Baker McMillen Cadet II - Scratchbuild

:: HISTORY ::

The Cadet was designed in 1929 by Dr. Gross, a former member of the Akaflieg Darmstadt, as an improvement offering some soaring capability over the existing primary gliders. Jack O’Meara, a demonstration pilot for Baker Mcmillen, flew a Cadet off South Mountain at Elmira, NY for 1 hour and 38 minutes in the summer of 1930 starting what was to become Harris Hill as the home of American gliding. One Cadet even flew on twin floats, and three of them (along with a Sky Gost, another Gross design) were towed at on time by a goodyear Blimp over Akron, OH. One remains airworthy.

Specs of the original aircraft

Span: 37.5 ft
Area: 162 sq. ft
Aspect ratio: 8.7
Empty weight: 230 lb
Payload: 180 lb
Gross weight: 410 lb
Wing loading: 3.1 lb/sq. ft
Structure: Steel tube fuselage, wood dual spar/dual strut wing, wire braced wood tail, all fabric covered.

Original Cadet II - 1930

:: PLAN INFO ::

Designed by:

Tom Martin
Designer at the Aerosente Glider Workshop

Build method: Balsa + Tissue paper
Build Time: 5 - 15 hours
Build Level: Beginner - Intermediate

 

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You can purchase printed plans from here: 

http://www.gliderworkshop.com/plans-little-flyer-series/baker-mcmillen-cadet-ii-38-wingspan-plans/

If you want, you can also purchase a laser-cut kit, from here:

http://www.gliderworkshop.com/baker-mcmillen-cadet-ii-1-12/kit-baker-mcmillen-cadet-1-12/

Please check out http://www.aerosente.com/ for more glider builds and kits.

Thanks to Tom Martin for making these great plans. The plans have been updated and improved since I did my build.

:: BUILD LOG ::

I started with the fuselage, to warm up my skills. The fuselage is built mostly out of 3mm square balsa sticks. They need to be wet down (so they get softer), bent into shape, and then pinned down in place.

Done pinning the frame. I use a sheet of EPS foam under my plans. It holds the needles very well. You could use cork or plywood if you prefer.

Now the long strips are pinned down, we need to cut off the excess sticks. Just cut them gently with a sharp X-acto knife.

Nice, clean cut.

Time to do the cross-struts. Mark the angles for cutting. Doesn't have to be so exact, just close. Glue it in place, guide yourself with the plan.

Cut and glue the other cross-struts. If you need to, pin them down. I use superglue (CA) to work with balsa. It creates a strong bond, and doesn't weigh a thing. I guess I used about 9 grams of CA for all the build.

First frame completed, now on to the next one.

Second frame done. As you can see I'm not cheap on pins.



Cut out the center sections for the fuselage. Slot the side frames into the center sections first, tack them in with glue, then slot the frame into the nose piece, and finally join the rear part of the fuselage.

Cut out and fit the bottom plates in place. Tack them in with glue.

Cut out and put the four pieces of the cockpit top frame in place. When you get a good fit, glue it in.

Install the wheel into the fuselage. I have no hobbyshop around, so I made a wheel from printer parts.

Go on with the main wing. Cut out all the ribs and the wing spars as well.

All the ribs slot into place very easily. Glue them in place. Now grab a 5mm x 5mm square balsa stick and test fit it as the leading edge of the wing. Use one 5mm x 3mm or two 3mm x 3mm balsa sticks for the trailing edge. Then glue the wing tip formers in. When you're done, it should look like this:



If it looks like this, eat a banana.



Using the fwd and aft wing joiners, I put the wings together, and added quite a bit of dihedral to improve its flying characteristics.



Test-fit the wing into the fuselage.

Next I did the tail parts - the rudder and the elevator. Start by cutting out the pieces for it.








The small ribs that make up the stabilizers have notches that fit perfectly into the leading and trailing edges. Glue the leading and trailing edges on the center spar (where the hinge goes) first, then fit the small ribs in place, and tack them down with CA.



I cut out all the pieces by hand. When it came to the ribs, I cut them out larger, and sanded them down to the right size when they were glued in place.



After sanding.



Rudder and vertical stabilizer done and sanded.



Elevator and horizontal stabilizer done.



Now, for the covering, I didn't have any fancy modern covering tools, not even the covering material itself, so oldschool glue and tissue paper had to work. This type of covering is really light, but it is also really fragile. It needs a couple of layers of tissue dope to become strong. However, I don't have dope either, so my model is just a shelf model. I'm going to experiment with clear epoxy to see if I can use that.

First, cut out a piece of paper roughly larger than the area you'll cover. When covering with tissue, keep in mind the following: Tissue will stretch in only one direction. You want that direction to be parallel with the wing. Try ripping a corner of the tissue. The rip will be clean in one direction, but in the other direction (perpendicularly) it will make an ugly rip.



Put a generous amount of glue on one side of the frame to be covered. Spread it out evenly. If the glue is too dry, it won't let you work with it smoothly. Place the tissue with the glossy side facing outwards. Try to stretch it out evenly over the frame, but don't pull too hard because you'll damage the tissue paper.



Using a sharp X-acto knife, trim the excess paper off. Be careful you don't cut into the balsa edges.



Some parts just won't be straight - but try to get as few wrinkles as possible. Small wrinkles will be taken care of later.



Cover the bottom first, then the top.



When you're done, it should look like this:



Cover the fuselage. It's easier, as it's small and flat.





I decided to cut a hole into the main frame of the fuselage - less weight.



Done covering!





To straighten out some wrinkles and to tighten the covering, get a refillable hairspray bottle, fill it with 50% water and 50% rubbing alcohol and moisten down the covering with the solution. I know this sounds like a bad idea, but it really works. When the liquid evaporates, it will start tightening the tissue paper. The rubbing alcohol doesn't stretch the paper, it's there to reduce the tightening effect so the frame doesn't warp. Note, however, Be really careful as wet tissue paper is extremely fragile.

Cover the elevator and rudder.





Install the rudder and elevator on the fuselage. Use CA hinges on the control surfaces. Note that the tissue on the stabilizers has not been tightened yet.



Install horns, rods, and electronics if you want!



The original plans ask for a carved nose out of a balsa block, but I found a nice way to make the nose much more like the original airplane! Two diagonal cross-sections do the job.



Looks great now!



I had to re-cover my wing several times as it was my first time using this technique. It takes practice to learn.



Ready to go! Hang it up in your room, as you will not be able to throw all these hours of work in the air :)



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Written by: colorex

Or check out the thread on the forum:

http://forum.flitetest.com/showthread.php?64-Baker-McMillen-Cadet-II

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