Bronco Type XXIII in 1/35th scale

[goshawk823]

understood David! you don't even have to caption them. lol.
-sam

[He Who Shall Not Be Named]

Sam,

At what point along the length of the Type-23 hull did you place your center-of-gravity? After three weeks of dicking around with this 1/35 Bronco Type-23 I still porpoise all over the place! I've moved the c.g. from the 50% point to nearly the 60% point with no joy. You're a long time 1/32 Type-23 driver. Tell me about how well the boat handles underwater; how well it can maintain periscope depth? Is it hands-off or do you have to fight the damned thing every second underwater?

Help me Oby-Wan, you're my only hope! (I hope I'm having an angle-keeper problem and this situation is not design related).

M

[Slats]

Sam,

At what point along the length of the Type-23 hull did you place your center-of-gravity? After three weeks of dicking around with this 1/35 Bronco Type-23 I still porpoise all over the place! I've moved the c.g. from the 50% point to nearly the 60% point with no joy. You're a long time 1/32 Type-23 driver. Tell me about how well the boat handles underwater; how well it can maintain periscope depth? Is it hands-off or do you have to fight the damned thing every second underwater?

Help me Oby-Wan, you're my only hope! (I hope I'm having an angle-keeper problem and this situation is not design related).

M

Whilst not directly addressed to me - I have to ask: David, did you bother to grid the boat's profile, count the squares and find the COG, or was your 50% along -chuck it here approach-, a case of using the force? :wink:

[He Who Shall Not Be Named]

I did more than that, I swung a card-board profile model around, over my head on a string made up to the 60% point. It was stable. But, not the actual model, not in pitch. I'm beginning to think I have an angle-keeper problem.

Jump in anytime, John. More heads are better than two. Good stuff.

M

[goshawk823]

Hi David- sorry for the late reply. If I recall correctly, the OTW Type XXIII COG was about centered under the tower, so about 50%. That was using Bob's compressor based dive cylinder, so the free flood area was in the center.
I had no porpoising issues with that model. It drove great on the surface and underwater. It wasn't completely hands off though.
My only screw up was not using better linkages to the rear dive planes; when going in reverse, the force of the water actually pushed the planes in a more exaggerated position. **** poor planning on my part. The linkage needed to be braced/tunneled better to avoid the linkage rod bending to an obscene angle.
I free floated the stern planes off an angle keeper, and drove the front planes off a servo. Hope that helps some!
Sam

[He Who Shall Not Be Named]

Hi David- sorry for the late reply. If I recall correctly, the OTW Type XXIII COG was about centered under the tower, so about 50%. That was using Bob's compressor based dive cylinder, so the free flood area was in the center.
I had no porpoising issues with that model. It drove great on the surface and underwater. It wasn't completely hands off though.
My only screw up was not using better linkages to the rear dive planes; when going in reverse, the force of the water actually pushed the planes in a more exaggerated position. **** poor planning on my part. The linkage needed to be braced/tunneled better to avoid the linkage rod bending to an obscene angle.
I free floated the stern planes off an angle keeper, and drove the front planes off a servo. Hope that helps some!
Sam

That helps a great deal, Sam. It's now obviouse I have an angle-keeper problem. Good stuff, pal. Thanks.

M

[redboat219]

David
Didn't you have the same problem with your scratchbuilt Hunley which was featured in Simply Submarines.

" It was the boat's static stabilizing forces at work which maintsined a near zero pitch angle. If I kept the speed of the boat below a critical point it could be controlled quite well. However exceeding this 'critical speed' underwater caused the Hunley model to pitch up and down uncontrollably, control restored only after backing off the throttle and waiting for the model to slow beneath the critical speed, at which point the model would respond to bow plane position again."

Could it be that the design of the Type XXIII's hull is suited for slow speed.

[He Who Shall Not Be Named]

Yet, observation of others Type-23's reveal a hull form that maneuvers very well underwater -- mine the exception at the moment. But something to think about, Romel.

M

[greenman407]

Dave, if you remember I had the same problem with the Albacore for a while. Your suggestion helped me to resolve it. If its giving you trouble.............heaven help us.

[He Who Shall Not Be Named]

Dave, if you remember I had the same problem with the Albacore for a while. Your suggestion helped me to resolve it. If its giving you trouble.............heaven help us.

Yeah, Mark. The first things I did was to move the c.g. forward. But the boat continues to dive uncontrollably, or rise uncontrollably. I blame you!

However, during this morning hideous walk (off toilet, my best thinking time) I came up with a likely cause of the wild porpoise acton evidenced by this god-forsaken 1/35 Type-23 kit: too much throw on the stern planes.

As originally set up, there is as much as 50-degree deflection on rise and almost as much in dive. Most control surfaces working a non-compressible fluid stall out at about 40-degrees to flow, and I think that situation is at the heart of the submerged underway pitch problem -- the stern planes are stalling out and providing only drag, but no pitching force at or near full deflection. What kind of dumb-ass puts a boat in the water with throws like that?!

An hour ago I reworked the stern plane linkage and now have it throwing no more than 40-degree deflection rise and dive. I'm filling Ellie's pool ... er .... test-tank for a final trim, then off to the local bug infested, disease saturated swamp to see how this piglet runs now. Film at Eleven, folk's.

M

[redboat219]

Can't wait for the result.

[ffr2608]

Dave,
My epoxy 23 kit drove like a dream. I had the stern planes on an angle keeper and drove with the bow planes. I never had any control of the stern planes.
Might not be what you wanted to hear.

Darrin

[goshawk823]

Dave,
My epoxy 23 kit drove like a dream. I had the stern planes on an angle keeper and drove with the bow planes. I never had any control of the stern planes.
Might not be what you wanted to hear.

Darrin

Yeah Darrin, same thing for me.

[He Who Shall Not Be Named]

Dave,
My epoxy 23 kit drove like a dream. I had the stern planes on an angle keeper and drove with the bow planes. I never had any control of the stern planes.
Might not be what you wanted to hear.

Darrin

Just what I wanted to hear. I'm doing something dreadfully wrong here. You're good experience with the hull-form points to this being a control issue, not a hull-form issue. Good stuff, Darrin. Thank you so much.

M

[He Who Shall Not Be Named]

Yeah Darrin, same thing for me.

Just got back from running the Bronco 1/35 Type-23 at the pond -- same problem. Is was not control surface over-response. Damn! Still chasing this problem.

M