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Measuring Mast Rake #79171
07/05/06 12:42 PM
07/05/06 12:42 PM
Joined: Mar 2006
Posts: 1,246
Orlando, FL
tback Offline OP
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Moving this discussion from "First Pics".

Quote
First trap measurement = hounds to bow tang. Set the trap at that (add some line if you need to)
Second trap measurement = First trap measurement moved aft to where it touches the deck. This is hounds to deck aft measurement and is equal to hounds to bow tang at foredeck measurement.


To be sure, you measure physically to the tang (bow), then to the center hull (aft); ie the aft measurement might be to the center of the deck hole (not from center hull forward to center hull aft -- which is okay if we keep consistent but does result with slightly different calculations).

When we compare numbers should we measure from the rear beam centerline? Might be easier and more accurate to measure from the aft-most part of the aluminum beam.

Last edited by tback; 07/05/06 12:43 PM.

USA 777
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Re: Measuring Mast Rake [Re: tback] #79172
07/05/06 02:22 PM
07/05/06 02:22 PM
Joined: Dec 2005
Posts: 443
Edmonton, Alberta, Canada
bobcat Offline
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I would think that the declarer would state his landmark.
He could be so much in front, so much behind, so much below transom etc. I have assumed that the edge was the reference point. Only when measuring a point on the beam would centerline be mentioned.

Re: Measuring Mast Rake [Re: tback] #79173
07/05/06 10:30 PM
07/05/06 10:30 PM
Joined: Jun 2005
Posts: 55
Wilmette, IL
Jamie Offline
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It's my belief, the greater distance from the two measurements, assuming it doesn't exceed 90 degrees, the more accurate the measurement. So I suspect, going from bow topside tip to middle topside stern would give you the most accurate measurement for a single style of boat. Haven't pulled out the calculator to confirm this, but just seems right.

Re: Measuring Mast Rake [Re: Jamie] #79174
07/06/06 01:41 AM
07/06/06 01:41 AM
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Essex, UK
Jalani Offline
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You're probably right, but given that most of us sail with some kind of aft rake, past efforts have shown on almost all classes that if you go from the tip of the bow, the aft measurement ends up behind the boat - not a lot of use! <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

Therefore cat sailors have established this 'protocol' that the forward trap measurement is always taken at EITHER the bow tang or at the deck above the bow tang in the case of boats with lowered tangs.


John Alani
___________
Stealth F16s GBR527 and GBR538
Re: Measuring Mast Rake [Re: Jalani] #79175
07/06/06 11:12 AM
07/06/06 11:12 AM
Joined: Dec 2005
Posts: 443
Edmonton, Alberta, Canada
bobcat Offline
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Ok boys, time to start talking numbers. I would like to start out but the computer is 60 miles from the boat.

With the intent of being to edit this later, I will now state that when I hold my forward trapeze line, after suitably extending it, to where the bow tang meets the hull, I find that my aft measurement is XX inches down the transom.

If I'm real keen, I will try to get some photo's to illustrate the thread with.

Re: Measuring Mast Rake [Re: bobcat] #79176
07/06/06 01:36 PM
07/06/06 01:36 PM
Joined: Jun 2001
Posts: 9,582
North-West Europe
Wouter Offline
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I always use the top of the deck next to the bridle tangs, not the tangs themselfs. Then I measure where the line touches to top of the deck on the rear.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Measuring Mast Rake [Re: Wouter] #79177
07/06/06 02:22 PM
07/06/06 02:22 PM
Joined: Mar 2006
Posts: 1,246
Orlando, FL
tback Offline OP
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I won't be able to take measurements until Gilligan's Run July 22.


USA 777
Re: Measuring Mast Rake [Re: tback] #79178
07/09/06 04:27 PM
07/09/06 04:27 PM
Joined: Jul 2005
Posts: 465
Oxford, UK
pdwarren Offline
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Did mine today: from the deck above the tang to the outer edge of the deck at the stern. I'm on the front edge of the rear beam. This is one hole more upright that I've sailed with up to this point - I'll let you know how it goes.

Paul

Re: Measuring Mast Rake [Re: bobcat] #79179
07/10/06 09:12 AM
07/10/06 09:12 AM
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Edmonton, Alberta, Canada
bobcat Offline
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So I have lost the ability to edit my previous post.
I measured and arrived at 3 inches down the transom. Looking at the picture I realize that I should have been closer to the pintles. But the idea is presented here. It's been a week and I haven't heard from VM on the concept that I can't rake forward enough.
[Linked Image]

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Re: Measuring Mast Rake [Re: bobcat] #79180
07/10/06 09:16 AM
07/10/06 09:16 AM
Joined: Dec 2005
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Edmonton, Alberta, Canada
bobcat Offline
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This is a pic of what I feel is extreme rake. Compare the mast to the flagpole and masts in the background. Strangely, I have not been aware of strong weather helm. The helm is so light that I'm not aware of a tug at all. It could be weather helming, it is just that it hasn't forced itself into my conciousness by needing two hands.
[Linked Image]

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Re: Measuring Mast Rake [Re: bobcat] #79181
07/10/06 09:38 AM
07/10/06 09:38 AM
Joined: Jul 2005
Posts: 465
Oxford, UK
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Quote
Strangely, I have not been aware of strong weather helm. The helm is so light that I'm not aware of a tug at all. It could be weather helming, it is just that it hasn't forced itself into my conciousness by needing two hands.


The other possibility is that your rudders are raked forward and that's concealing any weather helm.

Was your measurement from the tang, or from the deck above the tang? Not that that makes a huge difference (probably less than an inch).

In any event, it seems that my forestay is a little bit shorter than yours (presumably this is a European vs US thing).

Paul

Re: Measuring Mast Rake [Re: pdwarren] #79182
07/10/06 10:14 AM
07/10/06 10:14 AM
Joined: Dec 2005
Posts: 443
Edmonton, Alberta, Canada
bobcat Offline
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It was from the deck above the tang.

The rudder rake thing is something I haven't investigated. As far as I know, it isn't adjustable. I have the rope-based surf system and just pull them down and lock them.

Yesterday, I caught a race with winds in the high-mid teens (knots). Nice single-trapped ride, only a little extra downhaul pulled on. Downwind under spi was a bit intimidating. I am still avoiding trapezing and have yet to learn my angles. I gybed onto port way too late and the high reach scared me fierce. So I bore off deep for a while, doused it and sailed back to the mark on main alone. Certainly had lee-helm but only noticed it if I tried to put the stick down.

Re: Measuring Mast Rake [Re: bobcat] #79183
07/10/06 10:38 AM
07/10/06 10:38 AM
Joined: Jul 2004
Posts: 2,718
St Petersburg FL
Robi Offline
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Actually Bruce, your image looks about right compared to the ammount of rake I run. My mast leans pretty far back as well.

I am going to start sailing with my mast rake one point further foward.

As far as adjusting your rudders, the only way I think its posible for us, is by using plastic shims inside the rudder stocks.

Re: Measuring Mast Rake [Re: bobcat] #79184
07/10/06 10:45 AM
07/10/06 10:45 AM
Joined: Jun 2001
Posts: 9,582
North-West Europe
Wouter Offline
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Well I think we can conclude here that at least the rudders are perfectly balanced. Not unimportant I say.

I personaly FEEL that your rake it too much, 3 inches DOWN on the transom is alot, but I have no hard data to support that. I feel the line should touch the deck somewhere between the rearbeam and transom. Maybe we can have a sound-off with everybody giving their measurements ?

When I received the ordered stays for my boat I found the supplier misread the distances I gave him as well. But mine issue was the other way around. May mast was almost leaning forward. My forestay proved to be 130 mm to short and my sidestays were 70 mm to long. I made the forestay longer by looping a 4 mm lines several times through the eyes (I still use that same line) and I had my sidestays shortened by local chandler (while I was watching and checking) by having the old terminal cut off and a new terminal fitted. Now I'm all right.

How low are you on the forestay adjuster ?

How high are you on the sidestay adjusters ?


Quote

So I bore off deep for a while, doused it and sailed back to the mark on main alone. Certainly had lee-helm but only noticed it if I tried to put the stick down.


When confronted with this again, it is best to continue sailing optimal angles in the way of speed, then drop the spi and reach for the mark.

If you can make the mark by just pointing a little higher without collapsing or letting go of the kite then that is most efficient but when you CAN'T then the above approach is better, also in the way of time spend getting to the mark. Trying to do it both way simultaniously is NOT best.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Measuring Mast Rake [Re: Wouter] #79185
07/10/06 11:17 AM
07/10/06 11:17 AM
Joined: Dec 2005
Posts: 443
Edmonton, Alberta, Canada
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Quote

How low are you on the forestay adjuster ?

How high are you on the sidestay adjusters ?

Wouter


I only have 1 hole left to me on the forestay for more forward rake.
On the sidestay StayMasters I am currently at 8.5 where 10 is the longest.

Re: Measuring Mast Rake [Re: bobcat] #79186
07/10/06 01:38 PM
07/10/06 01:38 PM
Joined: Dec 2005
Posts: 1,121
Eastern NC, USA
T
tshan Offline
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I think it looks fairly dramatic. I'll try to measure my set up this weekend and forward it on for comparison.


Tom
Re: Measuring Mast Rake [Re: bobcat] #79187
07/10/06 05:38 PM
07/10/06 05:38 PM
Joined: Jun 2001
Posts: 9,582
North-West Europe
Wouter Offline
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I checked the settings of one EU Blade F16 just now. Using the method describe with top of deck variation, it touched the rear egde of the inspection hatch. It still looks like a considerable amount of rake but less then yours. Boat felt well balanced to me when I sailed it and the owners are getting faster and faster..

My own boat (modified Taipan) has now very little mast rake. The mast is almost straight up, I'm well ahead of the rearbeam when measuring. Uni-rigged it handles very well that way. I changed it at the beginning of this season. Haven't done to much sloop sailing yet this season and it may be a little too much forward for that. But I will know after this weekend I guess.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
Re: Measuring Mast Rake [Re: Wouter] #79188
07/10/06 08:08 PM
07/10/06 08:08 PM
Joined: Jul 2004
Posts: 2,718
St Petersburg FL
Robi Offline
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I cant wait to get mine measured up!!! I am sure I am close to what Bruce (UNICAN - Bobcat) is running. I remember by looking at the boat. Plus I am at usually between 2 and 1 on my chainplates.

Re: Measuring Mast Rake [Re: Robi] #79189
07/23/06 04:28 PM
07/23/06 04:28 PM
Joined: Mar 2006
Posts: 1,246
Orlando, FL
tback Offline OP
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okay, measured my mast rake at Gilligans Run.

My previous rake produced significant weatherhelm. After measuring I can understand why.

Measured from the Bridle Tang (center top of hull) then pulled back to centerline of rearhull, my measurement went down the aft transom about 2". This setting was with the forestay halfway down (5th slot).

For the day I took the forestay down 2 additional slots (which had mast rake measurement on the top-aft hull 2" behind the port inspection lid). The helm was much better (only slight weather helm)....just wish the adjustment could correct capsize(s). <img src="http://www.catsailor.com/forums/images/graemlins/crazy.gif" alt="" />


USA 777
Re: Measuring Mast Rake [Re: pdwarren] #79190
07/27/06 10:18 AM
07/27/06 10:18 AM
Joined: Jun 2005
Posts: 55
Wilmette, IL
Jamie Offline
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Wilmette, IL
Quote
In any event, it seems that my forestay is a little bit shorter than yours (presumably this is a European vs US thing).


The change that occurred is that the mast base became higher causing the forestay to be a little tight. I had to fight with mine initially to even get the forestay to the first hole. Talked to Matt because I know Robi's and Matt's are around 1 on the staymasters and I could get to maybe 7, so I knew something was different. Matt exchanged my forestay for a longer one and now I'm around the middle hole on the forestay and 4 on the staymasters. I'm carrying a lot of mast rake with the trapeze going 6 inches down the back of the transom. The boat feels good with very little weather helm. I did rake one of the rudders more forward to match the other. If I ever want to rake them back, I'll just glue in a piece of rubber. Also, my clew of my main must be cut higher as I have quick releases on both ends of the mainsheet blocks and I have yet to go block to block.

Jamie
Blade USA 714

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