Weak links in the macgregor

[Seapup]

I made 2 complete kick up rudders for a catamaran, was more of a project than I anticipated and not something I want to do again anytime soon.

[whgoffrn]

I should be getting my rudders back from jo woodwork in next 2 or 3 weeks .... after I get them back I'll take the brackets to the welder to have a "lip" welded on to secure the vice or vice grips as i sent my bracket along with my rudder and have changed my plans I believe on welding the grudgeons with rebar ..i plan to have a 12"x3" or so 1/8" thick piece of stainless under the grudgeon and bolt it into the hull to give more leverage so nothing can bend or twist .... Will post pics when completed ... to the best of my knowledge and in theory the boat will twist in half before the rudders or brackets break and grudgeons won't twist out of the fiberglass either

[Ixneigh]

When you think its unbreakable it usually turns out to be just barely adequate.

Ix

[whgoffrn]

Haha I hope not cause this project is costing me a kidney to do it lol

[Ponaldpe]

Hay who is buying Kidneys I have to replace a outboard on my other boat.

[Highlander]

Mmm Beef & Kidney Pie,s or Liver & Onion,s & mashed potatoes sign me up for Dinner LOL
Who,s Hosting for diner !

J

[whgoffrn]

Got my rudders back today from jo wood works .... quality work for sure for 180 bux per rudder .... I know it's nothing scientific to determine strength but I stood on both rudders (I weigh 190lbs) with on a step as shown in the pic and the factory ones flexed quite a bit but the white oak rudders didn't flex not one bit.... I know that's not anything scientific about the strength as it could shatter like glass and the factory ones are hollow up to a certain part but from my "bounce on rudder propped on step test" the wood rudders are considerably stronger - unofficially that is

[whgoffrn]

Bolt hole has been drilled out larger then filled in with resin and drilled out to size much tighter fit

[whgoffrn]

Hole for the line to lock it in down position is much smaller so 300lb braid can be used so it will break away if grounded yet I can still lock it in down position

[whgoffrn]

Next up brackets to the welders this weekend

[BOAT]

The rudder stock on the J21 is stainless steel. They need to be able to take a hit from a whale.

The keel is solid steel - Hugo Boss J21 broke rudder in vendeeglobe but not the keel - the keel hit the object first and the keel held firm but it broke the metal rudder at the cassette shaft. Alex saw the rudder dragging behind the boat at 22 knots and the hydro-generator got busted off too - (no electric power generation for the batteries).

He had to fix both on the fly.

Steel rudders are the best - but no good for the MAC because the transom mount is not strong enough to support the steel rudder on impact - the transom bolts will break out the transom before the steel rudder would break - so a super strong rudder is not a good idea unless the transom has steel plates in it also.

Actualy - steel plates in the transom to mount stronger rudder brackets for steel rudders is not such a bad idea for the MAC but the real issue here is speed - the MAC will never see the kinds of speeds that break off steel rudders so it's kinda usless - I must admit that I do worry that hitting a whale at 7 knots might pull the rudder bracket bolts right out of the transom and make a hole in the boat.



Man, just saying that is sort of scary.

[whgoffrn]

Haha that's why mine have breakaway .... I want them to be able to endure a lot of side to side forces and that is why I lengthen the grudgeon bracket horizontally by 12 or more inches so it can take much more forces side to side and and I have / will have 300 lb braid locking it down so when I hit this whale (lol) more likely bottom in my case it will break away letting rudders pop up ..... this is a 3 part upgrade rudders first then I'm getting a lip welded to the lower part of the bracket so I can put a vice on it to reinforce it from bending last is I will put large horizontal stainless stabilizer brackets with backing plates to distribute the forces placed on the grudgeons

[BOAT]

Yeah - I think the X rudders might be stronger than the M rudders. Watch out for that whale. (I'm scared of whales).

[whgoffrn]

I can't think of any other way to add considerable strength without totally redoing the entire thing from scratch so with a bolt through the top and a vice in place in the bottom it should add considerable strength and as far as grudgeons (the bracket that holds the entire assembly into the hull)....i think I've changed my plans to address it from the Inside putting thick steel backing plate that goes from the grudgeons to the bolts for the outboard ..... I think if all goes well it will still leave the rudders as the weakest point but at twice the strength of stock ..... at least I hope.... fwi don't ever do the bounce test on your stock rudders on a step because I cracked one demonstrating to a friend the difference in strength so yeah one destroyed fiberglass stock rudder now

[Ixneigh]

You can't pick up the rudder with that setup. How are you going to go into powerboat mode?

I'd be Interested in having a set of M rudders made if the guy can accurately reproduce the foil section. But I would cover mine in 3 layers of epoxy and fiberglass cloth to prevent cracking along the grain

Ix