The baffle journey continues! The overall theme here was to refine the interface between the inlet ramps, the forward side baffles, and the cowl inlets. As seen below, as provided, the ramps sit well below the lower portion of the inlet:
This isn’t what we want. We need those ramps to fit closely to the inlets, so they can eventually seal together. So I got to get even more practice taking the cowl on and off while tweaking the bends of both ramps. At least I was able to bend the ramps in place, instead of having to remove and reinstall them repeatedly; that at least reduced the tedium a bit. After a few iterations, I had both ramps resting gently against the bottoms of the inlets.
This led to the next tweak: since the inlets aren’t perfectly flat, we need more bending. The idea is to mark the spot where the ramps contact the inlets near the spinner, and draw a diagonal line outboard. Then the ramp gets bent along this angle, until the outboard portion of the ramp sits up nicely against the inlet as well. Unfortunately this did require taking the ramps on and off a few times (along with the cowl, of course).
The result is a nice close fit across most of the width of the inlet:
Next up, the ramps and side baffles need to be trimmed. They can’t actually overlap the inlets as seen above; if they did, then installing the cowl would require starting an inch or so forward of the final position and sliding it backwards. That can’t work once the prop is in place.
Instead, the ramps are trimmed until they stop just short of the aft edge of the inlets. This will allow the cowl to be lifted vertically into place, so it can work within the space behind the prop spinner. Eventually there will be flexible material added to the cowl, which will seal against the ramps…but that’s later:
With that trial-and-error work done, the next step was to fabricate a support bracket for the left ramp. This will prevent the forward board edge of the ramp from being pushed down by high-pressure air entering the cowl. The bracket consists of a flat plate that screws into the engine block and a thick angle to tie that plate into the ramp. Both pieces are precut, but the plate needs to be trimmed to fit. I ended up cutting off about half an inch or so to get it to clear the ramp.
Then the plate gets screwed into place, the angle is clamped to the ramp and against the plate, and the four holes get match-drilling. Here are the two pieces prior to drilling:
Then, after demurring and such, they get riveted together. The angle also needs to be drilled to the ramp. Curiously, the plan images show the angle having three prepunched holes in this spot, but my angle had none. The instructions say to only rivet the two outboard holes, and not the middle one – I think it ends up being in common with another attach angle that will be added later. So I just laid out and drilled the two outboard holes for now – I’ll figure out the middle one later.
Here’s the support angle after drilling the ramp attach holes:
The next step would be to rivet the ramp assemblies together, but I decided it was a bit late for riveting (these will require use of the rivet gun). Instead I jumped ahead to adding some bends to the forward side baffles. Previously, after finishing all that tweaking, I traced the edge of each ramp on the intersecting side baffle. These lines then are used to bend the lower flanges inboard; this bend provides some more support for the forward outboard corner of each ramp.
The instructions sort of gloss over the details here, but I had to do some trimming of both pieces to accommodate the bends. One of them I was able to do on my little bending brake, which was nice, but the other one I had to do the old manual way – clamping it with a piece of wood and beating the crap out of it with a hammer.
Once the bends were done, I remounted the side baffles on the engine; they’ll be ready to receive the ramps again once I get those assemblies riveted together:
Next session will involve some fun scratch metal working, as I address those square corners between the ramps and the side baffles.