I very much enjoyed your Encyclopedias, Volumes 1 and 2…Do you have an address for the manufacturer of the Paul Luke "Hyde" propellers? I have used several Barrett and Maxiprops over the years, and have found them to be VERY inefficient compared to a fixed pitch (like 2.5 knots worth) It always seemed to me that a feathering prop with a little twist would be the answer, but I didn’t know that they existed until I saw reference to it in your book. If it’s not too much problem, do you also have a source for your "Murphy" gauges?
You can usually pick up Murphy gauges from large automotive stores. Also, they used to be carried by McMaster Carr in their catalog. Re: props, you are quite right about prop blade twist. Paul Luke’s phone is 207-633-4971, and their web site is www.peluke.com. Also, you may want to check out the Autoprop, about which we’ve heard positive things.