Preparing Strut

Step 2 PREPARING THE STRUT FOR INSTALLATION

To keep the strut from being damaged while it sat for a while (I got it last year sometime) I made this hanger system for it. Just a couple of hangers and some 1x lumber.

I made the 8 degree cuts using some plywood cut on an angle for a guide. After clamping the plywood to the jig table, I made the cuts keeping the hack saw flush against the wood. Use a new blade for this - and use a new blade again for the second leg. The glass is really tough and the blade gets dull fast.

This shot is a closeup of the angle jig. You can see the short piece of gear leg in the background. Use a new, sharp hacksaw blade and go slow and this will turn out fine.

After cutting to length, the entire strut gets sanded dull with 36 grit. This took me about 3 hours total and I used about 10 sheets of 36 grit. I covered my hands and arms and wore a tyvek suit to keep the sharp needles of S glass from sticking to my skin and making me itch for a couple of hours after... This shot is of the strut about halfway done. I've sanded the top side but you can see the shiny bottom side not sanded yet. I turned it over lengthwise to sand the other side.

After sanding, and vacuuming, I marked where the nails would go. I then drilled holes for the nails and pounded them in. The strut is shown here after being floxed (with 5 minute epoxy) onto the nail heads for the torsional layup. I may pull it back off of the nails to make sure the two nails under the legs (not the middle) are at exactly the same height. I am paranoid that I didn't measure this exactly and I will build some twist into the gear legs when I add the torsional layup. I will also have to make some jig table extensions to catch the drips from the leg ends. I do want them hanging over like this - it will make doing the layup on the center of the piece easier. I may even change that setup as well - moving to the corner of the jig table to make reaching even a bit easier.

I ended up taking the strut off of the table. I wasn't happy with the height of the strut from the table (glassing the leading edge was going to be a chore that close to the table), I need to use that part of the jig table for some fiberglass cutting and we kept bumping (and putting greasy fingerprints on) the strut while it waited for its torsional layup. Once I was ready to put it back on, I laid plastic down first. Then, I made wood blocks which are screwed to the table through the bottom. They are tapered on top and have holes drilled slightly smaller than the nails. The middle one is a little longer, given the recess in the shape of the strut. Once those were mounted, I tapped in the nails being careful to make sure the two ends were the same height to minimize any twist I might build in.

I had a hard time envisioning the 35 degree angle for the major plies mentioned in the plans. So, I cut a piece of plastic the same size as the UNI that is to be cut for the next step. I added a bunch of lines with a marker to simulate the plies and then hung the piece over the strut. Ok, now I get how they go on there. I think I might even make some paper copies of this plastic piece which can be used to measure how long the piece needs to be - so it can be cut before hanging it on the strut.

Cutting glass was going to be fun for this step. So, I hung the roll from the ceiling, got out my PIA sticks and sheets of plastic tub surround and did it on the table anyway. It wasn't too bad working around the strut in this higher position. I only cut 12 pieces, vice the 13 called out in the plans, most people said they used 11 or even less. I do have one short piece - call it 11 1/2 pieces, so I hope we make it. If we do use paper patters to measure and cut the glass I think we won't waste much.

Once Kelly and I did the 4 layer UNI torsional layup on the strut, I tried a peel ply technique. Lightweight dacron does shrink a bit when heated, so, I wrapped the strut tightly end to end with 3 or 4" wide pieces. Then, I used my heat gun to shrink the few wrinkles that were left. Worked great - the leading edge got pulled together and it squeezed the strut overall to make for a nice layup.

Here you can see the peel ply being pulled off after the layup cured. Other than the bottom of the center part, the leading edge turned out pretty nice and the whole layup got squeezed evenly. It squeezed the layup enough that the epoxy was squeezed out and formed quite a few drips, outside/through the peel ply, on the bottom as it cured.

My kids like to pick the cured epoxy drips off of the plastic and play with them like play money. Here they are helping me clean up and collecting all the play epoxy money they can find.

After the first 4 layer UNI layup cured, the plans say to sand the layup dull. Some of the shortest instruction sets in the plan take the longest! I think it took me 4 hours to sand the whole thing dull, but, sometimes after a long hard day at work honest work like sanding is therapeutic. All in all, that was a pretty frustrating layup, but, once you remove the peel ply and sand dull you realize you did a good job. Don't spend much time on the edges on the leading edge that get trimmed off because this step has you sanding them off anyway.

I made some small jigs out of scrap pieces of vinyl house trim with with to mount the straws and do the micro fill. They're stuck on with double-stick tape and duct tape, after first being covered with box tape as a release agent.

I used CA glue to fix the straws to the strut once the jigs I made were placed. The jig held the straws in place real nice and made it very easy to make the micro fillet.

After the straws were glued in place, I added the micro fillet with a stir stick used as a scraper to just fill the slot with no extra. I ran one edge of the stick along the top edge of the jig, the other edge against the corner of the edge of the strut. I made the micro pretty thick, but, you can see it sagged a bit when I was getting the 2 BID layup ready. No sweat, the micro started to thicken a bit so I just re-scraped it back into place right before I applied the BID.

I used the duct tape as a sort of dam to keep the BID from sliding down the strut right after being applied. I also purposely didn't paint epoxy onto the strut where the BID was laid on, this made the spot were it was attached not dry but not sloppy with epoxy either - keeping the 2 BID layup from sliding down under its own weight as it cured.

Once the layup was on and stippled thoroughly, I removed the duct tape and let this cure. Turned out real nice and should be aerodynamically clean as I tried hard to make the jig blend in with the cross-section outline of the strut. There are a couple of air bubbles in the micro but that's OK - this isn't structural. You probably could have done this with foam vice micro, it's just a channel for the brake line.

Before I started the second 4 layer UNI torsional layup on the main landing gear strut, I needed to cut fiberglass. I looked through my scraps and realized I had a ton of UNI that might actually be usable. To make use of all those awkward shaped pieces, I made this sort of cutting jig. Using the plastic tub surround that doubles as my cutting mat, I put some blue tape on it at the desired angle and spacing. Then I laid the scrap pieces over this and cut pieces the right fiber orientation and width. I ended up having enough scraps to do the whole layup - with two pieces about 60 inches long left over! Glad I didn't cut the glass I needed off of the roll!

Here's the main strut after about 3 hours of work. It looks like we have at least 2 of the layers on in this picture. Kelly helped me with this layup - it took the two of us about 4 hours total. I'm a Nextel Cup fan - you can see the Pocono race on the TV in the background! Also not the blocks I put the nails on. This gave us a little more clearance under the bottom of the strut.

Here's Kelly working on the last layer with me. She said that this is not her best picture, most of us aren't very attractive after 3 or 4 hours of a tough layup like this. She's a good sport about helping me with the longer layups like this one though - thanks, Kel! You can see me in the picture - but only my hand.

When the layup was done, and it was time to peel ply, I did the ends and the middle (the parts that don't have brake line fairings on them) in skinny strips of peel ply. After it's on there, I then go over it with the heat gun, since peel ply shrinks just a little with gentle heating. The gentle shrinking action pulls the peel ply tight, and, since it's wrapped, it pulls the edges together on the bottom where the different pieces butt join together.

The rest of the strut got peel plied in a more normal manner with wider strips.

All 4 layers on, the whole thing peel plied and ready to cure. Time to sit down for a while and rest. This layup wasn't too bad, but, all that leaning over the table to get over and under the strut makes your back hurt after a while.

My faithful companion, Patch, often comes down to check on me when I'm working on the Cozy. He's there so much I felt obligated to take a picture and show him in there keeping me company.

Once the strut was cured, I used my Fein tool to trim the extra glass from the edges. Normally, you'd knife trim this sort of stuff but I didn't get a chance to. This tool works great for this sort of thing, it's oscillating action cuts the glass without overheating, melting the resin and gumming up the blade.

I also used the Fein to trim the edges of the brake line fairings. I took most of the extra off while it was still mounted on the nails.

To make sure I was trimming the brake line fairings in the right place, I re-measured the strut. Using a square against the table, after measuring, I marked the start and stop points for the brake line fairings. I also marked where the attach tabs go just to start to get a mental picture of the spacing of everything.

I also used a metal tape to draw a straight line on the brake line fairings to trim them. I measured up a consistent distance on each end, used the tape to make a straight line, along the curve of the strut, at the measured height. I then ran a pencil along the tape to mark where I would cut off the extra glass from the fairing.

The Fein made nice work of the extra glass beyond my pencil mark on the fairing.

I then used my spline to sand the fairings trailing edge square and straight.

Finished product. Nice, evenly proportioned brake line fairing sanded square and straight and ready for the next step.

After finishing the trimming of the brake line fairings, I sanded the major bumps and remaining peel ply strings off the strut. It's now ready for the attach tabs.

Next step - attach tabs!