arcdude

Anyone out there shed some light on the use of air rudders? Going to build me a snow board to help get through the winter but would like to use the board on water in the summer. The question is; is there a design or method to getting the rudders to get the board to lean into curves rather than the board staying flat and possibly catching the outer edge of a turn and rolling? Any input would be appreciated, Thanks

Jeremy_H

You can angle the rudders in principle, fit two, tops closer that the bottoms. This helps to apply a fore/aft rotation to counteract the rudder being above the pivot point. But, I'm curious, why do you see a risk of it digging in? Most of the boogie board vids I've seen suffer from chronic edge lift on the outside rather than digging in, usually it seems through the hulls being too light

arcdude

You could be right, some of the vid's I've seen they seem to have that tendency as well. The thought is if the rudders can be used to control this effect they may be adjusted in either direction whether it's lifting or digging in. So I thought it may be a good idea to incorporate that adjustability into the build rather than try to deal with an issue later Sometimes I guess we put a little too much thought into things

Jeremy_H

Perhaps. I think the trap is turd polishing, I see fine details of trim methods as best being used to optimise a sound design foundation. Once we have the base design topped out we can then concentrate on ways to step it up further. It's a bit like the transom trinkets you see on so many powerboats, at the end of the day a lot of the additional trim tabs etc are really compensating for a crap or poorly set up hull. I think those guys just like the techy look too tbh, which is fine.

fuma

maybe a v-tail could control pitch as well

arcdude

Thanks fuma appreciate the suggestion! Thanks Jeremy, although I'd normally agree on the performance of any machine is in it's initial design being sound whereas in this instance and to benefit those of us that are living in no mans land and buried under several feet of snow for 5 mths out of the year it'd be nice to have a machine to help pass the time until we can get down to a more technical side when it warms up. Obviously speed isn't in the cards with these designs and if an airfoil or two can gain some stability it would certainly enhance the experience. Once I took the wing off an airplane and put ski's on it and flew up and down the river out of desperation to fulfill the need which was fun but kind of boring. I will stop short of putting a platform on an old truck tire inner tube Actually re-visiting the airplane without a wing may not be a bad idea to take a second look at I have a few laying around

JUSS10

One of the things I thought of with my boat was to add two flat peices on the sides of the rudder that are perpendicular to the main rudder but at an angle up or down to try and create lift or down pressure from the rudder. mind you, since they are fixed they would always be applying that pressure whether you are turning or not.

arcdude

Interesting idea and as long as one used a high torque servo it should handle the job. Your board runs well you shouldn't need much if anything by the looks of it. The board I'm building will have a glow engine so it'll be considerably lighter and in all likelihood be prone to more lifting.

Jeremy_H

This pic of the Twin test boat shows rudder fins as JUSS 10 describes. These were quite small as an experiment, but they definitely had an effect aiding the side dig-in problem I had:

arcdude

Interesting Thanks Jeremy that's the kind of idea I was looking for. I suppose one could add those fins after the fact once the characteristics of the particular board are determined and have the fins adjustable for lift of down pressure

arcdude

A few questions in regards to air rudders if you guys would be kind enough to share your opinions. Is a single air rudder as efficient as having two and is the rudders more effective extending out the back of the transom or does it matter. Thanks

arcdude

Now that it's been snowing for the last couple of days and for the next week everyday with -10 degree temps it's time to hang up the boat until spring and get working on this project to have something to play with. Anyone that runs on snow I could use a little input as to the basic set up rudders 1 or 2 height and so on and whether they should extend out beyond the transom or not would be most helpful. In order to adjust the CG should the motor pod be separate from the rudder assembly for ease of adjustment? Thanks

crispyspa

Use whatever set up you have for the water. Nothing special is needed. I would however, recommend a servo saver on the rudder servo. When you blowover, the rudders generally take the brunt, so protect them if you can.

arcdude

Thanks crispyspa, I realize this isn't going to be high tech for sure but just trying to get in the ball park with the CG. With the rudders extending out the transom being a fixed point how do you get close to a CG at 1/3 length of the body, seems a lot of flying by the seat of the pants and a good measure of luck. Do you basically come up with a base idea material wise and place it on the hull and take your best shot? The only adjustable weight balance that I've seen in pictures is the radio box out front, is that all the adjustment that'll be required? Never attempted one of these beasties and don't want to waste time on constructing something that'll lift off at the drop of a hat. Thanks for the tip on the servo saver, good idea.

dadkins

Hi Arcdude,
I have run several boats on snow from a big swamp buggy with 4 air rudders and single rudders. I don't think it matters if there is one two or more as long as it is in the prop wash, and I do prefer them hanging beyond the transom as that is kind of your pivot point and the further back the more leverage the rudder will have - start big and trim it down to the size that gives the control you need. I use a nylon ball joint to attach my servo arm that has a break away ability - make a sturdy rudder attachment and a light weak rudder - you will likely break a few in a blow over.
Also I have had snow that is greasy fast and super hard to control and wet snow that sticks so bad you can barely move.
Best, is about 6" of FRESH light powder on a frozen lake - I have seen some pretty incredible speeds and nothing like driving by your ankles at 40 mph for a sensation of speed -Another bonus is my nitro motors seem to run really strong in the cold.

arcdude

Thanks for the suggestions dadkins, much appreciated! I was considering 2 rudders made out of an abundant supply of 1/4" ply laying around and considering the nature of the beast it won't be expensive. As memory serves when I was running nitro airplanes on the river in the winter they all seemed to do well in the cold, probably better than I did Lol. I have a choice of two engines for the project, one a Webra 61 and a Thunder tiger 61, hope one of these will provide adequate power. Just haven't decided on a one piece self contained module or keep the radio box separate to help balance things out, having never built one of these the weight and balance with the materials used is a mere guessing game at best.

dadkins

I usually run my servos exposed in the best leverage locations and put my receiver and batteries in a sealed Tupperware type waterproof container using heavy duty Velcro to position them in the box and the ability to shift the batteries a couple inches either way to re distribute some weight. keep the batteries warm till the last minute and pop em in and GO

arcdude

I like the idea of placing the servo's in the best location, do you water proof them? I'm still leaning more to a self contained pod with everything in it and the rudder assembly separate so the pod can be moved fore or aft as needed, just not finding a lot of info on that type of set up. Once I get it figured in the old grey matter the building itself should go quite quickly, lots of snow already to play in. Can anyone share their idea's for the rudder assembly and how did you mount them? Thanks

arcdude

Would air rudders be effective at about 22" from the prop to rudders, would there be a significant loss at that distance?

dadkins

22" seems a little far... they may have to be a little bigger. How big of boat are you making ?

arcdude

The size of the boat is 37"x19" and I plan on using the TT 61. What I'm considering is this, the plan is to distribute the weight from 1/3 back from the bow with the thrust line and the balance will be 1/3 from the stern. I'm under the thought that with the thrust line at the front there will be less blow overs and overall increased control and performance, I could be so far off the mark on this, and after watching several of these types running on youtube they seem quite responsive. Having never built anything like this a few aspects such as the rudders are a complete mystery, to me at least, so I guess I'll just have to build something and if it doesn't work make changes as needed.

arcdude

Can anyone shed some light on radio antenna placement? Where it's going to end up is on one side of the hull sticking straight up but will only be visible from that side of the hull, will that shorten the effective range if not visible from all angles? It's a 2.4 ghz Futaba radio. Thanks