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    Grooves and depths...

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    Stonedog
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    Grooves and depths...

    Post by Stonedog on Mon Sep 10, 2012 4:32 pm

    I am going to shoot 3/8" wide oak bolts with 2 feathers.

    How wide should I make my groove and how deep?

    Also, should the groove be half round, triangular or what?

    What are you using to cut them?

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    jds6
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    Re: Grooves and depths...

    Post by jds6 on Mon Sep 10, 2012 8:08 pm

    Greetings Stonedog;

    I had this same question about eight months ago on my first build! A wise man on the forum gave me good advice, so I will pass it on.

    The basic dimensions of the groove will depend on two things

    1. String diameter
    2. Bolt/arrow shaft diameter

    The diameter of the string is important. You need to know how high the mid-line sits above the track surface. Measure diameter of the shaft you are using. Place the dimensions one over the other so the string contacts the nock in the center. After that plot your groove and you should have your dimension.
    You can find a diagram in the topic first build by jds6 in early medieval crossbows

    As far as the groove I guess it could be what you want. I use a half round. I chiseled out the groove on my first build and used a router bit on my second build.

    Good Luck,
    jds6

    chaz
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    Re: Grooves and depths...

    Post by chaz on Tue Sep 11, 2012 2:25 am

    Stonedog,

    jds6 advise sounds good.

    Of course it would have to do with personal preference and if one was trying to achieve a period correctness, however, I.m considering the fact that I wonder about a "v" groove with a slot at the bottom to like wise accommodate a bolt with three fletches , making the crossbow abit more versitile. And then how deep to make the grooove would depend on what size the fletch is. This may be done easily with a table saw. Just something else to think about.

    Chaz
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    Todd the archer
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    Re: Grooves and depths...

    Post by Todd the archer on Tue Sep 11, 2012 2:35 pm

    Adding a third fletching adds another issue, that is clearance over the prod and how far down it is positioned below the top of the deck.

    With modern crossbow not so much a problem as most use two limbs bolted to a riser to give room in between.



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    jds6
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    Re: Grooves and depths...

    Post by jds6 on Tue Sep 11, 2012 10:06 pm

    Greetings,

    While on the topic of a 3 fletch bolt, what dictates that the third fletch needs to be in the downward position, riding in a deep groove in the center of the tiller? What if two of the fletches on either side of the bolt are positioned in the middle( bolt) and the third positioned in the center on top of the bolt. The side fletches riding just atop of the table on the tiller. Does such a bolt cause poor flight? Just curious!
    Thanks for any response !

    jds6

    chaz
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    Re: Grooves and depths...

    Post by chaz on Wed Sep 12, 2012 2:42 am

    Salutations jds6,

    Seems that configuration would be off balance, don't know. However one needs to consider the bolt and bolt clip. Seems the three evenly spaced fletches with one on the bottom in the groove that the bolt clip would not interfere with the fletches by being positioned between them, but if the portion of the bolt aft of the fletches were longer that would not matter. Bet Geezer or Todd will have more enlightenment. I have not made any bolts yet. This is interesting though.

    Chaz
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    ferdinand
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    Re: Grooves and depths...

    Post by ferdinand on Wed Sep 12, 2012 2:52 am

    Hmm, this all makes me wonder what problems i will run into next.
    I am making a replica of a bow with ivory on top and no groove, just a 'rest' in the front with a half-circle cut-out.
    Any suggestions are welcome! As long as it doesnt take over the original topic.
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    kenh
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    Re: Grooves and depths...

    Post by kenh on Wed Sep 12, 2012 9:40 am

    A three-fletch arrow has the feathers equally spaced 120 degrees apart. That's OK for a vertical bow where the feathers only touch the rest in passing. But on a crossbow, a 3-flech bolt at the rear would tend to rest on the tips of the feathers, with the shaft of the bolt above the surface of the tiller, not down flat where the string can get to it consistently. Two feathers and the groove ensure that the bolt is always in the same place for the string to strike.

    chaz
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    Re: Grooves and depths...

    Post by chaz on Thu Sep 13, 2012 6:29 am

    Kenh,

    Check out modern crossbows which use three fletches.

    Chaz
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    hullutiedemies
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    Re: Grooves and depths...

    Post by hullutiedemies on Thu Sep 13, 2012 7:42 am

    jds6 wrote:What if two of the fletches on either side of the bolt are positioned in the middle( bolt) and the third positioned in the center on top of the bolt. The side fletches riding just atop of the table on the tiller.

    That is the traditional way of doing it.
    Cock feather should have the helix.
    Just leave space behind for bolt clip, if you use one .
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    Geezer
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    Re: Grooves and depths...

    Post by Geezer on Thu Sep 13, 2012 9:11 am

    Payne-Gallwey shows three-fletched bolts, with feathers spaced 90 degrees apart. I have used such bolts and find they shoot just fine.
    You might think having one feather off-center (one on top, one to each side) would make the bolts fly badly, and maybe they would given sufficient velocity, but at practicable velocities (150-250 fps) three adn 90 degrees fly just fine.
    Geezer.
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    mac
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    Re: Grooves and depths...

    Post by mac on Thu Sep 13, 2012 11:19 am

    I am surprised to hear that the Payne-Gallwey style three fletch bolts actually fly OK. I would have expected them to wobble. I always expect the worst of Sir Ralph's inventions.

    Mac
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    Re: Grooves and depths...

    Post by Geezer on Thu Sep 13, 2012 11:36 am

    I have actually seen some old three-feathered target bolts... dunno how old, but not made recently. Indeed PG's bolts might wobble uncontrollably if you got them going fast enough, but given a reasonable amount of spin at moderate speed, they fly quite well.
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    Re: Grooves and depths...

    Post by kenh on Thu Sep 13, 2012 12:38 pm

    Learn sumpthin' new every day... Ida thought they'd wobble too. Mebbe heavily weighted forward helps...
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    jds6
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    Re: Grooves and depths...

    Post by jds6 on Thu Sep 13, 2012 6:48 pm

    Greetings all:

    While still on the topic of three fletch bolts, here are a few pics of my three fletch bolts. They seem to fly very well.







    jds6
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    mac
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    Re: Grooves and depths...

    Post by mac on Fri Sep 14, 2012 9:54 am

    A big advantage to using only two fletches is that the bolts pack well in your quiver.

    Mac
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    actionbow
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    Re: Grooves and depths...

    Post by actionbow on Tue Sep 18, 2012 4:05 pm

    I have a bow that was designed originally to shoot two fletch that I converted to shoot three by carving out the fin shape in the tiller top. Works well and is in fact my most accurate bow. It was painstaking work to carve the two extra grooves but well worth it. Looks great in the bocotye as a bonus.
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    actionbow
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    Re: Grooves and depths...

    Post by actionbow on Thu Sep 20, 2012 11:03 pm

    Here is the bow I am referring to.http://db.tt/Jiib3U1f
    It works really well. I recently got to try this bow (90 lbs@13") against a new 150# recurve shooting the same arrows. I got the same penetration with identical groups at 30 yards and my bow is basically sightless. In fact my buddy was able to shoot my bow better than his the first time he tried it. Add the fact that I can cock and load and put arrows on target in 1/3 the time with my slide cock mechanism and open tiller and it was an easy choice.

    Sorry...off topic, I love that bow.

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    Re: Grooves and depths...

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