New Rudder and Daggerboard Airfoil for Raptor 17.5 Outrigger Saling Canoe

Discussion in 'Boat Design' started by edvb, Oct 27, 2015.

  1. edvb
    Joined: Mar 2008
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    Location: Oshkosh,WI

    edvb Junior Member

    New Rudder and Daggerboard Airfoil design for Raptor 17.5 Outrigger Sailing Canoe

    Hi All

    I have tweaked my Raptor as far as I can go but wanted to get some input on what the proper size and airfoil shape for the daggerboard and rudder that would work best for where I am now. This is the last piece I wanted to get right before sailing season starts next year. Phil will be building the boards for me.

    I feel the current design need improvement but need advise on what way to go.

    Here is some up to date data on where I am now. I have the boat assembled in my basement and can get any data you may need.

    Any help would be greatly appreciated. Speed upwind is 6-8 Knots. Reaching 10-14 knots.

    Main Hull
    17.5 feet long
    13” max beam round bottom

    Ama Hull
    12.5 feet long
    8.5” max beam round bottom

    Total Beam
    8 Feet

    Total weight ready to sail
    165Lbs

    Sail
    90 Square feet. Just about right. Was larger but reduced to this size. Tweaked the head last fall so shape is pretty good now. The picture was before tweaking the head of the sail.
    [​IMG]IMG_0277 by evanbelkom, on Flickr

    Rudder
    20” long that is submerged under hull. I have enough control but feels draggy
    5.5” cord average NASA0018
    1” thick at 30% from front
    [​IMG]IMG_3259 by evanbelkom, on Flickr


    Daggerboard that I lost. It was about right.
    30” long that is submerged under hull.
    9.5” cord average NASA0012
    1" thick at 30% from front
    251 Sq. Inches
    Top daggerboard I lost. Bottom one broke but was too long was draggy all the way down. Both are NASA0012
    [​IMG]EVB106_Daggerboard[1] by evanbelkom, on Flickr


    Current Daggerboard. Too short not enough area. I can feel the slippage.
    23" long that is submerged under hull.
    9.5” cord average NASA0012
    1" thick at 30% from front
    184 Sq Inches
    [​IMG]IMG_3257 by evanbelkom, on Flickr
     
  2. messabout
    Joined: Jan 2006
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    messabout Senior Member

    It is terribly tempting to make the foils too small, weight, wetted surface and all that. (Been there, done that). The intended inference is that your boards are too small.

    I defer to the forum wizards but I suspect that the max thickness of the foil should be more like 40%, of the chord.

    Your boat is beautiful. My only criticism is that the run of the main hull is too steep for the highest speeds. It is conventional....sort of.... to have the deepest part of the bottom, somewhat forward of the mid section so as to reduce the run angle. The widest part of the hull somewhat aft of the mid section so that you can control the area distributions. In any case the boat is a beauty. I wish that I had one of those. If I did I would not be so picky. ;)
     
  3. edvb
    Joined: Mar 2008
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    edvb Junior Member

    Thanks Messabout

    It is unique and just retired I just want to make the best I have and get the max speed out of the old girl. I hope Tom Speer and the rest of the gang can help me out one last time.

    Basically the way it is designed with the Ama in the water on port tack pushing it down and on starboard with the water ballast and roller furling having the Ama just kissing the water is a design challenge to come up with the right size and airfoil shape to maximize speed without stalling either foils.

    The widest part of the main hill is 13". It is less at the water mark. and is 17.6" long.

    I sure hope we can come up with something that will work better than I have now.

    Ed
     
  4. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    You really notice board area in light and very light winds - if it's too small you make too much leeway but you point OK. This is relatively easy to see with similar type boats racing, harder with a unique hull. Note also that the faster you go, the smaller the board area required. Some daggerboard classes have two or more different size foils for different wind strengths. others with c/boards that pivot, rake back to reduce area and move the CLR.

    My gut feel (without seeing the boat sailing, especially in light air) is that even the first board is too small (short). For real windward light air performance, I'd probably be closer to (in Imperial) 38-40" length. Chord max thickness should almost definitely be moved aft on the board, less so the rudder. I would suggest something around 37-38% from leading edge for board, maybe 32-33% rudder. Worth playing with in XFOIL. Not convinced the 0012 is the best section for the speeds you are achieving. My own past experimentation has led me to be a bit open about what actually works when you race. However with tight one design stuff, you really can guage if there is a small difference.

    There are plenty of other real experts on here who will I'm sure give you sound advice. Nice boat and project, well done.
     
  5. edvb
    Joined: Mar 2008
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    edvb Junior Member

    SukiSolo

    Thanks

    The boat goes very well in light air. During the last few years of sailing her I found the sweet spot with the board that was 30" long below the hull. It pointed well with no loss in speed even in light air. The rudder seem to be too small but I do have control at any speed. Here is my chance to get a set of foils that are matched to the boat and sail I have now. I just do not have the expertize to know how to size them and what shape each needs to be.

    Thanks for responding and hope more will help me and chime in.

    Ed
     
  6. edvb
    Joined: Mar 2008
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    edvb Junior Member

    Here is a video of the boat sailing. The sail was reduced and refined to what I have now. I also tried an aluminum rudder as the daggerboard from a RS Tera. It was 31.5" long below the hull and a 8.25" chord verses a 9.5" chord I have on mine now. I believe it was a NASA0012 foil. When did a quick test I was 1 knot faster switching back and forth and was able to do 360's without the boat stalling at any point. This is why I was pursuing different foils as the boat seemed to preform much better during this test.

    Here are 14 pages of what I did during the years.

    http://www.raptor-uk.net/guests/eddievb/comments1.html

    I had a 1/2 tank of water ballast in the Ama during the test. Empty the Ama weighs 44 Lbs. With 1/2 water ballast it weights 73 Lbs.

     
  7. SukiSolo
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    SukiSolo Senior Member

    How long is a Tera?... and the board works OK on them, though it is a pain the newer aluminium foils sink, unlike the early ones which floated. PITA when you lose one on training courses....;) I'm not sure, but I think the section is sharper at the leading edge than a 0012 which would tend to stall when sharp turning on your craft when combined with a slightly too small area.

    Thanks for the vid, though it's not light air IMHO. I take it the longer ie 9.5" (fore/aft) foil gave the higher speed... less leeway. The fun of aspect ratios and area, there is significant discussion on this Forum on this topic. What does a 12" foil do? for example...

    Also do not be fooled by a foil stalling versus too little area. These things seem to work in combination as can be seen by too small a board boats going sideways out of a tack before the board gets 'lift'. If you want an example of too high an aspect ratio rudder IMHO look at the Hansa 2.3 - fine for an experienced sailor but one that stalls frequently when used by a novice, when tacking.
     
  8. edvb
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    edvb Junior Member

    SukiSolo

    It was about 2 years ago when I did the test. It was either the RS Tara or RS Vareo rudder (14' boat) that I tried as it was close to 1" thick and 40" long the chord was 8.25" when we measured it. My trunk is 8.5" deep so I knew that 31.5" stuck below the waterline.

    When testing the rudder as a daggerboard that had about 1.25" less chord it performed much better with 1 knot more boat speed and better handling. It was the rudder being used as a daggerboard that I was able to make continuous 360 turns without the boat stopping during the maneuvers. I switched back and forth about six times and the RS rudder just performed better each time.

    That showed me that the daggerboard with the longer chord had less performance for my boat.

    It was such a difference at that time that when I had a chance I would look at getting a more matched set of foils that would meet the performance profile of my particular boat.

    From this it seemed I need a set of higher aspect ratio foils to get the max performance I believe I can get from this lightweight outrigger sailing canoe.

    Just my thoughts

    Now what size and shape is next?
     
  9. edvb
    Joined: Mar 2008
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    edvb Junior Member

    Ok, after doing some calculations I decided to make a daggerboard using the aluminum daggerboard I got from Walker Bay.

    Here is where I need help.

    The dimensions of the daggerboard are the following

    8.0" chord
    .950 thick
    3.1" max thickness from front edge
    .150 Trailing edge thickness
    40" length

    What symmetrical airfoil is this?

    The daggerboard case was made for a 9.5" chord but the boat is so sensitive that moving my weight a few inches makes a difference in trim.

    I was going to make a wrap of fiberglass cloth on the daggerboard that fits the trunk having it all the way forward to fit the daggerboard trunk properly.

    Testing with different boats all showed that 245-250 Sq Inches was optimum for area needed for max performance. I can do that with this board as it is 31.5" below the hull.

    The original daggerboard was a NACA0012 section.

    Hope you all can help me on this

    [​IMG][/url]IMG_3292 by evanbelkom, on Flickr[/IMG]
     
    Last edited: Nov 17, 2015
  10. tspeer
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    tspeer Senior Member

    It's not possible to tell just based on these measurements.

    I think what's most important is whether or not the new board will fit in the trunk. A 9.5" chord NACA 0012 would have a maximum thickness of 1.14" at a distance of 2.85" back from the leading edge. That doesn't sound much different from what you say the new board is. So it ought to fit. You might want to put an insert into the trailing edge to support the smaller chord.
     
  11. edvb
    Joined: Mar 2008
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    Location: Oshkosh,WI

    edvb Junior Member

    Hi Tom

    Thanks so much for replying on my thread. Sorry I missed the thickness of the boards.

    I used a couple playing cards to extend the trailing edge until they met. I did it for the aluminum board and the carbon board. This is what I measured.


    Aluminum board
    .950" thick at 3.1" max thickness from front edge
    8.6" chord

    Carbon board
    1.1" thick at 3.2" max thickness from front edge
    10" chord

    Do you have an idea what airfoil they are now?

    I am thinking of using a NACA0009 tapered section if the aluminum board is not the proper airfoil. I have 1.1" thickness to play with. The trunk is 9.5" for the chord.


    [​IMG][/url]IMG_3297 by evanbelkom, on Flickr[/IMG]

    [​IMG]IMG_3274 by evanbelkom, on Flickr

    [​IMG]IMG_3263 by evanbelkom, on Flickr
     

  12. edvb
    Joined: Mar 2008
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    Location: Oshkosh,WI

    edvb Junior Member

    Well I was able to make a sleeve out of glass and carbon and got it epoxied in the old slot.

    I will make a rounded tip about 1.5" long that will be epoxied in the end of the daggerboard and faired properly.

    The nice thing is I can get the aluminum daggerboard for about $140.00 in case I trash it accidently. I also will make a mold of the tip and head in case I need to replace these later on.

    Thanks everyone for your help on this decision.

    Ed

    Sleeve epoxied in. A little cleanup and final faring on top and it will be done
    [​IMG][/url]IMG_3309 by evanbelkom, on Flickr[/IMG]

    I have 1/16" clearance all around the board. I can tighten with shims if needed
    [​IMG]IMG_3308 by evanbelkom, on Flickr
     
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