build Along, started by Jsknockoff (full details can be found HERE). The goal of the build-along is to give people a good opportunity to try building from balsa, with a supporting community of people building the same (or similar) kits at the same time. With help and encouragement we should all be successful in getting airborne!

Most of us are building a version of the Mountain Models EVA. Different wings are available for it to give the builder some choice in how they wish to fly. Some are going with the "Sport" wing, others the "3D", and I'm going with the Bi-Plane. The kit was ordered a few days ago and arrived today.

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Everything was in great shape, as per usual. I also just noticed that this 2 meter roll of covering would be enough to cover both sides of the elevator and horizontal stabilizer on the L-19, with a little left over! :)

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The wing and fuselage are packages separately, allowing Mountain Models to simply package the proper wing ordered with the fuselage.

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Hardware is included, including the needed nuts, bolts, and blind nuts. The manuals are actually written in ENGLISH, and aren't a horrible translation. You can download and print them from online if needed, but every order comes with the appropriate manuals.

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The fuselage also includes a cowl (you can order a replacement if ever needed), carbon fiber spar, wheels, aluminum landing gear, pushrods, tail wheel & wire, battery strap, etc.

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It's going to take a lot of restraint to hold off on construction until Dec 1 when this kicks off! :)
 
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rockyboy

Skill Collector
Mentor
#2
My strategy for stopping myself from opening the MM package before 12/1 is to cram another build project in the middle. :)

Good luck!
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#3
Good plan. I'm going to try and get a little work done on the big L-19 over the next few weeks, along with a little EVA planning.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#4
I forgot to emphasize this, but for anybody looking to build a kit and wondering why the MM kits cost more than the generic Chinese kits, you'll notice a few things as we get these builds underway.

First, the quality of the laser cutting is far superior to any Hobby King kit I've ever seen. It's easy to get spoiled by how easy the pieces can be removed from the sheets.

Second, you'll see that the accessories included with the kit are high-quality and NOT cheap-o stuff. From nuts & bolts to pushrods to wheels, it's all high quality.

Third, the hardware included is typically very complete, saving the builder time and effort buying last minute pieces. I will sometimes use different hardware than included with the kit, but that's only due to personal preference.

After these builds are underway, check back on some of my build threads for the Hobby King Cessna 182, the Red Swan, the DLG, and the Sun Bird. Quality costs more, but as the saying goes, "Buy the best and only cry once". :)
 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#5
Doing some pre-build research I found a couple areas on the EVA that builders should be aware of during construction. Nothing major, but it'll make the build better in the long run.

First, besides having sanding blocks I'd recommend taking a popsicle stick and gluing some 200 grit paper to one side. This will let you get in and sand some small areas without over-doing it.

Also, when you're building the wing note that the leading edge is made up of three pieces formed in a "T". Two pieces make the top of the T, a thinner and thicker piece. The thinner goes on first and is slightly narrower, followed by the wider and thicker piece. Make sure they're installed right, as they can be installed backwards. Also, VERY lightly sand the little nubs off as you take the parts out of the sheet. You DON'T want to do all your sanding until the whole piece is built, but you DO want to lightly sand the nubs off before gluing parts together to make sure they'll all fit properly.

Don't expect perfection. This kit is very well designed and the fit between parts is almost always dead-on accurate, but there can be variation between sheet thicknesses and minimal sanding may be needed to get parts to fit together.

More to come.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#6
Let the build begin! :)

Before starting, all the wood and parts with the wing kit were laid out for inspection. I found that almost every single piece was cut perfectly, with a couple that needed the help of the knife due to some hard spots in the balsa. Most pieces almost fell out of the sheet with absolutely no knife or effort needed, making this part of the build super fast and easy.

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Very quickly, the two halves of the top wing came together. At this point there is no glue, it's all friction-fit and ready for spars and thin CA. You can see I didn't bother sanding the edges. In fact, on this one I'm not sanding anything until the full wing structure is built. Sanding will be minimal, and is mainly to round the leading edge and knock off the little bumps where the parts were held to the sheet. DON'T be tempted to heavily sand everything! A few LIGHT passes with 220 grit is plenty.

Also, I mentioned it earlier, the two pieces for the leading edge need to be installed carefully. The THIN piece goes on first followed by the THICK piece. It's hard to see in this pic, but one of my thin pieces is installed wrong. It won't matter in the long run, but take care that all parts line up before adding glue. Also, the tabs that hold the two leading edge strips in place are very thin, and the balsa can crush VERY easily as you put the tabs into the LE slots. I just did the best I could and then dripped in a little CA to hold it all together. The crushed tabs won't be seen and the wing will be plenty strong once the sheeting and spars are added.

Getting this far was maybe 15-20 minutes (not including removing parts from the sheet). I did test-fit the two wing halves together and found the fit a little too tight where the "fingers" interlace, so I'll end up sanding them a bit to make it work.

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AkimboGlueGuns

Biplane Guy
Mentor
#7
That's an interesting detail that I've never seen before. Is that just for alignment/ease of build or does it do something else? I'm going to have to get me an MM kit one of these days.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#8
Many aspects of the MM design are for efficiency of design, lightweight building, etc. In this case it's that, plus it allows the plane to be self-jigging so no plans are needed (or even included). Everything is built based on the step by step instructions, so slots & tabs play a big part of it. All you need is a flat surface. When you watch the builds and see the Lucky ACE wing go together, you'll see that the entire wing (except for the ailerons, if I remember correctly) goes together without a single drop of glue. You can pick it up and move it around before dropping in the CA, quite an amazing design.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#9
With the EVA, the leading edge of the wing is sheeted top & bottom. To attach it, I put a line of slow-cure CA along the front edge and set the sheet in place. Pins were stuck down into the LE as a guide for force the sheet into place. It was left for a few minutes to set up before moving on.

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As mentioned previously, the "fingers" that interlace to hold the two wing halves together needed a little sanding to fit together properly. Once done, the wings were put on a flat surface and a little CA dripped into place to tie them together. This, along with the wing tip ribs were actually done before the sheeting was started, as the sheet goes on top of those pieces. Everything fits together in a way that makes a printed plan page unnecessary. All the builder really needs is a flat surface.

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Slow-cure CA was again used to attach the rest of the sheeting. After leaving that for a few minutes (and working on the L-19 to keep me busy during the cure), I came back and gave it a very quick rough-sanding and then squeegeed on some balsa filler to fill any low spots. I'll let that go for a day and sand it after it's dry. Note that the pockets for the struts are also installed now - they're simply glued to the sides of the ribs.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#11
A few quick minutes with some 220 grit to smooth out the filler and the upper wing is pretty much done. Since I'm using transparent covering I wanted to make it as nice as possible, otherwise I may not have bothered filling it before sanding.

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The wing tip ribs are thicker than the other ribs. Here the edges are all rounded slightly. The trailing edge just got the corners knocked off a tiny bit. This wing is pretty much ready for covering.

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I skipped ahead in the instructions and did the ailerons. They're designed to avoid any any excess end-grain by capping the ends with sheet with the grain running the long direction, a nice touch that gives it more strength and helps it resist bending. These will still need to be sanded on all sides and bevels added to the leading edges. These ailerons seem VERY big compared to the wing size, which makes me wonder if this plane will be crazy-aerobatic or if that's just what is needed for good control. The ailerons are connected top-to-bottom wing so one servo per side controls both ailerons on that side.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#13
I can't tell if that's sarcasm or not since I may be a bit of a MM fanboy. :p

"High quality"? Probably, depending on what you mean.

From my experience, the MM kits deliver some of the easiest to build and best flying kits for the style and size planes we're dealing with. They're in a different league than giant scale planes or highly detailed kits. When compared against other 30-40"-ish inch span laser-cut, electric, small-field planes they certainly are high quality. I've built kits from other companies and scratch built others from plans, and for my money MM is very hard to beat. The kits aren't perfect (watch the other build threads for confirmation on this - jsknockoff has had some issues with the laser cutting on his kit), but build a kit from Hobby King - I dare you! :) - and then try a MM kit and you'll be stunned by the difference.

Their instructions are high quality and normally include many pages, tons of pictures or diagrams, and actual ENGLISH text. Again using the HK kits as comparison, MM documents are light years ahead.

With that said, MM isn't the only company that produces high quality kits. The Telemaster I built certainly falls into this category, although the plane itself was slightly more involved/difficult to build than a typical MM kit. The Herr kit I got appears to be very well cut, although the instructions aren't quite as good. There are certainly more out there, those are just the ones I have first-hand experience with.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#14
Moving on to the bottom wing, construction is very similar to the top wing. The leading edge "T" is made from two pieces fit onto tabs. I crushed a few due to soft balsa, but it's not a big deal. I consider them mainly there to help align the parts, and a little thin CA wicks in nicely and holds it all together. The first pic shows the two spars that I didn't show for the top wing. These spars really give a lot of strength to the overall wing. Note that the ribs are thin 1/16" balsa, so be careful when moving the structure around as it would be fairly easy to accidentally break one. We've all done it....

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The inside sections of these wings bolt to the fuselage. A CF spar is also used to give it more strength and keep it all lined up, and a small wooden locating dowel is also used. The rectangular holes are to run the servo wires from the wing into the fuselage. Make sure to glue the captured nuts in place well so you don't accidentally knock one lose during final assembly!

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This shape was throwing me off a bit during construction. The wing tapers in quite a bit at the inside where it meets the fuselage. This IS correct, even though it looks odd. I lined it up against the fuselage parts to confirm I wasn't screwing something up. The CF spar holes needed to be sanded slightly to allow the spar to slide into place. It's still a little tight fitting, but I'll tweak that as the build continues. I also tapered the tips of the wood locating pins slightly so they'd fit more easily into the fuselage locating holes. Next up, sheeting the leading edge, filling, and sanding. Note I haven't sanded anything on these wings yet, but will use a small piece of 220 on a Popsicle stick to remove the little nubs before sheeting.

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Joker 53150

Mmmmmmm, balsa.
Mentor
#15
Some sheeting, followed by sanding with 220 grit and the installation of the servo trays, and the lower wings are about ready for covering.

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SlingShot

Maneuvering With Purpose
#16
I can't tell if that's sarcasm or not since I may be a bit of a MM fanboy. :p

"High quality"? Probably, depending on what you mean.
Nope. No sarcasm. Thanks for the report. I suppose the laser cutting is making everyone's life better. Back in the day, pretty much the Japanese had all the nice kits. Lots of die-cut balsa in the U.S.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#17
Some companies are still doing die cut, especially on the small stuff (like Guillows). My guess is that there isn't enough demand anymore for balsa kits to warrant changing old kits over to laser cut. I haven't built a die-cut (die-crushed) kit other than a Guillows, although the big Balsa USA Fly Baby 1/3 scale kits I recently sold were both die cut. While the cutting looked ok, it surely isn't as easy or accurate to work with as a well-cut laser kit.

It's sad to see the old classics go away as people turn more and more to foam ARFs, but hopefully the plans stay around on the internet for people to still cut their own kits.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#18
With the wings basically done for now (covering and ailerons still need to be done) I'm moving on to the fuselage. First up is laying out the sheets to make sure everything is in good shape. Laser cut quality is still very good, although the really thick pieces (1/4") for the wheel covers isn't cut all the way through in spots due to some hard spots on the balsa. Most pieces pop right out with no need to use the knife.

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The MM kit includes the cowl, canopy, pre-bent landing gear aluminum, wheels, pushrods, hardware, velcro for the battery, and more. It's all very good quality stuff.

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Getting things started with the fuselage kit I'm kicking it off with the tail feathers. Each piece is etched with a letter - "H"orizontal stab, "V"ertical stab, "E"levators, or "R"udder. The pieces all fit together without sanding or trimming, and check out how intricate some of the laser cuts are to make the pieces fit like jigsaw pieces! Since this build is done without any printed plans the builder has to pay a little attention to some of the pieces to make sure they're installed correctly. It's not difficult - if the piece doesn't fit it's NOT the right piece.

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Last up before turning attention to the L-19 is building the wheel pants. They're made from a series of stacked 1/4" balsa pieces and capped with some light ply and balsa. Not pictured, I sanded one on the 4" electric sander which made the job VERY fast. Then it was final sanded with a sponge sander to give nice round sides.

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SlingShot

Maneuvering With Purpose
#19
While the cutting looked ok, it surely isn't as easy or accurate to work with as a well-cut laser kit.
My enthusiasm is racing right along. I can see a few steps along the way, but I'd like to have one super plane one day. I'm looking hard at the Top Flite 1/5 scale P-51.