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.
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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.
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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.
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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.
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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!


Tail Spring Fairing & Breather Tube Mod

Friends have been bugging me forever to fabricate a fairing for my tailwheel attach bracket. It’s a big, draggy bracket that attaches to where the original leaf spring tailwheel attached. The first step in the process is covering everything with either shelf paper (the white stuff) or vinyl tape to protect it from my sloppy application of cloth and epoxy resin.

With the area protected, I used modeling clay to form the shape of the fairing. The flash from my digital camera really emphasizes the surface irregularities. It really did look a lot smoother than that to the naked eye. Not a huge concern for a part like this, I guess. And the fiberglass cloth itself kind of smooths out smaller surface lumps and bumps.

I covered the clay and the surrounding area with PVA mold release and then applied 3-4 layers of 6 oz. fiberglass cloth and epoxy resin. This is the part after the resin is cured and the part has been separated from the aircraft.

This is the part after I’ve finished removing the clay and pealing the PVA mold release. I’ve also done some preliminary trimming with a Dremel tool equipped with a cut-off wheel. It was still a little cool in my hangar so the part hadn’t really cured enough to start sanding on it. I’ll probably take time to sand, fill and prime it before I put it on the airframe for a test flight. I tend to get some oil back there and I don’t want an unprotected, raw fiberglass part to get oil soaked. It’d be nearly impossible to get the paint to stick if that were to happen.

Another little nagging project I’ve been meaning to complete is the installation of a modified breather fitting. The original O-200 breather tube fitting is simply the threaded fitting you see in this picture. When screwed into the case, the fitting is flush with the inside wall of the case which allows oil to easily run down the inside of the case and get sucked out via the breather tube. If you look closely at the fitting in this picture, you’ll see that it’s been machined slightly to allow a bigger inside diameter on the treaded end of the fitting.

The larger inside diameter allows a 1/2″ copper tube to slide in and be silver soldered into place. Once the tube is soldered, it is cut down to 2-3/4″ from the end of the threads. This extended breather vent still provides the “breather” function, but it makes it more difficult for oil to actually escape the engine. (Or so the theory goes…) Big thanks to Dave Biesemeier–friend and machinist extraordinaire for his efforts in modifying the fitting.

This is the original fitting as it was installed on the engine at overhaul time. It was powdercoated with the rest of the engine at that time.

I lost the red powdercoating, but I still think the gold looks cool against the red. You can also see the bead of Permatex thread sealant that oozed out of the threads as I installed the fitting. On the advice of Dave B., I’ve started using the sealant on pretty much all my pipe threads. Never had a leak on a fitting with the sealant. Forgot to apply to one fitting on my oil filter housing and had a leak. Definitely worth the time and effort to use.


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.
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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.
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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.
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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.
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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.
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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.
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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.
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What’s the next project? Stay tuned for pictures and a narrative in the next entry.


Oil Filter & Cooler Hoses & Fittings

I made a simple bracket to hold my oil thermostat. I’ll attach the bracket and thermostat to the engine mount using the 2 Adel clamps you see in the picture. I was shocked to see how much the AN fittings added in terms of overall size to the thermostat. Luckily, space isn’t much of an issue under my cowling.

Here’s an overview shot of the entire installation. The oil line comes out of the engine to the filter then from the filter to the thermostat. From there, it goes in and then back out of the cooler and then from the thermostat back to the engine. Lots and lots of hoses so I’m hoping this pays big dividends in terms of oil temp reduction.

Here’s a close-up of the installation of my hose fitting. I learned from a friend to put some tape on the hose before you start screwing the fitting together to make sure the hose isn’t pushed out of the fitting as the parts are joined. I’m using Aeroquip Lite hose. It’s about $8/foot, but it’s approved by all the different car race associations as fireproof. It’s also rated for 500psi so that should pretty much handle my 90psi (max) O-200!

A close-up shot of where the oil lines come in and out of my case. This is the same location Continental uses for the installation of an oil cooler, but it’s a custom fitting. The O-200’s rarely had an oil cooler installed in a Certified installation. They put oil coolers on Cessna 140 planes, but only in the seaplane configuration… Fairly rare. Cessna wants many hundreds of dollars for their official fitting so I was happy that the prior owner of my plane had this fitting custom built for this engine. You’ll remember that I tried the F&M or F&S or whatever brand oil filter adapter and oil cooler spin on adapter, but my engine mount interfered.

A close-up shot of the fittings and hoses coming and going from the thermostat and the spin-on oil filter adapter. If you look closely you’ll notice that the blue anodizing has been removed from the fitting on the right side of the oil filter adapter. I had a clearance issue so a friend cut the threads down by about a 1/4″ and then re-threaded the fitting. Worked perfectly.

A close-up shot of the fittings on the oil filter adapter. You can see where the modification to the right fitting gave me just enough clearance to account for the curvature of the firewall flange.
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I don’t have a picture, but a friend came over to observe an engine run to check for leaks. Good news! No leaks. With 6 hoses and 12 fittings, I’d never want to just assume I did everything right. It’s very satisfying to have a dry installation.
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The fiberglass work on the plenum is coming along nicely. I’m pretty much to the point of using tape to cover a few holes and testing the system. If the weather is good, I’ll tape up the holes and go flying. If the weather isn’t flyable, I’ll spend the day doing more fiberglass work, instead. I’ve got Monday, Thursday and maybe part of the day Wednesday of next week to work on the plane. I’m planning to head down to Abilene, TX on Friday for an air race on Saturday. I think the only thing that’ll stop me this time is weather.


Plenum, fittings, thermostat and cheeseburgers

This is a top-down view of the new oil cooler ducting with the fiberglass cloth in place. It’s not perfectly straight airflow, but it’s much better than the previous installation.

This is the oil cooler exit air plenum wearing a few layers of fiberglass cloth.

This is a sampling of the fittings I ordered for the oil cooler installation. The silver piece with 4 ports is my new oil thermostat. The brass right angle fitting is a new breather port fitting. I’m going to solder in a piece of copper pipe to reduce the amount of oil that finds its way to the belly of my airplane via the breather tube. More pictures of this mod later.

Some folks were asking about the weight of my new oil temperature thermostat so I took a picture of it laying on a postage scale. The weight of the piece isn’t significant, but when you consider all the related fittings and hoses, I’m sure I’ve gained a few pounds. Gotta be done!

Sometimes it’s hard for people to visualize just how the fiberglass process plays out so I included this picture. Since I used a combination of foam and clay for my mold (plug), once the epoxy resin cures, I have to dig the foam and clay out from the inside. It takes a bit of time and patience, but it’s kinda cool to see the part take shape.

Here’s the new exit air plenum box after a bit of trimming with the Dremel tool and some light sanding. I always end up leaving a few “pokeys” (extremely sharp shards of resin-impregnated fiberglass) on my layups so I do a little light sanding to minimize my blood loss when fitting the new part.

This is the bottom piece of the new oil cooler ducting prior to much trimming or sanding.

Here is the top half of the plenum with the new oil cooler ducting grafted into place. I’ll test-fly the new installation before I spend a bunch of time sanding, filling and painting. No sense in spending a bunch of time on cosmetics until I know the installation will work.

I submit this picture as evidence of my progress towards full-fledged adulthood. My new year’s resolution was to start acting more like an adult and less like a college kid. Part of my plan is to start incorporating furniture and vegetables into my day to day existence. I still don’t have any furniture in my house, but I have started putting vegetables on my cheeseburgers when I barbecue! Those are some darned-fine looking cheeseburgers if I do say so myself.


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.


Fiberglass ducting for oil cooler

I started the process of fabricating a duct to provide high pressure air to my oil cooler. I used a bunch of vinyl tape to protect different surfaces from resin. The resin releases easily from this vinyl tape. I used a few pounds of clay to form a reasonably smooth duct from my existing rear cylinder baffle to the oil cooler.

I painted PVA mold release on the clay. You can see where the mold release pooled near the oil cooler. If my dimensions were absolutely critical, I would have had to do something about the pooling, but since it doesn’t really matter, I’ll just accept the longer dry time and move on.

Here I’ve laid down somewhere between 3 and 4 layers of 6 oz. fiberglass cloth over the clay and PVA mold release. You can see where the green from the pooled mold release shows through the wet fiberglass. As I mentioned before, I wasn’t concerned about the pooling, but it *is* important that the PVA is dry before you start laying the fiberglass cloth over it. I let the mold release dry a full 24 hours before I did the layup.

I try to have multiple projects going on simultaneously while I’m doing fiberglass work. If you don’t do this, you end up wasting a bunch of time because you have to wait for each layup to cure before making any additional progress. This is the start of a mold for the oil cooler exit air diffuser box.

This is all I’m going to do in foam for the exit air diffuser. The rest of the shaping will be done in clay. This would be a huge chunk of clay if I didn’t start out with some foam. I’ve painted the foam with a mixture of resin and micro balloons so that the clay will stick to the foam core more readily and my clay won’t be contaminated.