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Building you own ruddders

F

FP1201

Well-known member
This subject has come up several times, and I would like to revisit it:
I'm thinking of building a couple rudders, or maby a PB style rudder by having a 4' x 6' sheet of aluminum folded in the center then placing something like a tube inside ~6" from the front, then riviting closed the edges. (I don't have a TIG welder and don't wat to buy another gun for to run aluminum wire thru the MIG)

Approximatly how large would a PB rudder need to be on a 4cyl boat? All the boats I've had exposure to have had dual 4' rudders, including this one....maby a couple YEILD signs bolted to 3/8" rods.... :roll:
 
you dont need a welder at all just cut notches in a piece of 1in aluminum angle so it will bend to the shape you want it and you can then rivit it all the way around angle to the rudder and top to the angle
 
I wouldn't cut and notch it unless you intend to weld :roll:

Fp ,
this one is 4'x3' and have a small one that is 3'6"x3' but doesn't have the beaver tail angle for dike crossing like the bigger one. you can bend a set of internal supports and rivet every thin together the newer air foil rudders you would put one clean break say about 40 degree but the PB rudders are bent around probably 3-4" wide in the front

Rudder_WPB_jpg.JPG
 
What are you using inside for the rod to go thru?
I sure would like to see a top down view and/or what's inside one.
Since most folks use dual rudders, is that the better choice? :?
 
I'll have to find you a top view picture of that rudder later. I have seen them both ways a piece of the inside run form the top to bottom and a rod run through it or like this one there is a plate rivets o with a Nut in it on both top and bottom then a bolt comes through the ball eye and actual pivots in that eye it self

here are some top view pictures that plate kinda hides everything but maybe it will give you a idea

Ruddersteeringbracketleftside.jpg


rddersteeringbracketrightside.jpg
 
FP1201, I built my boat's rudders, they are 4' by 21" they are made out of .025" 2024T-4 alu. they are called constant cord rudders. They are riveted at the trailing edge with AD 3's at 3/4" increments. the only welding is the end ribs made then riveted in place. Inside I use 3 foam ribs glued in place, and last I used a piece of 3/4" DOM tubing as the pivot point with the nylon bushings inside of that ,they only weight 9lbs. as compared to the norm which weights 16 lbs. I have run them for more than 5 yrs now with no problems. ZZ
 
ZoomZoom, I know you meant constant chord, would that be the same as high speed wing configurations (laminar flow?)?
The Palm Beach style, (big single rudder), looks to be a double Clark Y airfoil, (J-3 cub) or close to it, evidently they work very well. I just cant get use to seeing one big rudder, (never ran in glades) after using two all these years.
Two forces involved, impact pressure and airfoil action, according to shape of rudder, hey, we need wind tunnel tests!! 8)
In the early years there were naked sign posts here and there along the roads, but those flat rudders worked! :D :D
 
RL, my rudders are basically rectangular in shape. I don't know what percent is laminar,(although I do have the book"Theory of Wing Sections") I can say that the thickness ratio is some were between 10-12% of cord, and it's more than likely at 1/3 of cord. It was 5 yrs. ago, if I remember I use two criteria, first structural, and second aesthetic. I did build with weight in mind as I do with everything I do. To that extent the through rods that are used to pivit the rudders are purpose built. They are fabricated from 3/8"SS tube and 3/8"SS F.T. bolts, that I machined to fit and welded. One more thing I neglected to say, that the trailing edge has a .090" alu. doubler to stiffen it up a bit,I hope this info. helps, if you want I can probly put some pics. togeather. They say a picture is worth a thousand words. ZZ
 
Nope, don't need any pics, I've built light rudders, and damn heavy ones too! :D
For me, getting pivot point distance exactly right for balanced operation, (good response, leverage and power), is a problem with some rigs, (without using a lot of trim tab adjustment for straight cruise), due to difference in control leverage, travel and how rudders are mounted on rigging.
Hardly any one thing is cut and dried on air boat tuning, each boat and its use is a little different, this is hard for beginners to understand, being most changes are a lessor of two evils and a compromise. :roll:
 
For me pictures are important.
I would agree the hardest part is getting everything aligned, straight, and with syncronised movement especially when you consider the dynamic forces against a flexable framework.
Trial & error are the hallmarks of an Airboater. :lol:
 
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