« Archives in April, 2012

Baffles 6 – 7

12 hours.

I took Friday off to build. I take every other friday off to build, since I’ve got the vacation days, and Friday/yesterday were big build days.

This section is a lot of problems to solve, all interwoven and tangled. I had hoped to be finished with the snorkel this weekend, and I got pretty dang close. I got the filter mounts riveted to the snorkel, then got them drilled to the baffle. It was a little more complicated than that, but mostly just iterations of measuring, cutting a little, measuring, repeat. Now all that’s left of that is to dimple the screw holes on the filter mounts and install the platenuts.

It was during this process that I started the iterations on making the front baffles fit. Since my engine has a front-mounted governor, I bought a set (and an extra set) of the front baffles for the RV-10. I was able to cut them down to match the -7’s lower inlet ramp angle, and went through numerous iterations of grinding to get the contour right. The left one should fit the governor just fine, and the angle matches the inlet ramp perfectly. The right one might need a little work, but I have an extra one and I can use the current one as a template if I have to.

As if that wasn’t enough to make things interesting, I get to figure out how to install the top cowl inlet ramps in such a way that glassing them in won’t result in a hinge misalignment. The manual says (one of the few things the manual says about this area) to install the ramps with the top cowl on. Well, that’s just great. How the hell am I supposed to fiberglass that? Maybe drilling/clecoing for initial position, then glass it with the clecos still in, holding it together. In any event, all the baffling will have to come off before this happens.

I’m also going to have to order a new batch of Proseal to finish off the air filter mounts.

The baffles are going to need lots of trimming. A quick test fit shows the top cowl being not even close.

Snorkel and Baffles again.

8 hours.

Yesterday and today. I’ve been blowing this off, mainly because there was no good time to spew fiberglass dust all over myself, and the fact that I accidentally sheared off the cord of my Dremel tool with the fiberglass bit last time. The sparks were epic. Yes, that was stupid. So yesterday I went to Home Despot and picked up a new Dremel 4000, and this time, I got the flex-cable attachment that lets me use the thing a lot more like a pencil or some other fine instrument.

I tried to take a lot of pics, because the process of fitting the VA-132-1 snorkel to the AFP FM-200 fuel controller and the front inlet ramp is a complete and total whore. Hopefully my documentation can help somebody have less of a ride thorugh hell. There is very little in the way of direction in the plans that actually provides useful information. About the only thing I needed the plans for was to tell me which side of the snorkel the filter mount flanges go on. It’s the inside, in case you’re curious. Oh, and the reference photos on the plans are terrible, and there aren’t enough of them to give you any in-depth information as to how things are supposed to fit. Yes, I get that there should be a big square hole in the front inlet ramp that should have an air filter under it. All aboard the NS Sherlock. Even so, fitting it to the AFP fuel controller brings with it its own set of travails, which is largely the root of the issue. Now, the FM-150, released the year after I got mine, has a square flange on it, like the Bendix or Precision Silverhawk servo, which means the snorkel will fit a lot better. Too late for yours truly, however.

So today, I was determined to make the filter mounts and mash up the parts necessary to make the filter fit.

This was the state of affairs after trimming the snorkel to match the contour of the inlet ramp, bend and all. This was a tweaky, iterative process, the first of many. With the snorkel attached to the fuel servo (throttle body), I had to trim away millimeters of material until it was kinda sorta flush with the contour of the inlet ramp, including the bend in the material designed to match the contour of the cowl opening.

With this in place, I was able to trace the shape of the snorkel opening onto the bottom of the inlet ramp.

View from the top, before anything was cut. At this point, I’m test-fitting the filter retainer, which is going to connect to the whole apparatus by way of #6 screws.

I gave myself plenty of room to work. The initial cutout for the opening was about 3/8″ inward from the actual edge. I wanted to make sure things could shift around a bit when installing the W-sections that would become the filter mounts.

First step was the aft side, which is the hardest, because there’s a joggle downward from the angle attached to the cylinders and block to the actual ramp. This means that the W-section of metal designed to accommodate the filter needs to fit in there, and match the angle of the snorkel’s surface. This was not easy, and I think I’ve got enough edge distance to get by, but I’m not altogether sure.

So after cutting away a good amount of the flange on the filter mount, and bending the metal to match the angles, I got a pretty decent fit. Here, you can see the metal flange through the fiberglass, with positions marked for where the rivet holes are going to go. It was at this point I figured I should take a look at the drawings, useless as they are, to make sure I wasn’t committing an obvious error.

Once this one was nailed down, everything stopped moving, and it was much easier to work with the whole assembly with it anchored at both the servo end and the filter end. Good thing I checked the plans. As mentioned before, the flange goes on the INSIDE of the snorkel chamber, not like it is in the previous photo. Fortunately, there was enough give to let me squidge the snorkel back enough to make this work. But blocking it out like this gave me a perfect reference as to where to cut down the snorkel to clear the joggle on the W-section.

The next filter mount section was relatively easy. Too bad I cut the W-section too short with the bandsaw. Stupid muscle memory. I thought about it, I double checked it, I marked it, but I wound up cutting it too short anyway. Not a big deal, I have a template now, and I know how it’s supposed to go. Replacing it will be simple. The next step beyond the filter mounts will be opening up that inital cut to clear the horizontal part of the filter mounts. The idea is that the air filter rests on the joggle in the W-sections, but the forward lip of the filter just slides in under the opening.

To get the outboard one, I had to shave down the filter mount flange at a slight angle. I also finally had to bend the lower flange on the outboard baffle to match up with the inlet ramp. But this actually made things easier. Plenty of edge distance, and the third filter mount went on no problem.

A closer look at the outboard filter mount, from the front. The little piece of metal that looks like a ‘J’ is the horizontal part of the W-section where the filter lip rests. The snorkel will still have to be trimmed up front to allow the lip to clear. Probably should have photographed the filter a little. I will next time.

So that was the scary bit. I had no desire to start anew with a new snorkel (which is pricey), and other than the inboard filter mount, I don’t have to order new parts. It’s an iterative tweakfest, but eventually, things stop being awkward and you can actually get some stuff done. Just to make sure I wasn’t crazy, I put the lower cowl on, and everything seems to clear just fine, but the cowl will require a little bit of trimming.

Next is to enlarge the filter opening and make the filter retainers, and install the K-1000-6 platenuts that hold the whole thing together. Once that’s done, I can finish the front baffles, which are going to be interesting on their own.

More snorkel!

3 hours.

Short day today. This morning was an Easter Egg hunt and brunch, so I didn’t get going until about 1 or 2. My setup for glassing the opening ring of the snorkel worked great, but the resin adhered to the demoisturizer container/plug a little too well. It cracked the container when I wrenched it out of there, but it didn’t make a huge mess. I spent some time sanding down the inside of the snorkel to smooth out the bumps, and it seems like it’ll work OK.

I did get the snorkel on in preparation for trimming the filter end to fit the contour of the inlet ramp, with its bent-up section as called out in the plans. I’ll post some photos later, but the main issue is one of reference. To get the snorkel on in its pre-trimmed state, the inlet ramp needs to come off. But then there’s no reference to where the inlet ramp is actually going to be. fortunately, I marked on the side baffles and the engine where the inlet ramp fits, and through the use of cleco clamps, angles, and a steel ruler, was able to transfer those references to the snorkel. It’s going to be hard, and it will take some iteration, so the key will be not trimming away too much of the snorkel during the fitting process. However, if that does happen, it won’t be a total disaster, I can always cut away enough to make absolutely sure it clears, then extend it to the baffle using new fiberglass, and doing that will insure that it absolutely conforms to the inlet ramp shape.

Snorkel Again, and Exhaust.

5 hours.

Today I did some more work on the snorkel, this time trying to shape the throttle body side to allow for smoother airflow, fill in some voids in the opening, and generally beef the thing up where the interface is.

This is looking into the relief hole I made for the alternator. You can see that the demoisturizer container serves as a perfect plug in place of the throttle body and the tape wrapped around it is exactly where the lip on the TB would be. The dark bit on the right inside the hole there is a void that didn’t get filled on the last glassing pass. I roughed up everything, cleaned it out, and went to town.

This is looking in from the top, where the air filter will go. It looks pretty anatomical, I know. The thing I have to fix now is where the opening bulges up, which will create a turbulent airflow.

Weapons of the trade. That’s the Builder Shield plastic on the left, and West System 206/105 epoxy resin on the right with the pumps sticking out. Living 3 miles from Marina Del Rey, I’m fortunate to have a West Marine store where I can buy this stuff. I wanted to get the 206 hardener, because I needed more pot life from the epoxy. I can wait the 10-15 hours for it to cure.

The photos stop for a bit, because of the whole resin/iPhone thing again. The next step was mixing up a bunch of micro to fill in some voids and take a crack at shaping a more gradual transition inside the snorkel where that burble was going to be. The first thing to figure out was how to fill in the voids around the actual opening itself. What I wound up doing was fairly genius (assuming it comes apart properly tomorrow). I wet down a strip of glass cloth, put it on the inside of the opening ring, then jammed the plug through it. It should form a perfect shape around the plug, and I can easily cut/sand off the excess on either side.

Here, it’s about done. There’s micro in there, and a couple of layups of glass around the burble and the rest of the edges go hold everything down. I also put a couple more layups on the outside to thicken up the interface ring.

With that curing, I went hunter-killer on some of the smaller items that I’ve been blowing off. First thing was reclocking the prop governor cable bracket.

This bracket also goes on the IO-540 in the RV-10, but the -7’s cowl doesn’t have enough clearance to let that happen. I’ve seen one or two examples of putting a bump in the cowl to allow the bracket to clear, but since I want to do as little fiberglass as possible, I decided to reclock the bracket. That just involves drilling two offset holes. The bracket will stay on just fine with two screws. I didn’t need to do much, that’s maybe a quarter-inch of distance between those hole, but I managed to bring the end of the arm down enough to where there won’t be any interference issues with either the cowl or the #2 injector line.

Since it’s time to think about things like control cable and wire routing, I decided I should probably put the exhaust system back on. The more things that are actually on the airplane, the fewer guesses I’ll have to take when deciding where to run things. Forward of the firewall, the name of the game is keeping things from picking up too much heat, and the primary source of that is the exhaust. The recommended distance between the exhaust and anything else is half an inch. Anything comes closer than that, and it needs to be shielded.

What you see here is the 4-pipe Vetterman exhaust I had to purchase to replace the crossover 4-into-2 type I had before. With the Crossover exhaust, there’s absolutely no way to get control cables to the throttle body without a horribly complex series of bellcranks and other things I really don’t want to mess with. The 4-pipe setup has a nice wide space up the middle where I can route the mixture and throttle cables without getting them too close to the pipes.

Since the right aft baffle is already on the engine, and finished enough to matter, I thought it might be a good idea to get the two-pipe cabin heat muff set up, along with the suspension by which the aft sections of the pipes hang. I’ll admit, I can’t find the instructions or drawings right now, but it really only makes sense to put it together one way. This is all about making sure I have all the parts, which I do, except one of the nuts is defective. There are no threads in it. I don’t even know what that type of fastener is called, to be honest, so I’m going to tap it for whatever threads the connecting rods between the brackets are. Like the crossover version, the pipes hang from stainless steel tubes connected by sections of rubber oil hose, so that’s no mystery. But with this and the baffle in place, I’ll be able to hook up the cabin heat system.

Snorkel 1.

7 hours.

Saturday and Sunday. The snorkel fit fine with no modifications. April Fool’s! Seriously, this thing is the biggest POS in the whole inventory. There’s no way it will fit without mods, ever. It doesn’t even fit well with the engine Van’s sells. It is a black hole of suck, no two ways about it. Firstly, I hate fiberglass. Second, I have the AFP fuel injection system. Third, this thing has to line up in at least three places before it can be said to ‘fit.’ Let’s have a look.

What you see here is an attempt to make a plug in the shape of the throttle body intake. To do this, I make a ring out of .032 aluminum, then riveted it to another ring just inside that one, with the shop heads sticking out. This slipped over the throttle body intake and the idea was that I’d tape it off, fill it with spray foam, and have a perfect foam plug from which to form all my fiberglass and use as a sanding block later. No such luck. The foam can I used had probably been sitting on the shelf for about 6 years or so, and never quite cured. Mess. And before you ask, yes, I taped up the throttle body so no goo would get down inside. Back to square 1.

I don’t have a lot of pics of the snorkel in its totally hacked up form, because I didn’t want to get fiberglass dust all over my phone. Basically, I had cut away pretty much everything near the flange of the snorkel, leaving a hole big enough to get the throttle body into. A lot of people cut the snorkel in half and re-glass it back together after fitting each half, but I didn’t want to do that, for some reason. Since I was committed to glassing a whole new flange on it, I didn’t see the need to cut it in half. So that led to the next process:

When fitting this thing, not only does it have to line up on the throttle body intake, the filter end has to line up on the left front inlet ramp, and it has to do it while clearing the #2 oil line, the governor baffle, and the front side baffle. Plus there needs to be enough meat around the edge of the air filter hole to attach the supports and meet any riveting edge distance requirements involved. The only way to get it into position is to take off the inlet ramp and try to fit it that way. surprisingly enough, this does work. I wound up suspending the snorkel in a cat’s cradle of PVC pipe tape (all hail pvc pipe tape, that sh*t rocks!) in the position it would eventually be in once everything is glassed and cut.

I also found my new best friend for fiberglass work: Contractor’s carpet guard. This stuff comes on a roll like Saran Wrap, and it’s the stuff contractors lay down on your carpet before they start trudging in with muddy boots and taking out old sewer pipes. It has a mildly adhesive backing, and it clings to itself and smooth surfaces like crazy. Think of the blue stuff that comes with Van’s kit parts, but clear. It leaves no residue behind either, although they do recommend you don’t leave it on for more than 30 days. Anyway, this stuff became the new throttle body condom, as well as a wrapper for anything else I didn’t want to get stray resin on. I took the alternator off, because it was seriously in the way, but I just wrapped a bit of this stuff around the starter and the alternator bracket. Oh and all over the throttle body. Like so:

Here’s a mostly side-on shot of the opening in the snorkel next to the throttle body. As you can see, it’s not even close. But with the TB protected, I can slap glass on this thing until the cows come home.

From the back.

Now the photos stop, because I’m not about to get resin all over my phone. I used two layups of the same stuff I had when I did the canopy. I’ve got a crap-ton of it left, wo a few pieces got me through. I was able to make a decent connection between the TB and the snorkel, the end result of which is this:

A perfectly-shaped snorkel-to-throttle-body interface. OK, not perfectly shaped, but close enough to keep going. This is after 8 hours of cure. There are some voids where the plastic wrinkled around the throttle body opening, but that’ll get fixed in the next couple of days or so. I did find a perfect facsimile for the throttle body opening though. At the hardware store, they sell this demoisturizing stuff. It’s basically little balls of salt, but what’s of interest to me is the container. The container is smooth plastic, and it’s exactly 3.25″ in diameter, same as the throttle body. Half an inch up from the bottom, I wrapped about 1/8″ thickness worth of pipe tape around it to simulate the lip of the TB, and I was able to use that as a plug for the next 3 layups of reinforcement of the opening.

The inside is a different story. I’m going to be in there with micro, shaping a smooth guide for the airflow around the parts that indent too far into the snorkel chamber and will cause turbulence rounding the corner into the throttle body. That’s when I squidge some micro between the plug and the interface there to fill the voids as well.