StayQuiet's blog archive for March, 2012 - RC Groups
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Archive for March, 2012
Posted by StayQuiet | Mar 31, 2012 @ 10:27 AM | 3,841 Views
Attacking the problem of the canopy forming in a different way. (BTW, I haven't given up on the vacuum forming - yet. The shop vac only pulls about 5" of vacuum. I'm working on a two stage vacuum source using an old A/C system evacuation pump, capable of pulling 26" of vacuum, and a large air tank to store a vacuum supply. Opening a quick release valve to the table when the heated plastic is applied, and hitting it with 26" of vacuum should pull just about anything down.)

For now, however, I'm making up a canopy from 0.040" Lexan sheet, cutting it in pieces and bonding it together with Lexan cement, then gluing the assembly to the plane with some canopy glue. I've worked up a cardboard mockup of the pieces, since the cardboard is almost the same thickness as the Lexan sheet.

I also built a cowl for the nose, which houses some lead weight required to obtain the correct CG.
Posted by StayQuiet | Mar 25, 2012 @ 07:22 PM | 3,618 Views
My second attempt at vacuum forming a canopy went about as well as the first. Hotter oven, longer heat cycle, faster application - all no good.

I did some research (probably should have done that before I started, huh?) and found that the canopy form is too tall for vacuum forming. Something about draw ratios greater than 3:1 not working, and the canopy is above that ratio. Well, at least now I know why it didn't work. Time to re-think the problem. If I get some thicker material, I can score out the bend lines in the canopy. Prior to bending, I'll run some black trim tape across the score lines on the opposite side, then bend and glue everything into the proper shape.

At least it sounds good.

A quick check on the CG shows that the plane is tail heavy. Originally drawn up for glow power, the electric motor is much lighter than the glow engine and mount. So, out comes ModelCAD and a partial cowling is designed. Files have been sent to the LHS for laser cutting. That will give me an area to add weight as far forward as possible, so the overall weight won't be as bad.
Posted by StayQuiet | Mar 24, 2012 @ 03:42 PM | 3,557 Views
Covering went more quickly than expected. I changed up my scheme from all all-white fuselage, and went with the orange upper surfaces to blend in with the tail feathers.

I still have to make the canopy and finish the cockpit area, install control horns on the elevator and rudder, and finish connecting the control linkage. My wife is working on the graphics with some black trim sheet material. I'll paint the firewall as well.

The opening above the motor allows air into the fuselage, over the battery and ESC. Air travels over the wing and exits a hole in the bottom of the fuse just aft of the wing mount. Behind that is an access hatch for the receiver, so the aileron servo can be plugged in.

This is one bird I'll be proud to bring to the field. Built from plans, redrawn in CAD, laser cut and assembled. I hope it flys as well as I hope it will!
Posted by StayQuiet | Mar 23, 2012 @ 09:40 AM | 4,567 Views
Lexan sheets came in for the canopy. Got everything all ready, shop vac attached to the vacuum form table, oven warmed up and ready to go.

This is going to take practice.

I don't know if the oven wasn't hot enough, I didn't leave the lexan sheet in there long enough, or it took too long to move the sheet from the oven to the forming table, but it only shrunk down over the form about 1/2 way, then went solid on me again. Trying to re-heat it in the oven just allowed the top (formed) area to start to sag badly, so I re-applied it over the form and saved that part. I thought the best way to finish the forming would be to use a heat gun, but I overheated the sheet and melted a nice, large hole in it.

I may end up making the canopy a little less tall (cut down the form a bit, so the lexan doesn't have to stretch as much over it), raise the temp of the oven, leave the sheet in longer, and try again with the second sheet. Oh, and move the vacuum table right next to the oven door, so the sheet stays hot and flexible longer.

I need another excuse to send the missus out shopping while I take over her oven and kitchen.
Posted by StayQuiet | Mar 21, 2012 @ 04:57 PM | 3,899 Views
Hatch magnets are in, I've run the control rods for the elevator and rudder (temporary - they will be installed after the fuselage sides are covered). Everything is looking pretty good.

Now comes the part I dread the most: covering. I've never been very good at doing this in the past. I always used Monokote, but this time I decided on trying Ultracote. I started with the simple pieces - the tail feathers. Wow, what a difference working with this! It is so much easier!

For my color scheme, I chose bright orange for the tail surfaces and wing tips, white fuselage and wing top surface, and black and white checkerboard for the wing bottom. My wife has one of those craft card cutting machines, and she can put in any font and cut out lettering (she's made AMA numbers out of trim sheets before, and they came out great - thanks, honey!) Since this design is loosely based on a crop dusting plane, I've been trying to come up with a 'company name' to be applied to the fuse sides. Best suggestion so far has been 'TuLowe Crop Dusting Service'.
Posted by StayQuiet | Mar 17, 2012 @ 12:56 PM | 3,865 Views
I've been working on the canopy form. The term "soft pine" is a bit deceptive when you're trying to cut, plane, file, and sand a block of it into a shape. However, I think I've managed to get it to where it looks okay.

I ordered two pieces of 0.015" clear lexan that will be used to make the canopy over the form, using my home-made vacuum forming table, the shop vac, and my wife's oven. I should probably do that when she's not home, just in case it doesn't go well.
Posted by StayQuiet | Mar 14, 2012 @ 08:21 PM | 3,458 Views
Fuselage top is done. What was a balsa 'cockpit' on the plans is now an open cockpit area, which will be covered by a home-made clear canopy (I hope). Elevator and rudder servos are installed. It's a snug fit (narrow fuselage) but by crisscrossing the control rods I can maintain a pretty straight shot to the control horns. The battery compartment is where the fuel tank was supposed to go. I made up a hatch for access. Just have to install some rare earth magnets to hold it in place.

So far, so good.
Posted by StayQuiet | Mar 10, 2012 @ 06:42 PM | 3,538 Views
The fuselage assembly (F1, F2 - landing gear mount, F3 and F5) were glued together so that I could set up the wing mounting block bolt. F1 was also drilled and 4-40 blind nuts installed for motor mounting. I test fit everything today. It's almost starting to look more like an airplane than a pile of balsa.

Oh yeah, the top nozzle part of my CA bottle broke off, and some CA spilled onto my pantleg. I now have a nice, nickle-sized splotch on my leg where the skin blistered and pulled off.
Posted by StayQuiet | Mar 08, 2012 @ 08:55 PM | 3,599 Views
Wing is 90% done. I still have some sanding to finish, have to cut slots for the aileron hinges, secure the servo in it's mounts, and hook up the aileron linkage.

Then it's time to move the fuselage plans onto the building board!
Posted by StayQuiet | Mar 05, 2012 @ 06:30 PM | 3,604 Views
The rest of my laser cut parts showed up at my door today from National Balsa. Well packaged, no damage, and great quality wood.

The rudder had a slot cut into it for a 1/8" X 1/4" strip of balsa stiffener (which I installed before I remembered that I forgot to take a picture). Elevators will be joined with spruce. I checked the fit between the fuselage half and the wing half that is built, and it's perfect!
Posted by StayQuiet | Mar 04, 2012 @ 12:07 PM | 3,637 Views
Right wing half is almost completed. I made a few changes from the plans. First, instead of using a 3/16" square LE and then sheeting over it with 1/16" balsa, I used a 1/4" square LE and the sheeting butts up against it.

I also noticed that the plans call for 1/2" dihedral at each wingtip. But, there was no brace of any kind on the plans at the wing joint, which I thought odd. I modified the innermost W2 rib and added in a 1/16" ply dihedral brace.

The plans also call for the use of a single 3/16" thick partial rib (W1 and W1a) located at the center of the wing. W1 is slotted for a 3/16" dowel, used to locate the wing to the fuselage at F2. I had two of each cut when I did up the CAD plan, and I'm glad I did. By gluing both W1 and W1a ribs together, it will provide some additional support at the wing joint. I added two strips of 3/32" balsa on either side of the dowel and epoxied it in place.

I still have to apply the LE and TE 1/16" sheeting, and the cap strips on the bottom of the wing, but I'm going to wait to do that until after the left half is built and the two are joined together. That way, I can keep the build tab on the outermost W2 rib to make sure my dihedral is correct, and there is no warp in the wing. Once that is done, all the build tabs will be cut off and the bottom of the wing sheeted. Add in a servo mount and some aileron linkage and ailerons, and that part of the build will be done!
Posted by StayQuiet | Mar 03, 2012 @ 12:20 PM | 3,632 Views
The parts cut by the LHS (free plug to Creative Hobbies in Mendon, MA here!) are done. It's fascinating to watch the wood go into the laser cutter, see a little smoke, and end up with the parts you need, precisely cut, and just pop out of the wood sheet. I would much rather spend my time in front of a computer, teaching myself CAD, than to spend hours trying to manually cut those same parts, and probably not as accurately.

Who am I kidding? Definitely not as accurately.
Posted by StayQuiet | Mar 01, 2012 @ 07:18 PM | 3,730 Views
All major parts have been drawn up in CAD and are at the laser cutter. Servos have been ordered, and I'm making up a list of what balsa sheets and sticks, and hardware bits I'll need for my next trip to the LHS.

Once all the cut parts arrive and I can start building, I'll start taking photos of the progress as I go along.