My HDPE Rudder...

Zac Penn · Post by **Zac Penn** » Tue Aug 06, 2013 9:36 am

When we got the boat the rudder was in pretty bad shape. It was not secured properly when towing so it rubbed the asphalt for a while and the particle board was starting to split at the top so I just didn't want to mess with the fiberglass repairs.

So I used the original rubber as a template and sketched the outline onto a 3/4" thick piece of high density polyethylene that i had laying around the shop. The frame that secures the rudder to the tiller post has an inside opening of 1 1/2" so I cut some 3/8" PVC sheet to match the metal and keep the 3/4" HDPE rudder centered.

I know this isn't the best design fluid dynamics wise, but it will do for now. I did not have the $500 to buy a replacement HDPE rudder so as long as this one deflects the water and I can turn I will be happy. I still need to feather the leading and trailing edges and drill out the rope holes for lowering it but I couldn't wait any longer before i showed someone my creation!

Andiron120 · Post by **Andiron120** » Tue Aug 06, 2013 10:59 am

Looks really good to me, little bit of work around the edges with a belt sander or router and it should work as good as the original, if not better.

Zac Penn · Post by **Zac Penn** » Tue Aug 06, 2013 11:22 am

Thanks I am pretty happy with it. I was debating as to whether I should buy a large radius roundover bit or if I should just go at it with the belt sander.

What are your opinions on the leading/trailing edge shape of the rudder?
Radius on the leading edge seems to be very common, but I think a sharp leading edge would start the deflection of water quicker and make turning quicker. However it may make straight tracking harder and your hand would always have to be on the tiller?

Andiron120 · Post by **Andiron120** » Tue Aug 06, 2013 12:11 pm

I think I would stick with the conventional shape, symmetrical foil with the leading edge being rounded making it a bit stronger and more durable and more controllable.

Capt. Bondo · Post by **Capt. Bondo** » Wed Aug 07, 2013 9:13 am

Round over should be all you need, remember top hull speed if your lucky will only be 7kts.
With the narrow rudder body, you may experiance some water coming up through the rudder shaft/pipe the ropes that raise and lower rudder run through. Sometimes if I don't have the rudder all the way down, I get a little geyser out the top of the rudder shaft

tgentry · Post by **tgentry** » Thu Aug 08, 2013 9:54 am

That looks fine to me. Round the leading edge and taper the trailing edge and should be very efficient. I think a belt sander would be fine.

I don't know much about HPDE. Is that going to be stiff/strong enough for the forces involved?

With the 3/4" thickness, how are you attaching the retract and deploy lines?