Rudder thickness

[DavidD]

Dear all

I am new to the forum - Sorry to start a new post. Also apologies if this topic has already been covered but I have searched for hours.

Can anyone tell me how thick they have built their rudder. I have no problem in designing it but I just need to determine t (the maximum thickness relative to the chord).

The class rules has no limits and I was thinking of around 40mm (1.57 inches for you guys in the Northern Hemisphere) but this was only fairly arbitrary. I have a good supply of cedar which is 400 in width so it will be very convenient if 40 mm works.

It does look very tricky. The keel is pretty straight forward but the tape in the rudder will be challenging.

BTW, I am envious of you guys in the USA. There are some great prices on carbon over there but they don't ship everything to Australia. At the most, they will ship carbon tape so at least I can get that.

Kind regards

David

[jray]

I had a company from Canada do the rudder and cassette. CCI, Competition Composites Inc. Without measuring I think the cross section on my rudder might be 1 1/4" lots of builds used a naca foil #12. There are programs you can run to get the profile. I believe my rudder was based off the naca 64 section, a little thinner then the 12 profile.

Crazy that C-Tech doesn't export to Australia. I was under the impression that there are several boats down there using their carbon products.

[ryderp]

I used a foam core with an SD 8020 foil, which has a thickness of 10.1% of cord. I got the foam inserts from Flyingfoam.com, but you could plot the shape yourself. By the time that I added a couple of layers of unidirectional carbon fiber and a couple layers of CF sleeving, plus some fairing compound, the foil is about 1.25" thick. The rudder foil came out beautifully and was probably the best fabrication of my entire boat build.

[DavidD]

Thanks for your replies. It seems that 40 mm might be a touch thick. I will redesign.

CTech does deliver to Australia no dramas. I think that will be the way to go but that's a long way away. But there are heaps of online sites in the USA offering carbon cloth online but don't ship to Australia. Carbon is soooo expensive here.

Kind regards

David

[Chad]

One US supplier that seems willing to ship to Aus is Soller Composites:
http://www.sollercomposites.com

A (former?) i550 builder is Josh ("shazza"), who took a job at an Aus composites supplier not too long ago- you could bug him for i550 "family" pricing...

[Tim Ford]

And I might add, you never have to apologize for starting a new thread! We have tons of bits and bytes of room left on this board and redundancy is not a bad thing!

Here's a really cool foil generator on-line:

http://airfoiltools.com/airfoil/details ... ca0012h-sa

I used the NACA0012, myself (which is NOT the one shown when you first load the link, above)

...good luck!!

[micah202]

....I modded my rudder from the original ~3' depth,,1' wide,,1 1/2'' thick 'barn-door',,,

,,,,to 3'9''depth,,,11'' wide at top,tapering to ~8''wide x ~1/2'' thick at the bottom .....


...the blade grips very well when the boat's healed now,,,,,
..............anything much less than 4' and you'll be regretting it!

....http://www.flickr.com/photos/59103003@N ... otostream/
....http://www.flickr.com/photos/59103003@N05/9281114712

[Chad]

To add another data point, mine is 46" deep (beyond the hull) and has a 10" chord and is just less than an inch thick. It works in all but really light drifting conditions, and has no problems with heel -or maybe I'm more active with the sheet? Haven't been downwind in breeze yet, so that test is yet to be passed.

--all this without using the gybulator, of course

[micah202]

To add another data point, mine is 46" deep (beyond the hull) and has a 10" chord and is just less than an inch thick. It works in all but really light drifting conditions, and has no problems with heel -or maybe I'm more active with the sheet? Haven't been downwind in breeze yet, so that test is yet to be passed.
--all this without using the gybulator, of course

.
.............. the difference between the shorter and longer depth was the difference between loosing traction a 'bit early' when sailing high angles with chute.

.....sheeting and anticipation were useful with the shorter blade,,but with my handing the helm to irregular crew on downwinds,sometimes that anticipation isn't there.Now it's easy-peasy!!!


.....I've added a few more pictures to my album showing the rudder some more.... http://www.flickr.com/photos/59103003@N ... 076955693/
....go to 'sets' for more i550 pics

.

[ryderp]

I climbed inside my boat this morning to measure the rudder (which is put away for the season). Mine is almost exactly the same length at 5' long (not counting the lifting handle) and 3' 10" below the surface. I don't recall how I came up with the length, but it was probably from discussions on this board.

[micah202]

I climbed inside my boat this morning to measure the rudder (which is put away for the season). Mine is almost exactly the same length at 5' long (not counting the lifting handle) and 3' 10" below the surface. I don't recall how I came up with the length, but it was probably from discussions on this board.

....nice!--- 3 i550 owners agree on something!! ........rudder depth 3'9'' within 1''