Today was further proof that the lower cowl certainly is more challenging than the top. Even though I have determined some defining characteristics of the cowl and come up with a plan for the overall approach, it is still a challenge to blend these shapes and features together. It isn’t always intuitive how to blend complex intersections in 3 dimensions. I am a master of gettin into analysis paralysis, so for me, the only thing to do is get started.
That means lay splines and sand to shape. Unfortunately, when it isn’t intuitive to me, it normally means that I start in the wrong place and end up with the wrong shapes. That is what happened with the lower cowl. I had placed foam “control splines” in woefully wrong places. Since I was using these to define my cowl shape, sanding made it worse, not better.
At that point you need to be willing to get the saw out, remove the offending material, and try a new tack. Luckily, I have a good group of “phone a friend’s,” when I get to a mental blockade. This time, I talked with Thomas, and he said something that made sense to me. When he talked about how he would solve the problem he started with, “If this were a CAD problem…” That turned on a light bulb for me.
I have watched tons of youtube videos about how to loft a shape in both Solidworks and Fusion 360. That is essentially what I was trying to do in real life. So if I approached the problem in the way you would when drawing in CAD, it would be easier. This allowed me to better choose control splines and make the shape.
Yesterday’s session ended up with a majority of the left half of the lower cowl splined in foam and sanded to a rough shape that would allow me to evaluate if I was happy with where we were heading. Turns out that it seemed like the right approach and allowed for the best compromises in shape. I was able to keep retreating angles to a minimum by putting more emphasis on the lower surface. It still wasn’t intuitive, but it was better than what I had previously done.
Today I finished splining and sanding the left side of the lower cowl using that approach. It is really simple to do when the right “control splines,” and methodology is identified. I very quickly got to the point where I had enough of the shape roughed out and the foam was of a coarse enough resolution that I couldn’t improve the shape without going on to a material with more resolution.
At this point, I would normally spline in the other side trying to mimic as closely as possible the first side. However, I still had some lingering doubts about the shape at this point. The splines were disorganized making for optical illusions. The differing colors of pink foam/ yellow pour foam as well as areas with voids were making me question the contours. I needed to see a more refined shape.
Therefore, I started adding drywall mud. This would give me a more refined shape, more control and resolution with sanding, and a single color surface. Once I had the first layer of drywall mud on, I was convinced I had the right shape. From there, it is the familiar repetitive process. Add filler, sand to shape, find flaws, add filler, sand, repeat. I did a few rounds of drywall mud today and will have to do a few more yet.
The good news is I am happy with the shape, though there is still a lot of sanding and finessing to do. The not as good news is I now need to replicate it as closely as possible on the other side. All of this with out the benefits of being able to see the individual splines on the left side. Hopefully I have enough time lapse videos to determine how best to mirror the shape to the right side. Eventually templates will drive the shaping of the right side, but it is nice to get as close as possible from step one.
I can’t wait to see how the cowl shape looks with a wing installed. I can’t get over the visual of how tall it is when it is just the fuselage and cowl. I really think it will look sleek when the wing bisects the cowl and you only see part of it at a time. I have to keep reminding myself this is a ‘station wagon,’ not a sports car. It makes sense that I have a big cowl.