Hi Russ,
I figure the vast majority of my flying will be based at the local sailplane club and tow launched, but I'd like to keep the option to foot-launch so that the glider is still catagorised as a Class 4 hang glider (less regulation by our Aviation Authority.) I haven't looked at the fuselage around the bomb-bay doors in detail yet but I suspect the doors do not contribute significantly to the in-flight strength of the fuselage. Still, it shouldn't be difficult to add strength and rigidity to that area if necessary without a weight penalty.
Stainless steel is also susceptible to attack (over time) from the chlorine in sea air(!), resulting in micro-cracking around stress points (bolts and corners). I suspect the alloy used in sail boats is carefully chosen to avoid this... or just over-spec'd. Aluminium is both cheap and easy to machine, and as I'll probably have to buy it in 5m lengths (minimum order quantity) I could afford to treat the metal fittings as consumable items (like hang glider side-wires) and replace them every year or every 100 hours. My brother's engineering works has an X-ray rig for testing high pressure welds in boilers and pipework - I could probably get my old fittings tested occasionally to see how the metal around the bolt holes and root pins is holding up.
Phil.
From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of russell wilson
Sent: 26 September 2011 04:56
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Subject: Re: [Carbondragonbuildersandpilots] Re: Wing calculations
hi phil
good thinking with the weight saving on the foot launch door..i wonder if it cross braces the fuse.
the dragon is not practical for foot launch.plan for roll or bungy launch from a hill or better still tow launch in front and at the bottom of your hills will save you driving up the hill and you can land back at your tralor and it will be easier to set up on the flat out of the wind.
im surprized mask used stainless steel for fittings...crane cables are not stainless steel,they are steel.sail boats have stainless steel fittings and hang gliders.
ss superior in term of corosion but not fatigue.
aluminium needs to be over engineered ,to protect it from fatigue.
in cycling cromolly bikes never seem to brake.
in off road cars iv seen them come back from high carbon steel frames to lower carbon/softer frames becaus of craking,also they are painting them with a clear paint so they can spot craking.
russ.
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