Trent's RV14 Build: 47-08 -> 11 & 21 -> 22: Forward Baffles / Air Filter Frame /Baffle Tension Rods

47-08 -> 11: Air Filter Frame

The forward baffles followed much of the same procedure as the aft baffles, however also included the preperation of the air filter frame, which is located in the left hand side air ramp (and will be match drilled and expoxied to the snorkle later on).

The filter frame was cut to the scribe line with a japanese saw, the fitted to the air ramp. To get it centered, i used some tape to make some centrelines. It was then match drilled - i clecod with my black clecos.

Scribe lines marked with sharpie to help them stand out

An old blade works great - no airborne dust.

This method worked well for centering the filter frame in the hole.

These #8 screw clecos haven't been used many times, but come in handy occiasionally.

I then riveted on the #8 nutplates using some AN426-A3-5 rivetd. The "A" in the designation means they are of a soft temper - these work really well on fibreglass parts. They set very easily with the hand squeezer.

I had to angle the nutplates / relieve the fairing in some spots, to allow the nutplates to sit flat.

To trim the sides of the filter frame clear of the #2 cylinder baffle parts, i first made a couple of holes from the air ramp into the parts, then cleco'd on the side baffles, so i could mark a cut line clear of these parts.

Once screwed into position, the forward edge was trimmed flish with the air ramp.

47-21 0> 22: Air Ramp Cones

The corners of the air ramps on both sides get an 'air ramp cone'. The right side is a small piece which gets riveted to the air ramp itself, on the left side it is a part of the air filter frame cover (which gets screwed on). Templates are provided - i just had to get them printed at the shop, as i elected not to have the $80 USD printed plans included with my FWF kit order, and when I printed the plans here they scaled to print to A3. A trap for young players.

A hotel card was marked as a poor mans angle gauge, but i ended up using my actual angle gauge mostly.

The paper guides were pretty good, but it needed a fair bit of tweaking.

The left hand filter cover ramp is held to the side baffle with a screw and nutplate. Once it was bent to my satisfaction, i match drilled this hole and added the nutplate.

This little nutplate jig has drilled a lot of nutplates now!

The forward baffle parts were finally cleaned, etched and primed, then riveted together. I used high temp VHT primer omce again. The right hand air ramp gets a stainless steel screen, to evidently keep the possums out. The plans call for this to be riveted on with dome head rivets, but i elected to use flush. Some RTV was used around this screen.

This is the cylinder standoff for the #1 cylinder - this allows air to flow down the front of the cylinder where the fins have almost zero depth. Other kits use a washer in this location.

Bloody curious possums.

This screen is to give air to the heater muffs for the cabin heat (and to keep the possums out).

RTV Chafe Strips

There were a number of areas where the plans called for 1/32" thick stips of RTV, to prevent the baffles chafing the cylinders. I am aware of better methods, such as a fibreaglass / RTV sandwich between the baffles and the cylinders, or even a piece of baffle material.

Since i don't want the cylidners damaged by the baffles when we are test-running the engine on the truck, i elected to add these strips. I can still use other methods to seal the baffles later, when hanging the engine onto the airframe.

I found 2 pieces of fabric tape was approxiamtely 1/32" thick, so used this for masking.

47-14: Baffle Tension Rods

The baffle tension rods are made from some stainless rod. These are bent according to a template in the plans, then the ends are tapped. I found the best procedure was to clamp the rods with the bend at the back of the jaws - so as much of the bend is clamped as possible to help resist the rotation of the rods as you tap them. They naturally want to rotate in the jaws, but if they do, the bends are pulled out. They can be easily bent back.

I made sure to generously chamfer the ends before tapping.

Tapping the stainless was not a great job, but i managed to make it work. I found that the swarf would get trapped a bit in the die and make it hard to tap - the tool pressure would increase as the cut went along, eventually twisting the rod in the vice.

The best procedure ended up being to blow off the die so it is clean of chips, then clean with iso. Add some oil and tap about 1/3 the way down - going maybe 60 degrees of rotation, then backwards to break off the chip - you can actually hear it break. At the 1/3 mark, remove the die and clean everything with iso and air. Then add more oil and do the next 1/3rd etc.

I also thought i was galling the threads - however it turns out that the rods are undersized for a #6 screw. So it makes sense that the threads are not totally sharp - the material was a little small to start with.

Clamping at the 'back' of the vice worked the best - this way there is as much rod as possible to help resist the rotational forces when tapping.

This shows how some of the threads are not fully sharp - i believe this is due to undersized material.

This is the major diameter of the #6 screw. To get sharp threads, the material would need to be at least this big to start with...

... but is is 0.019 under sized. This is the cause of the square profile of the threads (not galling as i initially thought).

Finally, i cut some of the supplied plastic (nylon?) tube to prevent chafing on the cylinders. I just divided this into 8 equal lengths. I can trim this smaller if need be later.