Bronco Type XXIII in 1/35th scale

[Warpatroller]

Yours is the first XXIII model I've ever heard of having a porpoising problem.. It seems unlikely that the cause of the problem is due to the hydrodynamic form of the XXIII model itself. It has always been referred to as a well running model by its owners. I've even seen small 1/72 scale versions running with out porpoising while submerged.

Only thing I can add is that your stern dive plane throw of 40° to 50° is rather aggressive compared to the real boat. As you can see in the diagram below, apparently, 26° was the throw on the full-size boat. With 25° on the rudder.

How about this test for the pitch controller (angle keeper). Disconnect the angle keeper from the stern planes and lock the stern plane pushrod into a neutral position, leveling the planes. Run the boat that way and see if there is a noticeable decrease in the porpoising phenomenon. If so, I would think something is not right with the angle keeper device.

The hull itself is a sound design, so it must be some sort of control related issue.. It would be disappointing to find that this boat doesn't perform as well as the 32nd Parallel model. All that work and with such a nice scale propeller that you made, there has got to be a solution!

Steve

[He Who Shall Not Be Named]

Good stuff there, Steve.

I'll first try another angle-keeper. But your lock-the-stern plane idea has merit. Food for thought. Thanks. We'll find the problem.

M

[redboat219]

If that doesn't work. Might I suggest doing some flow pattern analysis around the hull.
A water tunnel or tow tank would be best but tuffs of cotton taped around the hull and a fan would do the trick.

BTW, can you show us q video of the XXIII porposing. Watching it can help analyse whats causing the problem.

[He Who Shall Not Be Named]

If that doesn't work. Might I suggest doing some flow pattern analysis around the hull.
A water tunnel or tow tank would be best but tuffs of cotton taped around the hull and a fan would do the trick.

BTW, can you show us q video of the XXIII porposing. Watching it can help analyse whats causing the problem.

...yeah, I'll get right on that, Mr. Wizard!

M

[ffr2608]

What happened to make it simple?
Proven hull. Probably more rc running time than any other sub here in the states. There were tons of 32p type 23's running in their day.

D

[He Who Shall Not Be Named]

What happened to make it simple?
Proven hull. Probably more rc running time than any other sub here in the states. There were tons of 32p type 23's running in their day.

D

I know. This is killing me. Simon's 23's worked great. And, as you indicate, so many have had no problem driving these things. Yet me, Mr. know-it-all (and, I do!) can't get this 1/35 Bronco 23 to play nice. Argh!

M

[Subculture]

Have got zero experience of Type XXIII, but lots of experience of Seehund which is very similar in hull design, like a baby Type XXIII. I ran that minus a leveller for several years, because you couldn't purchase one, and I didn't know how to make one, and it was a very easy to drive boat.

So maybe worth disconnecting the leveller altogether and see how it drives on manual.

[Scott T]

Try and duplicate the porpoise action on the workbench.
Raise and lower the end of the sub at the same rate of
motion you observed in the water test and see what
your leveler is doing with the control surfaces.

[He Who Shall Not Be Named]

Try and duplicate the porpoise action on the workbench.
Raise and lower the end of the sub at the same rate of
motion you observed in the water test and see what
your leveler is doing with the control surfaces.

Did that first off. Looks like proper response to changes in pitch. But hard to tell unless in crystal clear pool water, and have not had access to that kind of water of late.

M

[He Who Shall Not Be Named]

Sam, and you other guys who have just come to realize that the King has no clothes on:

As I said over at Manfred's Type-23 conversion thread, Gene Berger suggested that my problem with the constant wild pitching down of the boats bow in submerged trim might have something to do with an out-of-align thrust line. Last night I checked it out and he was right,

Yesterday, before attending our third Nauticus run of the year, I replaced the angle-keeper in the boat, thinking maybe that was the source of the problem. And it was not. Yesterdays disastrous runs with the Type-23 was again with a boat that pitched down once the boat was in submerged trim and underway. Damn thing!

That's when my mentor, Gene Berger, came over to me, pitching (get it!) the thrust line issue: that I had incorrectly mounted the propeller shaft bearing foundation piece into the stern. And last nights measurement of angular displacement proved him right -- the propeller thrust line was about three degrees negative to the boats longitudinal center line. That's not much of an angular displacement, but I'm clutching at straws at this stage. I'm fixing that this morning and will run in a local cess-pool (flood-control basin) this afternoon.

There are two people on this planet I don't question when they give me an asignment ... Gene is one of them.

[goshawk823]

Thanks, David (and Gene). Hopefully you'll have better news later from your modification.
regards,
Sam
My apologies to Manfred for stepping on his thread as well...

[He Who Shall Not Be Named]

My fault there, Sam. I started that chain-of-thought in Manfred's thread.

You going to make the SC SubRegatta?

M

[goshawk823]

no sir. we're helping our daughter move that weekend.
-sam

[redboat219]

Shouldn't the angle keeper counteract that downpitching?

[He Who Shall Not Be Named]

Shouldn't the angle keeper counteract that downpitching?

You would think. But, obviously not.

Just got back from running it with the corrected thrust line. No change. Pitches down when underway in submerged trim.

Now, one thing I'm doing that most don't do: The two big square holes where the shutter doors normally fair in with the hull are not present on this model -- I had planned to later equip it with practical torpedoes. Maybe that is contributing some sort of turbulence that works to push the bow down. I'll check it later in the day when the heat dies down a bit.

M