|Subject: Re: Fw: [harryproa] Re: sailing Elementarry|
|From: Mike Crawford |
|Date: 1/31/2006, 4:53 PM|
|To: rob dalton |
Mike , You may have mucked up the conversion. 15m is about 50' , 23m is over 75'
The extra weight of the complex folding system was a turn off which is why I was looking at the simplicity of the Farrier system. Not much extra weight at all and the beams need very little modification. The towing height for a 12m is a bit scary but probably not too much of a difficulty unless you have to go under overhanging trees.Anything bigger is a no no It may be worth it to have the Farrier folding system and dissassemble it once you are in the carpark. . Setting up the trailer with a gantry and building a trolley with lifting forks would reduce time of assembly considerably for a standard beam design.. It wouldn't take much time in storage fees to make the differnce in the trailer.(in Darwin there is a multihullclub with its own yardand costs about $200 dollars a year for storage on the hard and $50 dollars a year for a mooring. You have to take put the boats on the hard or way up a creek in the cyclone season.)I see no reason not to build either a Harry or a Visionarry to exactly the dimensions for non escort towing, It is just adjusting the size of the bridge deck to fit. I am attaching my idea of getting more cockpit accommodation. If you stretched the harry a little more to the 15m/50' lw hull and 10m/33'ww hull everything would fit more easily. Then you are getting into the Visonarry length but would weigh in the order of 1000-1100kg (working on the weight going up to the third power of the length). Bain has a very nice fold up roof on his 8.5m ww Harry that I think works well and he has the cockpit open to the lee. You may have to take a trip to Oz and have a sail or a trip to the Netherlands. Recommend a trip to visit Mark and crew at the factory and you could probably organise a sail on both of the boats as well as see them building them in the flesh. I stayed in the pub and also in the caravan park with very reasonable rates and had a very pleasant time.Recommend it before Bain sails his Harry to NZregards, Robert
Mike Crawford <firstname.lastname@example.org> wrote:
I do have to see these boats in the flesh before making any decision. The walkthrough-cockpit design Harrigami I saw in Rockland was much too small to justify leaving what I have, so I immediately made a mental switch to the Visionarry. However, I sometimes wonder if it's too big to have fun alone on a daysail, and if the Harry would be a better fit. A stretched-out Harry, with a 23m leeward hull and twin 28m masts would be an awesome thing to be hold. I think this is what Paul Nudd is intending (50' schooner rigged Harry).
What I really need to do is see the two boats in person before making a final choice.
Storing a multihull for the winter around here costs between $4.50 $5.00 US, which would be about $3,600 to $4,000 for a 40' catamaran. A Harry would cost less because of the windward hull, but that's still a pretty high price to pay every year. I normally don't mind spending money on boats, especially to purchase or upgrade them, but a fixed cost like that just gets under my skin. Regardless of how wealthy I become, it just doesn't sit right with me to spend that much for storage. A folding or demountable boat is key.
Like you, I'm not focused on pure trailerability, so I'm not trying to stay within a 2.6m width limit. Since I don't intend to move the boat more than once or twice per year, trailering is not a goal of mine, and I'm willing to have a boat that requires a wide load permit, provided it doesn't require chase vehicles. On US roads, the largest load you can trailer without having additional chase vehicles is 3.65m wide by 24.3m long. This is the size envelope that matters to me.
This could be a deciding factor between a Harry and a Visionarry. I've not yet measured the drawings to determine how wide the ww and lw hulls are, but they'll definitely need to total less than 3.6m if I'm going to meet my goal.
Have you looked at the folding mechanism of the cat2fold catamaran? They have a neat 60MB video of it in action on their web site. I also have a CD with a video that shows the boat going from trailer to the water, and I have to say that I am most impressed. I can post these for you to download, but they aren't small files. Anyway, Raphael Franke has really done his homework. I am currently trying to work out ways that this folding system could function with a harryproa, either for transporting the boat or just for reducing the beam in order to fit into a marina.
I'd probably go for this instead of a Farrier system because it has already been designed in carbon for a large beam, and also because it could extend fore/aft, and wouldn't increase the height of the boat on the trailer. An added stroke of brilliance on Franke's part is the use of large stainless pins to fasten the scissors-like beams in a full open position. Not only are these pins very strong, but they are turned by using a standard winch handle (both powerful and convenient). No extra tools are required, and there are no bolts to lose.
Rob said the idea would work, but he wasn't impressed with the additional weight the folding system would add. I'm sure it would be heavier, but there's something to be said about being able to transport a boat without the help of a boatyard, lift, or six buddies.
Thanks for all the info on the rudders. I think you're right in that the sturdiness won't be an issue once it is beefed up. I keep on trying to figure out a better way, and keep coming back to Rob's design. Barrels through the hulls, breakaway foils, and crash boxes are all unacceptable for the reasons you point out. And others as well.
I keep thinking about it, though, partially for those days when I want to lazy sail, and partially so that it will work with an autopilot.
You're right: if I'm tacking, there will be no need to reverse the foils. And if we're going to stick with my theory of lazy sailing, it's really going to happen only on days when the wind it light enough to tack in the first place. Problem solved -- no grinding of winches, no reversal of rudders. If there's a gale, I shouldn't be sailing with my feet up anyway, and certainly will want to keep the leeward hull to leeward, and shunt instead of tack.
I'd probably stick with the side-hung rudders instead of ones off the beam. This would present fewer obstructions when attempting to sail past lobster and crab buoys, and would keep the rudders free of a folding system, if one were to be used.
Thank you for continuing the rudder discussion. The more I go over it, the more I like what Rob has. I just needed to process it more.
I also would want to make the cockpit large enough to function as a bridgedeck saloon. I wouldn't want something enclosed like Rare Bird, though. I can see why someone would choose it, but I'd prefer something far more open. I think that Blind Date is a much better looking boat, and also closer to what I'd want. I just can't bear the idea of missing the breezes coming over the windward hull, or the idea of losing all that visibility.
I'd want to go with something like they have on the Maine Cat catamarans at http://www.mecat.com/ or http://www.abacomultihull.com/pictures/ . They have full hardtop over the bridgedeck, open sides that yield complete ventilation and visibility, and roll-down vinyl windows and screens that enclose the space when needed. On a nice summer day, the cockpit is a breezy open cockpit, but at night, or in bad weather, it becomes an enclosed saloon.
I'd also want to size it so that an optional table could stand in the center. I'd actually use a two-table system like they have on the Lagoon 440 http://www.istion.com/lagoon440.html . If you look at the two pictures of the settee in the saloon, you can see one with a large table set up for a meal, and another one with a small coffee table for just hanging out. I like the way this solves the classic table dilemma: how do you make a table large enough to handle a meal, but small enough to be out of the way the rest of the time? Folding tables can work, but they're normally not that attractive, and they still get in the way. If the seats were to be 2m long or so, they could even double as berths when it's time for everyone to turn in.
I won't quote you on anything that you don't post to the group.
rob dalton wrote:Thanks Mike.If you see the Visionarry in the flesh it is amazing, but it is a much bigger boat than the Harry. I am going for the 10m ww harry but extending the lw hull to bring it back to the original ratios. Hopefully the use of polyprop honeycomb will keep the weight down to that of the 8.5m ww Harry.Another advantage of the double ender is that you can go into a beach and sail straight back again. Simply shunt. Also for going over a bar you can stop and reverse under sail then immediately power up again. A schooner rig gives more control with boards raised for going through surf or shallows as you can steer using the rear sail only. If you've ever done a man overboard drill then you know how difficult it is with most boats. With the manoeveability of the two rudders it is theoretically possible to creep up and hold position within a few metres. The idea of being able to pack the boat up and trail it back to a place of security when you have to go away and don't want to leave it in the water, appeals to me also. In Australia it is possible to go to 3.5m without too many permit problems using flashing lights and signs. I plan to put the bunks sideways with feet under the outside seats. This allows the cockpit to turn into a reasonable sized saloon. I am also planning to incorporate a decent sized bevel at the bridgedeck/ww hull joint and a slight flare on the ww side to allow slightly more hip space in the ww hull . I was also considering a slight flare on the ww side of the lw hull but I think it interferes too much with packing it on a trailer though even 20cm makes a difference to a pipe berth. There is a possibility of using Farrier type folding arrangements with having the struts designed more for compression.On the rudders. I have probably been over many of these points so please bear with me. On the side ruddes, I know they look vulnerable but consider transom hung rudders on any boat being overtaken by a wave. They are actually more vulnerable as they aren't designed for the angles the wave is trying to push them. Admittedly they do fail occasionaly in those conditions. I can't see that there are any problems that can't be overcome with the right beefng up.On putting holes through the bottom of boats for the foils.To be able to use the boat in shallow water the foils need to be retracted or be spade and not so efficient. If retractable foils through the bottom of the boat you need a barrel for turning the foil which is quite difficult to make as the bearing surfaces have to be so much smoother and slipperier. If you hit anything at speed something has to give and so you have a foil that breaks off or a crash box to crumple and absorb the shock. Neither is easy to sort out at sea. Jerry of Southern Outrigger has an ingenious system to get round this problem but it is not as efficient as a foil. If you are serious about getting lift from the rudders they have to be foils.This led to the rudders on the sides, which do not appear very elegant but do work. One problem was that the loads were imagined to be almost pure compression on the top rudder and almost pure tension on the bottom with a bit of fore anft support needed. In hind sight it is obvious that the foil is going to flex and thus impart a vertical component to the blades which results in bending of the supports. Once a diagonal to the bottom strut is added this problem is overcome. The other problem was the small piece of wood designed to give under sheer if the blade hit anything unforgiving. It gave under bending. A small change in design has avoided the bending mode and it can still give under sheer.The time taken to pivot the rudders through 180 is no more than the rig. For manoevering at low speeds such as in docking, there is no reason why the rudders can't go in reverse as in any boat. I am not sure why if you were tacking rather than shunting that you would need to pivot foils 180. By the way, the ability to change the angle of the forward foil reduces getting into irons on a tack and is maybe needed to overcome the lack of rocker.On reversible foils. To use a foil it needs to be pivoted. It may be possible to use a symmetric foil but how to raise and lower them without interfering with the pivot? I came up with one possible solution of angling a curved blade so that as the blade lifted , it curved out to miss the pivot and the curve was such that it was balanced on either side of the pivot. This would work only if there was no difference in depth of the hull in the water. Can you imagine the chaos of trying to use a symmetric foil with the pivot off to the side?This left the foils to be the normal rudder blades such as you hang off the transom. Unfortunately this gave ridiculous loads on the tillers as the foils weren't balanced. I modified the idea of a curved blade to bring the base of foil more central with the means to kick up and be locked back down again. There is a copy of the idea in the proa files I think in proa file 1 called, I think, roberts rudders or caterans rudders , i can't quite recall. Rob liked the idea but regarded it as a bit more complex than could be afforded. He then simply raked the rudders forward to balance them without any fancy curves and that is the present state.The raked ruddeers, I think, aids in avoiding ventilation but I'm not clear on that one. A possibility is to use beam hung rudders but there is much less bury and further from the water so the point loads are pretty high. On the plus side it concentrates the loads in one plane and takes complexity out of the lw hull, especially with a schooner rig. Doable, the retraction isn't as complete but they can kick up and be pulled back down again and it may be possible to use symmetric foils but the problem of hydrodynamic instabiliy remains where the centre of lift of a foil is behind its pivot. Jet fighters overcome this problem with very fast electronic feed back controls but a simple system needs to avoid the whiplash effect of such systems. it may not be a problem at the speeds and loads on these boats but I suspect it is, especially if there is any give in the components.My only changes I'd consider at this stage is the possibility of having the supports creating slight lift, possible extending the cheeks into the water and adding an anti ventilation plate, possibly adding an end plate to the foil, having the bottom section of the foil sacrificial and underbuilt with a couple of spares to stick on again and possibly putting an angled buffer on the crossbeam to deflect the blade from jamming against it in the case of a collision.In Summary, I don't like putting holes in the bottoms of boots, the symmetric foils were beyond us, The side foils work if beefed up even if inelegant, beam hung rudders are a possibility, Personally I am tossing up between the beam hung and the side hung. Doubt if there is much difference in the rest of the boat but the side hung rudders need the internal supports in position early onHope this history is useful. Please don't quote me without checking with Rob or Mark on any of the points in case I have misrepresented them.Regards,Robert
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