I definitely wouldn't add that weight in the boom. We are talking about hundreds of kg here. The structural stress is enormous but the safety issue concerns me even more. Consider for example a 5 m lever arm (boom that is) with may be 400 kg of weight near the end. Then consider that weight moving over the cockpit when taken aback in high winds... And I can think of many other quite unpleasant situations too when I definitely wouldn't want that much weight in a boom... Keep weight low and centered is the ole golden rule in boat design and harryproas can do that very well if keeping with original design.
After considering many options I still prefer a hull shape that does these things automatically. Boards and rudders need to be adjusted when shunting but weight shiftings are not so desirable. If you want to do weight shifting build two fresh water tanks one to each end of the boat and pump water from one tank to another when shunting.
Arto
From: bjarthur123 <bjarthur123@yahoo.com>
To: harryproa@yahoogroups.com.au
Sent: Sunday, October 14, 2012 5:23 PM
Subject: [harryproa] bow down attitude
To: harryproa@yahoogroups.com.au
Sent: Sunday, October 14, 2012 5:23 PM
Subject: [harryproa] bow down attitude
stuck at home sick on a beautifully warm sunny day :( perhaps one of the last of the sailing season. sigh. perfect time to ask the folks here a question.
for awhile now i've had my eyes on a harry proa. more precisely, should i ever buy a big boat, which might or might not happen, that's definitely what i'd get.
my main problem though is that, without exception, every single video i have ever seen has shown them pitching down. unacceptably unsafe in my opinion. what can be done about it?
1. rob has suggested to minimize the pitch by putting more buoyancy in the ends of the leeward hull. but yet, the pitch is still going to be negative, albeit smaller. and how would that effect hull drag at low speeds and weight?
2. rick has suggested to shape the hulls to provide dynamic lift at speed. i think a static method would be safer. and again, drag and weight?
3. one could pantograph the windward hull. oh, but nasty moving parts puts one at risk for a huge catastrophe. damn it! i really liked this idea.
being primarily a dinghy sailer i am very much used to the idea of weight shift. my main question for you all (yes, i spent some time in texas), is how much weight needs to be shifted?
the lift of the sail times the height of the COE is a pitch moment. yes, it varies with the wind strength and a gazillion other factors, blah blah blah. order of magnitude please. how much weight would be needed on the aft beam to compensate? is it more or less than the weight of the motor, fuel, batteries, and fresh water (and maybe crew)?
here are two ideas:
4. put a sled just inboard of the leeward hull between the beams on which all the moveable weight is placed. slide it aft with each shunt.
5. better yet (thinking way way outside the box here as usual) put all this moveable weight IN THE BOOM. there is already some weight shift on a una-rig just from the sail and boom alone. but if the boom had internal compartments for batteries, fuel, and fresh water, and if the engine when not in use could be hoisted and mounted on the end of the boom... no need to slide a sled here, it's automatic!
tear it apart! be constructive!! give me a reason to start saving for a harryproa!!!
ben arthur
weta #358, "gray matter"
chesapeake bay
for awhile now i've had my eyes on a harry proa. more precisely, should i ever buy a big boat, which might or might not happen, that's definitely what i'd get.
my main problem though is that, without exception, every single video i have ever seen has shown them pitching down. unacceptably unsafe in my opinion. what can be done about it?
1. rob has suggested to minimize the pitch by putting more buoyancy in the ends of the leeward hull. but yet, the pitch is still going to be negative, albeit smaller. and how would that effect hull drag at low speeds and weight?
2. rick has suggested to shape the hulls to provide dynamic lift at speed. i think a static method would be safer. and again, drag and weight?
3. one could pantograph the windward hull. oh, but nasty moving parts puts one at risk for a huge catastrophe. damn it! i really liked this idea.
being primarily a dinghy sailer i am very much used to the idea of weight shift. my main question for you all (yes, i spent some time in texas), is how much weight needs to be shifted?
the lift of the sail times the height of the COE is a pitch moment. yes, it varies with the wind strength and a gazillion other factors, blah blah blah. order of magnitude please. how much weight would be needed on the aft beam to compensate? is it more or less than the weight of the motor, fuel, batteries, and fresh water (and maybe crew)?
here are two ideas:
4. put a sled just inboard of the leeward hull between the beams on which all the moveable weight is placed. slide it aft with each shunt.
5. better yet (thinking way way outside the box here as usual) put all this moveable weight IN THE BOOM. there is already some weight shift on a una-rig just from the sail and boom alone. but if the boom had internal compartments for batteries, fuel, and fresh water, and if the engine when not in use could be hoisted and mounted on the end of the boom... no need to slide a sled here, it's automatic!
tear it apart! be constructive!! give me a reason to start saving for a harryproa!!!
ben arthur
weta #358, "gray matter"
chesapeake bay
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