Johnson 18 Rudder

[Carson Downing]

Hello everyone,

I’m considering replacing the stock rudder with a 505 high aspect rudder from Fast Composites.

I have been in contact with a rep and he thinks the 505 rudder would have better bite and solve the cavitation issues at speed.

What do you guys think? The rudder is 7” wide and 45” deep. So a little deeper and a little narrower.

Link: http://www.fastcomposites.ca/site/marine/foils-a-z/505-international/

[Rick Paullin]

Sounds like an interesting idea. I know the extra length would definitely help when the boat heels upwind and the stock rudder loses bite. I'm not so sure about the decreased chord length - that might tend to cavitate a little more.

The 505 is a pretty light weight boat, so it doesn't take much side force to turn, while the J-18 is heavier and has a LOT more wetted surface area. But I've only sailed a 505 once, in light air, so I might not realize the forces on it at speed.

There's a long-time 505 sailor in North Carolina who used to own a J-18. He did some work on his stock foils, re-shaping them to more closely match the 505 profiles. I can give you his contact info if you'd like to ask him.

[Brendan Watson]

I had a 505 and a J-18 at the same time and compared a Waterat 505 rudder with the Johnson's. Heres a picture.

I spoke with Larry Tuttle at Waterat about the suitability of the swap. He was familiar with the J-18 and of course the 505, and his feeling was that the 505 board was a little small in the chord for the Johnson but that the Johnson would benefit from the greater depth. I sold the 505 shortly after getting the Johnson so away went the rudder never tried. I still have a nice old-school, Lindsey rudder from a 505 that I did try. Its about the same depth as the Waterat but a little thicker chord and straight, not tapered. It sailed well on the Johnson for the most part and was no doubt a far less draggy shape but it would cavitate and stall upwind when the wind came up and the boat heeled, so I ditched it for the stock rudder which for me only cavitates sometimes downwind and can be coaxed back with a couple pumps of the tiller. Very unsettling no doubt.

I second what Rick says. My bet is that a rudder more like the VX-One would be a better choice. Its bigger (more chord at depth) than the 505 rudder and a far more efficient shape than the stock Johnson rudder which is pretty crude by comparison. 505's are about half the weight of the Johnson and half the wetted surface so I think the Johnson needs more bight than the 505 especially with the extra beam. Just my 2 cents.

Cheers, and thanks for the great videos!

[Carson Downing]

Wow, sweet to see them side by side. I agree, the high aspect rudder looks pretty narrow next to the Johnson's. The only other idea I had was to get the Cassette version of the rudder, which is foil shaped from top to bottom. If I got that one, I could actually push it a few inches deeper than it was originally intended too, so I could gain some more surface area. You think the same surface area and less chord width would have the same bite as the stock?

Otherwise it is about double the price to have a new rudder designed and made from scratch, which is most likely the best bet. Or I could go with just a milled foam core and do all the glassing myself for a little cheaper than the 505 rudder.

Carson

[Carson Downing]

Well it looks like I can get a VX One rudder for cheaper than a 505 or having a rudder built. I just need to find someone willing to ship to U.S. Boat specs are actually very similiar!

Will post back when I have more info.

Carson

[Carson Downing]

No luck on the VX One rudder. You can buy one but it is 1k before shipping, so I will most likely wait on that. I do think it would be a great upgrade for the boat though.

[Rick Paullin]

Have you looked at old rudders for an I-14 or a Hobie 18?  Maybe a Tornado?

[Carson Downing]

I did find an F18 rudder when I was looking, but I figured they would be too short considering cats have dual rudders. I'll have to look into the dimensions.

[Rick Paullin]

Good call on the F18 -- the size might be decent because they steer while flying a hull.

And they've got to be a better shape than the stock J18 rudder.

[Carson Downing]

Well I can get the old style F18 rudder from Murray's for 375, or I can get the new style with carbon trailing edge for 575.

The dimensions on the old style are 37.5'' length, 8.5'' wide chord, and about an inch in thickness. The guy I talked to wasn't really sure if that length was wetted length, or overall length. I'm guessing it is overall length, which would mean it is a little shorter than the Johnson's Rudder. Will try and get some feedback from some F18 owners on a forum maybe?

I ended up hearing back from Bennet Yachting and they wouldn't sell me a VX One rudder because of proprietary issues I guess. Kind of a bummer that they wouldn't help out.

Carson

[Rick Paullin]

Sounds like that's overall length (Hobie 18 is 34" overall).

I'll bet you could get a bit more depth by adjusting the F18 rudder lower in the aluminum J18 rudder housing.

Or, get a foiling rudder and add a T-foil to the centerboard!

[Carson Downing]

Well, I think this is actually going to work. I got the measurements for the F18 Infusion rudder. It should actually stick about 1.5-2 '' deeper than the stock rudder. It is a little bit narrower, with a little smaller wetted surface area than stock. It looks like the wetted depth on our board is actually only around 29". I'm estimating that the stock foil's wetted area is around 255. So it is about 25 more than the Nacra foil.

I'd bet the Nacra blade is an awesome foil, considering the speeds they are capable of. This should give me better flow at speed and a little extra depth to help upwind. 

[Rick Paullin]

Sounds like a plan - a little more depth, a little less drag, and hopefully the foil shape will reduce cavitation - nice!

[Carson Downing]

Drawn to scale over the stock rudder. It should be perfect!

[Chris Herbster]

I am looking forward to hearing how this works out!

Chris H

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[sl...@ilinkusa.net]

I look forward to seeing what you come up with.

To post to this group, send email to johnson-18...@googlegroups.com.

[Carson Downing]

 

Nacra rudder arrived and it's an awesome looking foil. The trailing edge is 1/16" thick! Hoping to get it modified to fit in the stock 18 rudder housing in the next couple of weeks. 

[Mark Griffin]

I’m jealous.  I still have ice on our lake up north (and 15”+ of snow) so no sailing for a while for me. That said, I’m new to my J18 (purchased last year) so still getting acclimated to it.  However, even with limited time on it, I can see exactly why you’re making the upgrades.  Love my boat. Yours will be better.

Best to all,

Mark

Sent from my iPad

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[Scott Law]

Carson is the Thickness correct to just slip into the stock head?  Is the only MOD you need to make, is the hole alignment.  Can you send where you got that and the part number?

 

Scott

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[Carson Downing]

The Nacra rudder is about 5/16” thinner than the J18 rudder. I bought a couple of 1/8” Delrin plates that will go on either side of the rudder to accommodate the gap. I plan on making templates when everything is done and tested that I can supply to anyone wanting to do this mod.

https://www.murrays.com/product/56-4598/

[Carson Downing]

Rudder is done. I ended up having to modify the Rudder housing a bit to accommodate the narrow chord width of the F18 rudder. If you are going to do this mod, I recommend getting 3/16'' thick Delrin instead of 1/8'' for the spacers. I just added 1/8'' spacers at the lower transom pintle to compensate. It works just like the stock rudder, you have to drill a few holes, but it works great. I have the templates on the delrin pieces, so if you are going to give this a try, just shoot me a message and I will send them to you.

Anyway! I took it out for a sail in 10-15 yesterday and I was pleasantly surprised. This thing slices through the water with almost no turbulence at the trailing edge. I was reaching with the chute up with complete confidence. No cavitation and no stalls upwind so far. I even had a roundup upwind and was able to keep helm. I will report back when I test it in 20+ knots of breeze. So far so good!

[Carson Downing]

I'm sold on the rudder, we went out for a sail in 15-25 yesterday with no problems, the boat just feels great. No cavitation whatsoever, this rudder rocks. I can finally beam reach in heavy air with confidence. The most interesting thing is that you can actually feel the helm now, the rudder doesn't feel numb like the stock one. I may try messing around with rudder rake a little to see what is best, but it is feeling pretty good right now. Got close to my speed record of 18.1kts boat speed!

[Scott Law]

Carson, have you gone to a permanent forestay wire on the boat? Also, are you interested in making another Spinn launch tube?

 

Scott Law

(405)520-2442

 

From: johnson-18...@googlegroups.com [mailto:johnson-18...@googlegroups.com] On Behalf Of Carson Downing
Sent: Wednesday, April 25, 2018 10:11 PM
To: Johnson 18 One Design -2018
Subject: Re: [johnson-18] Re: Johnson 18 Rudder

 

I'm sold on the rudder, we went out for a sail in 15-25 yesterday with no problems, the boat just feels great. No cavitation whatsoever, this rudder rocks. I can finally beam reach in heavy air with confidence. The most interesting thing is that you can actually feel the helm now, the rudder doesn't feel numb like the stock one. I may try messing around with rudder rake a little to see what is best, but it is feeling pretty good right now. Got close to my speed record of 18.1kts boat speed!

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[Carson Downing]

Scott,

I have not gone to a permanent forestay. Mainly, because I love the ease of the furler enough to negate any benefits from mast rake.

I don’t think I’ll make any tubes for sale at this point in time, it was a ton of custom work and I don’t think there are a lot of people who are willing to cut their bulkheads. I may consider making more in the future if the right price was met.

Carson

[Scott Law]

Carson, 

Call. 405 520-2442 if you have time.  Your miss understanding the forestay.

Scott

Sent from my Sprint Samsung Galaxy Note8.

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[Aaron G]

So I think I'm going to go ahead and get the first gen nacra rudder from Murray's. My question is that since I no longer have my stock rudder with the original bracket, do you think the nacra bracket would fit on the j18 or am I going to have to come up with something new to fit?

[Scott Law]

This is Scott.  You will have to come up with something new to fit.  Have you called Catalina yet and asked if they have a rudder head and rudder in stock?  If you are interested in selling the whole boat and trailer as a parts boat, you can call me at 405-520-2442.   Thanks.  Scott 

Sent from my Sprint Samsung Galaxy Note8.

-------- Original message --------

From: 'Aaron G' via Johnson 18 One Design -2018 <johnson-18...@googlegroups.com>

Date: 7/22/18 12:18 PM (GMT-06:00)

To: Johnson 18 One Design -2018 <johnson-18...@googlegroups.com>

Subject: RE: [johnson-18] Re: Johnson 18 Rudder

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[aaron gralnik]

I'll give you a call here in a bit.

Aaron

781-864-6058

Sent from Yahoo Mail on Android

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[Scott Law]

Aaron my email address is sl...@ilinkusa.net

Scott Law

-----Original Message-----
From: 'Aaron G' via Johnson 18 One Design -2018 [mailto:johnson-18...@googlegroups.com]
Sent: Sunday, July 22, 2018 12:18 PM
To: Johnson 18 One Design -2018
Subject: RE: [johnson-18] Re: Johnson 18 Rudder

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[Carson Downing]

You would have to make a custom mount. It should be pretty simple if you buy new pintles. I also don’t know how well the first gen rudder will work, I installed the updated version.