Landing Brake

Step 6 LANDING BRAKE

I had to wait a few days for an order of fiberglass to come in to finish the attach tabs on the MLG and the elevators. In the meantime, I started on the landing brake. I used a 2x4 and a 4' ruler to lay out the shape and size of the landing brake, measuring from the firewall and F-22 to make sure it was straight and square.

I then used the Fein sander, with the HSS blade installed, to cut the slot called for in the plans. This made making the cut really easy, you just had to be careful not to let the blade penetrate the foam once it cut through the glass. I used the 2x4, weighted in place, to make sure I made a square and straight cut.

To do the corners, I used my Dremel with a small cutoff wheel installed. If I kept the Dremel slow it didn't melt the glass and cut pretty well.

Once I had cut all the way around, it was time to remove the landing brake "blank". I was pretty sure that some epoxy had seeped under the brake and I would have some foam repair to do, but once I lifted it all the way around with a putty knife, it came off OK.

Two decent sized chunks of foam to repair, otherwise this turned out pretty nice. I'm comfortable I can repair those and still have a nice looking landing brake since the bottom will get a couple of layers of glass over it.

I had quite a bit of epoxy leak into the cracks around the landing brake, obviously, when I did the fuselage bottom layups. Most of this damage will be sanded and routed away, however, then I perform that task in later steps. If any damage is left after that, I'll just cut and micro in a piece of foam to repair it.

I used a straightedge, held in the right place by a weighted down 2x4, to mark the outlines of the landing brake before I cut it out.

I used the HSS blade on my Fein sander to cut through the glass and free the brake from the bottom of the fuselage. Worked great, as long as you don't let the blade cut too deep of course, if you let it it will cut though the inside layups on the bottom of the cockpit as well.

I used a cutoff wheel to do the corners. The HSS blade can't cut this small of a radius without making a mess of the area around the cut.

I knew I was going to install an electric landing brake actuator, so, I moved my LB-19 further off center than the plans state to put the mounting point closer to the center of LB-19.

I drilled holes and installed nails per plan to find the right spot for LB-23. A stainless steel ruler, held flat against the nails, provided a way to measure the required 2 1/4" distance. I have set LB-23 temporarily in place in this picture, you can see it is sticking up because it's not in the right spot yet.

To rout the slot in the foam for LB-23, I taped a 45 degree triangle to my cordless drill. I then put a piece of straight-edge plywood on the bottom of the plane securely weighted so it would not move. I then slid the drill back and forth, after adjusting the position of the drill in the chuck to cut to the right depth.

The low tech router trick worked great. Here's a shot of LB-23, temporarily installed in the slot I just cut, with the duct tape applied and the hinge in there. Checks good, fits nice and straight and the landing brake fits well all around as well.

Here's LB-23 after epoxying on the aluminum slugs for the hinge bolts. No real tricks here.

I used a Dremel to rout out the foam for the recesses for the aluminum slugs. I tried to keep the top edges of them intact so I would not have to fill that with scrap foam or otherwise once the inside of the landing brake recess got glassed. Using a chisel and utility knife, I carved out any other foam necessary to get LLB-23 to mount into its correct position. I only took out the foam that I had to, however. I decided to wait until I did the actuator install and test fitted the angles on the inside of the landing brake before I would take out any other foam to avoid removing too much.

Half of the hinge installed once LB-23 is fitted into place. I did a lot of test fitting, adjusting, etc. all throughout the landing brake step. I wanted to be sure the landing brake fit into it recess properly - not crooked or not flush with the bottom.

Once the landing brake was ready for the hinge half and LB-19 to be permanently installed, I went ahead and fixed some of the foam that had been damaged when the brake was removed from the fuselage bottom in earlier steps.

Once LB-19 and the hinge half were installed in the brake, I went ahead and test installed everything once again to check the brake flush and square. Looks good! The brake won't close all the way here, though, because I haven't removed any of the foam from the inside of the recess yet.

Once I had checked, and re-checked, and re-checked, all the fit and location of the brake, it was time to permanently install LB-23. This is another step where you check and check and check and check things to fit properly, then apply the "glue" (eopxy, flox, whatever) then hope all is well when things cure!

Once LB-23 was permanently installed, it was time to drill the hinge and the aluminum slugs. I started with small holes just in case I didn't get them lined up right. I then drilled to size and tapped the slugs.

Most folks building a Cozy nowadays opt for an electric landing brake option. This, aside from being sort of cool, cleans up the center console and gives the option for a little more hip room in the front seat because all these parts and hardware required to manipulate the landing brake go bye-bye. Further, most folks complain the manual brake, when the grab the handle to close/retract it, has a tendency to slam and bang their knuckles. So, I, too opted for the electric version. There is a kit you can buy that includes all you'll need. However, a couple of builders I know have simply purchased the actuator and then make the rest of the kit themselves. Geez - if I can build a plane I can certainly make a mount for the electric actuator!

I checked out a couple of other builder's designs and decided I didn't like them. They all were mounted with bolts in some way or another, I didn't want to to that. I drew up a design in AutoCAD (see this page for all my AutoCAD drawings) and then manufactured it out of some urethane foam pieces and a bunch of layers of BID and UNI.

Here's the blank for my landing brake actuator mount. Yes, it looks sort of messy now but wait until I clean it up. If you look at the drawing above, you can sort of see where the layers of glass were supposed to go. I made the part extra wide so it could be trimmed to size once laid up.

Here's the actuator mount after band sawing it to width. You can see here how it was constructed. IIRC I used 5 layers of BID and UNI, each, for each of several sub-layers in the part. The foam was used to make the slots (on the left) and the offset (the piece set at a 45 degree angle to the bottom of the part.) As the part was assembled, the layers were squeegeed out, stacked on top of one another, then the second sub-layer was applied, folded back on itself to make room for the foam part. Once the microed foam was installed, the sub-layer was squeegeed onto the foam and the process continued until the entire part was made.

Here's the part, after the hole for the mounting bolt was drilled, hooked up to the actuator for test fitting. This is how it will mount into the fuselage. I will need to cover the foam in the center of the part with a small BID layup at some point.

Another shot of the part and the actuator as they will be installed in the fuselage. I intend to cut a square into the side of the front seatback brace, same size as the part (but only through the glass on one side) then remove the foam from from that square. I'll then push the part down into that square hole and do a small 2 BID tape-style layup over the mounting flanges of the part to keep it in place. This mount should end up being very strong once completed.

Since the linear actuator has a fairly large diameter end on it, I turned my LB-18 parts around to make more room for it. I then closed the brake, after mounting it and tightening the bolts, and used the marks made in the foam by the LB-18s to locate the hole for the actuator.

I used paraffin and a propane torch to fill the bolt holes with wax in preparation for the landing brake recess layup. You can see the hole in the recess I made for the actuator arm and the LB-18s. I made sure there was a half inch or so of bare glass so the layups would not pull apart on the edges. The duct tape kept the paraffin from getting onto the foam.

Here's the landing brake layup recess after the layups have been installed onto it. I have not yet trimmed the edges in this picture.

I tried an experiment on the landing brake recess. Using some 2x4s, I made a frame around the brake recess and held it together with clamps.

I then stapled 6 mil plastic to the frame and filled it with water. I ended up with about 6 inches of water depth, I'm guessing this is about 100 pounds or so of water. It did press the glass down into the recess nicely, but, the plastic was a little too thick for it to stretch into all the compound curve corners.

Emily decided she needed to have her picture take near the plane as the layups in the landing brake recess cured. I hope to give her a ride in this plane someday - she can look at these pictures and remember when she was only as tall as the fuselage!

Once the recess layup was done, it was time to drill and re-tap the holes in the aluminum slugs. A cordless drill works great for tapping - it's easy to (using slow speed of course) stop and reverse after a few turns to clean the threads out. It's also less likely, as compared to a T-wrench for taps, to wobble back and forth as the threads are cut.

Now I needed to mount the actuator bracket I made. I started, after locating its position exactly by tracing it while the entire assembly was bolted together, by cutting the slots on all four sides with the Fein sander and a HSS cutting blade.

I then removed the foam behind the cutout. The bracket I made will fit into this recess, and, I'll put a 2 BID layup over it to keep it in place. The push and pull loads from the actuator should be absorbed by this recess and the layups over the bracket will only serve to keep the bracket from popping out of the recess.

Here's a shot of the bracket set into the recess. It fits perfectly, and, doesn't need any bolts to go into the map pocket or through the seatback brace.

The actuator is then mounted into the bracket with one bolt. I rebuilt my actuator - it came with the control box on the other side of the motor and screw drive assembly. Once I placed it in its designated spot, I realized it would fit better if disassembled and re-assembled to look like this. I did make a CAD drawing of this assembly - the landing brake, the bracket and the actuator - to ensure my geometry was right and there would be no binding. See the AutoCAD drawings pages for the bracket and overall geometry drawings.

I ordered a vacuum bagging kit from Aerospace Composite Products with some profit sharing money I got this year. Anxious to try it out on something on the plane, I waited for it to come in before doing the landing brake. Here's a shot of the brake after starting on the 3 BID layup that it gets on the inside.

Once the 3 layers were on, I used my Dritz electric scissors to scissor trim the inside layup close to the edge of the brake, especially near the front where the hinge half is mounted.

I then applied 2 layers of peel ply. The Cozy Girrls do this LoVac technique wherein they use cheap paper towels and cling wrap instead of bleeder ply and vacuum bagging materials designed for that purpose because the cling wrap and paper towels are much less expensive. Well, I decided I would use 6 mil plastic I use for various plane building tasks and some Bounty towels my wife buys for my workshop. They say they have trouble pulling off the peel ply and paper towels so I used two layers of peel ply.

Here's my first vacuum bagging experiment ready to go. Again, the layers are landing brake with 3 BID layers applied, two layers of peel ply, cut with plenty of overlap all around the part, and two layers of paper towels over that. I put 6 mil plastic down first, then folded it over and taped the edges. Add the vacuum pump connection, turn on the pump and let it work its magic.

The plastic and tape I used didn't seal very well. I ended up using a ton of tape to try to get a good seal but to no avail. I added cling wrap over the 6 mil and I eventually was able to pull say 5-7" of Hg vacuum, but the pump was running about 15 seconds on, 15 seconds off. It is rated for continuous operation but it got pretty hot after a while. I got a desk fan and put it next to it, blowing on it constantly, to keep it cool.

Once the layup cured, I had to open up the bag. The big scissors made quick work of the bagging materials.

Here's the brake, still wrapped in two layers of peel ply and two layers of paper towels. You can see a few spots where excess epoxy made it through both layers of both peel ply and paper towel, but most of the paper towels are still dry.

The peel ply and paper towels came off pretty easily. I think this was partly due to the two layers of peel ply and partly due to the fact that I wasn't able to pull a really strong vacuum on this part.

The brake turned out great. No, you don't need to vacuum bag your parts. I have been curious about this technique since I'd seen others do it, though, so I tried it. No bubbles, the glass is forced down into recesses and around compound curve corners without wrinkles. The surface is nice and even, no wrinkles if you work the peel ply down well.

After the edges of the brake were trimmed and sanded, I re-mounted it into the plane. Works great. I didn't have any clearance problems at all. It fits nice and square and flush.

Once I knew the everything was assembled (hinges, bracket, actuator, etc.) properly and fit correctly, it was time to install the landing brake actuator mount. I started by scraping the micro and foam from the inside layer of fiberglass on the seat back brace. After sanding around the recess with 36 grit, I installed a 1/16" plywood spacer to take up the extra depth. You can see it installed here. I painted some epoxy on the exposed fiberglass, then, painted more on the piece of wood after installing it.

In goes the mount I made. I filled the sides of it with micro earlier in the day. This installation should be pretty sturdy, the recess prevents the mount from moving in/out or left/right, and, the layer of BID over the mount will keep it from twisting.

I made a paper pattern for the layer of BID I would need. Wetted out the glass in waxed paper, put this over the glass. Cut the glass to shape, then, pulled off the waxed paper. Slid the glass over the part, pressed down to set the glass into the epoxy that had been painted on the part and the surrounding inch of seatback brace, then peeled the paper off. Nicely sized BID layup (with rounded corners even) properly shaped, sized and placed.

Here's a shot of the mount completely installed. The slightly darker area around the part/recess is the layer of BID I installed it with. This mount should work fine - time will tell. At least I didn't have to put any bolts through the seatback or into the map pocket.

I will need to buy some additional hardware for the brackets on the inside of the landing brake. This will prevent the actuator from being able to move side to side. Other than that, though, and some sanding and etc. the landing brake is now done.

Wanna' see the whole thing work? Click here for a video of the landing brake going up and down via the electric actuator. Dial-up users beware, it's 1.7MB!

That completes the landing brake. On to the canard!