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2 questions guys. I cant seem to figure out how airboat steering works, not alot of good pictures or schematics that i can find. Would any of you mind posting some detailed pictures of your steering set up? or maybe some easy sketches of how it should work?
2nd question, why dont airboats use propellers wider than their hull? seems like a lot of lost thrust on a mini (using a reduction). If i am building a 4x8 hull, can the cage be built 60-72" wide?
thanks
I have always herd it a branch and brush thing.
Prop bigger then the boat more likely to hit it, maybe?
Eric; keep in mind that the bigger the prop, the higher up you'll have to mount it. That will move weight higher on the hull, thus resulting in a top-heavy condition. I'll guess that you don't want an unstable boat, especially in a turn, so it's a "balancing act", if you will, between max possible thrust and overall safety and stability. Additionally, you can spin a given diameter of prop only so fast. Once the tips of a prop pass the speed of sound, harmonic vibrations start in the prop tips, and can destroy a prop in short order. There's a fair bit of engineering in all of it.
Steering; consists of the operator's stick, a push tube, a bellcrank, a rudder (or two), and a connecting link between rudders. It's arranged such that you push the stick forward/aft, moving the push tube for/aft. This movement then gets turned sideways through the bellcrank, giving a crossways movement in order to rotate the rudder(s) on their axis. I don't know if the for/aft is universal to left/right at the rudder, but it seems to be sensible that it would be.
The operator's stick is mounted such that there's maybe 6 inches of stick hanging below the pivot bolt so that it can be used to attach the push tube at the bottom.
An alternative to the mechanical method is to replace the push tube, bellcrank, and connecting link with a push/pull cable. The cable can bend around, allowing fewer moving parts.
Roger
Anybody have any pictures of their steering set up? There aren't much airboats around here to get ideas from. What i really cant seem to figure out is: how does the push tube attach to rudders and how do rudders attach to boat.
Eric
one more question, has anybody used a generic motor mount cushion to mount their engine to engine stand? something like this
Attachment 4277
here are a couple of links to what some have done for the steering, and attaching the rudders to the cage. in most of the builds that have been posted, most everyone had shown their method, you can always use a cable also.
as far as motor mounts, as long as they are rated for the HP & torque, that the motor & prop will put out. there are so many different options available, and each home build is just a little different. some have used bolt through poly-urethane bushings, me I used snowmobile motor mounts, similar to what you have pictured. because they were on hand.
these decisions on what will work best for you, with what you have access to, is what I have enjoyed about building my mini, and don't worry, if it is anything like what I do. the plans will change half way through, and after I think about it for a while...
http://miniairboatassoc.com/forum/showthread.php?2654-Corky-s-Build/page14&styleid=4
http://miniairboatassoc.com/forum/sh...ge12&styleid=4