Re: Re: Re: Re: Carbon Fiber Bell


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Posted by John Swensen on December 14, 2001 at 12:59:56:

In Reply to: Re: Re: Re: Carbon Fiber Bell posted by Rick Denney on December 14, 2001 at 10:41:23:

The highest quality carbon-fiber composites are made with "pre-preg", which consists of carbon fibers, pre-impregnated (hence the name) with a partially-cured epoxy resin. The epoxy is designed to be autoclaved (heated under pressure) for a full cure. The advantages of pre-preg are that a much higher carbon-fiber/epoxy ratio (hence, a higher strength-to-weight ratio) is possible than with a wet-layup, that the carbon fibers are completely wetted by the epoxy, and the epoxy used has a higher softening temperature than wet-layup versions (used by most experimenters and home-builders). The disadvantages include the need for an autoclave of some sort, and the limited shelf life of the pre-preg (often shipped and stored under refrigeration).

Given the higher softening temperature of pre-preg, it might be possible to use low-temperature epoxy to glue a carbon bell to the ferrules and leadpipe, and use soldering temperatures to soften the epoxy enough to remove the bell from the horn, after which the remaining epoxy would need to be scraped off.

Alternatively, the bell brace and/or leadpipe attachment could be attached via screws to nut plates molded/bonded to the bell, and the bell-to-bottom-bow joint could be fastened with hot-melt or solvent-based glue, since it is a relatively low-stress joint.

John "who knows that bell, yards, and bows of baroque trumpets were held together with tapered joints, sealed with beeswax" Swensen


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