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Mast Rake traditional measurement |
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DJgun
Commander Joined: 04 April 2020 Location: SydneyAustralia Status: Offline Points: 150 |
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Posted: 22 March 2021 at 01:44 |
Lots of mention is made of the North Sails document (which is no longer available) for setting mask rake. However this assumes the mast foot is standard etc., and compares hounds height to firestay length.
I have a problem with Huka, that she has too much weather helm and will round up with even 12-14kn and a competent mainstream trimmer. This boat has cockpit mainstream traveller. The mast appear to have ben shortened at some stage by previous owner, probably because of the common foot damage.
The more traditional way of measuring rake is to use a weight on the main halyard, and measure the distance from halyard to back of mast at the foot.(minus the distance of halyard exit to mast face at mast head). This technique is independent of mast length. Does anyone have this traditional mast rake measurement for 2005-2007 Hanse 400 or 400e? |
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Captain Cook
Admiral Joined: 23 May 2006 Location: Denmark Status: Offline Points: 1009 |
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Freya H400 #27 (2006), 40HP 3JH4E, 2-cabin, 3-blade Flexofold, Aries LiftUp Windvane, Exturn 300, Jefa DD1,Simrad NX40,Icom M603(VHF)+M802(SSB)
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DJgun
Commander Joined: 04 April 2020 Location: SydneyAustralia Status: Offline Points: 150 |
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Thanks Cap. Cook.
I hadn't seen the IMS rating for the 400 before. What I find interesting is the difference in J dimension in particular recorded as 4.62m, whereas my 400e has J=4.35. The measurement I am looking for is not recorded under measurement systems because it changes according to light weather/heavy weather etc. I am looking for mast rake, measured either as an angle from vertical, of line from max hoist point on mast to bottom rear face of mast. The way that is normally measured (when there is no wind), is to hang a weight (1/2 bucket of water maybe) using the mainsail halyard. The bucket is lowered until just above the deck, the the distance from back edge of mast to the centreline of halyard is measured in mm. Knowing the height of the mast the actual rake angle can be calculated. Actually the distance of the halyard from back of mast is a more accurate way to measure the rake, which is affecting the longitudinal centre of pressure. This has just as much effect on how the boat performs as differences in rig tension. if the distance is too much the boat will have too much weather helm and be slow due to rudder drag. If that distance is too small there will not be enough weather helm, and there won't be enough lift from uderwater foils. I have used this method racing Etchells, because the North Sails method has too many areas for error. In the case of Hanse 400 where J or any other mast dimension is different to North Sails base boat, the North rake dimension will be wrong. This direct measure works even when J is different, or the mast has been cut a little bit for repair I am hoping that forum members can measure the rake on their400/400eso we can fine tune the best rake for different conditions.
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DJ Sailor Ordinaire
HIN DE-HANJ0331J708 |
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