Building the Mountain Models Dandy

[Joker 53150]

A new build has hit my bench, and this one should be very quick. It's an easy build, easy enough for a first time builder with limited space and resources. It will take a minimum investment in tools, most of which we all have already. I'll be documenting this build to hopefully convince new builders to give it a shot.

The plane is the Mountain Models Dandy. I've done a few MM kits and also some cheap Chinese kits and the MM stuff is worth every penny. Good instructions, a complete kit, great laser cutting, and a rabid fan base willing to help at every turn.

Since some people haven't tried building from balsa, I'll also try and shed some light on the basic tools needed.

 

[Winglet]

I built a Dandy several years ago. Pretty good flyer but easy to damage. Doesn't take a crash very well.

 

[Joker 53150]

It's a lower performance version of the Switchback which is a great flyer. They certainly won't handle a hard crash, but if built lightly itt won't be a rock at impact so damage may be limited.

Not long after I built my Switchback it was involved in a head-on impact with the ground, breaking the fuselage in half. It took a few hours to fix, but it still flies as good now as it did then, and you can't see the damage.

 

[Joker 53150]

To get the build thread going, here are a couple examples of what I'm building. In this case, I'm building it for my dad who has limited stick time, but can fly a 4-channel plane. Most of the construction will be done over one weekend, and once the motor and electronics get here it should be easy to finish it up.




Mountain Models does a great job packaging their kits for mailing. Everything was sent in a large USPS mailing box and arrived in perfect condition. They wrap all the wood together and secure it with the pushrods to a section of cardboard for a little stiffness. The plans and manual are included, along with the wheels and a lot of misc hardware. While it isn't a 100% complete kit, it's pretty close.




Every balsa kit I get gets inspected for damage prior to building. I've never had any damage to the MM kits, knock on wood. The Hobby King balsa kits are usually in good shape, but there have been broken pieces in the past. Also, the quality of the wood for the MM kits is above average. When inspecting the laser cuts I occasionally find spots which need a little extra cutting to remove, but usually the cuts are fantastic.

 

[Joker 53150]

Since the idea of this thread is to get people interested in trying their own build, I figure it's useful to include information on what kind of tools are needed. This build is pretty basic so I won't need a lot of fancy tools. As you get into more advanced builds you often need a bigger selection to work with.

For this build, this is most of what is needed. A mat to cut on, glue, wax paper, a sanding block, pins, and weights/clamps.




My glue of choice is Titebond II wood glue. I also use thin and thick CA and 30 minute epoxy. The CA and I don't get along that well, so I use it only when needed. Building from balsa isn't normally a race, so waiting for the Titebond II to dry isn't a big deal for me. Notice the paintbrush - I use it to apply glue evenly across the surfaces. It's also used to paint some glue along edges for a little extra strength. You'll see it in some of the upcoming pictures. Is it necessary? No idea, but it works for me so I'll continue doing it.




I use a Great Planes sanding bar, and have two different sizes. You can get great results sticking the sandpaper to a block of wood, or as the first picture above shows, a paint stick or popsicle stick. The smaller sizes are great for sanding confined spaces.




There are a lot of choices for pins. I like this style as it doesn't hurt when I push them into harder balsa. I try to avoid putting too many holes in the wood and will use weight bags when possible (shown below). If you use pins you'll also need a surface that the pin can stick into. In my case I'm using a ceiling tile cut to 2' x 2'. Cork board, drywall board, or other surfaces work as well.




You can never have too many clamps. These are from Harbor Freight, and I think they were around $5 for a dozen or so. They're about the perfect size for balsa building.




These larger slide clamps are also very handy, although with a little creativity you can get the same results without spending any money.




These are one of my favorite tools - bags filled with BBs. I picked up two containers of BBs from WalMart for about $12/ea and made big and small weight bags. They distribute the weight well when holding parts down. You could make something similar with sand for less money.




Last is my Master Airscrew planer. You could sand wood to remove it, but the planer does it more quickly and with no dust. I use it most often on leading and trailing edges, removing material to get the desired shape.

 

[Joker 53150]

Time to build! The tail feathers don't get much easier than this. All you need to do is pop the pieces out, LIGHTLY sand the edges to remove some of the laser residue, and glue the pieces together. The design by Mountain Models gives you clean ends without a lot of end-grain. Once the parts are glued together and dry I'll give them a light sanding to make sure it's all flat. The instructions were done over a decade ago so they call for painting the surface. Instead this bird will get lightweight shrink covering.

 

[Joker 53150]

The wing construction went so fast I forgot to take pictures! The overall design is very simple and lightweight. Lighter in this case helps the plane fly more slowly and should result in less damage in a crash. The two wing halves were assembled and laid on the build board with the weight bags to hold pressure on the spars. Some pins were used at the trailing edge to hold that piece in place while the glue dried. Once that was done the two halves are simply glued together. They feel very flimsy at this stage, but once the covering is installed they become much stronger.




Ailerons were also a quick build. As with the other components, I'll wait until the structures are complete before sanding.

 

[Joker 53150]

Well, the wing is done. Wing tips were about the most difficult part as they had to be installed in two steps. First the section from the spar to the trailing edge is glued in place. When the glue is cured you push the front portion up into place, glue it, and secure it until the glue cures. Pretty easy, meaning the entire wing was super easy to build.




There is a little very thin plywood used at the center section of the wing, sheeting it top and bottom. The aileron servo mounts right into the top of the wing, which doesn't look great, but this plane is designed to be an easy build and easy flyer, so the aesthetics aren't that important.

After these pics were taken the entire wing was sanded lightly and set aside to wait for covering.




The fuselage is pretty easy to build as well. To start some doublers are glued to the main balsa sides. These give some strength to the sides and also help locate the internal formers. As mentioned in a previous post I like to use a small paintbrush to add some Titebond adhesive along the edges in areas like this which won't be sanded.




While the sides were drying the formers were glued onto the bottom sheeting. The picture shows I was building the fuselage while I was building the wing. Since the glue takes a little while to dry I jump back & forth to keep the build moving. The small weight bags work well to hold everything flat.




After the formers are secure to the bottom sheet I add the sides. The front and rear of the fuselage taper in, so I focused on the center section (where the battery will go) first. Once this dries I'll pull the front and rear of the fuselage into place.




The squeeze clamps work well to hold the side sheeting in tight to the formers while adhesive dries. This type of clamp is a little more expensive, but they're very handy to have.




The bottom has a pretty large cavity for a battery. Probably because the plane was designed before LiPo batteries, I'm guessing. The plan for this one is to use a 1000mAh 3S pack which will fit with lots of extra space.




The next two pics show how this plane's battery mount is designed. It's simply a light plywood section which will have a little Velcro on it. The hatch on the bottom provides easy access to the battery.







Squint your eyes and rub 'em real hard and it'll start to look like a real plane!




Top and bottom sheeting go on quickly, and the fuselage construction is complete. Tomorrow the glue will be dry and I can start sanding it. Once sanding is done it'll be ready for covering and electronics. By end of day tomorrow I should see the finish line. Motor and ESC should arrive Monday.

 

[Joker 53150]

Time to cover up that naked wood! I've covered a few planes over the past few years and used a bunch of different brands of covering. One of my favorites is the lightweight covering I get from Mountain Models. It sticks well, shrinks well, and looks good. Some people think it sticks too well to itself when you're installing it, but that's a small price to pay in my opinion.

To use the covering material you need a few specialty tools. First is the iron used to tack it down. Many people also use it to shrink the covering, but I prefer the hot air gun for that. Along with the iron you should also invest a few bucks into a thermometer and covering sock.




This is my preferred method for shrinking covering on large areas, like wings. On closed areas like sheet fuselages or wings I'll use the iron, set hot enough to stick the material down, but not hot enough to shrink it. That's kind of the key with the shrink covering - temperature. Each brand has their own temp range, so be aware of it.




The instructions with the covering should include details like temps for sticking vs shrinking. Test scrap balsa with it to be safe, it makes a big difference in the final product.




First parts to get covered on this plane are the ailerons. Like the wing, these pieces are pretty flimsy until they're covered, at which time they are a lot more rigid.




3M makes "Blenderm" tape, which works great for hinging surfaces like ailerons, rudders, etc. It's not invisible, but when you have thin surfaces too small to easily use mechanical hinges it's a good alternative. I've had this stuff on some pretty aerobatic planes over the past few years and have found it to work perfectly, with zero lift.




With the ailerons done, the wing was next. I haven't used the transparent film much in the past and was waiting for a good candidate to do some large areas. I'm building this plane for my dad, and he has no idea what it looks like yet, much less what colors are being used, so I get to have some fun with it.




A little extra shrinking is needed in the corners, but the overall look is pretty good. On nice smooth laser cut panels the transparent film shows off the construction. Also note that the ribs each have a small hole laser cut in front and behind the spar. I think that Mountain Models added these to allow airflow between the ribs. Without air holes you get trapped pockets of air which balloon up when you are trying to shrink the film. This allows an easy escape for otherwise trapped air.




The wing is held down with rubber bands, allowing some "give" if the plane cartwheels in some day. It might make the difference between minor and major repair. If it were being built for myself I'd change it to a bolt-on wing and take my chances.




All green would be overkill, so the fuselage is getting treated to silver film. The nose will end up green, but I'm waiting on that until the motor is installed in case I need to do any minor surgery to the nose to make the motor fit. I'm thinking of adding a little pinstripe of third color just to finish it off. But this is as far as I'll take it for now. Once the motor and ESC arrive I figure I'll need only a few hours to finish it up so it's ready for a maiden.

 

[Foam Addict]

That was a quick (and stunningly good) build!
I love that scheme, it really pops on that open structure.

 

[earthsciteach]

Another beautiful build, Jeff! Thanks for the BBs in a bag tip. That's a good one.

 

[Joker 53150]

Thanks guys. I'm just hoping it's as easy to fly as I have heard it is, so my dad can get plenty of stick time with it.

 

[Joker 53150]

A quick statement about getting what you pay for. I just received another balsa kit, the Cessna 182 from Hobby King. $49, not too bad, slightly less expensive than the Mountain Models Dandy. The Dandy instructions are 7 pages printed on both sides, well written English, decent (although dated) pictures, suggested throws, etc.

The Cessna's "instructions" are one large glossy color page (one side), 20 or so pictures slightly larger than a postage stamp, limited text instructions in poor Chinglish, and no set up instructions.

I really don't understand why Chinese companies don't hire native English speakers to write their manuals. Yes, it would cost a little, but I'm guessing nobody would notice an extra $.25 aded to the price to offset the cost. I'd happily pay a little more for decent instructions.

 

[Joker 53150]

All done and ready for a maiden! The final details were slow as usual, but all went well. Interesting note on the CoG, it's a little tail heavy as-is, probably because it was designed before lightweight LiPo batteries. I can get a 1000mAh pack forward enough to balance it, although I might add 1/4 oz weight to the nose to allow easier battery placement.

More pics and info on tools when my internet connection is fixed.

 

[Joker 53150]

A last few words on tools to build a balsa kit. As with foam, knowing how to use a soldering iron is important. In this case I needed to attach the bullet connectors to the motor and ESC and attach the battery connector. Quick and easy work, and the tools are cheap. An inexpensive soldering iron will work for most projects, although more expensive ones are usually more powerful and more easily able to solder thicker wires. Solder, soldering iron, and some flux should run under $20. The flux really aids in getting solder to stick to the wires, I highly recommend using it.

Hobby King sells shrink tubing cheaply by the yard, so I ordered various sizes and cut the lengths to fit into the box below, so the best size is always easy to find. While you're buying the shrink tubing, also buy various gauges of wire. As I was building this plane I noticed that the wires to the ESC would be a little short so I spliced in some 3" sections. Having the right parts on-hand always makes a job faster and better.

Although it certainly isn't needed, the hobby-holder pictured makes soldering easier as it holds the wires right where I want them. I could do a good job without it, but it makes the work cleaner and helps keep me from burning my fingers.




Today was the moment of truth - the maiden flight! The sun was going down quickly and my dad was in town so I wanted to make sure the plane flew before handing it over to him. Up first was my Mountain Models Switchback, to warm up my thumbs. The Switchback and Dandy are about 70% the same plane, although the Dandy is a high-wing, doesn't have a canopy or turtle-deck, and uses solid sheet tail feathers. The wing is exactly the same.

Once properly warmed up, my dad showed up and the Dandy took to the sky. My motor/prop combination isn't very strong, but this plane is so light it was easily cruising at 1/3 throttle. It tended to climb heavily so I added some down-elevator. It has more rudder authority than I expected, and was pretty stable as it should be. However, as mentioned it is very light so every little breeze was noticeable as the plane got bounced around a bit. Not a major issue if you've got flying time under your belt, but just something to be aware of. My Switchback is slightly more stable, possibly because it's heavier from the repair work.

In general, I found this kit ridiculously easy to build, and the quality of the cutting and fit of the parts is better than any kit I've built to date. Mountain Models kits are highly regarded in the kit-building world for a reason.

Thanks to all who have followed along with this quick build, if anybody has questions on the plane I'd be happy to answer them. Next up: a Cessna 182 balsa kit from Hobby King. I've started dry-fitting the parts already and know I'm going to swear a lot during this build...

 

[paulnb57]

Thanks for sharing! As a newb, I find this type of post educational and inspring.....

Looking forward to ypur next!.....

Paul

 

[Joker 53150]

Thanks Paul, I'm glad it's useful for you. The next build has already started, the thread is:

http://forum.flitetest.com/showthread.php?13198-Cessna-182-Balsa-Build

 

[Joker 53150]

A quick follow up on the Dandy. I gave it to my dad, and we flew it a couple times last year. It then sat for a while as it doesn't like the wind - the wing is huge for how light the plane is, so calm days are by far the best for it. Dad has enough stick time now to fly it, and it's become his go-to plane in the morning before winds pick up. He did lawn-dart it a month or two ago, and completely re-built the nose. I didn't even notice that it was re-built! He's running an 850 3 cell and getting over 10 minutes per flight. The light weight plane easily flys at under 1/2 throttle and just cruises around in a nice, lazy manner.