two transponders or one for depth sounder ?

[kds]

My long keel GRP hull has no horizontal surfaces under water - 20+ degrees is minimum. Do I need one transponder each side (like in the old days) which will mean a switch also, or will one suffice. I did wonder about setting it dead centre, ahead of keel, but GRP thickness there seems pretty substantial and it may affect signal ? I don't really want to drill another hole. Any advice - the guy at NASA did not seem sure.
Thanks, Ken

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[john_morris_uk]

One technique is to make a block that fairs the transponder into the hull at the correct angle. You end up with a sort of half cigar shape blistered onto the hull, and a wedge shape inside, but it usually works ok. I've made them from teak before. (or hardwood ie mahog' but we're not supposed to use it!) If you wander round any boat yard you should see something similar on various hulls.

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[Talbot]

A better solution would be to install the transponder inside the boat, however, only a few versions are suitable for this. I used a Silva echosounder, and they actually sell an in-hull fixing kit! IIRC the ST60 depth can also be installed in-hull.

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