Need Advice to Complete My Steel Rudder

[raahell]

I appreciate the attraction of building from scratch. I would've done that if it were not for the 1st Mate's strenuous objections. So we bought a used steely and are basically doing a lot of the work we would've done with a scratch built boat. In the end, however, we still won't have the boat I dreamed of.

I really liked the SK41 by Roberto Barros BG Yacht Design - Multichine 41SK though I would've changed the interior completely and added a hard doghouse. The steely we have is a swing keel like the SK41 but 36 LOA. It does have a hard dodger, however, which is nice.

[sy_gilana]

I think all the advice you need is above.
Just some comments.
I know someone who used a truck to drive over the plate to pre-bend.
Slot, or Plugwelding is the way to go.
Do weld in a threaded plug top and bottom, and fill the rudder with HFO or other heavy oil.


I would make the plate longer than needed and weld a bar and pipe levers to the waste portion. Pull and tack all the way then cut off the excess.

[steamgoat]

Maybe ,when finished,weld a threaded fitting in the top,then fill it with oil.

[captlloyd]

76 year old steel fabricator, started welding at 8 years. Forget about heat. Take your plate and place a 4 x4 under each edge length wise. Try driving the front wheel of a light vehicle down the center, the vehicle should cause the plate to deform but you will get some spring back. Basically you want to get as close to the radius of your frame as possible, you may need a heavier vehicle to achieve this. It doesn’t need to conform perfectly, a small variance can be easily be drawn in with clamps. Once steel loses its straightness it becomes easier to form. You will never be able to heat that piece, even with a large torch, to get a even bend. The front edge is a different matter though. To get that sharp a radius your best bet would to be to step brake it on you bench. You need a stout bench to do this, but you are bending only one side at a time so you are only making half a bend. Or, you could find a steel fab place that possibly has a brake or power roll. The could do all of the forming for you or just the leading edge/ edges. You also might be able to do the leading edges on your bench with a combination brake/ rosebud heat method. Good luck, show us the results, frame looks super !

[raahell]

Hi Captlloyd, Steamgoat and SY Gilana

The holes are already in place at top and bottom for the oil. I'll also use an air quick connect in one of the holes to pressurize and check for leaks after it's all welded up.

I might try the run-over-the-plate-with-a-car trick. I didn't know that a plate is hardest to bend when it's straight.

I am also going to make a bender at the front of my welding table, just to get the initial tighter bend going. Worth the time to make as it'll come in handy for other projects.

Great tips!

[MicHughV]

I fabricated a homemade bender to bend my deck frames....I also fabricated my own " crane" to help me hoist steel sheets up the side of my boat...
In addition, in my collection of tools, I had several car hydraulic jacks..these would be positioned whenever I did not have the physical strength to bend something...
Also, several " come-a-longs"...chain winches...I would weld an eye to what ever I wanted to bend, attach the come-a-along, and pull the thing into position.
I had dozens of clamps, vice-grips, etc...

What I'm getting at, you will need to buy or fabricate a number of tools and devices to assist you...some times a simple job, requires several days of tool fabrication, but such is the nature of the beast..

[sy_gilana]

Oh, put the plate in the sun to see which way it was rolled, use the same direction when bending.

[NSboatman]

Raahell- you’re doin’ it right. Great to see and hear about your work. Well done! Make sure you let us know how it goes- want to see pics of the final result.

... the 7’ back? Yeah, she was a bear to steer before, to be sure. The boat is a 47’ Bruce Roberts- sort of. I haven’t been able to find one exactly like her- a lot of Mauritius 43’s are close, but I think the builder on this one simply lengthened her by 3 or 4 frames...and the rudder didn’t move from its original position. Speaking with one of the fellows who drew boats with and for BR in the day, the rudder placement was a common issue for those designs, and many have been fixed this way. I took it a little further because there was a nice solid bulkhead 7’ back that I wanted to tie the new rudder post into; and it seemed to work in the end. Another pic here- [ATTACH]233053

You can see from the photos where it used to be (just aft of the prop) and where it is now. The whole lower keel extension was done solely to protect and support the heel of it.

I considered filling it with oil.. but since I was adding about 350 lbs of new steel with the construction, and moving it significantly aft; I decided to make it hollow and air filled, for the net buoyancy it would provide. In the end- it works. There was no detectable change in how she sat in the water, despite the addition and placement of the weight new steel. I was worried that the buoyancy might cause strange rudder behaviour when heeled as well- but I haven’t noticed any. I guess if I get a leak, my indication will be that we’re suddenly down by the stern for no reason!!

[RaymondR]

The advantage of pulling the sides in together with bolts all the way through both is that you don't run the risk of pulling the internal support frame out of true and getting the rudder sides non symetrical or it ending with a twist in it.

!/8" plate on a structure like you have would be more than strong enough just fully welded along the front and rear edges. Compared with the foam filled, FG skinned things they use on plastic fantastics yours will be 50 times or more stronger even with just the front and rear edges welded. Frameless steel boats have hardly any frames and rely entirely on their shape and steel skins for hull integrity.

[MicHughV]

Looking back......boat building in steel, in my day, was relatively new...especially for the home builder...
Steel boats were being designed and built like wood boats....lotsa frames, stringers, etc...

If I had to do it all over again.....I'd have frames only around the keel area to help provide support to keel, and weld tabs elsewhere to provide support for bulkheads, etc.
for the rest....I'd use 3/16" plating, I like 3/16" over 1/8" as there is less distortion from welding...

The interior of my boat was essentially built around the frames. This was awkward as the frame spacing did not lend itself to furniture layout.

Steel is immensely strong, and the shape of the hull, with chines and deck essentially provide a monocoque structure, where the whole is stronger than the part.

People don't realize just how strong steel is. I speak as a retired structural engineer. It is immensely strong.

I could have easily saved several 1,000 lbs of unnecessary weight out of my build. Easily, by eliminating unnecessary structural elements.

I built my hull upside down. When time came to roll it over, I simply welded two eyes to each side for the crane to pick it up. At one time, the hull was hanging by only two eyes. Try that with a fiberglass boat.

My rudder was also built with frames and plates, waaaaay over built...in my opinion...

I remember seeing a documentary about a guy building a steel hull over wood frames. The wood frames were there to provide support during the build and subsequently discarded after. Smart move, in my opinion. Wish I had thought of that.

[Cheechako]

Yeah, steel is something else, not only strength but stiffness compared with Aluminum. And of course fiberglass is like a noodle comparatively.

[raahell]

NS Boatman. Thanks for your compliment and the pic of your boat's fanny. Nice work! The small amount of water in your rudder (<100kg in my estimation) will not have any visible effect on how a boat that size will sit in the water.

I thought about moving my stern post back as well. The original design specified the rudder hanging off the transom which would've added 3' of leverage. I could still move it back by 16" and keep it in the same place between bulkheads with few modifications to the steering set-up, but I'm hoping just changing the rudder itself will give enough improvements. If this doesn't work well enough I would consider going with twin rudders, and since I'll be doing new posts/sypports for these I would also move them back.

But I'm getting ahead of myself! Hopefully this new rudder alone will do the trick.

SY Gilana: I already have the plates cut but I'll use the sun-tan technique next time I've got a similar job to do.

RaymondR: I hear ya about twisting the rudder. I've got jigs mounted to my welding table that has the profile cut into them. I tack weld or clamp the rudder to the jig/table and then bend one side at a time. This way, I don't think the chances are very high that I'm going to get any warp.

[MicHughV]

While I was building my boat, I got to know at least another dozen folk building a steel boat, all sizes, designs, naval architects, etc.....

I learned a lot about steel boats.

If I was 10 years younger, I'd do it all over again, but differently.

One thing is a given, I loved being offshore in my steely. I never worried about hitting anything, etc..it was strong as a rock...and I've been in some dismal weather.

I seen several video's of people pulling a steel boat across a reef....just a few scratches to show for the experience..

Steel boats get an undeserved bad rap. A few rustbuckets here and there seem to sway a lot of people, but it's my # 1 choice for an offshore sailboat..

[Disailor]

For my 2 cents worth: The eye bolts near the top of the trailing edge is right on! The only steel rudder I've had experience with had two 1/8" pipe plug tapped holes (one near top & one at bottom) so that the interior is filled with oil. Graphite powder mixed in with the epoxy makes a great slippery surface!
Be patient when welding; go slow with plenty of time between welds to prevent distortional heat from building up.
Applauding your efforts - it looks great!

[raahell]

Thanks DiSailor,

Yes I've been thinking it'd be a good idea to have something at the trailing edge to tie lines to in case of steering gear failure. Also good to secure the rudder if I ever have to remove it when the boat is in the water. I had to do that on my first sailboat.

I would probably not use eye bolts but just bend some SS rod to a U and weld it in place. The fewer holes in the rudder the better.