trimming rudder

[anthony_marquart]

The rudder I'm running on my current 12 boat is bigger that what I've seen on some sport 21s.. It's an older one from ray fuller. I'm thinking of cutting it back from the trailing edge about 3/16. I don't need the water pickup anyway. The axis of rotation will still be well ahead of the TE.

Is this a bad idea? I think it's slowing me down.

 

[tnrcboatracer]

If you don't need the water pick up, you should consider running a knife blade for a rudder.

 

[anthony_marquart]

Huh? what kind are you talking about?

If you don't need the water pick up, you should consider running a knife blade for a rudder.

 

[Tom w]

.

 

[Andy Greene]

Huh? what kind are you talking about?

If you don't need the water pick up, you should consider running a knife blade for a rudder.

Kitchen knife blade- a lot of F/E SAWS guys use em(or used too). Maybe someone with some hands on will chime in

Andy

 

[anthony_marquart]

Thanks for all the replies,.. but,.. no one has said if trimming this one would work... I try not to buy things if I don't have to.

 

[Andy Greene]

Thanks for all the replies,.. but,.. no one has said if trimming this one would work... I try not to buy things if I don't have to.

No need to buy anything, as long as the wife doesn't miss it , your good to go -

I know that STILL doesn't answer your question, sorry.....

Andy

 

[anthony_marquart]

Can I REALLY use a flippin knife blade?... Like a kitchen knife,... I don't think that's a good idea.

 

[jayt]

You want to use a tapered smooth blade, like a carving knife. No serrations, no blood grooves, no hollow ground. I usually bolt it to a cut down top of an aluminum rudder. You do have to be careful not to cut yourself.

The one in the photo has exceeded 80 mph and I'm hoping for more.

.

 

[Andy Greene]

Thanks Jay-

I'm not sure Anthony believed me

Andy

 

[glenng]

You want to use a tapered smooth blade, like a carving knife. No serrations, no blood grooves, no hollow ground. I usually bolt it to a cut down top of an aluminum rudder. You do have to be careful not to cut yourself.
The one in the photo has exceeded 80 mph and I'm hoping for more.

.

Anthony, years ago Prather made a mod engine kit for the K&B 7.5's- exh. throttle, venturi and a S.S. rudder blade .088" thick X about 5 1/8 long. Someone on this forum may have one they don't need-put a WTB in for sale section/attach as jayt showed his. Good luck, Glenn

 

[moparbarn]

glenn, i think the 7.5 blade would be too big on a .12 rigger. prather also made that kit for 3.5 k&b's, to go on their spitfire ob rigger. smaller, thinner - prolly better suited for a small rigger, jmho.

 

[glenng]

glenn, i think the 7.5 blade would be too big on a .12 rigger. prather also made that kit for 3.5 k&b's, to go on their spitfire ob rigger. smaller, thinner - prolly better suited for a small rigger, jmho.

Your right Robin, I did not know they made them for the 3.5. On a .12-a piece of .060 1/4 hard stainless would be o.k.. Glenn

 

[Big roy]

So this is a home brew thing, knife blading a rudder, does it really cut back on the drag and how will it effect turning since there will be some flex in the knife blade? thats pretty wild, and think you can filet a fish when you wack one, lol seriously this really worth doing?

 

[glenng]

So this is a home brew thing, knife blading a rudder, does it really cut back on the drag and how will it effect turning since there will be some flex in the knife blade? thats pretty wild, and think you can filet a fish when you wack one, lol seriously this really worth doing?

Big Roy, They work great when the carp are spawning :lol: :lol: Just kidding. A piece of .090 stainless steel is very hard to bend but much narrower than the 1/4" alum. blades with a water pick-up built into it. I use a tapered 7075 alum blade on my sport hydro and one of my outboards has a .088 thick S.S. blade. I like em but if you ask 4 different people you'll probally get 4 different answers. Just my opinion. Glenn P.S. like Drew said - if your wife dont miss the knife - it wont cost anything to find out! Glenn

 

[Andy Greene]

So this is a home brew thing, knife blading a rudder, does it really cut back on the drag and how will it effect turning since there will be some flex in the knife blade? thats pretty wild, and think you can filet a fish when you wack one, lol seriously this really worth doing?

For a SAWS application or a .12 boat I would say, yes- it is worth trying as long as a water pick-up isn't required.

Like Jay said, use a tapered smooth blade like a carving knife. Your using the meat of the blade so to speak, so it really doesn't flex.

Andy