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Thread: Sky ski Arc 40 T bar

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  1. #31
    Foilforum Addict Suicidal-Element's Avatar
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    Yep, looks like the bend is going the wrong way, unless they completely redesigned it. If not, someone put the fusilage on backwards. WTF???!!



     
     

  2. #32
    Senior Foiler Elite hossdog's Avatar
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    Whats the word? Which direction is it supposed to go. Is it backwards or is the photo playing tricks on us?
     
     

  3. #33
    Foilforum Addict EricR's Avatar
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    Quote Originally Posted by hossdog View Post
    Whats the word? Which direction is it supposed to go. Is it backwards or is the photo playing tricks on us?
    Original add.....


    http://myemail.constantcontact.com/Sky-Ski---Comptech-Marine-Specials.html?soid=1100479843526&aid=7haO0zRQ6Xw


    Looks like they changed the design. It was curved back and now its curved forward....

    What is the tune on the leading edge like Drossiter?
     
     

  4. #34
    Foilforum Addict nobrainsd's Avatar
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    Well, the swap in orientation would make some sense from a "quickness" angle. If you look at airplane wings the more a wing sweeps back the more stable it is in flight. That is because small changes in the leading edge of the wing move the swept back sections of the wing farther which exerts a counter acting force. You will see most aerobatic planes incorporating wings with little or no sweep back. There were a few military planes made with swept forward wings and they were capable of tight turns, but were unstable. I don't know if the forces created by basic geometry would be significant in an arc this small, though it does seem like having the arc sweep forward would make for a quicker turning strut.

    What do I know :) Still look forward to hearing how the ARC 40 rides and would like to ride both versions to see what the strut shape is doing! Be sure to check out the rooster tail off the strut David.
     
     

  5. #35
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    Having significantly participated in the design of the new Arc 40 hydrofoil, I can tell you quite a bit. (I will have them up on the site soon @ yourgearstore.com, and I am sure other dealers will as well)

    -The new ski comes standard with a carbon fiber seat plate instead of the G-10 stiffy plate. (saves your back, and about .5 pounds)
    -It also comes with the new Aero rear wing which is larger than the fling wing, and has rounded ends as opposed to the thin sharp super bendy fling. The larger wing adds more stability that was lost when we introduced the Apex front wing, which is 20% +/- larger than the max air. Pairing the front wing with a larger rear wing was a huge plus for those who don't care for the "air chair stealth" or whatever they call that thing now - ride. It is still quick, but it is much more stable and controllable, and yes I can still whip doubles when I feel the need (which is less often as I am now getting OLD!)
    -The original design for the arc 40 was actually a forward arc, and I believe this is the reason why they at first glitched under certain conditions. My idea was if we put the arc in the back, we can still take advantage of the water hitting a curved edge instead of a flat edge, and pick up some forgiveness. If you land a bit short, the curved back arc catches and tends to swivel you more to the front like a cantilever. With it in the front, it didn't recover as well.
    -the extra 2.5" is pretty sweet, I feel I am going higher now, and there is more forgiveness with the "top out" when climbing too high. I still have to get used to the extra length and do more of an up down up motion. Old habits are hard to break. Been riding the Anser and G-38 for a long time.
    -The cost is more.... the only drawback I can see. However, as in the past, if you order any high end foil from me and it isn't right out of the box, I will make it right for you. There should be no problems, but just in case, you know I have your back.

    Feel free to contact me if you have any other questions, and for those of you who have purchased any sky ski products over the years, on behalf of everyone at Sky Ski, we thank you. Have a super summer! IT is already hot here in Florida!!!Click image for larger version. 

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  6. #36
    Foilforum Addict Drossiter's Avatar
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    I was able to take my first spin on my Arc 40 today! I only have a couple of runs on it but here is my first impressions.

    One the positive side:
    It was very quick and had minimal drag. The quickness maybe a result of a really sharp leading edge.
    I did not hear or feel any twang from the tbar.

    One the negative side:

    Several times while riding today I experienced what I will call "catching an edge", snowboarders know what I am talking about. Your cruising along and all of a sudden you get taken out without warning. At first I thought I was hitting small fish but it must be something with the tbar because when I switched to my AC V41 the problem went away.

    It had some glitching at the wake, the leading edge is sharper than I would normally like so I am going to tone it down and hope the glitching goes away (however, this may effect the quickness). This might also help the "catching an edge" issue.

    Not sure I noticed any benefit to the curve or the curved back arc catching you and a swivel to the front like a cantilever but I am sure I could impress people with this technical insight when they ask "what does the curve do"?

    The front wing does not sit flush on the fuselage and you can see space between it, to make things worse some of the bolts won't bottom out leaving the head a fraction of an inch above the wing (I am using the short 1/2" bolts). I was riding the N2O Phoenix front wing and I don't think it is any thinner than any of the Skyski wings so I think the holes might not be drilled deep enough. The fuselage is very thin at the tip so I will probably opt to grind the tip of the bolt down instead of going any deeper.

    I will be riding the tbar again on Friday and will let you know how it goes after I make a few adjustments. I would appreciate any suggestions to help me fix the issues that I am having.
     
     

  7. #37
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    I would definitely want the leading edge to be dull compared to the trailing edge of the strut. The first few Arc 40s were not tuned to my recommendation. The concern beyond safety is it will glitch when hitting the air bubbles from the boat wake. The Tbar also picks up air from carving quickly from one side to another when it is too sharp on the leading edge. I am also concerned with the hole depth, and if you try to force it you will strip out the holes. Shorter bolts are for sure needed. You can call sky ski to have them ship you one, or as you say grind one down. My concern first an foremost is that these are tuned correctly, and the big problem is there are different water temperatures that will ride better with a sharper or more dull edge. Personally I think that if you tune a tbar perfectly you can get it to ride great in both. Unfortunately it doesn't always come perfectly tuned, and part of riding high end hydrofoils is ultimately you need to know a bit about tuning. When fixing this bar yourself, you have to make sure you are consistent up and down the leading edge, and you get a perfectly round edge from your tune. Also pay attention to the wings. Leading edge of the front wing needs to be slightly dull like the strut of the Tbar, and sharp but not so sharp it will cut you on the trailing edge. The rear wing needs to be sharp on both leading and trailing, but again no edge should be so sharp it cuts your hand. It should just be a bit uncomfortable to hold or to press your hand on it, but if you slide your finder down it you don't bleed. any sharper and it is dangerous. good luck with the mods. I hope it goes well. Just curious, where did you get the Arc from?
     
     

  8. #38
    Foilforum Addict Drossiter's Avatar
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    Quote Originally Posted by Geno View Post
    I would definitely want the leading edge to be dull compared to the trailing edge of the strut. The first few Arc 40s were not tuned to my recommendation. The concern beyond safety is it will glitch when hitting the air bubbles from the boat wake. The Tbar also picks up air from carving quickly from one side to another when it is too sharp on the leading edge. I am also concerned with the hole depth, and if you try to force it you will strip out the holes. Shorter bolts are for sure needed. You can call sky ski to have them ship you one, or as you say grind one down. My concern first an foremost is that these are tuned correctly, and the big problem is there are different water temperatures that will ride better with a sharper or more dull edge. Personally I think that if you tune a tbar perfectly you can get it to ride great in both. Unfortunately it doesn't always come perfectly tuned, and part of riding high end hydrofoils is ultimately you need to know a bit about tuning. When fixing this bar yourself, you have to make sure you are consistent up and down the leading edge, and you get a perfectly round edge from your tune. Also pay attention to the wings. Leading edge of the front wing needs to be slightly dull like the strut of the Tbar, and sharp but not so sharp it will cut you on the trailing edge. The rear wing needs to be sharp on both leading and trailing, but again no edge should be so sharp it cuts your hand. It should just be a bit uncomfortable to hold or to press your hand on it, but if you slide your finder down it you don't bleed. any sharper and it is dangerous. good luck with the mods. I hope it goes well. Just curious, where did you get the Arc from?
    Geno, Thank you for the tips, I plan on dulling the leading edge a little, shorten the bolts and leveling out the fuselage before I ride it again on Friday. If that does not seem to help I will seek professional help tuning the tbar because I don't feel comfortable going any further. Don't get me wrong, it rides decent but it just has a few issues. Your explanation of picking up air bubbles makes sense but the flutter/glitching seemed worse at the wake vs. right behind the boat in the bubbles. FYI, the water temp I am riding in is in the mid 70's.

    I ordered the tbar direct from Skyski back in October and just got it a few weeks ago. Sounds like I should have ordered it from you and had you tune it for me.
     
     

  9. #39
    Foilforum Addict EricR's Avatar
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    I watched Shu work on a brand new XAir DD at PI... The DD is machined by SS and I believed tuned by XAir? The DD also needs to be dulled down to ride well. Going through the AC tour with Collin and seeing their tbar's leading edge radius done by the mill in such a way that the strut just needs to be blended into the leading edge seems like a good method for consistency. I use to be a big believer and Gary's sharp FT tbars as they always rode great for me in the water I rode in. When the tbars got thicker, and my river's current sped up I found my FT's not riding like they use to. However, the AC tbars in the same conditions rode great. I am now a believer that duller is better! Keep us posted on the Arc and if you decide to bring your Arc to have Collin work on it let me know. I can give you a tour of the Strip!
     
     

  10. #40
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    I have had the wake cause issues as well in the past with improperly tuned foils. Typically it is from all of the movement in the wake from the boat, and with the water moving in so many directions it again increases the likelihood of a glitch. Combine that with the bubbles from the outside wake and it will take you out if not tuned right.
    I didn't know they sold any arc bars prior to a few weeks ago. Hope your tune goes perfect.

    Quote Originally Posted by Drossiter View Post
    Geno, Thank you for the tips, I plan on dulling the leading edge a little, shorten the bolts and leveling out the fuselage before I ride it again on Friday. If that does not seem to help I will seek professional help tuning the tbar because I don't feel comfortable going any further. Don't get me wrong, it rides decent but it just has a few issues. Your explanation of picking up air bubbles makes sense but the flutter/glitching seemed worse at the wake vs. right behind the boat in the bubbles. FYI, the water temp I am riding in is in the mid 70's.

    I ordered the tbar direct from Skyski back in October and just got it a few weeks ago. Sounds like I should have ordered it from you and had you tune it for me.
     
     

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