Firewall Tape

Time: 0.5hrs

Just did some quick fixing of a few cuts in the heat shield. If I waited until I knew exactly what holes I needed then it would of come out near perfect. But there I go trying to save myself some time and messing things up. Oh well this tape seems to work pretty well. It’s rated to like 350 degrees F so it should hold up. It’s also very flexible and blends in very well with the covering on the heat shield.

Fixed the area around the ground lug where I cut out the hole for the GPS antenna that I didn’t use. I also added a little tape above each if the GPS antennas just to clean it up a little.


Firewall Heat Shield

Time: 2.5 hrs

Today I worked on finishing cutting out the necessary holes in the firewall heat shield. I cut the heat shield to size a long time ago and cut out a few holes that I knew weren’t going to change. I did unfortunately cut out the hole for the GPS bracket which I’m not using and I cut slits where the rivet lines were for the overflow bottle and battery box (which I didn’t need to do either). The slits aren’t noticeable but I will probably need to get some of the tape TAF uses to repair the heat shield just to make sure it doesn’t tear in those spots.

I saw a few people made templates out of paper of where everything went on the firewall and then transferred that to the heat shield. I was able to poke holes through the rivnuts from the inside and then fit the particular item to the firewall (like the GPS antenna brackets or heater box) using screws. This gave me the exact location I needed to cut out by just cutting around the item. I think it worked out pretty well. I also noticed when installing the heat shield that if something was a little off you could stretch or push it to fit closer. You can’t be really far off, but 1/8″ to 1/4″ off you can make up for and get a really close fit.

Once I had all the major holes cut I removed everything and peeled back the backing on the left corner and stuck that down to the firewall. I proceeded to just keep pulling off the backing and working my way down to the bottom doing this on the left half of the firewall first. The process was then repeated for the right half of the firewall. The heat shield installed fairly easily the main issue I had was that the backing didn’t want to come off of the heat shield material. Maybe mine was old and the glue started to bond more with the backing or maybe it was from heat (I’ve had the heat shield exposed to the sun for a long periods of time). In any case it was pretty frustrating having to remove small strips of backing as I worked in a very small area between the firewall and the back of the heat shield.

Photo of the heat shield all stuck down. Starting to install some of the items onto the firewall. I need to fix the area around the ground lug (upper right). This is where TAF puts the GPS antenna and I had cut that out thinking I was going to put the antenna there.

Most of the items installed on the firewall. The GPS brackets are just in temporarily. I will need to remove the left one to get the battery in so I won’t really install that until much later. The oil tank bracket was riveted in with 4mm rivets. I made sure to use medium strength loctite on all the screws as well. I will need to cut out holes for the fuel pumps as well as the start relay and in my case master relay. I didn’t cut these because with the relays I’m not sure if I will be using the Vertical Power PPS or not. I don’t think it will be too difficult to cut these out and remove the heat shield material for these couple of items. For the fuel pumps I believe they come with the engine and I’m not sure if they are the same as what TAF supplies. It looks like the TAF ones have a cover that mounts to the firewall while the ones I’ve seen that come with the engine the cover mounts to the bracket that holds the fuel pumps.

Photo of the heater box installed with 6 M3 screws. There’s a silicon gasket behind it that you can’t see. Note: I put both the clamps on there so I don’t lose them đŸ™‚

Photo of the fuel and push/pull cable bulk head fittings.

Here’s the idea I had for mounting the overflow bottle. TAF uses cable ties which look a little cheesy I think. I cut an 8″ hose clamp and did a hard bend on the ends, which could also be riveted. I then bent the clamp around the bottle to give it a bit of a squared off shape. It seems to hold the bottle well, maybe a little more bending to get it to fit better. I don’t want to tighten it too much or it will crush the bottle.

GPS Antenna Mounts

Time: 1.25hrs

Installed the 2 larger GPS antenna mounts on the firewall. I’ll be using 2 Garmin GA-35 WAAS antenna. One connected to the GTN650 and one to the G5. TAF mounts the GPS antenna under the cowling which seems to work fine. I have two and they’re a big larger then what the standard mount can accommodate so I had to relocate the antenna positions a bit. Also because I’m using the EarthX battery I don’t need the mount for the strap that holds in the battery and I was able to mount the battery a little lower to give some room above for the antenna. I needed to make these removable because the right side will need to come off to get the battery in… well I suppose I could also unscrew the battery box. In any case I use M3 screws and rivnuts to mount them. I should have measured out the bottom holes rather then use the bracket as a template since the mounts aren’t perfectly straight on the bracket. So now one of the rivnuts is a tad bit off when you look at it… not a big deal though.

I used a laser level to make sure both brackets go in the same place

Brackets are mounted and level. The left side is hard to see in the photo. It’s right above the bracket for the overflow bottle. I used some cardboard to simulate the cowling and checked clearance. I have about 1/2″ or more of clearance and my faux GA35’s (made from styrofoam) are a little higher then the actual ones, plus they aren’t as curved so I think I’m OK.

I think the next step will be to template some of the mounts on paper so I can cut them out on the firewall blanket. I already have the blanket cut to size and a few holes cut in it. The one thing up in the air is if I’m going to use the new Vertical Power  solid static box for the master and starter relay. It’s a bit pricy and it’s not available yet. It probably won’t be too difficult to cut those after the blanket is stuck down on the firewall… Hmmm


Overflow Bottle

Time: 1 hr

While I was picking up the GMU bracket at TAF yesterday I also got a Rotax overflow bottle and the mounting brackets.  I was going to make a bracket out of aluminum, but it proved to be a bit tricky because of how the bottle is made and my lack of ability to accurately bend the aluminum. I’ve order some stainless steel hose clamps that I will cut and install on the TAF provided mounting brackets. This will create a reusable way of attaching the bottle to the firewall rather then using the tie wraps. If all else fails I’ll just use the tie wraps.

I also cleaned and alodined the 2 water bottle mounts and the 2 GPS antenna mounts.

It’s just going to be too difficult to get a good accurate bend that fits the indentation on the water bottle. If the bracket doesn’t fit in nice and tight the bottle will fall through. I think it will be safer and easier to use a thinner metal like a hose clamp that can be formed around the bottle. I’m planning to cut the clamp and bend it so that it will attach to the TAF supplied mounts. The water bottle can then be installed or removed by screwing together (or apart) the 2 halves of the clamp. Well we’ll see if it works the clamps should be here in a few days.

Heater Box Finished and Firewall Pass-thrus for Cables

Time: 2.5 hrs

I finally finished up the heater box. That took a lot longer than expected, but I think it came out pretty good. The mounting holes lined up well except for the top right one which I had to open up a little so I could get the M3 screw to go in. I also used aluminum rivets on the bottom instead of the stainless steel ones I bought. The thought is that I may need to take the heater box apart to replace the foam or silicone, etc. and the stainless steel rivets are REALLY hard to drill out. Since there are 6 stainless steel M3 screws holding everything together in addition to the rivets the screws would probably out last the rivets in a fire and still hold the box together.

I also did some work looking at the different push/pull cables I have and some firewall pass-thrus that I bought for the cables. The heater cable is a fairly large (0.25″) cable and the standard pass-thru fits well on the cable. The choke cable that I purchased is a bit thinner so I also bought a few reducers that fit around the cable and into the pass-thru. The throttle cable works with the standard pass-thru, but the catch is that it already has cable terminates on it so I’m not able to slide the pass-thru over the end. I found they make a split pass-thru as well and this allows you to put the pass-thru on without having to slide it over the cable end. The other parts (nuts and lock washer) fit fine over the cable end so that’s not a problem.

Some photos of the completed heater box. The base plate, flap, and cable attachment (on the flap) are stainless steel.

I made a gasket out of 0.40″ silicone sheet. I used a single hole punch to make the holes for the rivnut heads and the two rivet heads that I added on the firewall.

The heater box fits well and the gasket seats against the firewall fine. I only had an issue with the top right hole not lining up so I had to slightly elongate the hole so the M3 screw would screw in OK.

I found these pass-thru bushings on Aircraft Spruce. They’re called “Cable Safe” (the standard one) and “Cable Safe II” (the split bushing). The regular one was around $10 and the split one is around $18. I thought these would be nicer to use then the rubber grommets that TAF uses. I had to figure out the combination of fittings though since the push/pull cables I have are all a little different. Above is a split bushing. a standard bushing, and a reducer (in the bag).

The standard fitting just slips over the end of the cable and fits fine on the larger (0.25″ outer diameter) heater box cable I purchased.

The choke cable I bought is a dual cable (because the Rotax 914 has 2 carburetors) and each cable is fairly thin so you can use the standard fitting, but it needs a reducer ring so it fits tighter.

The throttle cables (there are 2… remember 2 carburetors) are large like the heater box cable, but since there are ends already on them I had to use the split bushing. These are the TAF supplied throttle cables. The split bushing is a bit of a pain to get the nut onto because the halves move around and the treads don’t always line up correctly, but with some patience it threads on fine.

Here’s a photo from inside the firewall. This is the right side so there are 3 cables here: the heater box (bottom), Choke (middle), and throttle (top). I got lucky because there was just enough room for the the lock washers to fit. I had to upsize the holes a little bit so that the bushing would go through. BTW The fittings on the far right are -6AN fittings for the fuel send and return lines.

Here’s the firewall so far. All the pass-thrus are done and almost all the rivnuts are installed, except the ones for the fuel pumps. Once I get the overflow bottle I can make the bracket for that and then figure out the final location for the 2 GPS antenna brackets and mount those. I’ll mount those with M3 screws and rivnuts. When that’s done I’ll put on the heat blanket and finish up cutting the holes in that. Then the firewall will be ready for the engine install.


Heater Box Flap and Cable

Time: 1 hr

I finished up the silicone on the heater box flap and messed around with the cable that controls the flap. I’m goin to see if I can find a cable attachment that swivels rather then the crew and washer design that’s in the manual. I wanted to try out the cable because I had made new parts for the heater box and was to make sure they work. The push pull cable seems to work fine and it clears the opening in the heater box when fully close (no heat) position.

I had previously tried to use the Barge cement I bought (for sticking the leather to the glove box) for the silicon sheet on the flap, but the silicone pulled right off. I purchase this Sil-Poxy from Amazon from around $20 and it worked amazing. It seems like maybe it’s just RTV, but I didn’t try RTV so I’m not sure. It smells exactly like it though so maybe a cheap tube of RTV would have worked just as well.

The bottom of the flap seals up nice now. I just had to add a thin silicone sheet over the other one I cut out. The thin sheet extends over the hinge piece as well.

I cobbled together the push pull cable onto the flap just to make sure it’s going to work. It operates very smooth. I don’t like the screw and washer design so I need to see if I can get a swivel mount that will screw into the flap bracket and allow the wire for the push pull cable to more freely move as the door opens and closes. Also because the wire for the cable is so thick it will be difficult to do a 360º bend in it to wrap around the screw. I purchased the cable terminal from McFarlane and it will need to be epoxied when finally installed. I don’t want to install it yet because I will probably need to cut the cable back a bit.

Here’s the control cable I purchased for the heater. I purchased it from Aircraft Spruce, but you can get it directly from McFarlane’s for about $20 cheaper. It locks in position so that will prevent the heater door from moving. It’s a little large so I’m hoping it will look OK when it’s mounted to the instrument panel. It’s a really well made cable with a Teflon inner core so it very smooth and doesn’t need to be lubricated. Also for $20 you can get them to etch cabling on the handle. I didn’t get that done, but I should be able to get a new handle later with “Cabin Heat” printed on it. My whole cable says “Choke” so at least I can tell them apart even if I don’t get it labeled.

Tomorrow I should be able to rivet the heater box together… Yay!

Misc Firewall Work

Time: 2 hrs

Did some misc firewall stuff today:

  • Clean and alodined some firewall parts
  • Cut hole in base plate for cabin heater box
  • Drilled 4 new holes in heater box plate
  • Installed cable bracket and foam on heater box door
  • Fit inlet pipe onto heater box
  • Countersunk holes in heater box plate for the rivets that hold the side and top on

I cleaned and alodined a few parts for the firewall. I think this will hold up better then paint. I hadn’t alodined anything yet and these parts came out pretty good. I found that I really needed to scotchbrite everything then clean it with the BONDERITE C-IC 33 and then dip it in a 3 parts water, one part BONDERITE M-CR 1201. The battery box is a little blotchy but not bad.

I fit the aluminum pipe to the heater box. You need to bend the tabs out on the heater box top piece. It’s a pain to try to figure out where to drill the hole in the pipe for the rivets. I bent the top one and drilled it then clecoed that. I held the pipe to the box with clamps and then bend in the sides and drill those and clecoed them to bend and drill the last tab on the bottom.

I’m a bit perplexed at how I get a rivet in this hole. The flange for the top of the heater box is in the way. I’ll have to ask TAF.

I ordered a 1.5″ hole saw to drill the large hole in the base plate that I made for the heater box. It worked very well. I drilled an 1/8″ pilot hole and then drilled it with the hole saw on top of a block of wood.

Hole is done.

I put the TAF supplied foam on the front of the heater box flap. It seals up well now.

The flap in the open (heat on) position. The foam seals up the gap nicely. I’m not sure how long this foam will hold up though. It looks like the same stuff TAF supplied for the sound proofing. Unfortunately I didn’t have a thin enough piece of my soundproofing material to use in it’s place.

It’s a bit hard to see in the photo… The flap is in the closed (heat off) position. There’s still a bit of a gap between the flap and the base plate. I’ll see if I can get a little thicker piece of silicone, maybe 1/8″ should do it. Also the Barge cement didn’t work on the silicone so I ordered something else that should work.

Lastly I drill two more holes on each side to rivet the top onto the base plate. The other 6 holes (3 on each side) are for M3 screws to attach the heater box to the firewall.You don’t need the rivets, but I’d like the heater box to stay together without the screws.

Since the base plate I made is .060″ I countersunk the rivet holes and will use some stainless steel countersunk rivets. The new holes that I added (where the clecos are) also where countersunk.