Hi,
I am trying to adjust mast rake as per original specs on my 1989 Prindle 18 for the first time.
My owner's manual specifies a 6-to-10 inch mast rake, measured from the aft side of the black line to the main halyard (with wrench straightening it down). The shorter I can get is about 20 inches, with the smallest 1/4'' shackle I could find at the forestay bottom attachment, forestay shortened to the maximum, and shrouds pined to the 5th or 6th hole from top.
1)My forestay was replaced 2 years ago, don't tell me they could have made it wrong!? What are your experiences with your Prindle forestays and mast rake?
2)Is there an other way to measure mast rake than with the carpenter level on trampoline? This technique doesn't seem very ...precise.
3)I am having big problems adjusting my rudders, the old stuff being very loose and Murrays parts being lost in the mail several times... I have also been trying to toe them in as per Hobie recommended, with very poor performance at my last race! Anyway, I just wanted to say that I can not tell if I have a ''mast rake'' helm because of the bad rudder adjustment. I can also say that the old Prindle was pointing more than brand new Nacras and Hobie Tiger Last year with same forestay... :)
Thank you!
Prindle 18 mast rake specs
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Posted: Jun 20, 2017 - 04:22 PM
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Posted: Jun 20, 2017 - 06:53 PM
Mast rake helm will result in a heavy pull or a push of the tiller... pull being the least of the two evils.
Just so were clear, we're talking about a Prindle 18 classic not a 18-2. If so, I just went down this road myself... for the life of me I was not able to find the sweet spot with no pull on the rudders.... for this boat... But alas this past weekend It seemed to have worked out...
Here is what I did...
1.) New rudder hardware on both the rudder itself and the casting... that include all new bolts and springs.. Rudder lock bolts are pretty expensive, but....
2.) I have the rudder adjusted to where this is -0- rake.... my straight edge is right in line with the leading edge of the rudder at the bottom of the rudder. I have had as much as a 1/4" forward the leading edge in the past.
3.) As for the mast rake, I have the turnbuckle turned 11 rotations from the out side... that is I took the turn-buckel apart, tuned in the top 11 rotations and tightened the nut, then did the bottom 11 times & ditto.. This is giving me a shroud adjuster setting of the third hole from the bottom.. I did a quick measurement of the forestay and got 20' 11 7/8" this if from the shackle pin to the bottom of the mast hound hole for the forestay.
I still get a little twinge of a pull to weather, but that is normal for these boats..
Let me know if this helps...
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John Schwartz
Ventura, CA
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Posted: Jun 22, 2017 - 01:23 PM
Yes, your forestay might be a little long, or the pigtail that it attaches to aloft, or the shackle at the mast hound above may be big. Measure them and Call Murray's or Salty dog and see what they think standard length is.
To measure, hold each end of the cable or pigtail with a screwdriver in the thimble and measure from the outside edge of the screwdriver.
With 20" of rake, your mast is not crazy out of whack, it is close to what some ocean sailers use in heavy air. If you end up replacing either the forestay or pigtail, keep it for use when you sail in heavy air and ocean chop.
Do not feel bad about buying fresh shrouds. By far the most common catastrophic failures are the shrouds and forestay.
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Sheet In!
Bob
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Prindle 18-2 #244 "Wakizashi"
Prindle 16 #3690 "Pegasus" Sold (sigh)
AZ Multihull Fleet 42 member
(Way) Past Commodore of Prindle Fleet 14
Arizona, USA
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Posted: Jun 22, 2017 - 07:44 PM
Lou, can't give you a stock measurement on the forestay, cuz I swapped mine out for a murrays furling kit. I have about 30 rotations on each side of the turnbuckle now. (With too few or uneven threading and you could be demasted). Maybe there's a shorter turnbuckle you could find at a riggers shop.
With 20" of mast rake, it seems like your rudders would need to be raked forward quite a bit to compensate. What is your rake setting now? Is there still room on the lock bolt to do this?
I recently spent a lot of time shimming and tuning the rudders to get all the slop out. I shimmed the rotation bolts and also the hole in the castings where the pintle sits. Nice and tight now. That should help with tacking and all points of sail.
Anyway, I started out with weather helm on the starboard tack side and ended up with a slight port lee helm at high speed, that I need to address now. Rudders are aligned and raked a little over -.25" Shrouds are set at the 4th hole from the top and pretty tight.
But here's the thing,..In the process of adjusting the rudder with negative rake, I was surprised to find that the kick up tension changed dramatically. The rudder became very hard to unlock/lock, all due to the slight change in geometry with the locking pin. (They become worn in one position over time). Rather than filing the pin head, I gradually stretched all the springs to allow for easy operation with the up down lines. It's an inexact science on this boat, and the setting that felt right on the trailer turned out to be a bit loose on the water. Fixing that now.
So my point is, it's ALL connected. But starting with fixing any rudder slop will make the rest more "scientific". HTH
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Prindle 18
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Posted: Jun 22, 2017 - 09:19 PM
How big if a turnbuckle do you have? Mine was good for 20 on the top and about 18 on the bottom... this was the replacement from Murray's
Edited by JohnES on Jun 22, 2017 - 09:20 PM.
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John Schwartz
Ventura, CA
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Posted: Jun 22, 2017 - 10:13 PM
Maybe a tad longer than the stock. The original non furling had about 35 winds in it judging from the tarnishing.
The Murrays kit required you replace the toggle end (bottom) with an eyelet.
That pins to the fuller top. A very tight fit, that leaves very little room on the Harken for the Jib downhaul line to pass through.
I don't want to steal Lou's thread. This is an upgrade, https://www.murrays.com/product/30-5061/
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Prindle 18
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Posted: Jun 30, 2017 - 12:13 PM
Wow you guys are devoted and helpfull!
(--->>> Prindle 18 CLASSIC)
I am slowly getting trough rudder system slops. Especially going full speed broad reach, I can feel (and ear) the rudders wobbling in their castings, after what they seem to get stuck on one side, braking the boat.
It is incredible how the mast rake influences the cat's helm. Half a day of testing and mast rake tuning (which can not really be achieved alone...) is definitively a good investment. I had a disappointing lee helm, trying to get to the user's manual 6-10 inch mast rake. I have not measured my new one, but I can tell it's around 20 inches. The forestay is tightened approx 2/3 of it's maximum run with short turnbuckle, and the shrouds as seen below. These may look upside down, but that's the way they are pictured in the manual... The cat is tracking straight like a train!!! ...going close hauled with the tiller extension bar just laying down on the hand palm, grip opened. That is satisfying! (For passing readers, note that I don't know if my forestay was copied exactly as per the original one).
For the moment, I can not ease the rudder rake because the locking mechanisms are worn out and the rudders kick up to easily. The adjusting bolts are 3/8'' from being completely screwed in.
What is the rudder rake consequences on boat helm, speed and handling?
Photos ... : https://www.thebeachcats.…ictures?g2_itemId=128201
Thanks!!
Edited by louispp on Jun 30, 2017 - 05:59 PM. -
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Posted: Jun 30, 2017 - 02:38 PM
I would get a copy of Rick White's Catamaran Racing for the 90's. There is a whole chapter on Mast Rake & Helm and dives into your very question..
https://www.amazon.com/Catamaran-Racing-90s-Rick-White/dp/1880871009
There is also another good book that details this as well: The Catamaran Tuning Guide
https://www.amazon.com/s/ref=nb_sb_noss/141-2093051-6630820?url=search-alias%3Dstripbooks&field-keywords=the+catamaran+tuning+guide
By the way, that is a very nice looking Prindle.
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John Schwartz
Ventura, CA
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Posted: Jun 30, 2017 - 05:13 PM
JohnES, thanks for the book suggestions. I have to try again, but last time they wouldn't ship to canada, even used ones, whatever website I tried. Something about the rights maybe.
I am indeed very proud of my Prindle. Nice Decals, great blue sails. Old boats need a lot of maintenance, time and money investment. You comment is very much appreciated! -
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Posted: Jul 01, 2017 - 08:59 AM
Check your local library
http://www.worldcat.org/title/catamaran-racing-for-the-90s/oclc/25998753
If they don't have it, they can get it with Inter Library Loan... ILL
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John Schwartz
Ventura, CA
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Posted: Jul 02, 2017 - 10:40 AM
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Posted: Jul 03, 2017 - 09:55 PM
Here'yago Lou,.. https://www.thebeachcats.…s/15/about-weather-helm/
This place is a treasure chest!
Thanks Damon.
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Prindle 18
96734
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