Hi,
I have been occupying myself with what seems to be my favorite hobby; designing harryproas that I never get around to building. One of the things that occurred to me, is that I don't seem to have a good way to predict performance. I have been using the typical SA/D and Bruce number calculations, but I can't get these to provide me with number I can believe, based upon my personal experience and the speeds shown by Rare Bird on the Youtube videos.
Here is a table I compiled:
Boat Type Length Disp Sail Area SA/D Bruce #
ME Cat 30 catamaran 30' 6000 500 24 1.2
ME cat w/screacher catamaran 30' 6000 720 35 1.5
Elan 7.7 trimaran 25' 2000 310 31 1.4
Rare Bird harryproa 50' 10000 774 26 1.3
Harry harryproa 40' 3500 452 31 1.4
Harrigami harryproa 35' 2500 333 29 1.3
Camper (mine) harryproa 30' 2000 392 39 1.6
Contrarry (mine) harryproa 38' 3500 728 50 1.8
It is a little hard to read, but basically it says that Rare Bird should be slower than my Maine Cat with the screacher up, or my Elan trimaran at any time. The Maine Cat never got over 12 kts, and that was surfing down a wave. With the screacher in 15 kts of wind, it would top out at about 10 kts. The Elan may have hit 15kts at one point, but that is when it was blowing 20+ kts and I was terrified of a capsize.
So, given that the longer, sleeker, harryproa hulls are the deciding factor, what metric should I use to compare a harry design with "normal" multihulls?
The reason I ask is that I may be overreaching for sail area on my designs, based on these numbers.
Thanks,
- Gardner
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