Doc - I Appreciated you comments.
I find it interesting about your schooling to leave all three openings open. I have found (I think I have observed) with all three intake holes opened, the removing of sawdust from the saw blade is essentially the same as with two of them shut. Plus any ambiant dust gets picked up. In that sense, the DC works better. Yes, I believe air movement is the Key (as SS says). However I have also found that when using the floor vacuum system, it is better to close off the other two intakes - it yields a cleaner floor!
As for the hood and that nasty job- Your idea of putting the hood in a can is a good idea. I wonder what is meant by a cake layer of dust. I've noticed that when a dirty hood (I'm talking about the smaller hood) is cleaned of the thick cake - the air movement is decidedly improved. In fact many times, I have removed the small hood - pulled out the metal strap - turned it inside out and beat it like a rug. Boy!! That effort really improved my dust collection on all operations.
Cake or no cake - That is the question! (Apologies to William S.);)
My new and "improved?" method of cleaning. That is; paint brush sweeping of the dust from the inside of the hood is kind of a trade off between cake or no cake.
My guess is the cake cuts down on micro particles of dust escaping the hood. It is given - Air pressure inside the hood is pressing against the fabric. I can reason a cake will cut down on the openings in the hood fabric therefore cutting down on escaping micro dust particles. However this cake also will increase the pressure in the hood thereby cutting down on air movement. (Still reasoning!) Guess it is all
a trade off. The larger hoods offer a much greater surface area upon which to dispell that same pressure, therefore much less PSI - yielding better air flow.
I remember reading in one of the SS notes that I could wash the hood in a washing machine. Never have, because didn't want to get the rath of wife. Guess I could have washed it in the laundry tub in my shop - but I'm just too lazy. Also didn't want to wait for the fabric to dry.
The book PTWFE has a section on cleaning the hood. (Page 314 in version 4) They say, every 8-10 hrs. vacuum the outside of the hood. I've never done that. Have you? I wonder if that operation will help make that cake of dust.
Octogenarian's have an earned right to be a curmudgeon.
Chuck in Lancaster, CA