Another visit to a builder for inspiration

I was posting some questions to the Canard Aviation Forum and noticed that Chris Barber had started flying his Velocity. Since I'm about 5 minutes from his hangar, I invited myself over the next Saturday morning to inspect his creation. Chris was in the middle of troubleshooting an electrical problem, so his plane was in perfect condition for an inspection. Chris has a rotary engine, so I will be following his progress - by the time I'm ready to make a decision on my own engine, Chris should have plenty of data on the performance and reliability of his engine to review.

Cutting out the hard points

Well, they're cut out, but none of them to the proper size. Dang it!

I wasn't crazy about the sharp internal corners and tried to round them out a bit, but ended up drilling too far into the corner.  Most of the others were 1/8' to 1/4" too short around the edges.

 

Hardpoint Layup Part II

After trimming the edges, I noticed I had some white areas around the outside of the layup. Not sure I'm going to get 4 hardpoints out of this layup after all. It wasn't completely flat, but I'm hoping it wont be noticeable when I cut the smaller pieces out.

I bought a new wood/metal blade for the Multimax to replace the wood/drywall blade I had been using before, since the old blade was staerting to wear down. I gave it a test cut and saw that the sliver that I cut off the LG bulkhead hardpoint layup was still pretty flexible, even though the whole piece seems ridgid. Not sure what this means yet (if anything).

Since the layup was just shy of the thickness I needed, I decided to just add a couple more layers to get to the right thickness. With just two plies, the layup went pretty fast, but I noticed some darkening of the layup while I was working. After the layup was cured and I had pulled the plastic and peel ply up, I discovered the culprit. I had thought that I had a layer of plastic under the layup, when I actually still has the paper template underneath. The wet epoxy had wicked into the paper, leaving several fairly large areas with the paper imbedded in the cured epoxy.

I first tried using the chisel to prt the paper loose, then switched to sandpaper, and then to the Multimaz flexible scraper. The scraper seemed to be doing a good job of removing the paper, but it also removed the roughness of the layup from the peel ply.

I went out and bought a new rigid scraper blade and abrasion attachment. I went straight to garage to try out the new scraper. It seemed to be peeling up the paper okay, but I couldn't tell if I was digging into the core layup as well, so I switched to 50 grit sandpaper on a palm sander. The sandpaper seemed to be giving it a smooth finish, which I didn't want, so I switched to the abrasion attachment. This gave a much rougher finish, but I started to see tufts of glass and quickly backed off. I decided to stop until I could figure out what grit I should be using.

It wasn't till I took a break that I noticed that I has gotten fiberglass dust everywhere, including myself. I hadn't even put a shop apron on, so the painful fiberglass itching started as soon as I got back into rhe house.

After another trip to the hardware store, I came home with a Tyvek painter's jumpsuit and some 40 grit sandpaper. It's amazing how hard 36-grit is to find theae days. I got a much rougher surface with the 40 grit, so I was then ready for cutting out each hardpoint.
I squared up some of the edges first and started cutting. I expected that I would have to switch to a jig saw for some of the cutting, but I was able to use the Multimax and then follow up with some sanding. I wasn't really keen on the sharp inside corner of the hardpoint, so I rounded it out by drilling a hole there and then cutting straight lines to the hole. I thought I was done with that piece, but I wanted to match it up to the bulkhead just to be sure. I saw a few areas where things didn't line up too well. I sanded some of the edges down till I got them too match. I was afraid I might end up sanding the piece until it was too small to use but I think it turned out ok.

Hardpoint Layup Part I

This weekend I decided to do some work on the LG bulkhead hardpoint layup. I cut 5 more plies to get to the total of 22 plies needed for the layup. I laid out the paper template, the plastic and the peel ply prior to the first layup. I had used masking tape to hold the edges when cutting each ply, so I was confused when I started having a hard time getting the fibers lined up with the paper template. The second ply was even worse. I stood there scratching my head (figuratively - you don't want epoxy covered gloves anywhere near your hair) before I realized that I had cut the last 5 plies to 8" by 12", the exact dimensions required for the finished layup. I knew it was going to be almost impossible to get the edges to line up correctly with the undersized pieces, so I switched to using the bigger plies that Steve and I had cut earlier (with a 2" margin on each side). They were a LOT easier to keep the weave lined up on.
A lot of builders ended up with layups that were too thick on their first try, and I wanted to make sure that didn't happen with mine. I made sure I used the hair dryer with each ply I laid up, and let each ply pull up epoxy from the ply below.


I started to see a ridge running down the layup, and noticed that it was directly over a crease on the 4 mil plastic I had laid the layup over. I couldn't believe that a small crease like that would show up all the way through heavier plastic I had used over it, as well as through the peel ply and several layers of heavy wet fiberglass. I cleared off another section of the work table and moved the layup over to it to get away from the crease.




I was baffled by some funky looking round spots that kept showing up on the workpiece before I realized that they were simply where I had pressed my fingertips into the glass doing the layup.








When I finished laying the oversize plies, I decided to trash the undersized plies I had made and cut and laid up new oversize ones. I laid peel ply and plastic over the top, then laid a square across two 1/4" plates to check for thickness. I was surprised to see that the layup was bit too thin instead of too thick. I added the another oversized ply and checked again. It still looked too thin, but I saw that the square was resting on the tape around the edges of the layup (I didn't scissor trim the plies) and figured that I was probably the cause.



When I cut the edges off the layup the next morning, though, I found that it was just shy of 1/4" thick.

Fun with the F-28 Bulkhead

Back to building again - Yay!

I figured my shoulder was well enough to start building again, so I called up Steve Robbins and took him up on his earlier offer to come inspect the workshop and maybe do a layup or two.

Steve arrived early Saturday morning and took a look at my garage/airplane factory. Aside from a few suggestions, he was happy with layout and outfitting of the shop, and suggested we do a layup while he was there. I decided on doing the F-28 bulkhead, since it was a fairly small piece.

I figured that cutting the glass for the layup was going to take about five minutes, but Steve was VERY careful about making sure the weave was straight with each piece before cutting it, and with taping the edges to make sure the cloth didn't shift after we cut it. This seemed a little over the top at first , but paid off later when laying the glass.

I started pumping the epoxy into the cup and was a little nervous when the hardener came out with a brown color, rather than looking clear like I had expected. We proceeded anyway, and I made a note to myself to check the forums to see if this was going to be a problem. I had planned to use only slow hardener for all my future layups, but since I had some fast hardener from my first epoxy order, I used a little bit of that in the mix as well for this layup. Steve suggested forgoing the first pass with with the micro, since the Clark foam was so dense there really wasn't much weight savings. I agreed, so we proceeded straight to the first layer of BID. Steve brought a 2" paintbrush to stipple with, and I found it was easier to spread the epoxy with a brush than with a squeegee, especially for a part that small. The hardest part was making sure the weave was straight. Even for a small piece that was still taped at the edges, it was tough getting the fibers to line up right until the epoxy started to set in. The second layer of BID and final one of UNI seemed to go on a little easier. Using the hair dryer helped keep the epoxy runny enough to work with, but Steve was a little surprised at how fast the epoxy seemed to be curing. We ended with the layer of peel ply tape on top, scissor trimmed it, and called that one done for the day.

We next moved on the cutting the 22 layers of BID for the landing gear hardpoints. After a few false starts (it's amazing how something so simple as figuring out the weave angle can get so confusing), we got into a nice rhythm. We used up the first roll of BID pretty quickly since I had bought smaller rolls of BID rather than one big roll. Steve was recovering from a cold and was starting to look a little worn out by this time, so when we used up the second roll, I took pity on him and told him I could finish the last few plies myself so he could go home and rest.

I came back to the garage that evening and tore the the peel ply from the layup. The finish ended up looking pretty nice, although I saw a lot of specks from the air bubbles that had formed under the layup. Some epoxy had gotten underneath the workpiece, so after staring at the underside for awhile wondering what to do, I just hit it with the Multimax sander to remove the dried epoxy (or at least rough it up enough to do a layup over it). I started trimming and was surprised at how hard it was to get around the inside corners with the Multimax half circle blade. I ended up using the sanding attachment to get the final trimming complete.

I came back out to the workshop Sunday evening to finish the other side. Since the epoxy had set a little fast the day before, I only gave the epoxy a tiny squirt of fast hardener and used slow hardener for the rest of the mixture. I went ahead and tried to micro this side of the bulkhead and ended up taking all the micro off the surface with the squeegee, so Steve was right about that. (But you know I HAD to test it myself). Getting the fibers to line up right on the first layup was frustrating to say the least - I'll have to work on laying it down more carefully. I was surprised when the epoxy started feeling thicker when I got to the UNI ply. I had forgotten to plug in the hair dryer and got it all sticky trying to get it set up. By the time I laid down the peel ply, it was already starting to gel. I quickly mixed a new batch of epoxy and poured it over the peel ply, but I left the gelled epoxy alone, since I didn't want to disturb the layup underneath. I was really confused at how fast the epoxy had cured, especially since I was using mostly slow hardener.

Or was I?

I opened up the epoxy box, noted the location and numbers on the cans of hardener, and double checked them against my MGS data sheet. Sure enough - I had gotten the two hardeners mixed up and was using mostly fast hardener for the layup. Doh! I grabbed a Sharpie and marked the two types of hardener on the hot box so this wouldn't happen again.

When I inspected the layup the next morning, it looked awful. When I tried to pull the peel ply off, most of it stayed on the workpiece. I spent the next evening sanding down the epoxy clumps and then chiseling the peel ply off. I ended up with a pretty crappy finish. Oh well.

Hiatus due to surgery recovery

Project on hold as of November 1st due to rotator cuff surgery.  Hoping to be able to start up again by February 2012.

Firewall Bulkhead

I decided to hold off on glassing the bulkheads until I was able to type up more detailed steps for doing it.  I was finding way too many things in the plans that I might miss if I didn't have them written out step by step.  In the meantime, though, I decided I could move ahead and cut out the firewall pieces.

I tried to pin the firewall templates to the plywood sheet, but the birch plywood was too dense for that, so I taped it down instead.  I then tried  drawing a line around the edge of the template with a pencil, but keeping the line on the very edge of the template got very tedious very quickly.  I went ahead and cut the firewall out with the template still attached.  I made my first cut an inch or so from the edge to see how the jigsaw I was using would handle the thin, dense plywood.  When I saw how much the wood blade was tearing up the veneer, I stopped and switched to a metal blade, but it didn't seem to want to change direction too well.  I switched back to the wood blade and used it to rough cut the firewall shapes, leaving an inch or so around the edges.  I decided it was time to buy myself some new jigsaw blades and use those for the final cut, so I called it a night.

I came back the next evening with a new set of blades made specifically for plywood and got to work making the final cuts on the upper and lower firewall pieces. I found that my hands weren't as steady as my eyes wanted the lines to be. After awhile I moved to cutting out the shapes about 1/8" from the edge, then came back again for the final cut.  The straight edges were more difficult than the curves.  I clamped a straight edge along one side and tried to use it for a guide, but the jigsaw still wanted to wander off on its own.  When I made cuts near an edge, the blade would start to bend away from the cut, giving me a beveled edge that I obviously didn't want.  I ended up spending a lot of time using my wood rasp and sanding blocks to finish the edges and get them reasonably straight and square.

The next night I cut out the two side pieces.  These pieces were smaller and all straight cuts. I scored along the cuts this time before cutting them with the jigsaw to give me straight edges to work from and to keep the wood from splitting.   I used the jig saw again because I didn't want to have to haul out the table saw only to find that it was shredding the wood with its blade. The jigsaw has a laser that marks out a straight line for you to follow, but I found I couldn't see the blade clearly when I used it, it so I ended up turning it off.  The cuts were a little better than before, but I still had to spend some quality time with the wood rasp and sanding blocks to get straight clean lines.

I cut out the temporary firewall a few days later. I wasn't sure how to handle the sharp turns around the sides, so I just rounded them off.  I'm not sure what any of the holes are for yet, and I'm a little reluctant to start cutting them out until I'm sure.  I couldn't find any fir plywood, so I used pine. I figure I'll have to add a couple of stiffeners to it as well.

I waffled over the engine mounts; several builders were uncomfortable with how close the bolts were to the edge when installing the engine mount and suggested making the mounts 2" square rather than the 1" called out in the plans.  The blank that I ordered was 2" by 4", so it would have been easy enough to do, I guess, but I decided to stay with the 1".

After my troubles with trying to cut straight lines on the firewall with the jigsaw, I didn't want to repeat the experience on the engine mounts. I asked around on the canard aviation forum about cutting the aluminum, and got several ideas, but I ended up getting the urge to DO SOMETHING again, and simply had at it with the jig saw using new metal cutting blades. The blade did wander a bit, but not as bad as I had feared, and filing the edges flat didn't take nearly as long as I expected. I had marked the lines with a permanent marker, only to discover that they're not permanent at all on aluminum.  Next time I'll use a nail to scribe the edge, as someone in the forum suggested. Of course, they weren't exactly 1" on each side, due to the kerf of the blade. They weren't exactly square, either, but I figured if I kept filing them down to try to fix it, they'd end up being too small to use.

I also asked around the forum on securing the screws to the firewall, since there seems to be a strong consensus that the plans method leaves a lot to be desired.  I liked the idea of using pieces of welding rod that fit into a slot cut into the firewall, but I don't have any idea how to weld them to the screws, and I'm not keen on having to learn welding for such a simple task.

A week after building the engine mounts, I had the day off, so I decided to go see what more I could do on the bulkheads. I had never really studied what all the holes in the firewall were for, so I spent some quality time with the plans trying to figure it out.  Hmm... seems there are FOUR engine mounts required, not just the two I has built earlier - doh!

I pulled out the jig saw again and tried to cut two more mounts out of the blank.  I got about halfway through the first cut before I ran out of room on the workpiece - either the jigsaw shoe would hit one of the clamps I was using to hold the blank down with, or the piece would wander off while I was cutting.  I scratched my head for awhile, then decided to try mounting the jigsaw upside down in my Workmate stand and using it like a band saw.  I was VERY nervous about doing this even though I had seen it used before.  The workpiece was pretty small, and I'd have to get my fingers pretty close to the blade.  The first cut went okay, and the second was doing alright until I noticed the workpiece getting hot - as in too hot to hold on to!  I slowly backed the workpiece out and shut down the saw, then put on a pair of auto mechanic gloves. I also decided to swap my regular glasses for a pair of safety glasses.  I carefully started the cut again, but it started getting hot again, and even with the gloves I had to back the workpiece out again to let it cool.  When I slid the workpiece back into place, it caught the blade wrong and jumped out of my hand.  The scared me enough that I gave up the idea of using the jigsaw altogether and resigned myself to spending half an hour or so with a hacksaw to make the final cut.  I clamped the workpiece into my Bench Buddy vise and had at it with the small hacksaw.  I was amazed when it cut through the workpiece in less than two minutes.  So much for the best laid plans - I could have done all of the pieces by hand in less than half an hour if I had tried the hacksaw in the first place!  I had cut the pieces oversize so I could file them down to the right measurements, which took less than ten minutes. They weren't perfectly square, but I knew that if I kept trying to fix them, they would just keep getting smaller and smaller.

I marked the locations for the engine mounts on the firewall. I have to say that it took awhile to find a good reference to measure from.  The plans spell out the B.L. and the W.L. for the mounts, but there isn't a zero level W.L. to work from.  I measured the dimensions on the plans to find the W.L. for top edge of the bottom piece and the bottom edge of top piece and used those to mark off the mount locations.  Since my hard points weren't exactly square, I traced the outline for each one, then used a wood chisel to make the cuts.  I worked pretty well and I got a good close fit with each mount. I did get some tearout on the back side of some of the holes, but I can probably fill that with flox or micro before I lay the glass down. I also numbered each hole and each hard point to make sure I matched them up again when I was ready to lay the glass.

I screwed a 1x4 to the back of the temporary firewall to straighten and stiffen it up, then cut out the longeron holes.  I'll probably have to open the holes a bit when I attach the sides to the firewall, but I cut them as close to the correct size and location that I could. for now.