Forum Home
IntroductionBrowse
Our MacGregorExploringArticlesAbout this Website
ManualsDealer InfoSailing LinksSupport this Website
Forum Home

Making rudders

A forum for discussing boat or trailer repairs or modifications that you have made or are considering.

Moderators: Paul S, tangentair, beene, Heath_Mod, Hamin' X, kmclemore, Catigale

Re: Making rudders

Postby Jimmyt » Thu Aug 09, 2018 7:46 am

Correct. NACA 0012 is symmetrical with the max width occurring at 30% of the length (fore-aft), and being equal to 12% of the length (fore-aft). Although our rudders taper top to bottom, I picked a section with 10" length so I could do the math. :) Thus, max width at that section is 1.2 inches. The rudder blade is a pretty good design and fabrication project - similar to building a hull shape as it is continually changing from top to bottom, fore to aft, and presumably maintaining NACA 0012 shape for most of the blade. I haven't checked other sections to see how well the mold was made, nor have I checked side to side symmetry. Can't find my profile match gauge since the fire.

You may have to compromise at the trailing edge, like Roger apparently did, to keep it thick enough to hold together.

Anyway, I'm not an aeronautical or marine engineer, nor am I a naval architect. But, I did get thrown out of a holiday inn last night. The body of knowledge on rudder design appears to be extensive, and the little bit I've reviewed shows a lot of variation from one source to the next regarding shape, size, foil/flat, mounting position, canted/vertical, single vs twin, etc.

One source stated that rudder size should be 1-2% of sail plan area. Based on a 241 sf sail plan (I didn't verify this number) and wetted area of both rudders of about 4.2 sf, the M has about 1.7% rudders (not accounting for heeling). So, it looks like Roger didn't wander too far off the path on the rudder area decision, anyway.

The wetted height/width aspect ratio of approx 3, is on the high side of at least one source's recommendation. This source says 2 is upper limit unless you're building high performance, which might get up to 3-4 range. Higher aspect ratios are reportedly prone to stalling at lower attack angles compared to lower aspect ratio rudders. This might be an area where some improvement could be made. Anybody got one of those exercise pools with a 5 knot current in it? All we'd need is a scale hull model and a selection of rudder shapes, and we could take a crack at figuring out what a better rudder might look like. My guess is, Roger didn't do a lot of tank testing on rudder design - due to the expense of it. We did some model testing on some of the labs we worked on and I was always amazed at the expense of it. If you feel that stock rudders are a problem, you could build a couple of different shapes and sizes and try them out. You wouldn't need to even put a finish on them as long as they are faired. That is one area most sources agree on - fairing is important.

Again, I'm not posing as a marine engineer, just relating what I found during my enjoyment of this thread.
User avatar
Jimmyt
Captain
 
Posts: 597
Joined: Sat Jul 18, 2015 11:52 am
Location: Mobile AL 2013 26M, 60 Etec
Sailboat: MacGregor 26M

Re: Making rudders

Postby beene » Fri Aug 10, 2018 10:49 pm

Ruddercraft PERFORMANCE rudder for my Mac 26m

https://drive.google.com/open?id=1BoNE4 ... 1f4V5xiuqf
https://drive.google.com/open?id=1p-eTx ... kKr8ro40O6

Made of plastic!
Both Snapped at exactly the same place just below the brackets.
Over stressed the rudder brackets, bent them out at the bottoms.

Fun.... :evil:

G
User avatar
beene
Site Admin
 
Posts: 2553
Joined: Tue Sep 19, 2006 7:31 pm
Location: Ontario Canada, '07 26M, Merc 75 4s PEGASUS
Sailboat: MacGregor 26M

Re: Making rudders

Postby vizwhiz » Fri Aug 10, 2018 11:00 pm

So I think I just found what I’ve been looking for with regard to a new rudder. An aluminum extrusion of a NACA0012 foil sized pretty close to what we need. It’s on duckworksbbs, called windknife... they have a full foil about 10.5” chord by 4’ long, and about 1” thick. Best part is that it is modifiable simply by deforming slightly (can be made thicker by stretching it). I’m thinking an square aluminum tube thru it from top to bottom, projecting out the top long enough to carry the bolt in the rudder bracket. That way it would swing up farther also. I am some kind of stoked about this!

They also have a nose section only, where a custom tail can be added simply. This allows customizing chord length and thickness. Good stuff here! I think it’s playtime!

http://www.duckworksbbs.com/product-p/wk-parent.htm
vizwhiz
Admiral
 
Posts: 1376
Joined: Mon Aug 23, 2010 11:48 pm
Location: Central Florida
Sailboat: MacGregor 26S

Re: Making rudders

Postby Wayne nicol » Sat Aug 11, 2018 9:55 am

thats an awesome find, love it.
how do you plan to finish tops and bottoms?
will the weight of the ali, counteract the natural buoyancy of the entrapped air.
or will you drill a hole in the bottom, like the mac rudders, so that they can fill and sink?
Wayne nicol
Captain
 
Posts: 611
Joined: Thu Feb 14, 2013 12:21 pm
Location: Queen CHarlotte Islands,B.C.---------------- lightning white 2012 26M "Merrylegs"
Sailboat: MacGregor 26M

Re: Making rudders

Postby jimmy alonso » Sat Aug 11, 2018 12:40 pm

Ruddercraft PERFORMANCE rudder for my Mac 26m

https://drive.google.com/open?id=1BoNE4 ... 1f4V5xiuqf
https://drive.google.com/open?id=1p-eTx ... kKr8ro40O6

Made of plastic!
Both Snapped at exactly the same place just below the brackets.
Over stressed the rudder brackets, bent them out at the bottoms.

Fun.... :evil:

Beene
I broke a rudder last May and bent this rudder post a number of times on my sailing trip. Last year the both rudder post bent and broke the bolts.
So this year had 2 new thin rudder posts we would bend the starboard post back to shape with a C-clamp daily, had 16 NM left of a 190 NM run to reach homeport when the rudder broke.
BWY told us that Macgregor some time after 2004 made rudder post thinner.
Old rudder post were 4.7 mm thick new post 3.4 mm. I'm waiting for a set of thicker ones to be made.
Aren't Rudder Craft rudders covered by a lifetime guarantee ?
I was thinking of getting a set, not sure now.

Image
Still enjoyed every minute :) :macm:
Image
User avatar
jimmy alonso
Engineer
 
Posts: 112
Joined: Mon May 02, 2005 11:27 am
Location: Puerto Rico, 2004 26M,Yamaha 50
Sailboat: MacGregor 26M

Re: Making rudders

Postby 1st Sail » Sun Aug 12, 2018 9:14 am

My concern has always been the rudder bracket. It appears they are not strong enough to handle a rudder with less flex and more surface area. Comments? MacGregor's seemed to be engineered to work with in a defined limit.
1st Sail
Captain
 
Posts: 505
Joined: Wed Dec 31, 2008 2:58 pm
Location: Moline, IL '06M 50hp Etec
Sailboat: MacGregor 26M

Re: Making rudders

Postby Jimmyt » Sun Aug 12, 2018 9:51 am

No question the rudder post and rudder on the M were business-engineered. If Roger managed to cut $100 off of 7,000 units, well - you get the idea. River, lake, and in-shore, you probably could use them forever. Bad weather, big seas, another story. Beene' s and Jimmy Alonso's photos clearly show it

Once you get into it, you will have to beef it all up. If you make the rudder bost, bracket, and rudder strong, it will probably pull the fasteners through the transom.

If I had a blank sheet of paper, I'd try a lower aspect ratio rudder, wider and shorter, but stick with a NACA 0012 profile. I feel like stalling is a problem, and a lower aspect ratio might help. I'd try it on the existing hardware first, though.

I'd like a cassette style bracket similar to Farriers - with shear bolts that allow the blades to exit the cassette if you hit something. These would have to be mounted outboard - which would impact the aesthetics. Also, you'd have to get the steering linkage worked out. Big project.

I'd want to be absolutely certain that it made a big difference before I tried it.
User avatar
Jimmyt
Captain
 
Posts: 597
Joined: Sat Jul 18, 2015 11:52 am
Location: Mobile AL 2013 26M, 60 Etec
Sailboat: MacGregor 26M

Re: Making rudders

Postby whgoffrn » Sun Aug 12, 2018 11:05 am

I have no idea what a person with an M model macgregor could possibly do to remedy the situation but for an x it's a much simpler fix that works .....where the rudder is recessed into the hull of an M I dont know what is feasibly possible ...it may still be possible to do what I did with my X iv modified .... look for "weak links in the macgregor post" and scroll to the last several pages (it has quite a few) to see the pics of the end product .... I've still not put the backing plates in that's this winters project... but I've had my x out in some fairly steep following seas and also tested the drogue out a decent amount and it works .... if there is any problem I see now it could possibly be the steering cable .... the rudders nor brackets flexed or broke but yet the steeper the waves the more I really had to work those rudders to correct the boats steering.... the drogue helped that part out tremendously
I know it probably seems like overkill for our boats but for me it's just additional safety equipment ....if I just went in lakes and ponds with my boat it wouldn't be an issue .... I carry both a drogue and a sea anchor ....... with the upgraded rudders brackets and soon to be backing plates I have SOME more confidence in the overall durability of the whole system however since they were made almost exact same specs as stock it still doesnt solve the problem of the near flat rear end wanting to slide and broach the whole boat ONCE the wave height surpasses the beam width of the boat .... so while the rudders and or brackets may not break the boat is still at risk for broach ...that's where the drogue does help out.... past that I carry a sea anchor for when its gotten so bad that it's a danger to navigate even with a drogue ....thankfully my sea anchor is collecting dust ......Roger's infomercial is a bit misleading showing the boat handling 18ft seas .... those were 18 foot almost rollers and the boat was going into them ...I would have loved to see how the boat handled with those waves as following seas
Last edited by whgoffrn on Sun Aug 12, 2018 11:19 am, edited 1 time in total.
whgoffrn
First Officer
 
Posts: 484
Joined: Tue Sep 30, 2014 11:55 pm
Sailboat: MacGregor 26X

Re: Making rudders

Postby vizwhiz » Sun Aug 12, 2018 11:13 am

Wayne nicol wrote:thats an awesome find, love it.
how do you plan to finish tops and bottoms?
will the weight of the ali, counteract the natural buoyancy of the entrapped air.
or will you drill a hole in the bottom, like the mac rudders, so that they can fill and sink?


So in my head i wasn’t worried about the top. The foil would start below the rudder bracket anyway, and that is turbulent water, so i don’t think it will impact anything significantly. Leaving it open just allows it to drain and air out. The bottom i would probably make a cap for, similar to the way people make a mast cap - with one portion as an insert, and a wider section that actually covers the bottom and serves as a shoulder to locate it. But i would drill drain hole(s), definitely, and mount it with a couple small screws or rivets. I’m thinking about 1/4” to 1/2” projection would be enough to protect the bottom from scrapes and keep stuff out of it. Just thoughts at the moment, but wanting to keep it simple.
vizwhiz
Admiral
 
Posts: 1376
Joined: Mon Aug 23, 2010 11:48 pm
Location: Central Florida
Sailboat: MacGregor 26S

Re: Making rudders

Postby Ixneigh » Sun Aug 12, 2018 11:37 am

How are you breaking those rudders?

Here is a link to images of my wood blanks.

http://southernislands.com/blog/uncateg ... d-rudders/

The tiny pic site has become unusable. Too bad.

Ix
User avatar
Ixneigh
Admiral
 
Posts: 1852
Joined: Thu Sep 09, 2010 1:00 pm
Location: Key largo Florida
Sailboat: MacGregor 26M

Re: Making rudders

Postby whgoffrn » Sun Aug 12, 2018 11:47 am

Lx did u have him use white oak???
whgoffrn
First Officer
 
Posts: 484
Joined: Tue Sep 30, 2014 11:55 pm
Sailboat: MacGregor 26X

Re: Making rudders

Postby whgoffrn » Sun Aug 12, 2018 11:57 am

Image

The oak rudder upgrade is one of my fav that I've done for my boat ... it may be a false sense of security but I really do firmly feel they are much stronger and it gives me the peace of mind to go that extra mile out knowing I SHOULD be ok if I get caught 15 miles out and weather turns bad ...it gives me the added feeling of safety to go out a bit farther and chase those bigger fish.
whgoffrn
First Officer
 
Posts: 484
Joined: Tue Sep 30, 2014 11:55 pm
Sailboat: MacGregor 26X

Re: Making rudders

Postby Ixneigh » Sun Aug 12, 2018 6:46 pm

Yes oak. Soon to have glass and epoxy, and a bronze pivit bushing for 1/2 pin. I was going to weight them, but if they float, it will make clearing the weed off them easier.

Ix
User avatar
Ixneigh
Admiral
 
Posts: 1852
Joined: Thu Sep 09, 2010 1:00 pm
Location: Key largo Florida
Sailboat: MacGregor 26M

Re: Making rudders

Postby whgoffrn » Sun Aug 12, 2018 7:40 pm

If u got white oak like I did...they sink like a rock ...they are heavier than the water they displace
whgoffrn
First Officer
 
Posts: 484
Joined: Tue Sep 30, 2014 11:55 pm
Sailboat: MacGregor 26X

Re: Making rudders

Postby Ixneigh » Mon Aug 13, 2018 4:47 am

Ok good to know. Any idea sourcing the pivit bushings?

Ix
User avatar
Ixneigh
Admiral
 
Posts: 1852
Joined: Thu Sep 09, 2010 1:00 pm
Location: Key largo Florida
Sailboat: MacGregor 26M

PreviousNext

Return to Repairs and Modifications

Who is online

Users browsing this forum: No registered users and 3 guests

Copyright 2004 - 2018 © HK Innovations