BR, please note: I am posting a saved draft from yesterday that I didn't have time to proof read. Sliding Gator's previous post was not here then, so realize what follows
should be considered in addition to,
and NOT in lieu of, his comments. I don't believe we are in disagreement about anything but maybe using different verbiage to describe similar thoughts. In other words, I didn't edit this post on account of his; it is ALL good information for you to consider, imho.
BR5491972 said:
. . . My airboat is a homemade 12' long× 74" wide fiberglass over plywood hull, dd 60" prop that is powered by a 65ish dodge 318 motor
Looks like a VERY COOL little project to me. :salute: I trust that it is all strong & solid. Of course, the existing superstructure under the deck and supporting your engine and torque loading of the hull are of paramount concern. Even a small block can wreak BIG havoc.
Problems... The rudders don't turn equally to the right as they do turning left. I think I've got that issue figured out. The rudders are 36"×22".
The method for centering your steering is to unhook one end to attain some slack, then turn the wheel so that were the cable is centered on the drum is displaced either CW or CCW and then reattach and recheck. Hard to tell much by the pics, but there should be springs at the terminating ends if there currently is not. Cable routing likely could be improved, but preferred rudder placement should be accomplished first in any case.
How far away from the prop leading edge do the front of the rudders need to be? How far apart? And how high off of the transom? I'm going to redo part of the cage so that's the start of my steering issues.
These are all good thoughtful questions, but more applicable to the design of a new build than the preexisting circumstances that you currently have to deal with. Specifically, where height of the rudders above the transom goes, there would generally be an intrinsic assumption that the prop shaft is not nearly as high compared to the rudders, as yours appears to be. Note that your rudders are currently mounted in a more vertically traditional position. Then note where your prop shaft is in relation to the vertical center line of your rudders. Therein lies the bulk of the steering issue you need deal with.
It has a steering wheel not a stick. It might be kinda sketchy looking but it gets on plane and it feels like your strapped onto a rocket with really sketchy steering. . .
IMO, nothing wrong with the wheel (provided it is ALL strong and solid), and given the configuration/setup or the hull it may be the better option. Where it me, I would use all of what is there to see if I could correct it enough to be usable. AFTER that, I would start tweaking and making changes to improve what I started with.
Realize that the outermost perimeter of the prop provides little forward thrust, as the air moves down the blades toward center before actually moving aft. Consequently, the current position of your rudders renders the lower half of them ineffective at best (ie. below the prop wash thrust column).
To a large extent, the majority of your steering issues are that your rudders are mounted so low as to be largely below the thrust column of air that you are generating. I would expect that 36" rudders should work with a 60" prop, however they need to be centered vertically in thrust column of air in order to maximize their effectiveness. This will most likely be the one change that you can make that will provide the biggest single improvement in your steering.
With all that having been said, be aware that ANY and EVERY thing you change, has a bearing on everything else.
Sometimes a small change here can make a big change there. Moving your rudders up to where they will work as intended could potentially create or compound other issues that we may be unaware of. Not to beat a dead horse, but strong and solid are also applicable to your cage and rudder mounting. Be aware that the higher the rudders are mounted, the more torque loading there will be on the cage and mounts.
In this particular case, leverage will not be working in your favor.
Kept in mind, that is not a big deal to address. It is important though, to NOT overlook.
Such suggested change could make the overall feel of the steering more 'top heavy', so go easy at first, and be careful. :idea:
Slidin Gator it seems you are feeling your oats these days have you got in to the private stash. :dontknow: