Firewall Forward VII
It was a big day at the hangar today. Not as far as time was concerned, but as in I got a lot done for a change. About a week and a half ago, I spoke with Van's about the snorkel that makes up the forward induction system. They said that there was indeed a revised design, and that I couldn't return the old one. Well, I was somewhat disappointed by that, but figured that the time saved cutting a shutting a terrible part was well worth another $104 plus the $4 handling chanrge. While I was at it, I ordered a new right hand baffle floor too. I'm going to remake it longer, as I need to trim a fair bit off the cowling to make the left floor work, and I want the cowling to be the same on both sides.
If anybody wants the old one, feel free to drop me a line. Pay the shipping and it's yours.
Here are some shots of the old intake versus the new one. There really is no comparison. The flange is thicker and truer, the whole part is thicker, the air cleaner area is squarer, and the air intake area is further inboard than the original one since it was designed for the wider 200hp angle valve Lycoming.
The perspective in this photo is a little deceiving, as it makes the new one seem a lot smaller than the old one!
On to fitting the new snorkel... Doh! It crashes into the alternator mounting! Looks like I'll need to mould in a bleb here. This was the start of a lot of iterations...
I want the bleb to be as small as possible, but it just kept getting bigger and bigger and bigger!
Before I knew it, I was left with a gaping hole!
Once I'd got the intake hole in the snorkel aligned with the throttle body (I used a wooden plug to centre everything), I went ahead and trimmed the flange to size.
Here's the hole I was left with. Now I need to fill it back up again! I sure did make a lot of dust today!
Here's the patch I'll be using for the bleb. I laid up four layers of fibreglass cloth on one of the wing light cutouts I made the other week. Glad I didn't throw these away now! I had to open up the bend a fair bit to make it work, but it looks like it'll do the job perfectly. I put some PVA mould release on it before laying up the cloth. By the time I get back to the hangar next week, this will be ready to fill the hole with. I was hoping it would be ready today, but even though I used the fast hardener, it still wasn't firm enough by the days end.
While that was going off, I had the bright idea to torque the propeller. Now then, these are 1/2"-20UNF threads, so according to the manual they need 66 lbs-ft of torque. It's the typical torque the prop situation where you can't get a torque wrench on there, so some clever extending and some simple mathematics will get you on your way again. In my case, my original torque wrench length was 16", and the extension spanner was 8". This was an easy calc, as it turned out I need 2/3rds the torque specified in the book. 44 lbs-ft.
OK, enough distractions already... Get back on the intake system! I drilled the four mounting holes in the flange and fitted it to the throttle body. Looking good!
Here, you can see the fit around the starter. It clears it nicely.
Here's another perspective. It would've been nice if whoever made this snorkel would've put some black dye in the resin. It would look a lot nicer in black. I might paint it.
Time to figure out the angle of the left floor. To do this, I put the cowling on, without the snorkel, fitted the baffle floor and bent it to an angle that came pretty close the the cowl intake. In the picture below, It's still horizontal. I don't know why I put the aircleaner in there already. I've got a long way to go yet!
Here is the angle about right. Next I measured a line around the snorkel to allow for the thickness of the air filter, and started trimming. Again, there were lots of iterations here. If you're at this point, don't go mad with the cut off wheel!
Here's a shot of the whole shebang trimmed. The air cleaner sit's in there nicely now.
Another shot of the same.
I saw on Dave Parson's site that he had bent the leading edges of the baffle floors down to add some rigidity. I figured that it was such a good idea that I'd do the same! Thanks Dave! Makes a lot of sense really. I don't know why I didn't think of doing that myself. Call me an Engineer?!
Here's the lip again. I bent it as close to the air filter as possible to help maintain a rigid line for a good seal.
I trimmed the cowling inlet back to suit the air filter location. Here you can see that keeping the filter and baffle floor flat results in a less than ideal situation as far as clearance goes to the cowl. I decided to incorporate some twist in the baffle floor to fix this issue. Basically, I trimmed about a half inch off the intake snorkel at the front inside corner, leaving all the other corners at their original height I'd trimmed them to.
As you can see, this fixed the problem quite nicely. It's tough to even see the twist in the baffle floor. I will have a doubler plate on my baffle floor for the air filter to snug up to. I don't think the floor is thick enough to really take the force of screws pulling it all tight to make a nice seal. That's about all I got done today. Not too bad really. Some good progress on an area I'd been dreading. Now it's coming together though, I'm quite happy about it. Next week, I hope to finalise all of it and glass in the bleb and fit the alternate air door.
Oh, lest I forget.... I even did some painting today! I snuck to the hangar one evening last week for an hour and primed all these parts. Here, they're finish coated. They turned out quite nice too for a change!
