When welding fuselage tubes fittings should be no gaps larger than welding rod and welding rod should be thickness of material being welded. This means when welding 2 tubes, .035 wall, max gap would be about .035, welding rod would be .035.
When gas welding tip should be sized so it will just melt material when set to max heat. Tip used on .035 tubes should not be large enough to weld on .049 tubes.
When joining two tubes drill a small hole in cross tub in area of weld, it will be inside of tub, a 3/32″ hole is great, do not let bit hit opposite side of tube. This is to vent gases and prevent blow out when welding last weld sealing tub.
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