Discussion Starter · #21 ·
What happened was about a 35-degree temp swing over the last 24 hours. Didn’t consider the thermal expansion abilities of 2-part foam. The amount of movement is minimal... almost imperceptible, but it’s enough to throw fairing all of of whack. Basically the areas between the bulkheads dropped down about .25mm. We could fill back in and re-sand, but then when temps rise again everything is off once more.
Trying to figure out the smartest move forward: build up a CSM “exoskeleton” on the plug to give us a hard, (hopefully) unflexing surface, then fair out from there and prime/polish, or cut the losses, call it an interesting experiment, and foam-sandwich our way through it.
The pic above is of that hard chine from before much sanding or shaping was done. Ignore the roughness. Tried to get an angle that shows the curve in its most extreme form. Really not as harsh as it looks. In the foreground you can see the upwards sweep. That sweep then straightens out until it hits a point about even with the transom, then it takes a very slight concave shape towards the back of the sponson. Think it’s an artifact from CAD conversion, and instinct tells me it should be a long, straight shot back, but when you sight along it it looks aerodynamically “correct,” if that makes sense. Almost like the shape itself should trim the chine downwards. Hard to explain. Like the anhedral shape on the back of an F-4.
Still debating what to do going forward.