bow planes for control - movable bow planes, fixed stern planes?

[steve_of_ar]

Hi,
I've seen mention of boats with only stern plane control sticking their rears out of the water when diving steeply from the surface. Also I'm guessing there's a similar problem when skimming the bottom of a pool, where to come up by means of stern planes only, the rear is forced down and would hit the bottom.
It seems that if the bow planes were controllable, then both of these problems would be avoided, since you'd be lowering/lifting the bow instead of lifting/lowering the stern respectively in those two cases.
So, lacking an extra channel for separate bow plane control, how well would it work to control only the bow planes, and leave the stern planes fixed? I'm sure people have tried this - if it didn't work, why not?

Steve

[jdlockh]

How many channels are in

How many channels are in your radio? How many channels are in the receiver? From my understanding you could control the bow plane from the radio, and place an APC-4 on the stern planes to keep the boat level. I'll need to check my instructions on how to connect it, but the APC-4 should function with out a signal to keep the boat level. I think that you would use an empty receiver channel or a Y cable and disconnect the signal line. This should keep the stern of the boat from coming out of the water when you dive. Also the Dumas Bluefish is controlled by the bow planes only, and it seams to do a good job.


Hope this helps

James

[steve_of_ar]

James,
I've got 4 transmitter channels

James,
I've got 4 transmitter channels and 6 receiver channels.

About using the angle keeper on the unused planes - it seems that in that case the angle keeper would be endeavering to keep the two sets of planes parallel more or less, ie. both up or both down. If that's the case I guess if there's enough speed then the boat would "translate" up or down as the case may be, while the boat itself stayed relatively level in pitch - is that the intended effect? That would be sortof neat in intself, but I'd like to be able to pitch up and down at significant angles too - I like the look of a sub headed down into the deep!

> Also the Dumas Bluefish is controlled by the bow planes only, and it
> seams to do a good job.

Didn't know that, thanks for pointing that out.

[jdlockh]

Yes that is the intended

Yes that is the intended effect. The only ways I know of to get the high angles on diving and surfacing are to lock down one set of planes, control both sets of planes, or try a dual ballast tank system, one in the bow and one in the stern. If you lock down the stern planes, I would rig up the planes like the Dumas boat. They have you attach a rubber hose between the stern planes and the hull so you can make adjustments to them if necessary.

James

[slats]

All my subs only have

All my subs only have the stern planes working, and all are linked to APC-4.
The only time the stern comes out of the water is if I drive like an idiot. To dive the boat I take on sufficient water into the tank and provide only slight down angle.

I have noticed that dynamic divers are more prone to this problem of the prop out of the water, but I have seen experience operators resolve this problem by not slamming the controls around like a speed boat, and providing a slight down angle on the stern planes and holding speed constant.

When I was new to the hobby the best info I source was an old sub regatta video, where Skip Assay provided a lecture on RC subs. One of his topics was dive planes. Skip imparted in that video the following facts. Stern planes are far more sensitive and responsive in changing the boats pitch than bow planes, and therefore, particularly on subs of small lengths, bow planes really dont have much effect at all.

I have built 4 subs thus far, including a dynamic diver, and I have never found a need for bow planes.

I understand the Dumas boat uses bow planes only and this works well. Given Skip's lesson, I'd think it would work even better if you locked the forward planes off and used the stern planes and attached an APC unit to them.

Hope this helps
John.





Edited By Slats on 1100476586

[jaschwink]

I have a Bluefish that

I have a Bluefish that was built by Dumas, and they built it with the control on the stern planes, in spite of their own instructions. The bow planes can be adjusted manually, but as it now sits, I tend to leave them horizontal.

I added an APC-3 to the stern plans, and that makes all of the difference in the world to keep the boat from porpoising (sic?). I also slowed the speed of the boat down considerably.

With a little extra speed, I just nudge the planes down and the boat heads underwater. The APC keeps things pretty level, maybe with just a touch of down control to counteract the positive bouyancy. I was able to skim along at periscope depth very nicely with this configeration. It's also vital that the boat sit level when on the surface.

Friend Mike also has a Bluefish with only bow plane controls. He also was a little heavy in the bow. He had a lot of problems keeping the stern down with the bow planes trying to control the dive.

The real boat manual for fleet subs states that bow planes control depth and stern planes control pitch. I like the stern plane control that I have. The sub makes realistic dives once you convince the bow to go under.

Jim S

[steve_of_ar]

John - glad to hear

[color=#000000]John - glad to hear the stern control isn't a problem, especially since I saw in the other thread that you have an Alfa (just got mine yesterday woohooo!)

Jim, your report that the dumas bow-only control can have control problems got me thinking - why would the bow controls not be just as effective as the stern controls? I'm thinking it's probably the weight distribution]

[craigf]

I was pondering the bow/stern/both

I was pondering the bow/stern/both planes thing myself recently (new Albacore, some versions had bow planes too). I don't mean to be flippant, and fluid mechanics (any fluid, air/water) was my worst subject in school, but I'd say the stern planes control pitch better for the same reason that planes have their elevators at the rear (they don't *have* to, but there's a reason). It has something to do with the fluid flow, the bow fluid flow is much more disturbed than the stern flow, the stern flow is more "even" (there's a proper term that I forget) and the stern planes get a better "bite" and have more effect.

[Guest]

I would say the reason

I would say the reason for having an elevator at the rear is more to do with the moment of force. The further away the elevator is from the main wing the greater force exerted.

In the case of submarines forward or rear planes work equally well with regards to diving the boat- ask any Graupner Shark owner. It all depends on where you decide to balance the boat with regards to the c.o.g (centre of gravity).

Bare in mind, most subs work well when you follow aircraft conventions.

Looking at the average nuke- they are shaped like a symmetrical wing profile. Balance a third of the way in from the nose and you are pretty much in the right ball park.

Move the c.o.g further forward and the boat will still work, but will likely be a little over stable- just like an aeroplane.

Further back and the boat will be skittish, just like a tail heavy aeroplane.

For ultimate control, all control surfaces should be spaced as near to the end of the hull as physically possible. In the case of scale designs, the positions are already decided. Sometimes (infact a lot of times) these are a compromise, flow characteristics, stresses and noise often playing a factor, most of which have no comparison on a model.

Andy