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Old 12-23-2016, 06:10 PM
revintage revintage is offline
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Bulb for 49er

Quit sailing just over 30 years ago as Swedish number two Tornadoteam behind Marstrom, to raise a family. Haven´t sailed since. This summer I began sailing again with a crappy old Flipper Scow, rebuilding it with wide wings, selftacking jib and a Contender main. Got in contact with a former 49er sailor having an old hull without wings, boom with complete GNAV, rudderstock and trolley. Found another sailor having two complete old style 49er rigs, a rudder and a half dozen sails. It was all close to a giveaway as the parts where useless for racing. The only thing I had to buy new from Ovington was the rudder gantry, by whom I also found a centerboard of the old design at a bargain price.
Anyway, being 65+ and not very athletic anymore, I skipped the idea of trapeze and of sailing it as is with crew. Being a loner I set out to modify the 49er for singlehand. One rig has been modified by cutting one meter from the bottom of the main and cutting the lower mast the same. I have also cut down one of the three jibs from the Swift Solo instructions. Total area ca 14 sqm. This is actually done for an old French dinghy I have at my summer house.
The other rig is left uncut but this is planned to be sailed with only a main where the leech will be cut about 50cm at the bottom in a straight line up to the top batten leaving ca 11 sqm. This leaves me with a high CoE, albeit moved forward. Both rigs will have about the same heeling moment. I also bought an old 29er kite of one of the 49er guys to be tried downwind.
Still both versions will be too much to handle for a stiff old man(172cm, 80kg) refusing trapeze, even with very wide wings. My idea is to build wings from the same 50mm aluminium tubing and polyester net used for the scow. I have to give them a steeper angle than the original 15 degrees as I guess it will be hard to always sail flat enough. Making them 80cm a side gives me a beam of 3,4m. When sailing single handed RM will not be enough.
Checked out all the small, light keelboats from K1, to VX ONE and up to Viper 640 and from that guesstimated I should have to add a bulb of 40-50kg, 1m below, giving a design wind in the ballpark of 12 knots. Still needs to be properly calculated and this is where I am lacking knowledge.
Except for telling me this is a lousy way to treat a 49er and that this is an extremely bad idea, someone might maybe help me to find the correct bulb weight for the ******* ;-) ?

Merry Christmas!
Lars
Attached Thumbnails
Bulb for 49er-img_2097.jpg  Bulb for 49er-img_1765.jpg  Bulb for 49er-img_0047-1-.jpg  

Bulb for 49er-img_1845.jpg  

Last edited by revintage : 12-24-2016 at 03:28 AM. Reason: missing signature
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  #2  
Old 01-07-2017, 05:27 AM
revintage revintage is offline
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Bulb

Have now got a descent price for casting the bulbhalves locally when I supply concrete molds.

Talked to my friend Per and found out he uses Vectric Aspire for his CNC-router. Will let him make a halfbulb to be used as plug.

"Designed" the bulb in bulbcalc.exe, where you can trick the program to make bigger bulbs than stipulated 20kg. This one will be just below 50kg. At 770mm length and NACA 65A015 profile, max diameter will be just below 120mm.

With a CSV-gadget for Aspire from Paul Rowntree, the 150 point data from bulbcalc was converted to CSV in Excel and then easily imported into Aspire.

Basic design, no beavertail, circular cross section all the way. File from Aspire is *.crv3d
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Bulb for 49er-bulb.png  
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File Type: csv bulb77150.csv (3.3 KB, 16 views)
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Last edited by revintage : 01-07-2017 at 06:08 AM. Reason: adding csv
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  #3  
Old 01-07-2017, 10:21 AM
upchurchmr upchurchmr is offline
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Thats a neat project.
Sorry I can't help on a good bulb weight, but a difference in weight will just change the target windspeed.

My main concern would be controlling the board with that weight. I.E., retracting it and keeping it attached when extended.
I assume you have little issues with catching seaweed, etc?

Have you looked on Woodenboat.com? They have a thread called "Old Codgers Boat" where there is a wide diversity of desires and suggestions.
Yours would be an interesting addition.

Good luck.
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Old 01-07-2017, 03:09 PM
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Doug Lord Doug Lord is offline
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49er

The only problem with a bulb is that it only works when the boat heels and the 49er hull isn't designed for sailing at an angle of heel?
Just out of curiosity have you considered using the 49er as the main hull of a trimaran? You could probably use relatively small hulls-maybe salvaged from a local cat.
Anyway, best of luck and I hope you have great sailing and lots of fun!
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Old 01-07-2017, 04:27 PM
upchurchmr upchurchmr is offline
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Good point about the heel angle.
Especially with the wide wings
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Old 01-08-2017, 03:42 AM
revintage revintage is offline
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About the heel angle there are lot of keeled sport boats that also should be sailed flat. The bulb is for helping when things get ruff. Will definitely help to slow things down in gusty conditions. Will help in case of capsizing.

The wings will be 90cm instead of 80 making total beam 3,7m. The leeward wings will also automatically lift from 17 to 30 degree angle which will prevent from dips.

Have done some calculations and the version with only a 11sqm main having a design wind of 5,7 m/s without and 6,3 m/s with bulb and heeling at ca 25 degrees. Penalty is 50kg plus the water resistance of the bulb. A VX ONE with two persons should have about the same design wind. Bongo is for even smaller design wind.

If I had a single Tornado hull lying around I would consider making a small tri but the wide 49er will probably not be the way to go. About multihull I have an old Nacra 5.5 that I am satisfied with.

Will of course report if this project fails this spring. At the moment it is -10 centigrade and lots of snow. Brrrrh!
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Old 01-08-2017, 04:51 AM
CT249 CT249 is offline
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Have you considered the problem of things getting jammed under lifting wings? The 18 Foot Skiff sailors used them for a few seasons, but gave up on them because there were significant issues if any weight came on the wing at a time when anyone had any part of their body between wing and hull. If I recall correctly the score was at least one severed finger and several other significant injuries.
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Old 01-08-2017, 05:13 AM
revintage revintage is offline
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Yes, it has crossed my mind ;-) . Still have to try. Being single on the boat, risks for injurys hopefully are smaller than three on an 18 footer.

Using the 29er small kite might be a problem though, as sheeting is a little to the rear, but should anyway be in front of the wings. Will measure a 29er to find out sheeting points, halyard exit on the mast and distance from mast to end of spinnaker pole.
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Old 01-08-2017, 07:52 AM
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Doug Lord Doug Lord is offline
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49er

Quote:
Originally Posted by revintage View Post
About the heel angle there are lot of keeled sport boats that also should be sailed flat. The bulb is for helping when things get ruff. Will definitely help to slow things down in gusty conditions. Will help in case of capsizing.

The wings will be 90cm instead of 80 making total beam 3,7m. The leeward wings will also automatically lift from 17 to 30 degree angle which will prevent from dips.

Have done some calculations and the version with only a 11sqm main having a design wind of 5,7 m/s without and 6,3 m/s with bulb and heeling at ca 25 degrees. Penalty is 50kg plus the water resistance of the bulb. A VX ONE with two persons should have about the same design wind. Bongo is for even smaller design wind.

If I had a single Tornado hull lying around I would consider making a small tri but the wide 49er will probably not be the way to go. About multihull I have an old Nacra 5.5 that I am satisfied with.

Will of course report if this project fails this spring. At the moment it is -10 centigrade and lots of snow. Brrrrh!
==================
For reference here is Banshee Ambulance, a tri using the Cherub for the main hull:

UPDATE-----More on the main hull here: http://www.uk-cherub.org/doku.php/designs/banshee

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Old 01-08-2017, 07:58 AM
upchurchmr upchurchmr is offline
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Looks like you already had your answer

Quote:
Originally Posted by revintage View Post
About the heel angle there are lot of keeled sport boats that also should be sailed flat. The bulb is for helping when things get ruff. Will definitely help to slow things down in gusty conditions. Will help in case of capsizing.

The wings will be 90cm instead of 80 making total beam 3,7m. The leeward wings will also automatically lift from 17 to 30 degree angle which will prevent from dips.

Have done some calculations and the version with only a 11sqm main having a design wind of 5,7 m/s without and 6,3 m/s with bulb and heeling at ca 25 degrees. Penalty is 50kg plus the water resistance of the bulb. A VX ONE with two persons should have about the same design wind. Bongo is for even smaller design wind.

If I had a single Tornado hull lying around I would consider making a small tri but the wide 49er will probably not be the way to go. About multihull I have an old Nacra 5.5 that I am satisfied with.

Will of course report if this project fails this spring. At the moment it is -10 centigrade and lots of snow. Brrrrh!
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Old 01-08-2017, 08:09 AM
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I tried to make the point with the Banshee that a wide mainhull for a small performance tri is not a handicap.
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Old 01-08-2017, 02:37 PM
CT249 CT249 is offline
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How does the Banshee prove that? How has the trimaran version performed and in what conditions and against what boats?
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Old 01-08-2017, 03:16 PM
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Banshee Ambulance

I was trying to illustrate the potential of using a light, relatively wide mainhull on a tri. It is not necessary to have a high L/B hull like a Tornado to have a fast mainhull-planing main hulls work very well.
The Banshee has 166sq.ft. SA in the main and jib on a 100lb main hull. Normally Cherubs are sailed doublehanded but it might be possible to sail the tri version singlehanded if it was wide enough. Can't find any performance info on Banshee Ambulance -the trimaran- but the numbers seem to suggest it has the potential to be fast.
I've personally designed and built two fullsize tri's with relatively wide main hulls and Richard Woods has a new tri design-Zeta*- with a wide main hull.There are other examples of planing main hulls like the Weta and a 20 footer designed by the Weta designer.
* http://sailingcatamarans.com/index.p...anded-trimaran

Banshee(main hull only) under sail and Frank Bethwaites HSP with planing main hull. He had a two person version with an even wider main hull:




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Old 01-08-2017, 08:29 PM
CT249 CT249 is offline
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The later owner of Banshee stated that the trimaran version was never built, so she appears to demonstrate nothing. The HSP had a very narrow hull. The Weta is a lovely boat but not particularly fast, and cannot pace it with old boats like the Hobie 14 Turbo in a breeze. Richard's boat looks fun, but is there any evidence that it has shown significant pace? It probably gets down to one's definition of "performance".

The 49er's hull is pretty damn big for the float for a 5m tri, weighing in at 90kg+. Add floats that can work with that size hull and rig and it's a big unit. Trying to right a trimaran of that size singlehanded would be damn near impossible, one would imagine.
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  #15  
Old 01-09-2017, 06:28 AM
revintage revintage is offline
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Might this 49er waterline be realistic when loaded with 80kg(me)+50kg(bulb)? Heeling just above 29 degrees.
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