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Thread: n-Arrow3b build

  1. #1
    Join Date
    Nov 2010
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    Johannesburg
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    249

    Default n-Arrow3b build

    Hello,

    This is a log of my attempt at Claudio's n-Arrow design.
    Dick and TArmstro are busy building an extremely narrow version with a chine down the side (V5 if I'm not mistaken)
    Claudio kindly supplied this version based on the earlier Version3.
    It has been modified for a higher PC for our wind conditions.

    I mentioned that this build would be an attempt for me at doing a female mould, which I could then offer for any other local builders to use should they wish to attempt a first build.
    Upon hearing this, he kindly adjusted the design to give a much more forgiving weight allowance and still be "in spec" for all us new builders.

    So here are the files supplied by Claudio for V3b
    NARROW3B.pdf

    Appendages and sail plans

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    Be very careful if you use the above graphic.
    The sail plans are the correct dimensions, but the hull/appendage drawing is double the scale, so all dimensions need to be divided by 2.

    The following PDFs are the line drawings which are 1:1.
    You will need to adjust the printing scale to allow for the thickness of your chosen planking.

    Shadows n-Arrow-3B.pdf

    The following files have a common line added to the line drawings so you have a common flat point for when you print/cut your stations.

    n-Arrow-3BWithCommonStationpg01.pdf
    n-Arrow-3BWithCommonStationLinepg02.pdf
    Last edited by Naptalene; 12-23-2015 at 03:35 PM. Reason: formatting

  2. #2
    Join Date
    Nov 2010
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    Johannesburg
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    249

    Default Re: n-Arrow3b build

    So in continuing with my idiots guide to building mini boats to encourage others to give scratch building a bash......

    I planned to use 3mm balsa to plank the hull.
    Therefore i need to adjust the scale when I print out the line drawings to make them smaller to accomodate the planking thickness. After much gnashing of teeth I did this and it worked (and should work for any drawings)

    The given beam at the deck is 96mm.
    I needed that to be 6mm shorter (3mm balsa for each side) which gives me 90mm

    Take the desired beam (90mm) and divide it by the original Beam (96mm) and multiply by 100.
    That gave me 93.75 which is the size I printed them out at and got the correct size when measured.

    I then cut them out and glued them onto 3mm ply using my kid's PritStick glue.
    I literally used a blade and steel ruler to cut the frames out.
    I cut the linear lines as accurately as possible and did rough cuts around the curved sections.
    Then I just had to sand the final shape of the curved section. I used a piece of wood as a sanding block and 60grit sandpaper. I cleaned the edges quickly with 100 grit.

    This is what they looked like.

    Click image for larger version

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    I then placed them on a building board at 65mm spacing, using the centre line of the print outs to align them on the board

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    Its very hot and Summer......hence the swimming towel :P
    Last edited by Naptalene; 12-23-2015 at 04:17 PM. Reason: replaced oversized image

  3. #3
    Join Date
    Nov 2010
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    Johannesburg
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    Default Re: n-Arrow3b build

    I then started planking. I shall refrain from any input as I did a horrible job with many holes.
    Fortunately It's going to be a plug so it doesn't matter and I can use lots of body filler without worrying about weight etc.

    Here are some progress shots.

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    And the finished hull before putting resin/epoxy inside to re-enforce the balsa planking for sanding.

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    And for those who are pondering a scratch build but are worried about the tools needed - here's what i used so far (I see I omitted my balsa stripper for the planks but you can do that with a ruler/blade anyway)

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    I have started sanding and will begin attempting to build straight and consistant rudders and keelfins until I get a chance to get fibreglass
    Last edited by Naptalene; 12-23-2015 at 04:30 PM.

  4. #4
    Join Date
    Aug 2003
    Location
    Minnesota USA
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    Default Re: n-Arrow3b build

    Looks like you have a good start on your build. On the "nARROW" version, both Thomas and I found the bow to be really difficult to strip the entire length of the hull and still have a such a very narrow bow.

    On mine, I wound up cutting and shaping a piece of foam, to which I glued my strips and then faired them in to the rest of the hull.

    Keep going - and you should have a good plug from which to make your female mold.

    Dick

  5. #5
    Join Date
    Apr 2005
    Location
    Toulouse (Fra)
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    Default Re: n-Arrow3b build

    I Andrew
    Not bad at all, this is the first N-Arrow 3 under advance construction.

    For sure : 'narrower the Beam - narrower the Bow'

    BTW please look at the drawing attached, any comments about the jib being masked partially by the deck sheer line when at 35 ?


    Merry Christmas to all.

    ClaudioD

    Attached Thumbnails Attached Thumbnails Click image for larger version

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  6. #6
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    Nov 2010
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    Johannesburg
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    Default Re: n-Arrow3b build

    Hello gents

    When I got the hull planked I giggled to myself when I tried to imagine fitting the electronics in your V5 skinny ones.
    It must be sooooo tight.

    WRT the 35 degree issue - I'm no physicist but my logic would say this...

    If the wind is coming at such an oblique angle then yes I assume will mess with the flow.
    But then all boats will have a similar handicap unless designed to address this issue specifically.
    I can imagine the "cut away" sections of the v5 would help aid this issue.
    But then you could always sail a slightly different angle to avoid it?

    Those are uneducated comments btw

  7. #7
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    Nov 2010
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    Johannesburg
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    Default Re: n-Arrow3b build

    I had a sudden thought,

    If the wind hits the hull it will be diverted up and cause turbulence of the wind layer( not sure of the correct term) above it, which would cause a swirl into the jib? I spend hours watching the flow in my fish tank and wherever there's a diversion in laminar flow you get that vortex that curls around the obstruction. It's quite a chaotic flow but it definitely curls back in after the obstruction.

  8. #8
    Join Date
    Aug 2003
    Location
    Minnesota USA
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    Default Re: n-Arrow3b build

    During planning phase, I had corresponded with Claudio about turning the winch on it's side and allowing the arm to travel vertically. Still limited by height of deck from bottom of keel, I could substitute a drum for an arm winch, I suppose. I just the speeds available with arm winches compared to drum winches (i.e. drum speed = money) More decisions will soon be needed, once I get the exterior of the hull cleaned up from the sandpaper sterate contamination. Photo attached is the normal winch I have used on all of my RG65's (Hitec HS-645-MG) You are correct, however ---- very tight spaces - but once the templates are removed there is a bit more room fore and aft. The sides however aren't going to change any.

    Click image for larger version

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    Merry Christmas and Happy New Year to All !!!

  9. #9
    Join Date
    Nov 2010
    Location
    Johannesburg
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    249

    Default Re: n-Arrow3b build

    I've been filling and sanding before glassing the plug as practice using body filler.
    I suddenly thought I should measure the width at the station on the line drawing with the 96mm dimension.
    It's currently at 97mm and I still need to add the glass so I think I'll sand some more to get it slightly closer to spec to allow for the glass. I have quite a bit of the balsa left so it shouldn't be an issue.

    I'm off camping so I'll take the opportunity to wish you all a"Happy New Year!!"
    Chat in 2016

  10. #10
    Join Date
    Apr 2005
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    Toulouse (Fra)
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    Default Re: n-Arrow3b build

    Happy NEW YEAR !

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