Archive for the ‘Fiberglass Plenum’ Category

Plenum & Oil Hoses

PA220002.JPGWhile I was in the process of replacing my accessory case, I decided to modify the inside of my plenum to even out my CHT’s. I added a small ramp about halfway between the 2 cylinders on the left side of the engine. Before the mod, the back cylinder was cold so the theory is that the ramp will deflect more air towards and through the aft cylinder instead of letting it pass to the back of the plenum. It worked pretty well, actually.





PA230003.JPG I guess I didn’t take any pictures as I was building these new hoses. I was so disgusted at having to re-do all of them that I just wanted to get it done and not stop for photos.

I ordered brand new Aeroquip AQP fittings and brand new Aeroquip stainless hose. I know you don’t have to use fire shield on stainless lines when used for oil, but stainless really scares me in terms of chafing potential so I went with the fire sleeve. Making hoses out of high quality stuff is REALLY expensive. I hope when I decide to sell my plane the buyer appreciates the difference!

I also pressure-tested 2 out of four of these hoses to 600psi. They really shouldn’t leak or fail again! Two dead stick landings are plenty for me for about the next decade or so!

Still more cooling…

These are my upper and lower inner cylinder baffles. They rest on the top side and bottom side of the cylinders and are intended to force the air through the cylinder fins rather than allow it to flow through a big, gaping hole. I’ve been using nothing but safety wire to hold these in place, but have decided that a spring would be nice and would allow for easier removal and installation.

Here’s a birds-eye view of my engine installation with the inner cylinder baffles in place. Keep reading to see where I ended up modifying this setup to open up the top side of the cylinders a little more.

An overhead view of the engine with the newly redesigned plenum. Unfortunately, as near as I can tell, the new plenum design did absolutely nothing for me! Bigtime bummer.

Believe it or not, this little mod was good for 10 to 15 degrees in oil temperature! I bent a 3/4″ x 6″ piece of aluminum to a 45 degree angle and taped it to the aft lip of my cowling. The idea is that this lip causes a low pressure area in the exit airflow and helps to suck the hot air out of the engine compartment. Pretty snazzy.

It’s annual time so I started an oil change. This is the first oil change with a spin-on filter so I cut the filter apart to look for any signs of engine wear–like big pieces of metal stuck in the filter. I’m happy to report that none were found.

Since I’m now filtering my oil with a real live filter, the oil screen is no longer necessary. I used a torch like you’d use for sweating copper pipe to de-solder the screen from the big oil screen nut. This way, I can just change the filter and not worry about pulling the screen off for future oil changes.

While I had everything apart and just to make sure I wasn’t chasing a ghost, I decided to re-check the accuracy of my oil temperature sensor. I heated some water and stuck a cooking thermometer in the water alongside the oil temperature probe. I then compared the reading of the thermometer with what I was seeing on my oil temp gauge in the cockpit. I’m happy (I guess) to report that the two read within 2-3 degrees. (The width of the needle.)

I decided to open up the top side of my cylinders even more. I used a bent piece of wire about the gauge of a coat hangar to slide around the cylinders to provide a mounting point for my inner cylinder baffles. I took the fiberglass baffles that were on top of the cylinders and moved them to the bottom of the cylinders. You might also notice that I trimmed down the cylinder baffles a bit where the intake air first hits the cylinders.
I had a little issue a week ago or so where I had no oil pressure on startup after leaving the plane sit for about 2 hours. After a bunch of troubleshooting, I came to the conclusion that my oil filter and cooler system was plugged up. You’ll remember that I used a port off the left side of the engine to connect oil lines that would feed my spin on filter and oil cooler in series.
What I failed to account for in the original installation was that if either the cooler or the filter became plugged for any reason, the engine would be starved for oil. There were no bypass valves. Duh. Luckily, I discovered this problem on the ground and not in the air or we could have had serious problems.

After realizing the error of my ways, I decided to purchase an Air Wolf spin on oil filter adapter kit. When I called Air Wolf to talk to them, they said they’ve got a new filter fin kit that supposedly reduces oil temps by 20 degrees. What the heck, I thought, and I bought it. This thing really looks like a porcupine. It’s going to be a bit of a challenge to find a place to mount this bad boy.

Here’s another view of the filter fins. You can see that they cover about 300 degrees worth of the cooler. I’ll duct some cooling air to the filter to maximize the effectiveness of these fins.

Just in case the fins aren’t enough, I bought this spin on oil cooler port adapter from Steve’s Aircraft up in Oregon. This little baby spins on between the Air Wolf remote mount pad and the filter. It provides a pressure bypass valve and an in and out port for an oil cooler installation. After talking with the folks at Air Wolf, I discovered that the Air Wolf system doesn’t have a bypass valve per se… They, instead, count on the bypass capabilities of a CH43108 aircraft filter. That’s why it’s important to have a bypass valve for the cooler installation.
With all this stuff going on and a bunch of other things going on in my world, I’ll be lucky to have my plane flying again before the end of July. Bummer, really, because I was hoping to make it to a fly-in at Alamosa, Colorado on July 16th. I don’t think that’s going to happen. Oh well, there’s always next year!

Plenum Progress

Here’s a bird’s-eye view of the new plenum pieces painted and installed. I’m very happy with how they turned out. Now it’s just a matter of connecting the dots–joining the original plenum with the new pieces by fabricating a fiberglass lid.

Once again my good friend Phil came to my aid with my fiberglass work. He’s got more fiberglass experience and tools than any sane person ought to have. Using Phil’s equipment and expertise, we made a vacuum-bagged layup consisting of 2 layers of cloth, a 1/8″ layer of foam and another 2 layers of cloth. To complete the vacuum bagging package, we laid on a layer of peel ply and then a layer of breather cloth. The whole mess then goes into an airtight bag and a vacuum is drawn.

This little pump supplied the vacuum. We placed the whole package on the top of my engine with bags of lead shot to hold everything down nice and tight against the existing plenum and my new metal pieces. It took about 6 hours to cure to the point where I could remove the vacuum. I left the weights and everything else in place until the next morning.

I was back at it again first thing Saturday morning. This is what it looked like as I started pulling the peel ply and breather cloth off the cured part. The gold color is the foam core as the 2 layers of fiberglass are pretty much transparent once all the excess resin is sucked out. The piece is surprisingly light.

I laid the piece back on the engine to get a feel for just how much I’d have to trim. It fit surprisingly well, but will obviously need to be trimmed.

With the front-to-back trimming complete, I next marked strips along each side. I’ll use a Dremel tool with a small cut-off wheel to carefully remove the first two layers of fiberglass from the strips along the edge. This will allow the fiberglass, without the foam core, to rest on my new metal flanges.

Once the first two layers of fiberglass were removed, I just had to scrape the foam core out to leave the remaining 2 layers of glass exposed. This wasn’t a difficult process.

To finish the flange, I used a Dremel tool with a cone-shaped grinding tool to grind a 45 degree bevel in at the edge of the remaining foam core along the length of the flange. Even using the vacuum process, it’s easier to get fiberglass cloth to lay down over something less than a sharp 90 degree angle. After the bevel was cut, I applied another 2 layers of cloth tape along the flange so that the finished flange is 4 layers thick. 4 layers of cloth wouldn’t be enough for the entire plenum (without the foam core), but it’ll work well for the flange.

I drilled and clecoed the new fiberglass piece in place. I laid the blue tape on a flat surface and made my marks for the holes so they’d be equally spaced. It’s tough to determine the spacing on a curved surface so the tape works well. I drilled through the new plenum and into the flanges of my new baffle pieces. I also drilled and clecoed a few holes through the new plenum into my old plenum pieces.

I took the entire plenum off as a single piece. My plan is to remove 2 layers of cloth and the foam core where the new piece will mesh with the old plenum halves. This should make it easier to graft the new piece to the old pieces and create an invisible transition so that the entire plenum will be a single piece. Obviously there are some openings in the corners that I’ll have to address with additional wet layups.

More cooling issues

Looks like I did the victory dance a little early with my cooling issues. When I went out to fly my plane in 74 degree temps, the oil temperature went straight past redline. I landed as quickly as I could to prevent any damage. I’m convinced that the oil cooler isn’t doing much at all. I’m thinking the only reason it worked last year when it was mounted on the top of the case is that cool air blew through the cooler and cooled the case itself.

Before I started on more drastic measures, I decided to bypass my new thermostat to make sure it wasn’t causing my cooling issues. In this picture and the last picture, I’ve capped off the thermostat and joined the hoses with AN couplers. No change. Still ran right to 225 degrees and was headed higher when I landed after 3 laps overhead the airfield.

I dug through all the junk that came with my airplane when I purchased it 7 years ago and found the original baffles. There’s no way I’m putting this junk back on my shiny new airplane, but maybe it’ll be good for a pattern. Or not. In the end I decided I like the plenum over the cylinders and how it fits… I just need to extend it over the top of the case to (hopefully) provide better cooling.

I used my contour tool and some foam core board to make a few patterns. I have previously used poster board in these situations, but find that it gives too much for an accurate pattern. My plan is to seal off the case from just behind the spinner to just in front of the engine mount bolts.

Here’s the aft piece fabricated from .032″ aluminum. It fits the contours of the case well enough that it shouldn’t be a problem sealing it up airtight with some RTV. If the combination of the RTV and the plenum isn’t enough to hold the piece in place, I could always attach a few brackets to mechanically hold it in place.

Here’s the nose piece just setting in place for a preliminary test fitting. There are two attach holes on either side of the crank flange that will allow me to attach this piece to the case. I think the holes were used as part of the stock baffling installation. In any case, a quick trip to the aviation aisle at Ace Hardware and I’m all set with the proper 1/4″ coarse threaded bolts.

With the fore and aft partitions in place, it was time to plug up the irregular-shaped holes on either side of the front of the case. Again, I used foam core board and my contour tool to come up with the shape. After I took this picture, I marked the patterns to be trimmed so they’ll just meet up with the forward partition.

I needed a flange along the top of the forward and aft flanges so I broke out my stock of Van’s-supplied stiffener material. Van’s fabricates this stuff for use as control surface stiffeners. It’s the greatest thing since sliced bread as far as I’m concerned. I ordered a bundle of it and have found many uses for it during the Midget Mustang project. Here I’ve cut notches along one side so it can follow the gentle contour of my new baffle.

Here’s a shot of the baffles after priming and after the flange has been cleco’d in place. I always get excited when things start to come together like this.

With the flanges in place it was time to fit the pieces at the front of the case to the left and right of the crank flange.

I’m pretty happy with the way these fit. After a few tweaks I separated all these parts, primed the remaining pieces and riveted everything together. The next day I painted everything black to match the existing pieces at the valve covers. I don’t have a picture of the freshly painted pieces because they were still tacky when I left the hangar on Saturday afternoon.

While waiting for the paint to dry, I decided to tackle another little squawk that’s been bugging me for almost a year. I just don’t have enough elevator trim authority. At different phases of flight I find myself trimming to the full up and full down positions and wishing I had more. The painted piece to the right side of this picture is my existing trim tab. The one on the left is the replacement.

Here’s a better shot to see the difference in size between the old and the new. Believe it or not, the new tab is more than 50% larger in surface area. I’ll start with this and if it’s too much I can always trim it down a bit. I can’t believe I put this project off for almost a year. Once I got started on it, the project probably only took me 30 minutes to complete.
I was really busy at work during the months of April and May, but I’ve vowed to be less busy during the month of June. I’ve already missed some fantastic flying days so I’m highly motivated to return my Midget Mustang to flying status as soon as possible. I’m off work for 5 days in a row starting next Thursday. I’m hoping for some serious progress during that time.

Gotta show a picture of my new beater truck. I bought this in anticipation of my next project… finishing my basement! 4 x 8 sheets of drywall will certainly fit better in this truck than they’ll fit in my VW Passat! It’s not much to look at and it doesn’t get very good gas mileage, but it’ll serve a purpose. I’m finding it really fun to not have to worry about where I park for fear of door dings, too!

Plenum, Oil Cooler Duct & Upholstery

My poor plenum tops have taken a beating with my oil cooler installation and then relocation. It was a shame to screw up my checkerboard paint, but it’s all in the name of progress, right? After grinding out all the previous ducting I had to re-glass the holes near the inlets. I used clay as a backing and then glassed the holes shut.

The lower half of the new duct to the oil cooler is attached to the cylinder baffles. As you can see, the cylinder baffles are held on with safety wire. I put a couple of nutplates in the lower duct that the top duct will attach to. The gap will eventually be filled with a neoprene ring. I needed a little space because there will likely be movement between the engine and the oil cooler (because the cooler is mounted to the engine mount).

The plenum is in place and completes the new duct to the oil cooler. With all the screws in place, it’s really a solid setup.

Here’s a birds-eye view of the engine compartment as it currently stands. You can see the patches towards the inlets where I removed the previous ducting. I used duct tape to seal the gap in the new plenum for now. Once I know the system is going to work, I’ll fabricate a neoprene sleeve for the gap.
I went up on Wednesday of this last week to test the new installation. I ran the plane wide open for 30 minutes to see how high I could get the temps In the old days, I could easily flog it into going to 225 degrees. I’m happy to say that the best I could do running around at 3000+ rpm for a full 30 minutes was 210 degrees. I have no intention of running around at 3000 rpm in normal operations so I’m calling this a success.
I de-cowled the airplane after the flight and found 2 small oil leaks. The first was an easy one… in fact it was one of those “duh” moments… The hose on the breather port was night tightened down. Woops.
The second leak came from my modified reducer fitting on the right side (looking at it) of my oil filter adapter. I remember being excited to see if the modified adapter was going to solve my clearance issue so I put the fitting on without using the Permatex teflon sealer. It leaked. Woops again. I stopped by the hangar last night at about 9pm on my way home from work and fixed both these issues in hopes of flying to breakfast this morning.

The other thing I did yesterday was that I picked up my new seat cushions with the new upholstery. A guy over in Brighton, CO built the seat cushions and did all the sewing, too. I could have picked from any material in the world for my upholstery, but ended up picking sheepskin. I purchased 2 pelts from Colorado Sheepskin Factory in Denver.
I was originally planning to go with a dark grey color, but nothing I found really blended well with all the other colors in the interior. I ended up going with black because black seems to go with everything. Now that it’s installed, I’m very happy with the look.
I went out to the airport today (Friday) with hopes of flying over to Greeley (KGXY) for breakfast. Unfortunately, by the time I arrived at the airport at about 7:30 this morning, the wind was already blowing in a direct crosswind at 16 knots. It would have been do-able, but I figured I’d get my fanny kicked all the way to and from Greeley so I decided to stay on the ground and work on the next project.
What’s the next project? Stay tuned for pictures and a narrative in the next entry.

Upper plenum and exit air diffuser box

I spent a little time out at the hangar today and continued my work on the ducting for my relocated oil cooler. I’m making the new duct as a 2-piece part. The lower half will be attached to the cylinder baffles and the upper half will be a part of my fiberglass plenum. There was a pretty large volume of space to fill so rather than use 20 pounds of clay, I first filled the void with shop rags and then put duct tape over the rags so the clay wouldn’t stick to the rags.

With the rags and the duct tape in place, I started adding clay. It took me about 40 minutes to achieve this shape. As a little tip, it is tremendously easier to work with this clay if you first heat it thoroughly. I’ve got a microwave I use to heat my lunch in every so often. Turns out it heats the clay up fine, too!

Once I was happy with the overall shape of the clay, I painted it with 2 coats of PVA mold release. Again, it pooled in the low spot, but these dimensions aren’t critical to the thousandth of an inch so I’m not too concerned. It’ll just take a while to dry.

This is the plug for my oil cooler exit air diffuser box. Again, to avoid having to work with a 20 pound glob of clay, I started with a foam core. To help stiffen the foam up, you’ll remember that in a prior work session I coated the foam with a mixture of micro balloons and epoxy. This method seemed to work pretty well.

In the process of poking around the engine compartment looking for air leaks in my cooling system, I think I may have discovered the cause of my erratic CHT readings on my #2 cylinder! I’m not sure if this worked its way to being loose or if I somehow failed to torque it down, but this is how I found my #2 cylinder temperature probe when I de-cowled the engine. I love it when a solution is simple and obvious!

Oil cooler ducting

I spent about 1-1/2 hours out at the hangar this evening after I finished my 4-day trip. This is my new piece after I’ve pulled it out of the clay mold and scraped the clay off. Of course I’ll need to trim it and do a bunch of sanding and filling before it’s anywhere near finished.

Since I’m abandoning my “Y-duct” near the front of my plenum, it was time to hack off my handiwork. Obviously the entire plenum will need to be refinished once I’m finished with the new oil cooler installation.

In this picture I’ve trimmed the new piece and have cut back the original plenum. I’ve also sanded a strip of the plenum all the way down to the original fiberglass. This will give me a nice surface to splice into the old plenum to continue the chamber back to the oil cooler. The plan is to have the bottom piece of the chamber attached to the cylinder baffles and the top top piece will be an integral part of the plenum. I’ll probably end up creating a gap between the cylinders and the oil cooler and bridging the gap with neoprene. I’m afraid the part would crack due to the shaking/twisting of the engine relative to the engine mount. Since the oil cooler is hard-mounted to the engine mount and the cylinders are attached to the engine which is attached to the mount via rubber mounts, I’m guessing I’ll need to make allowance for the movement. I’ll take a picture and point it out when I get to that point. I’m having a tough time describing it.

Oil Cooler and More Photos

I test-flew the oil cooler installation on 07-16-10 to get an idea of how well this setup was going to work. It lowered my oil temps by a solid 25-30 degrees! Success, as far as I’m concerned. I still needed to plug the gap between my diffuser box and the oil cooler fins. I applied vinyl tape and some Part-All mold release to my diffuser box.

I then attached the diffuser box to the oil cooler and applied some black RTV to fill the voids.

The next morning, before flying the plane again, I took it all apart and removed the tape. What was left was sort of a crude-looking custom gasket. I think I can make this look prettier, but that will have to wait until I do the finish work on the plenum itself. I’m having too much fun flying to make stuff like this look real purty.

After a fantastic 1.2 hour flight on 07-18-10, I decided it was time for a few photos. This is one of my favorite viewing angles for the Midget Mustang. I just love the shape from an overhead view. I’ll have to find a little better lighting the next time I do this.

I think this is the first time I’ve posted a picture of my panel with all the labels applied. Aerographics made the labels for me. I think they did a fantastic job. If you look on the GPS, you can see my track line for the first 5 flights. Lots of laps over the top of the airfield!

As I mentioned above, today’s flight lasted 1.2 hours on the Hobbs meter. The temps were under control and I finally felt confident enough to leave the pattern long enough for some steep turns and a few stalls. I’m very happy to say that it stalls clean, power off at 70 mph indicated. Each notch of flaps lowers the stall speed approximately 3-4 mph with the full-flaps stall occurring at 58 mph indicated. MUCH better now than before the rebuild.

The stalls also broke straight ahead with plenty of warning in the form of reduced control effectiveness and a gentle buffet. Recovery was immediate by reducing back pressure and applying power. I also did a few 90 degree banks and rolled rapidly from 90 degrees left to 90 degrees right. Wow! This thing is wicked quick in roll. I banged my head on the first one. I’ll have to work hard to learn to NOT introduce a pitch input when rolling left/right. The elevator is very sensitive.

I wanted to put in a plug for these nav lights. I’ll have to update this post to include detailed information about manufacturer, but I’ve been really happy with these little lights. They’re obviously LED and also have a strobe light. There’s a single power pack for the strobes which I have mounted under my baggage floor. The wingtip lights are VERY lightweight at something like 11 ounces. I modified the wingtips to include a mounting base for the lights.

I’ve probably already got a picture of this somewhere, but here’s a shot of my cockpit lighting installation. The row of blue lights on the canopy provides just the right glow to see the instruments at night. The good news is that there’s a lip of plexiglass from the canopy that shields the pilots eyes from the strip lights themselves. All you see from the pilot’s perspective is the glow from the lights, not the lights themselves.

I’m away from home at work this week from Monday through Wednesday. I’m hoping to fly again this Thursday and Friday. I’d like to do some touch and go’s to make sure I can land this thing in a reasonable distance. I made 4 landings this morning using an over-the-fence speed of about 90 mph. I think with a little more confidence, I’ll drop that to 80-85 mph. The plane was very controllable at that speed and still had plenty of energy for a flare and a little float. I did 2 wheel landings and 2 3-point landings. They were all very controlled and the plane showed no signs of darting in any particular direction.

If all goes well, I’m planning to fly up to Mitchell, SD this weekend to hang out with the Air Venture Cup racers. I’ll spend the night in Mitchell on Saturday, watch the race start on Sunday morning and then head home before noon on Sunday. I’ve got a little bit of vacation time at the end of this month that I had planned to use for an Oshkosh visit, but since that’s not going to happen, I’ll probably just get to work installing wheelpants and fabricating my aux. tank. I’d like to participate in a few of the SARL races this year.

Oil Cooler

Here is the assembly with the front half of the tubing bonded in place and sanded lightly. I’ll install it and test fly it before doing any finish work.

Here it is installed on the engine. I’ll need to plug some holes at the oil cooler with a little RTV, but other than that, it fits perfectly. I’d rather not have the air change directions so much and so abruptly, but everything’s a compromise so we’ll just see how this works.

You can see how the oil cooler ducting has a separate intake within the cowling intake. I haven’t measured it, but my highly-calibrated eyeball says it’s a little over 1 square inch of intake area.

I re-routed the 1/8″ copper line for my manifold pressure transducer to go under the oil cooler hoses rather than over the hoses. There was clearance before, but I was afraid the heavy hose might sag in time and put pressure on the copper tubing. Copper tubing has a tendency to crack anyway. No since in irritating it unnecessarily.

You know what they say about guys with big feet… They don’t fit too well in little, tiny airplanes. The sneaker on the left is my standard work at the shop shoe. I purchased the Simpson racing shoes on the right because they are far less cumbersome when flying my little plane. It’s amazing how much difference a quarter inch here and there can make when fumbling for the rudder pedals.

Oil Cooler & Aux Tank

With easy access to the inside of the oil cooler ducting, I used a little clay to radius the corners of the box. This is a pretty simple layout, but it still takes time because once you place the glass, you’ve got to wait a day or so for everything to cure.

Once I was pretty happy with how the diffuser box was going to mount to the oil cooler, it was time to bond the tubes to the cylinder intake plenum. I had originally considered making the tubes detachable from the plenum, but decided this wasn’t necessary.

Since the front half of the assembly hasn’t been bonded into place, I took advantage of the good access and applied a few layers of cloth to smooth the opening.

I decided to continue the tube to the front of the intake plenum to make sure the cooler received plenty of air. I used modeling clay to establish the shape.

It was a little difficult applying cloth and resin to the inside of the cavity, but you can see in this picture with the clay mold removed, it actually came out pretty good.

I made extensive use of my Dremel tool with the cone-shaped grinding stone attachment to smooth the rough edges of the fiberglass layup. With this portion completed, my next goal will be to join the front half of the intake to the rear half.

Keeping in mind that all of the stuff I’ve described above happened over the course of a few days, I’ve always found that it’s good to have something else to be working on while you’re waiting for resin to cure. I decided to start working on my auxiliary/ferry fuel tank. This is the big block of foam I started with.

I cut the big block of foam to the approximate size and shape and then added a few pieces along the edge to minimize the amount of filler I’d have to use to achieve the final desired shape. I glued the block of foam to the seatback so that I could test-fit the seatback to make sure everything fit.

Once the block of foam had been sanded to final size and shape, I applied Bondo to the foam. Bondo sands well and can be painted. My standard practice is to finish the Bondo as if it were going to be the finished piece. I sand and fill all the imperfections and then paint the Bondo so that (a) the fiberglass will release easier from the mold and (b) the finished surface of the fiberglass part will be very nice right out of the mold–minimal, if any, sanding.