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Mountain Models EVA Sport Build Thread

rockyboy

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#1
I'm joining a bunch of ruffians doing a 2017 winter group build-along of the Mountain Models EVA (Extremely Versatile Aircraft). http://forum.flitetest.com/showthread.php?30782-Balsa-Forum-Fall-Build-Along

Also in this thread are build along pictures and some excellent tips from Try-n-glide starting around post #141
While the official start is on December 1st, I'm starting the unboxing of parts now cause I'm impatient. :)

The EVA platform comes in three flavors that all share a common fuselage and just switch out wings between the Sport, 3D, and Biplane configurations. I'm going with the EVA Sport for my build http://www.mountainmodels.com/product_info.php?products_id=215

The kit arrived in four days from Wisconsin to Virginia - and Brian at MM was extremely helpful in correcting a mistake I made in the order so I have the right components on hand.

The box took a little beating on one end from the trip

2016-11-07 20.03.04.jpg

But was well protected on the inside with stiff paper and air bags

2016-11-07 20.05.10.jpg

And inside are the pretty rolls of covering, trim, and plane parts

2016-11-07 20.05.58.jpg

The fuselage and wing kits are bundled separately, but very securely

2016-11-07 20.08.00.jpg

The only damage sustained in transit is a ding in the spoil section of one piece of balsa - no parts harmed at all!

2016-11-07 20.08.43.jpg

I've got the electronics on order from Heads Up Hobby - expected arrival in just a couple days.
 
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Joker 53150

Mmmmmmm, balsa.
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#2
Let the games begin! I've updated the list of builders to link to this build thread, and I'm really looking forward to your opinions on how the build goes together.
 

rockyboy

Skill Collector
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#3
And here's most of the electronics I'm going with, all ordered from http://www.headsuphobby.com/ - I love their quick shipping, good prices, and excellent customer service. Highly recommended.

2016-12-05 20.41.27.jpg

The motor is a PowerUp 370 (2208/14T 1400kV) putting out 140 watts. Should be plenty for sport flying as the spec sheet says 100 watts or more.

For some reason I ordered a 20amp ESC to go with it, but I need to do some workbench testing with a higher rated ESC and a couple different props - a might need to upgrade to a 25 or 30 amp ESC in there depending on power consumption. I'd rather not add the extra weight of a larger ESC if it doesn't need it - but letting the smoke out and going deadstick on a hammerhead isn't a fun thing to do. :)

There's a set of 9g metal gear servos, and a steerable nose gear to round out the initial package. I think the nose gear I got might be a little too heavy duty for this plane - it's 3/23" wire and seems like overkill looking at the main landing gear.

It'll get a FrSky receiver too, with a voltage telemetry sensor. I do love me some telemetry. :)
 

rockyboy

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Mentor
#4
Wings - Part 1

Time to make some balsa dust!

I'm attempting to document each step of the build here, especially the parts where I scratch my head at the pictures and instructions and need to pause and think for a bit. Hopefully if I get anything wrong, one of the excellent experienced builders will help correct me. And if I help someone else either get the confidence to take on this build, or avoid a problem in their own execution, then I'll feel all these pictures and explanations have been worth it. :)

So, first up is taking a look at the materials. Couldn't be happier with the balsa quality or laser cutting. Seriously - it's beautiful. One tiny place on one wing rib where the laser only got 95% of the way through, but a quick slice of the razor and it was free. One of the cleanest kits I've seen - right up there with Zeke's Park Scale Models and Stevens Aeromodel on parts design and quality.

Also, for anyone interested in my metal work surface it's a 45" IKEA Fjalkinge shelf that only set me back $20. Works great with various magnetic jigs and so far I've left the blue protective plastic in place too.

2016-12-05 20.43.44.jpg

Starting the leading edge assembly here - parts press fit together snugly, no need for glues yet.

2016-12-05 21.23.42.jpg

In just a couple minutes all the ribs are laid in place. For cutting the pieces loose from the balsa sheet, I highly recommend using a straight razor blade like shown here rather than the classic #11 exacto blade. The straight razor is thinner, and doesn't put any sideways stress on the balsa when cutting the parts free.

2016-12-05 21.36.33.jpg

Here's my sanding station. A square of 220 grit spray glued onto a very flat board. Check it with a straight edge if you do this at home - seriously, this is piece 3 before I found one in the scrap pile I was happy with. With very little downward pressure and a steady pull, the little nibs clean right off the long straight balsa pieces which will save me headache later at covering time.

2016-12-05 21.37.12.jpg

Putting in the bottom spar here. Workspace is a bit of a clutter, but I do try to keep tools in easy to see and grab places. In particular, there is a magnet to the right side of the row of pliers that I use to hold my straight razor blade when I'm between cuts. Keeps it easy to find, and out of the way of curious little fingers that might visit.

2016-12-05 21.40.46.jpg

My interpretation of the instructions here is that the lettering on the leading edge frame and spar all goes towards the inside (i.e. towards the fuselage) of each wing. This way a right and a left wing get built. However the instructions didn't have a close in picture of this so I'd appreciate a confirmation from one of the more experienced builders I've got this part correct before I glue in all the ribs.

Yes, that's right - nothing has been glued into place tonight except the plywood reinforcements I'll show in a moment. It's all just friction fit. Great design work. :)

2016-12-05 21.42.31.jpg

Time to put the blind nuts into the plywood reinforcements. The barrel of the nuts are about twice the size of the plywood, so to press them in securely I placed them over a hole in a piece of scrap wood before I applied pressure. That way the nut can keep going in until the shoulder is flat against the plywood.

2016-12-05 21.45.20.jpg

And to make sure the blind nuts don't decide to pop free in a couple weeks from vibration or Murphy's law, a bead of thick CA carefully placed around the shoulder. Don't get it in the threads - it can be a pain to clean out with such small bolts.

2016-12-05 21.47.01.jpg

Time to attach the plywood reinforcements to the first three ribs. Note that each of the plywood pieces is different for each wing, getting progressively smaller going away from the fuselage.

2016-12-05 21.52.50.jpg

To make sure the plywood holes aligned with the balsa holes, I pulled the carbon fiber rod from the fuselage kit. After clamping everything in place, I used just a small drop of medium CA on the plywood far away from the carbon fiber to make sure I didn't accidentally glue it all together. Once that was set, I pulled out the carbon fiber rod and clamps and wicked thin CA around the plywood edges for a solid connection.

2016-12-05 21.55.15.jpg

One other thing I'm not sure of - there is occasionally a very thin gap between the top and bottom spar plates (can see a little blue peeking through here). But when I squeeze the spar pieces together, I can hear the faint sound of balsa crushing, so I do believe the fit on the ribs is as snug as it can be.

Is this a fit problem that's worth worrying about? My gut says no, just run a little medium CA in there and lightly clamp and everything will be just fine - this isn't watch making after all.

2016-12-05 21.59.10.jpg

One final tip for tonight for everyone who made it this far (and a reminder of my question above).

The tip - if you hate that feeling when your exacto knife rolls off the table and drops point downward towards your feet, just put a zip tie around the end of the handle and snip off the tail. That little nub will prevent it from travelling on it's own towards your tender bits.

And one final time for the key question of the night - before I put glue to all the ribs, is this the correct interpretation of the 'all text goes to the inside' instruction?

2016-12-05 22.35.19.jpg

Thanks!
 

Turbojoe

Active member
#5
I'm becoming a big fan of HeadsUpRC. Good guys and great service. I think you'll find that 5/32 nose gear is going to be difficult to fit. Too big and too heavy. I use the Dubro #234 on just about everything I convert to trike. On my EVA trike conversion I drilled it out and bent up my own 1/8" gear wire because I knew I'd be flying at a very rough field. Stock should hold up under normal conditions.

Joe
 

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rockyboy

Skill Collector
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#6
Thank you Joe! Appreciate the advice on the nose gear and close up picture - ordering the smaller size now :)
 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#7
I think you'll be in good shape with your wing spar. Add a little medium CA to fill the gaps if you want, but don't sweat it. The EVA is lightweight and shouldn't put a ton of force on the spar.
 

rockyboy

Skill Collector
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#9
Wing Continued...

All of the ribs have been glued in place now, and here's putting the trailing edge on. Using all the fun magnetic hold downs because why not - they are just sitting there anyway. For weight to keep the ribs flat, I am using little bags of lead shot. I made those from a 2 pound scuba diving weight bag and a bunch of those little zip bags that seem to come with every RC part.

2016-12-06 18.44.07.jpg

For the bottom of the D box, I also used blue tape to hold the front edge around the curve of the ribs.

2016-12-06 19.35.08.jpg

After dinner, it'll be on to the top of the D box and the next page...
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#10
I've gotta thank you for your detailed build thread. Your info showed me where I screwed up and missed the extra CF spar plywood supports! I was able to go back and fix the issue, luckily before covering or flying the plane and finding out the hard way. The mistake will be added to my thread as an additional warning to people to slow down and read the instructions. :)
 

rockyboy

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#13
Since we're all above ground still, I took some time tonight to finish building the first wing section. :)

Next step was gluing in the leading edge of the top D box sheeting. Some hold downs on the trailing edge to make sure everything stayed flat.
2016-12-06 20.53.48.jpg

And then it was time to glue the sheeting down to the ribs, using the shot bags to hold things tight to the curve.
2016-12-06 22.27.22.jpg

And the servo mount goes in nice and flat with the bottom of the wing surface.
2016-12-06 22.48.46.jpg

After a little work with a sanding block, the leading edge is rounded over and the ends are squared off.
2016-12-06 23.24.54.jpg

Pretty neat how the pile of sticks at the bottom turns into this large and sturdy structure.
2016-12-06 23.43.26.jpg
 

rockyboy

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#14
The right hand wing goes together much quicker than the left one. :)


I've got a phone holder coming that should give me a better angle for the workbench on my next attempt - but I'm pretty happy with this for my third or fourth time ever editing something together - and with a sound track too! Thanks Eric!
 
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Turbojoe

Active member
#15
I've gotta pick up some lead shot one of these days. So many times I have situations that it would really come in handy and I can only smack myself in the head for never following through.

Can't remember who sells those magnet holders you're using. Can you post the link? I have one of the original Eldon J. Lind "Magic Magnet" building boards and those iron magnets sandwiched between metal plates suck out loud. Neodymium are the way to go. There are several laser cut holders available but I like the ones you have.

Joe
 

rockyboy

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#16

Turbojoe

Active member
#17
Thanks for the links. Prices are really good on both of them. I'll have to make some orders when I get home. Good thing I can't use PayPal while I'm bored at work or I'd need an extra job to help cover all the online spending I'd be doing.

I leave the credit cards in the safe at home so that's an extra layer of protection. :)

Joe
 

rockyboy

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Mentor
#18
It would be better for me if they blocked that too. The number of new kits in the workshop is growing faster than I can get them flying around here. Have you seen the new Pacemaker from Stevens Aeromodel? Just released with this quarter's Balsa Builder magazine. I am trying so hard to resist picking that up before I finish the EVA.... Must get one kit flying before buying any more... Not counting the two FT planes I have coming of course... They were on sale! :)
 

Turbojoe

Active member
#19
That Pacemaker is a cool looking plane. The old timers are starting to grow on me. Brian sent me a Tom-E-Boy 150 kit a year or three ago. Didn't think I would like it because it's RET but I was wrong. It flys great (with rudder on aileron channel) and it looks like something out of R/C yesteryear. These are nice slow laid back machines. Gotta love 'em!

Joe
 

Turbojoe

Active member
#20
Just ordered 8 fingers, 4 thumbs and 50 magnets from RetroRC. It turns out they don't take PayPal so I had to use the card anyway. :( The lead shot is in my Amazon cart with a bunch of stuff for the grand kids. When the grand kids order is full I'll send it all off. Thanks again for posting the links!

Joe