Budget Redneck Ride

**dlight** · 08-14-2010, 11:46 PM

Just starting an Air Jon - 15 HP Kohler on a 14' Jon Boat. 42-16 Prop On the Way.

**dlight** · 08-14-2010, 11:52 PM

I need some advice on the rudder(s) for this project.

Using a 42" prop on the jon boat should I use 2 rudders or one? I am thinking one due to the narrow boat, I think one would probably allow the boat to be more stable..??

What should the dimensions of the rudder(s) be?

Should the rudder pivot point be parallel with the plane of the prop or slightly tilted in/out toward the front of the boat at the top?

**buster** · 08-15-2010, 01:52 AM

dlight,

I have no jon boat experience, but just thinking out loud here, I would go big on the rudders. My thinking is that a jon, with all it's bottom runners, probably is a lot harder to turn than a flat bottom airboat hull.

I guess one rudder might be enough, but if possible, set it up so you could add another one later if the need becomes apparent.

I've built two boats with the rudders parallel with the prop. I see no need to slant them in or out.

Dave

**Papee** · 08-15-2010, 01:15 PM

Looks heavy, is that aluminum angle or steel? Since your setup will most likely never see any really speed I would suggest that you put two rudders on it, it will help you turn better. rudder length will be determined by how far off your transom the bottom of your prop is, it should be just above your transom. 3ftx14 inches should be plenty of rudder for that setup. If you do a lot of slow idling you may want to consider a water rudder to help you turn even better. Here we use ones that will flip up if they hit bottom, a rock, or other obstacle. Try to keep it as light as possible and make changes now rather than get it in the water and have to make a lot of changes later.

Even though the plan is not to have a speedster, you still want to get the best performance you can out of that setup. You also have to distribute the weight differently than we do in our faster boats. You may need to keep some weight forward to keep the front of the boat from lifting and pushing water. If you keep the nose in the water it will go faster. If you have a second person in the boat most of the time this is not an issue. I see some boats go at a pretty good clip even though not on plane if set up correctly.

When we build a lightweight boat such as yours we just build a small pedestal stand and put a few braces on it to the sides to keep the weight down. I just put a plate on the bottom that attaches to the rib braces on the bottom of the boat. I've run up to 25hp with that setup. Weight is a big thing with any low hp setup.

**Duane Scarborough** · 08-15-2010, 08:20 PM

dlight,

As usual, Buster and Papee have given you some very
good advice.

I had ideas about doing something similar to what you're doing way back in 1972. I was planning to use a VW engine, but it was the same idea.

It took me a LONG time to get started on my boat. And it's taking a LONG time to get it done.

But I'll get there someday. The longer it takes, the more time I get to enjoy the build part...

Both Buster and Papee made good points.

Keep in mind that AIR rudders have absolutely ZERO directional control unless you've got the engine/prop going fast enough to generate air flow across it...

A water rudder will work at even a very low forward speed.

For that reason, you may want to consider a combined air/water rudder. What I'm suggesting is that you extend the rudder low enough that it makes "some" contact with the water, but not so far as to extend below the bottom of the hull.

I'm just thinking out loud here.

What you got done so far looks very good.

Keep us informed.

Thanks,

Duane

**dlight** · 08-15-2010, 11:53 PM

Thanks for all of the good comments and suggestions.

My frame/motor support is constructed of thin wall aluminum square tubing. The cage will be aluminum conduit - 3/4" for the main hoop and 1/2" for the remainder.

I will probably use 2 air rudders as I do not plan on any slow idling. Also, I plan to use the boat in the shallow rivers and there are lots of rocks/obstacles which would most likely cause problems with a water rudder.

Thanks again for the help and I will keep you posted!

**dlight** · 08-15-2010, 11:58 PM

Originally Posted by buster

dlight,

I have no jon boat experience, but just thinking out loud here, I would go big on the rudders. My thinking is that a jon, with all it's bottom runners, probably is a lot harder to turn than a flat bottom airboat hull.

I guess one rudder might be enough, but if possible, set it up so you could add another one later if the need becomes apparent.

I've built two boats with the rudders parallel with the prop. I see no need to slant them in or out.

Dave

Buster - Thanks for the info. You are right on track on my thoughts about the runners on the jon boat, but I was thinking they could potentially cause extra resistance when attempting a sharp turn; causing instability if the rudders were too large/effective. That is why I was considering a single rudder...? I guess I will just be very careful until I see how it handles.

Thanks Again!
dlight

**Papee** · 08-16-2010, 12:22 AM

D I have run many Jon boat setups and the only thing you have to worry about is keeping your weight low becasue of the narrower hull. You will not see speeds that you have to worry about the hull grabbing in a turn. They turn very well BTW, they just don't slide at all. If you had a fast boat it could tip becasue of this. With 2 rudders you will have more surface area to turn and won't take quite as much air on them to turn at a lower rpm. I've always like the looks of the two rudders also on a small boat. With one rudder it has to be bigger and just looks awkward. It will also blow you around more if you are floating trying to fish.

**dlight** · 08-21-2010, 10:59 PM

How much should the rudders rotate in a full turn? I was thinking about 45 degrees...??

**buster** · 08-21-2010, 11:54 PM

dlight,

I would say 45 degrees is about right. I had to make up rudder stops for mine because when they went further than that, they seemed to block the propwash and not turn the boat as well either.

Dave

**Duane Scarborough** · 08-22-2010, 04:40 PM

dlight,

You and Buster are probably both correct here. About 45 degrees sounds like a practical limit.

Buster,

Check you Yahoo inbox. I tried sending you something, but got a failed delivery response. I suspect that your inbox is FULL.

Thanks,

Duane

**buster** · 08-22-2010, 09:10 PM

Duane,

Please try again, my Yahoo inbox gets emptied at least once a day, and it never gets full. If that doesn't work, drop me a PM.

Dave

**Duane Scarborough** · 08-23-2010, 06:53 PM

Buster,

The problem seems to be on MY end. I don't know yet what it is, but it seems to be on my end.

Thanks, I'll keep trying.

Duane

**Duane Scarborough** · 08-23-2010, 07:28 PM

Buster,

I sent a PM with Tach info.

My computer is croaking now, so I don't know if you'll get it.

Duane

**dlight** · 08-26-2010, 11:36 PM

If I am using a 42" prop and two rudders, where should the rudders be positioned along the transom? I am guessing about 12" from the center of the prop on each side, making them 24" apart??

Thanks,
dlight

**buster** · 08-27-2010, 12:12 PM

dlight,

24" seems ok, but I would just put them where you figure they will catch the most prop wash. Maybe someone else has a "rule of thumb" about that, but I don't see how you can go wrong doing it that way.

Dave

**dlight** · 08-27-2010, 04:45 PM

Thanks Buster. My prop arrived today and after looking at the prop, I am thinking they may need to be a little farther apart... 12-14" from center looks about right.