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Perfect cruising bermuda dinghy
Perfect cruising bermuda dinghy
I put this as what I believe best for a 18' cruising dinghy, main 10,5m2 (unstayed mast)... which is probably wrong, but maybe not all.! ;o) # Loose foot # Full battens # 2 reefing lines (which type?) # Boltrope # Foot slightly raising (5-15deg) # Telltales # Crosscut Polyester (weight?) # Does weave manufacturer matter? # Jib around 35% of SA (reasonable big, reasonable reef step) # Same weave? Anything else that cannot be missing on a modern (?) dinghy rig? Further hints? Morgan O. |
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Morgan Ohlson ) writes: Anything else that cannot be missing on a modern (?) dinghy rig? some things to consider..... preventer? (eg., boom vang) how would the main be sheeted? center sheeting or transom? would it need a traveller? all the jibs I've seen have had adjustable fairleads. some way of tensioning the jib luff so it doesn't sag. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
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On 23 Oct 2004 21:30:00 GMT, William R. Watt wrote:
Morgan Ohlson ) writes: Anything else that cannot be missing on a modern (?) dinghy rig? some things to consider..... preventer? (eg., boom vang) how would the main be sheeted? center sheeting or transom? would it need a traveller? all the jibs I've seen have had adjustable fairleads. some way of tensioning the jib luff so it doesn't sag. Is the vang mounted further out on the boom if transom sheeting is used? What about kick rod? Center or transom sheeting is what I'm just conserning my brain with. It looks as there can be a problem to fit in a center traveler properly without a bulkhead to build it on. ....but on the other hand that bulkhead may be needed. Isn't a traveller allways good to have to gain rig controll? Morgan O. |
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Morgan says:
Center or transom sheeting is what I'm just conserning my brain with. If you have a loose-footed main, then I would seriously recommend end-boom (transom) sheeting, or the bending moments in the boom will be extremely high. Steve |
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Stephen Baker ) writes: Morgan says: Center or transom sheeting is what I'm just conserning my brain with. If you have a loose-footed main, then I would seriously recommend end-boom (transom) sheeting, or the bending moments in the boom will be extremely high. you can run the sheet from the boom end to a block in the middle of the boom. that keeps it up out of the way and drops it pretty well into a block mounted, say, on the rear of the centreboard trunk. with a 70 sq ft main sail you'll need the leverage (mechanical advantage) of a multi part mainsheet fed through blocks. if you are going to be cruising small lakes and rivers with shifty winds you won't be able to cleat the mainsheet. you'll have to hold it in your hand all the time. you probably won't cleat the mainsheet on an 18 ft dingy anyway. too light and responsive. a rachet block is quite common and would take some strain off the arm holding the mainsheet. something to consider later if you find the strain on the arm too uncomfortable. the centreboard has to be top braced against lateral (sideway) stresses, sometimes done with a seat, sometimes with a simple thwart, on which a traveller and compass can be mounted. I seem to recall the back end of dingy centreboard trunks being braced by a metal mainsheet traveller alone. the traveller mostly just helps keep the sail flat when close hauled but also helps as a preventer. it's not essential for dingy cruising. you can see these things on photos and diagrams of sailing dingys like the Wayfarer. I don't know if there are any formulae covering these things, except of course for the mechanical advantage of the main sheet blocks. It's mostly trial and error and tales told by old dingy racers. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
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On 24 Oct 2004 14:06:56 GMT, William R. Watt wrote:
Stephen Baker ) writes: Morgan says: Center or transom sheeting is what I'm just conserning my brain with. If you have a loose-footed main, then I would seriously recommend end-boom (transom) sheeting, or the bending moments in the boom will be extremely high. you can run the sheet from the boom end to a block in the middle of the boom. that keeps it up out of the way and drops it pretty well into a block mounted, say, on the rear of the centreboard trunk. with a 70 sq ft main sail you'll need the leverage (mechanical advantage) of a multi part mainsheet fed through blocks. if you are going to be cruising small lakes and rivers with shifty winds you won't be able to cleat the mainsheet. you'll have to hold it in your hand all the time. you probably won't cleat the mainsheet on an 18 ft dingy anyway. too light and responsive. a rachet block is quite common and would take some strain off the arm holding the mainsheet. something to consider later if you find the strain on the arm too uncomfortable. the centreboard has to be top braced against lateral (sideway) stresses, sometimes done with a seat, sometimes with a simple thwart, on which a traveller and compass can be mounted. I seem to recall the back end of dingy centreboard trunks being braced by a metal mainsheet traveller alone. the traveller mostly just helps keep the sail flat when close hauled but also helps as a preventer. it's not essential for dingy cruising. you can see these things on photos and diagrams of sailing dingys like the Wayfarer. I don't know if there are any formulae covering these things, except of course for the mechanical advantage of the main sheet blocks. It's mostly trial and error and tales told by old dingy racers. It's quite common with slightly bent travelers (low at ends)... more seldom straight. (correct?). What is the main benefit? To get a transom sheeting an extended boom may be necessary. Does that have any complications in other ways? Morgan O. |
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Morgan Ohlson wrote:
On 24 Oct 2004 14:06:56 GMT, William R. Watt wrote: Stephen Baker ) writes: Morgan says: Center or transom sheeting is what I'm just conserning my brain with. If you have a loose-footed main, then I would seriously recommend end-boom (transom) sheeting, or the bending moments in the boom will be extremely high. you can run the sheet from the boom end to a block in the middle of the boom. that keeps it up out of the way and drops it pretty well into a block mounted, say, on the rear of the centreboard trunk. with a 70 sq ft main sail you'll need the leverage (mechanical advantage) of a multi part mainsheet fed through blocks. if you are going to be cruising small lakes and rivers with shifty winds you won't be able to cleat the mainsheet. you'll have to hold it in your hand all the time. you probably won't cleat the mainsheet on an 18 ft dingy anyway. too light and responsive. a rachet block is quite common and would take some strain off the arm holding the mainsheet. something to consider later if you find the strain on the arm too uncomfortable. the centreboard has to be top braced against lateral (sideway) stresses, sometimes done with a seat, sometimes with a simple thwart, on which a traveller and compass can be mounted. I seem to recall the back end of dingy centreboard trunks being braced by a metal mainsheet traveller alone. the traveller mostly just helps keep the sail flat when close hauled but also helps as a preventer. it's not essential for dingy cruising. you can see these things on photos and diagrams of sailing dingys like the Wayfarer. I don't know if there are any formulae covering these things, except of course for the mechanical advantage of the main sheet blocks. It's mostly trial and error and tales told by old dingy racers. It's quite common with slightly bent travelers (low at ends)... more seldom straight. (correct?). What is the main benefit? To get a transom sheeting an extended boom may be necessary. Does that have any complications in other ways? I have seen no end of trouble with boom end sheeting on dinghies. The usual problems include the common pin and swivelling strap boom end fitting failing in heavy weather, the multi part mainsheet wrapping round itself when gybing so you cant let the sail out without hauling it right in to clear the jam, and the mainsheet catching on the rudder stock or the corner of the transom when gybing causing all sorts of grief :-(. For a crusing dinghy, it will also make it unsafe to keep an outboard on the transom. I strongly reccomend reconsidering the boom end sheeting. If you go to centre sheeting, you will also need the foot of the sail attached to the boom which is no problem with a bolt rope on it. Have eyelets fitted in the foot of the sail just above the boom 2" aft of vertically in line with the reefing clew eyes on the leech so the sail doesnt get worn through by being trapped against the boom by the reefing lines. Each reefing line should be tied off using a bowline round the boom through the eyelet, leaving just enough slack to not affect the set of the sail when you arent reefed and led up through the appropriate reef eye in the leech and down to the end of the boom and then to whatever system you use for cleating the reefing lines. Although the eyelets just above the boom wouldnt be needed if your reefing lines were secured to the side or bottom of the boom like on a yacht, that would put a massive twisting load on the gooseneck, which dinghy goosenecks are NOT designed to withstand. Dont bother with single line reefing, a spring gate hook at the gooseneck on the same pin as is used for the Tack eye is much better than the extra friction and complexity of having shuttle blocks inside the boom. I have thin bungee threaded from the luff to the leech and back again through all the cringles for each reef with small plastic hooks on one side of the sail so I dont have to bother with tying reefing points, they just hook together under the boom round the hanging 'bag' of sail. The bungee should be just slack with the sail streched tight along that line of cringles before you hook it round the boom. Also if you forget one when shaking out a reef, there is enough stretch in the bungee to save the sail from being ripped. The only difficulty I have with the system is that the luff has a boltrope that slides into the mast groove so I have a lot of loose sail + the boom to control when lowering it. For a cruising dinghy 15' I'd strongly reccomend having slides up the luff retained by a pin or a gate at the bottom of the groove and a topping lift or better yet lazyjacks so the sail can be dropped quickly under full control without bashing the helm on the head with the boom or loosing the crew under the heap of sail. An unstayed rig with a jib is going to be a lot more trouble than having shrouds as the mast will need to be a heavier section and there will be a lot of stress on the partners and step. You will also have a LOT more trouble getting satisfactory jib luff tension. Avoid highfield levers for the jib halyard tensioner, IMHO they are the invention of the devil. I have a tensioner setup that uses a 2:1 tackle that sweats the halyard sideways before the cleat. Looking at the angles I reckon its worth a 4:1 or 5:1 advantage pulling on the halyard. You may not be able to use this setup, but if I had to use a different setup I'd rather have a muscle box that can be released in a controlled fashion (even though they are very inefficient) thatn a highfield lever which will do its bset to take your fingers off if you are tired or careless when you let it off. Figure on carrying a minimum of two jibs if you are not having roller reefing as you will want to keep the rig balanced with one reef in to avoid excessive weather helm. N.B. most small jib roller gears are only designed for furling ie. 100% out or 0% out and will break if used for reefing eg. 50% out in strong winds. The roller reefing gears are quite a bit more expensive, so I decided NOT to get one. On the subject of travellers and sheeting etc. The total sail area of my Albacore is ~125 sq feet (11.65 sq m) and she's 15' LOA and LWL which would be pretty close to the LWL of an 18 footer that doesn't have a vertical stem so the loads are closely comparable to your proposed design. The beam is 5'6" which would be less than you'd want for an 18' cruising dinghy and my traveller horse is unsupported 1.5" aluminium alloy tube running right across the full beam. Three parts of the four part center mainsheet lead to the traveller car, the fourth part runs to a swivel block with a cleat (which does get used quite a bit, mostly to rest my hand) on the back of the centerboard capping about 6" behind the traveller. The mainsheet leads through two single blocks on the boom, one over the traveller, the other over the swivel block. This spreads the load on the boom. When gybing I grab two parts of the mainsheet and control the boom as it comes over (keep your elbow bent :-) ). The traveller control line is a 3:1 continuous loop with turning blocks and cleats on the centreboard cap so I get a streight pull on it when I want to use it when sitting out. The original system was 2:1 cleating under the gunwales which was pretty useless in a blow. The traveler horse bends up about 3" in the middle if close hauled in a force 5 with two people hiking. Its been doing that for the past 40 years without any problems. I reckon you'd be fine with a modern X section track bolted to an alloy tube to stiffen it for a span of about 6 feet. No bulkhead required. Remember a 6' long track at mid boom is equivalent to one 12' long :-) at the transom. With centre boom sheeting and a traveller you dont need quite as powerfull a kicking strap (boom vang). If you stick to boom end sheeting you will need about 16:1 to get the leech flat enough off the wind in a blow. This will mean you will need either a massive boom section or to internally sleave it for the forward third of its length to stop it buckling. You will also have problems with the amount of mast bend it induces pulling all the shape out of the luff of the sail. I find 4:1 works well for me with centre sheeting and a full width traveller. Finally I hope you are fitting a pivoting centreboard not a daggerboard as the ability to fine tune the CLR to match the CE when reefed and reduce the weather helm if using main only is worth all the added complexity alone and if you touch bottom with it at speed you will be glad it can kick up rather than snapping off or ripping the trunk out of the hull with you miles from where you launched. -- Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* SPAM TRAP set in header, Use email address in sig. if you must. 'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded wooden racing dinghy circa. 1961 |
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Ian Malcolm ) writes: Albacore details As someone who has also raced Albacores it was not only nice to read so much familiar detail but to recall the thrill of hiking out while keeping the boat planing in a stiff breeze. I knew a fellow who went on a short inland camping and cruising voyage in his Albacore. There was a photo of him sitting in a folding canvas "deck" chair perched precariously on the deck. However I doubt a cruising dingy needs to be as intricately rigged as a racing dingy unless the crusing dingy has a planing hull, and that would be a racing/crusing dingy like the Wayfarer. In "Dinghies for all Waters", Eric Coleman strongly recommends a heavier, high freeboard, dingy for crusing as a light responsive boat is too lively for relaxed crusing. He prefered converted small fishing boats for cruising to racing boats. I belive his Roamer design was well accepted among British dingy cruising sailors. I've seen a photo of one on the Internet. Reading about the Albacore I realized I had forgot a useful feature of a jib is the ability to drift with the sails hove to while eating, etc. I've done that between heats at regattas, and for jumping overboard to cool off. While I'm on this topic I'd like to suggest for the home builder an inexpensive wooden boom with an X cross section, a design pioneered by TF Jones and described in his book "New Plywood Boats". He's had one on his catamaran for some time. He describes inexpensive home made hardware for the boom as well. I don't think his boom is made of plywood but I would think it possible. -- Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* SPAM TRAP set in header, Use email address in sig. if you must. 'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded wooden racing dinghy circa. 1961 There was a hot mouled plywood Albacore here in Ottawa, unique and very attractive boat. The layers of plywood strips are laid 45 deg or so to the waterline and 90 deg or so to each other. Light, strong, long lasting construction. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
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#10
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William R. Watt wrote:
Ian Malcolm ) writes: Albacore details I primarily wrote what I did because the OP's intended sail area was comparable to the Albacore with a slightly larger hull and I thought he might be making a mistake to go for end boom sheeted loose footed unstayed BERMUDAN rig. As someone who has also raced Albacores it was not only nice to read so much familiar detail but to recall the thrill of hiking out while keeping the boat planing in a stiff breeze. I knew a fellow who went on a short inland camping and cruising voyage in his Albacore. There was a photo of him sitting in a folding canvas "deck" chair perched precariously on the deck. I have been known to stand on the foredeck, occasionally with a drink in my hand, and this summer I did a cruise of about 90 NM on the east coast of England. I usually day sail however as after 8 or 10 hours under way, I like my creature comforts :-) However I doubt a cruising dingy needs to be as intricately rigged as a racing dingy unless the crusing dingy has a planing hull, and that would be a racing/crusing dingy like the Wayfarer. I also race Wayfarers although as I don't own one I don't cruise in one. An Albacore in racing trim is a long way from being an ideal cruising dinghy, but if one eliminates all the racing refinements and go-faster gadgets of the last 40 years and outfit and rig the boat in a style that Uffa Fox would recognise, it is quite practical for coastal day sailing. Sleeping on board however would not be a restful experiance. None of my secondary sail controls (vang, outhaul, cunningham, jib tensioner etc.) are lead to the helmsman, they are the crew's job. Given a 10.5 sq m bermudan mainsail and a total sail area of about 15 sq m (OP stated: 18' cruising dinghy, main 10,5m2 (unstayed mast); Jib around 35% of SA ) I think if it isn't a planing hull, it will sail under in the first decent breeze. If it has a planing hull form then add a bowsprit, an assymetric and some trapeze wires and you'd have an outright racing machine. To control 15 sq m of bermudan (marconi) rig on an 18' hull in anything more than a light breeze, I reckon you need either a super powerful vang or a good traveller system. If the OP was considering a spritsail or boomless lug sail, it would do away with the complex controls. In "Dinghies for all Waters", Eric Coleman strongly recommends a heavier, high freeboard, dingy for crusing as a light responsive boat is too lively for relaxed crusing. He prefered converted small fishing boats for cruising to racing boats. I belive his Roamer design was well accepted among British dingy cruising sailors. I've seen a photo of one on the Internet. The trouble with displacement dinghies for cruising is they are so slow that they cant get out of their own way if they are small enough for the crew to manhandle on a beach. You need 15' length to make 5 knots and that will be very heavy for a two man crew to haul out and impossible to lift. If its big enough to have a decent hull speed, its the size of a small yacht, in which case you might as well have a cabin, cruise in comfort and not call it a dinghy. A slow dinghy may not be able to reach shelter before the weather deteriorates. Reading about the Albacore I realized I had forgot a useful feature of a jib is the ability to drift with the sails hove to while eating, etc. I've done that between heats at regattas, and for jumping overboard to cool off. I'd not trust a hove to Albacore to stay put for long ecough to swim. One gust and you'll find it on the other tack sailing away into the distance. If its squally you really dont want the jib aback unless you want to swim *with* the boat. Works fine for eating however. While I'm on this topic I'd like to suggest for the home builder an inexpensive wooden boom with an X cross section, a design pioneered by TF Jones and described in his book "New Plywood Boats". He's had one on his catamaran for some time. He describes inexpensive home made hardware for the boom as well. I don't think his boom is made of plywood but I would think it possible. I am still using a wooden boom. Rectangular section about 2"x4" with a groove for the boltrope in the top. I belive it to be original although I cant prove it was in use more than 30 years ago. snip 'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded wooden racing dinghy circa. 1961 There was a hot mouled plywood Albacore here in Ottawa, unique and very attractive boat. The layers of plywood strips are laid 45 deg or so to the waterline and 90 deg or so to each other. Light, strong, long lasting construction. Must haver been a MK 1 Fairey marine hull originally with the stern decked in. Mine is a MK 2 hull with the outer veneer running fore and aft. The inner veneers are 60 deg or so to each other. Extremely durable so long as you dont leave standing fresh water anywhere in the bottom. -- Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* SPAM TRAP set in header, Use email address in sig. if you must. 'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded wooden racing dinghy circa. 1961 |
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