DF photo logo: Dragonfly Trimarans User Forum  
 
   Magnifying glass
Search the Forum
           
Rudder downhaul cable

 
Post new topic   Reply to topic    Dragonfly Trimarans Forum Index -> DF35 Hull
View previous topic :: View next topic  
Author Message
EarthBM



Joined: 17 Sep 2010
Posts: 196
Location: USA, So Cal -- So Florida

Rudder downhaul cable   Posted: Mon 29 May 17, 19:24    Reply with quote

I got a couple splintered strands in the cable that connects the rudder itself to the downhaul line. So remembering Larry's advice I want to replace it, but the eye fitting doesn't get through the 90-degree elbow in the metal tube. I could just cut the cable and replace it with one that has one of the eyes removable on a thread. Is there an easier/better solution?

Does anyone know the length of this cable?

A pretty mission-critical part, so has to be done right.
_________________
Ivan -- DF 35 #29 "Lykke"
Back to top
View user's profile Send private message
Mika Harju



Joined: 02 Nov 2006
Posts: 197
Location: Finland, Turku

Re: Rudder downhaul cable   Posted: Tue 30 May 17, 9:18    Reply with quote

Why not Dyneema?
I have had Dyneema downhauler for years now without any problems.
_________________
Mika Harju
DF1000 Racing #8
Back to top
View user's profile Send private message
EarthBM



Joined: 17 Sep 2010
Posts: 196
Location: USA, So Cal -- So Florida

   Posted: Tue 30 May 17, 18:13    Reply with quote

I am thinking about that. What diameter Dyneema do you use? Do you use thimbles and splicing to preserve breaking strength or just oversized rope?

At least on the 35 it goes through a 90-degree bend in the pipe and would rub against it (no way to have a block there). I guess the pipe is smooth enough not to chafe Dyneema, but there is no way to inspect rope for chafe in that pipe. Also when the rudder is turned all the way (as in heaving to) it would rub against the exit hole.

A little scary to lose steering if it breaks, but on the positive side much easier to repair.
_________________
Ivan -- DF 35 #29 "Lykke"
Back to top
View user's profile Send private message
Mika Harju



Joined: 02 Nov 2006
Posts: 197
Location: Finland, Turku

   Posted: Wed 31 May 17, 10:34    Reply with quote

In DF1000 there are no sharp edges to chafe the rope. My rope is over sized Dyneema SK75 diameter 5mm without overbraid , Brummelman splicings on the both ends. I am replacing it with a new one every 2nd year. My rudder is a One-Off without any fitting for the rope, just a hole near the leading edge for the rope.

How about double rope for safety? The primary one is for normal use and a secondary, just a few millimeters longer, is for backup? In DF1000 this would work if needed.
_________________
Mika Harju
DF1000 Racing #8
Back to top
View user's profile Send private message
EarthBM



Joined: 17 Sep 2010
Posts: 196
Location: USA, So Cal -- So Florida

   Posted: Thu 01 Jun 17, 0:46    Reply with quote

Great idea about the second rope! This way it will also give the signal that the first one broke (when the rudder slips aft)!

Thanks Mika!

One-off rudder? Just higher aspect ratio or something else? Have you considered adding winglets? I asked about them here: http://forums.sailinganarchy.com/index.php?/topic/173397-t-foil-rudders-on-non-foiling-multis and the responses are pretty positive.
_________________
Ivan -- DF 35 #29 "Lykke"
Back to top
View user's profile Send private message
Mika Harju



Joined: 02 Nov 2006
Posts: 197
Location: Finland, Turku

   Posted: Thu 01 Jun 17, 7:18    Reply with quote

Take a look at this topic:
http://dragonfly-trimarans.org/phpBB/viewtopic.php?t=690

I bought it from Canada, CCI Competition Composites Inc
http://www.fastcomposites.ca/site/marine/foils-a-z/dragonfly/

I can not recommend this factory . I designed the rudder blade and they made load calculations and engineered the core structure. The first rudder blade broke after 4 hours and 30NM. They made another for free, but the quality was not as good as in the first one.

Now they are selling my design without asking a permission from me. When we started I told them it is my design.

Now it has been in use for 4 seasons and every year I need to make some carbon fiber work to fix it.

Anyhow it is faster and the grip is much better at high speeds.

Yes, I thought about winglets and theoretically they would help but I rejected the idea because of rocks. We have shallow waters here and a lot of rocks. I hit a couple of rocks every year.

If you need 3D CAD models, photos or more information just ask.
_________________
Mika Harju
DF1000 Racing #8
Back to top
View user's profile Send private message
EarthBM



Joined: 17 Sep 2010
Posts: 196
Location: USA, So Cal -- So Florida

   Posted: Thu 01 Jun 17, 16:59    Reply with quote

Thanks Mika, looks like a good improvement.
_________________
Ivan -- DF 35 #29 "Lykke"
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Dragonfly Trimarans Forum Index -> DF35 Hull All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2006 phpBB Group
No responsibility is accepted by the publisher of these web pages for contents submitted by other people!
All Trademarks and Copyrights shown or mentioned on this website are herewith acknowledged.
Copyright 2001-2016 Bo Wetzel