1/16 scale J boat

Discussion in 'Boat Design' started by Mitch M, May 19, 2006.

  1. Mitch M
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    Mitch M Junior Member

    Hi All,

    I am considering building a 1-16 scale remote control J boat model to race. The class rules allow 2" deeper keel and 2" wider rudder. Any suggestions on how to best fair the 2" extended keel and rudder without changing the Center of Lateral resistance?

    I still haven't picked which hull I will use. Ranger is the longest but also the heaviest. 65.25" LWL, 80# disp, 4245 sq in sail. Shamrock V is one of the smallest at 60.81" LWL, 65# disp, 4241 sq in sail. Any thoughts on which would be the prefered hull to build? By the way, retractible centerboards can be used if was on the original. Nationals are expected to be in Texas next year and I would expect light winds of 8 knots and below.

    Below are some links:

    http://www.cse.unr.edu/~arnold/jclass/about/j_class_official_specifications.htm

    http://www.cse.unr.edu/~arnold/jclass/jyachts/shamrock_v/

    http://www.cse.unr.edu/~arnold/jclass/jyachts/ranger/

    Thanks for the help,
    Mitch
     
  2. Earl Boebert
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    Earl Boebert Senior Member

    Since you'll be going to a single-headed rig, the geometric CE will change so I wouldn't get all hung up on maintaining the the design CLR. Sketch a nice fair line of the new profile and give yourself a couple of inches of range for mast adjustment and tune it on the pond.

    According to Taglang and Chevalier, the J with the best VPP was Whirlwind, but she also was seriously unbalanced. My personal favorite is Yankee, but then I'm biased :) (http://www.swcp.com/usvmyg/YankeeIII/YankeeIII.htm)

    Cheers,

    Earl
     
  3. Mitch M
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    Mitch M Junior Member

    Thanks for the reply Earl,

    I added the keel and rudder area's without concern of the Center of lateral resistance to Ranger just for the fun of it although I am still of the camp that Shamrock V might be the better choice. 5" of waterlne will not give me that much better boat speed, but 15# additional weight on Ranger will certainly slow the acceleration.

    Which Chevalier do you have? I have the 1851 to 1986 Americas Cup book, but I would sure love to get the J boat book. If you have the J boat book, is Ranger shown with a centerboard? I was told she has a centerboard, but my book doesn't show it.

    Thanks, Mitch
     
  4. Earl Boebert
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    Earl Boebert Senior Member

    Looks like we have a bit of a mystery here. The drawing in Olin Stephens "Lines" does not show a centerboard. The drawing in Chevalier and Taglang's J Class book shows two [!]. Vanderbilt's "On the Wind's Highway," which contains detailed descriptions of sailing Ranger, makes no mention of a centerboard. I believe there are people on this forum that know Olin, maybe somebody could ring him up and ask :)

    As an aside, Yankee's centerboard was intended to be used only on the run, not on the beat.

    As for hulls, I'd still be tempted to go with Whirlwind, unbalanced hull and all. I'm not aware of anybody building a 1/16 model of her -- all the ones I know of are the 1/20 hulls that started the AMYA class.

    Cheers,

    Earl
     
  5. Mitch M
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    Mitch M Junior Member

    Now I am even more confused. They sailed Yankee with the board up when going up wind? I can understand leaving it down if the boat was rolling when going down wind, but I would think it would be best used during the upwind legs. Any Naval Architects out there with thoughts on this? Can a modern shaped centerboard increase upwind performance in a full keeled huill like a J boat?

    I'll check Whirlwind tonight. It was not one of my favorites so it's not on the top of my list to build, but it could be interesting. Whirlwinds have done very well in past regattas, with a Shamrock, Endevour and Ranger somewhere in the middle of the pack. I would obviously like to build a competitive boat, but the boat will spend 99.99% of the time on display so athetics to my eye are going to play a big part of this decision.
     
  6. Larry Ludwig
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    Larry Ludwig New Member

    All of the J's that are currently being sailed in the AMYA Class had centerboards (Enterprise had 2) that were retractable and most certainly increased performance. You are quite correct in the scale area that Whirlwind was done in 1/20th scale and created the class. I have the ACCR winning boat from (if I remember the year correctly) 1972 in my collection. It is a nice sailing boat but would struggle against the larger boats in light air because of the sail area that it is allowed.

    My Ranger was originally built with a working centerboard, but it has locked up over the years, and would do more damage to release it than it is worth. The plans I have for the new hulls will all include the option for operable centerboards. The amount of increase in performance in the models will be small, and the subsequent cost of adding this feature will make it a question to the owner of just how much do you want to spend to go fast? Whenever anything is raced, the basic formula is: Speed increases by the square of the money.

    The information that I have handy, does not show Whirlwind using a centerboard, but that doesn't mean it didn't have one. I don't have a lot of info on that boat, and I am not planning on producing it at this time. Later on when I am caught up (HAH... I can't say that with a straight face) we might put it on the list of things to do, but it is WAY down the list.

    The current hull of choice for the winning skippers *appears* to be Shamrock V, but this could reasonably be because just as red cars have a higher chance of being involved in an accident (because, there are MORE red cars) the Shamrock hull seemed to be the most available and best quality hull you could find. Now that there are more hulls available (all of them except Enterprise and WW, and we are doing Enterprise first, but because of it's abilities... not because of availability that is just a happy, lucky coincidence) this may be on the change. Bob Sennott in Maine is producing Endeavour, and Kem Dunnebacke is producing Ranger, Dave Brawner was producing Shamrock and I believe Rainbow, but I am uncertain if he still is making them?

    There is a rumor of another Rainbow mold on the loose in the N.E. somewhere, and GRP has been advertising their Shamrock hulls as well.

    We do have the honor of John Hanks the J Class sec asking us to host the 2007 J Class Nationals here in San Antonio Texas through the AMYA #224 club RAMYA Randolph Area Model Yacht Association www.sailramya.org so the preperations are actually already under way.

    If there is anything that I can do to help, please don't hesitate to ask as we are working long and hard to see the J Class grow, and with no small success either. There have been 7 new boats on the water in the last 8 months.

    Larry
     
  7. Earl Boebert
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    Earl Boebert Senior Member

    Here's the reference on Yankee:

    New York Times, 3 Mar 1930, by James Robbins (who knew his stuff, BTW). Headlines and subheads:

    New Sailing Use for Centreboard

    Yankee's Will Be Dropped When Yacht Is Off The WInd Instead of On It

    Is To Prevent Yawing

    Will Enable Craft Which Will Seek Right To Defend America's Cup to Steer Better

    Unfortunately, the body of the article hasn't much more detail. It mentions the conventional use of the centerboard to increase lateral area on the beat, discusses squatting on the run:

    "There has been a tendency to place the lead of the keel on yachts further aft. This has been carried out with success until now there is a longer run forward from the keel to the bow. As a result, when a racer is running before the wind, with her sails eased off, there is an inclination for the bow to lift, especially if there is a following sea.

    Affects Steering of Craft

    This causes the yacht to yaw, or swing from side to side and steer wildly. Frequently craft have become almost unmanageable with their mainsails swung far out and spinnakers set."

    Goes on to say that other boats track so well bow up that they concentrate the crew on the stern. Talks about "tacking down the wind," supposedly invented by one William Dennis, skipper of Elimina II. Mentions that Yankee's centerboard is well aft, and that's about it.

    Whirlwind did not have a centerboard. Taglang and Chevalier repeat the conventional wisdom that Whirlwind was a fundamentally sound boat that just wasn't given a chance by her syndicate. However, a metacentric shelf analysis (itself a disputed technique) of her hull shows her to be seriously unbalanced. More tellingly, WIlliam P. Stephens (no relation to Olin), dean of American yacht designers, read a paper to the SNAME in 1935 asserting that Whirlwind was fundamentally unbalanced. L. Francis Herreshoff, her designer (and no wilting flower, for those unfamiliar with the family) was in the audience and there is no record in the proceedings of him challenging this remark. Isn't J Class history fun?


    Cheers,

    Earl
     
  8. Mitch M
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    Mitch M Junior Member

    Interesting information. Centerboards are used to prevent yawing. That's just a reminder of how much sail they would carry.

    I just went back and looked at the other hulls specs and Endevour looks promising, plus I like the blue hull color! I'm thinking to just mold the centerboard in lead and leave them down at all times. Lower center of gravity plus better performance upwind and minimize mechanical complexities.

    I am planning on a plank on frame construction with laser cut frames and cedar planks, athough I'm sure purchasing one of the fiberglass hulls would save me time and money. I've got two years right and it should be fun!

    Mitch
     
  9. Larry Ludwig
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    Larry Ludwig New Member

    If you work steadily, without any long breaks (no more than 2-3 days) you can complete an all wood boat in 9-10 months. On the other hand, you can wood plank a deck on a fiberglass hull and have the boat on the water in 30 days. If you go with an all FRP hull deck rudder etc, you can be on the water in a week.

    Glass hulls are lighter, stronger, and easier to repair. J Collisions are common, painful, and expensive. I just shipped spars to one of the finest skippers *period* with the championships to prove it... and he nailed one and wiped out the rig on both boats... so it can happen to anyone. Mitch said 99% display... so might be a hobby decision for him, but if the hull is done properly, you cannot tell it from a fiberglass hull on the outside. Only when you open up the boat does it become apparant that it's a wooden hull.

    In other words... no wooden hulls for me. Life is too short. I would much rather be sailing than building.:cool:
     
  10. Earl Boebert
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    Earl Boebert Senior Member

    Larry said:

    "If you work steadily, without any long breaks (no more than 2-3 days) you can complete an all wood boat in 9-10 months."

    Wow. You're *much* more careful than I am :) Here's a 36 inch restricted free sail hull, strip planked from 3/32 x 3/16 cedar over a structural foam core. Planking is done from the sheer down; this means you have to spile the garboard (shutter) plank but it looks much nicer.

    Daily log, no more than 3 hrs per day:

    Days 1-2: Lay out core on vertical lifts, carve, fair and epoxy (surface finish not important)

    Days 3-7: Plank in courses.

    Day 8: Fair with longboard, apply layer of 5 oz glass and second layer of epoxy.

    10 oz. for the shell.

    Summary: A little slower and heavier than all-plastic, greater "ooh-ah" factor at pondside, more enjoyable to make for those of us who prefer wooden boats.

    Cheers,

    Earl
     

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  11. Mitch M
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    Mitch M Junior Member

    I do like the plank on frame boats, especially when they are finished in clear so the beauty of the wood is seen. It took me about a month to complete the hull on the Vanquish IOM which was balsa planks on shadows. All added up about 40 hrs of labor total. Granted the J will be a whole other ball game due to the size. Larry, do you know off hand what the fiberglass hulls cost?

    Mitch
     

  12. Larry Ludwig
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    Larry Ludwig New Member

    9-10 months was complete boat, from laying the keel to launching. This also includes all the scratch building the deckhouses, brass fittings.. the whole ball of wax.

    Hulls for the J Class models in glass are between $400.00 - $500.00 depending on which one you get.
     
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