Looking ahead to the cowling. I was originally looking at the now standard MS20257 hinge closures on the firewall and along the parting lines of cowl, then looking at just making fiberglass hinge halves for my bird so they can be directly bonded in my fiberglass structure. Then last summer a prominent contributor on this forum told me “Camlocs with adjustable receptacles”. So I am looking at them, and looking around. The forums devoted to RV’s have a lot of folks with opinions on using hinges, AN screws and anchor nuts, Camlocs/Skybolts/Mil-Spec, and Southco's. The trick is always discerning the reasons to use or not use each scheme and then each of us can make up our own minds.
Being the good mechanical engineer I am, I started with an estimate much load is joints. With my minimum Vdive known, some estimates of pressures inside and outside the cowling were made. Hmm, between pressure lowered on the outside (fast moving air) and pressure raised inside (pressure recovery), I get a delta P 559 lb/ft^2 or abut 3.9 psi trying to inflate the cowling. That works out to about 136 lb/inch on the hinge of the horizontal parting line. I have not worked out the net lift and moment on the cowling at Va, Vc, and Vd yet, but I will.
For me the really big question is: Which types of fasteners are being used in fast (200 mph) homebuilts and what are the pros and cons of each type?
So far, the big gripes on MS20257 hinges are some tend to lose a tab or two and the wire can be a pain in the butt to put in or take out. Any other comments on hinges as connectors?
Camlocs and their imitators have a following. We can get studs that are long enough and adjustable receptacles so every stud can be made tight. Grommets can be bonded in. Skybolt even makes aluminum mount plates and tools with magnets to make alignment easy. The big draw backs appear to be installation time/effort and that going Skybolt will run me over $900 just in hardware.
Then there are folks advocating SouthCo’s. They seem durable on the storebought wheel pants, but they are a bit of a chore to get set up right, as well as to put on and take off.
Some folks jump at regular AN screws and nutplates. I would be going with ClickBonds on this scheme.
So let’s hear it. Which to use and why? And if you are advocating the Camloc type, which of the three brands would you go with, and why?
Billski
Being the good mechanical engineer I am, I started with an estimate much load is joints. With my minimum Vdive known, some estimates of pressures inside and outside the cowling were made. Hmm, between pressure lowered on the outside (fast moving air) and pressure raised inside (pressure recovery), I get a delta P 559 lb/ft^2 or abut 3.9 psi trying to inflate the cowling. That works out to about 136 lb/inch on the hinge of the horizontal parting line. I have not worked out the net lift and moment on the cowling at Va, Vc, and Vd yet, but I will.
For me the really big question is: Which types of fasteners are being used in fast (200 mph) homebuilts and what are the pros and cons of each type?
So far, the big gripes on MS20257 hinges are some tend to lose a tab or two and the wire can be a pain in the butt to put in or take out. Any other comments on hinges as connectors?
Camlocs and their imitators have a following. We can get studs that are long enough and adjustable receptacles so every stud can be made tight. Grommets can be bonded in. Skybolt even makes aluminum mount plates and tools with magnets to make alignment easy. The big draw backs appear to be installation time/effort and that going Skybolt will run me over $900 just in hardware.
Then there are folks advocating SouthCo’s. They seem durable on the storebought wheel pants, but they are a bit of a chore to get set up right, as well as to put on and take off.
Some folks jump at regular AN screws and nutplates. I would be going with ClickBonds on this scheme.
So let’s hear it. Which to use and why? And if you are advocating the Camloc type, which of the three brands would you go with, and why?
Billski
