A new rudder for the little DeFever

The rudder on my boat is way too small. I think the 2 previous owners just learned to live with it.

I tracked down the man who ran the DeFever 40 assembly line at Jensen Marine and he said that since most of the hulls were twin engine it was possible my boat (a single) was shipped with a single twin rudder. Sigh.

I've talked with Mr. DeFever and he says it sounds like my rudder is too small, but that he does not currently have access to his drawings from the 70's.

So I'm building a new rudder. It's not finished but if you would like to see my progress to date click on the link below.

I did the calculations on the shaft myself, and hired Eric Sponberg, N.A. P.E., Univ. of* Mich, MIT grad to back me up.

More work ahead. The Aquamet22 shaft costs 62 USD a foot!

I need to machine a keyway in the shaft, and weld a plate to it. I've found a company 80 miles away that builds rudders for production sailboat builders and uses a proprietary 20 pound foam. I may take it to them, or I may use 16 lb foam from US Composite. Not sure yet.

Visit Fullstep Warning - I'm not much of a web site designer.

Edit link fixed. Colons are important

Mike
Palm Coast FL


-- Edited by Mike on Thursday 23rd of February 2012 09:29:49 PM

Hey Mike. Great looking work. Keep us posted.

Wow, very impressive work. Keep the pictures comin, love to see the steps.

Metal OTS rudders are avil'able if a flat plate of larger size would do.

why are you not using metal for this? What will you use to keep the shaft from slipping (rotationally) in the rudder?

twiisted71 wrote:
why are you not using metal for this? What will you use to keep the shaft from slipping (rotationally) in the rudder?

Click to expand...

*The rudder on my littler Defever is metal.

Very nice workmanship , Mike

twiisted71 wrote:
why are you not using metal for this? What will you use to keep the shaft from slipping (rotationally) in the rudder?

Click to expand...

*pins

Here are my DeFever 48 rudders

I could have welded ½ inch SS to the leading and trailing edges and kept the balance point at 18% to increase the area, but I wanted a NACA foil section - specifically a 0012 section, with a McLear/Thistle trailing edge.

I have equipment to roll sheet metal in my shop, but the thickest stainless I can roll is 090 - way too thin. I can roll aluminum up to 150 thou but for obvious reasons I'm not making an* aluminum rudder.

So in this place, and at this time the quickest way to a new rudder was epoxy/glass. I have spent very little time on it - the frames for the mold were made on a CNC router with almost no human intervention. Because they were so fair it took no more that 2 hours to build the mold.

45 min for my wife and I to lay up each skin. One hour to glass them together. No fairing was required except on the leading and trailing edges - 4 hours.

The longest job will be welding the 12 by 24 plate to the shaft. Once the shaft and plate are positioned in the rudder shell I'll wet out 1708 and roll it up - like the cardboard tube in a roll of paper towels. These are slid between the plate and the skin and set up in place.

After that the whole rudder gets filled with 20 lb. density 2 part foam. For comparison most foam used in boat construction is 2 lb. density. 20 pound is really hard - you can not dent it without a hammer..

Finally, the upper end plate gets glassed on and the rudder is done.




The new rudder will be equal in size to a DeFever 41, which is almost an identical boat.

Thanks for the kind comments on my work. I'm not sure if I own multiple boats because I like to use them, or just work on them.


Mike
Palm Coast FL*

OK now I see. It is going to be like a reg. rudder you are just going to put a fairing around it to give it a more efficient shape. At first it sounded like you were just going to try to attach a f'glass form to the shaft.

Mike,

Very nice job!* I wanted the McLear thistle cross section to improve the low speed handling on our tug (30' Sundowner) and downloaded the Dave Gerr rudder article in Professional Boatbuilding.* It was an easier task for me as I simply built a poplar cored thistle shaped sandwich to go over the existing flat plate rudder (no end plates or center ribs on mine.* I'm sure that the CNC mold making process sped things up a lot, but I still managed to crank mine out in a couple of days working time.* How did you calculate the McLear cross section?* If you'd like, you can take a look at mine on our club website* *http://www.sailangle.com/group-forum/topic/id/1871

Rick H on the hard in Chicato

Finally got some time to work on the rudder project -

This morning I milled the tiller arm keyway. It’s such a simple job I used a manual mill rather than a CNC.





Next my business partner welded the plate to the Aquamet22 shaft - I don’t know how to weld.





Welded plate -





Shaft and plate in rudder shell -






Next, a little glass work to lock the plate in position, and then a 16 pound density foam fill. Finally the top plate goes on.


Haul and install. And report success or failure.


Mike
Palm Coast Fl
DeFever 40

Thanks for the update and especially the photo's. They gave me the inspiration on how to solve a nagging little problem at the shop with something totally different Monday morning.

Time to dust off my mill

Nice job! I wish I had your shop, and your skill to use it.

If that does not work to you satisfaction, may want to convert to a fish tail trailing edge?

HopCar said:

Nice job! I wish I had your shop, and your skill to use it.

Click to expand...

HopCar - Drive up to Melbourne and I'll let you play with any of my tools, provided I can come down to Miami and wander around in your place. I'll bet you have a lot of things that would interest a boat owner like me.

Mike
Palm Coast FL

Mike, Drive down tomorrow! We're having a "Kick Off the Dolphin Season" event this weekend. We served Churassco steaks on Friday, Roasted Pig today and Sunday is Swordfish steaks.
John Graviskis from Ship Shape TV came by today, did some filming and ate some pig.