Retractable bow planes

[cstranc]

Does anyone have and pictures & words of wisdom for building retractable bow planes? I am looking for the style used on a modern Russian sub like an Akula where the bow planes rotate back into the hull.

Back at the 2006 Carmel regatta I took the following pictures to inspire me.





I am thinking you have to figure out how to:
- Retract & extend the planes.
- Rotate the extended planes.
- Make sure you do not rotate the retracted planes.

So how are people doing this?

[KevinMC]

Hi Chris,

Long time no hear!

I've

Hi Chris,

Long time no hear!

I've had the bowplanes operational in my OSCAR for a full season now, and by and large they work very well.

I based my retract mechanism design off of some photos of an Engel Akula (thanks again Libor!) but it's all built up from a pair of brass tubes, one riding within another. The brass tube dimensions are not critical, I used the sizes I did based on the minimum diameter I could get a 3/32" wheel collar to fit in. Here's a parts breakdown:



The 3/8" brass tube forms a base, or retract support which can be glued to the hull directly or to some removable assembly. (I glued mine into the hull, which is why I have the angled cut on the top of this part.) You'll have to cut a "track" that runs ~90deg around the circumference of the tube for the plane shafts to ride in. This track defines the allowable retractions angle of your planes and also prevents the inner tube from sliding out once the plane shaft is inserted.

The 11/32" brass tube with a short control arm soldered to it forms the retraction mechanism. You'll need to drill a hole that runs clean through both sides that the plane shaft can rotate in. Since the inside surface of this hole forms the bushing that your planes will ride on, make sure the hole is closely sized to your plane shaft diameter.

The 4-40 ball link assembly is used so that when the planes retract, the servo which drives them can remain connected. Although there are sound technical reasons for the mechanical systems I've seen which disconnect the plane pitch servo from the planes when in the retracted position, they require careful realignment of the servo with the planes before the mechanism is engaged (otherwise having the potential for jamming up)- My solution requires that the pitch plane linkage not be actively driven when the planes are in the retracted position, but will not jam up if the planes are driven or not set perfectly to neutral when the planes are retracted or extended.

Here's a couple more shots of the system when I first installed it.







To answer your question of how to not control the planes when in the retracted position, I currently have them driven from a mixer in my Tx, and that mixer is activated by the same switch which controls the retract servo. As a result, when the planes are retracted the mixer is not enabled and no motion on these planes is commanded when I move the pitch stick on my radio. (Motion does however take place on the stern planes.) When I extend the bow planes, the mixer is engaged and moving the pitch stick on my Tx now actuates the bow planes. (FWIW, I have another mixer electronically connected to the stern planes so that when the bow planes are extended the stern planes are only driven by the APC.) Unfortunately, all this mixing is somewhat complicated and beyond the capabilities of some radios. (I'm not sure what you're running from.) It also does not allow the use of an onboard depth keeping device so this is a temporary solution. I have an electronic module planned that will take care of all this and make things much easier...

[cstranc]

Kevin,
Thanks for the

Kevin,
Thanks for the excellent info. I have tried to build something like this. I find it tend to bind. I was really careful with the alignment but still it's not really smooth when rotating the planes (when extended).

Do you use two servos - one to extend / retract, and one to rotate while extended?

[KevinMC]

Yes, that's correct. In fact,

Yes, that's correct. In fact, my retraction servo is just that- a retract servo. The advantage is that it's designed to always rotate through 180 deg, but you've got no proportional control over it so all the end points must be adjusted by your linkages. The really nice part about the non-proportional control however is that I'll be able to dual-use this channel for other things like radio mast retraction control.

As far as the binding is concerned, this is why I chose to use lengths of brass tube as the "bearing". The only thing I had to be really carful of to prevent introducing binding was in the milling of the radial channels that the bow plane control shafts ride in- if they're not filed/sanded smooth they will make the mechanism difficult to operate.