Model Boat Mayhem
Mess Deck: General Section => Model Boating => Topic started by: funnel on September 01, 2021, 05:42:36 pm
-
Hello
I can foresee with one of my models that at high speed it may want to roll too much on the turn. Obviously a slower speed could be done on the turn but I wondered whether anyone had designed a counter- balance device one could place inside the Hull to counteract the problem.
Toby
-
Moveable trim tabs on the transom reverse connected to the rudder linkage?
They'd need a very fine adjustment capability to get the anti-bank amount correct, but it should work I'd have thought.
-
It'll take a fair amount of effort for any weight to overcome the centrifugal (centripetal? I can never remember which) force, either for an in-hull pendulum out from the keel or a slide/screw across under the deck. This assumes that the roll is outwards. If it's a powerboat banking inwards, then the forces are on your side.
-
You are probably correct, but I just recall that a modeler had installed a device, but now I cannot remember where.
The boat is a German Wal schnellboot. I have to check photos etc but I don't think that it has trim tabs on the transom on the original.
Toby
-
Depending on the model a movable lead battery could solve the problem(or part of it), connected either straight to the steering or preferably through a gyro stabilizer that keeps the boat horisontal.
I had my batteries come loose in my springer tug recently and it got quite alot of slant i belive its called(the boat banked heavily to one side).
-
Helpful and interesting idea. Thanks!
-
If you add weight then the model is likely to go slower anyway!
It may be that you are attempting to drive the model faster than it was designed for. The Scnellboots were fast but they did not have planing hulls so they would natuarlly roll in a tight turn unless speed was reduced.
A quick Google brings up the following:
Small rudders added on either side of the main rudder could be angled outboard to 30 degrees, creating at high speed what is known as the Lürssen Effect.[5] This drew in an "air pocket slightly behind the three propellers, increasing their efficiency, reducing the stern wave and keeping the boat at a nearly horizontal attitude".[6] This was an important innovation as the horizontal attitude lifted the stern, allowing even greater speed, and the reduced stern wave made E-boats harder to see, especially at night.
Colin
-
I would agree with Colin- the E boats or S Boats were fast in a straight line but they aren’t planing hulls but a really good all round sea going boat which what made them so effective in the war. I’ve seen people try to get lifeboats up on the plane- once again they are not planing hulls but good all round sea going boats. The only real boats that properly plane are hard chined boats like British MTBs and HSL used by the RN and RAF but these boats have limitations in sea going capabilities- very fast in calm conditions but in heavy sea states they tended to be quite fragile.
Personally I would just slow down in the turns but most lightweight boats will roll in to the turn whilst heavier vessels like destroyers will lean out. Trying to fight the natural compulsion of the hull may cause other problems as it may put more stress on the drive system or steering mechanism.
-
As Nick says, heavier vessels tend to lean out.
Colin
-
Colin and Nick,
Thank you for your thoughts. Likely as not it will be the usual slowing for turns, for I am not really a speed merchant, but some interesting thoughts have been raised.
I am working on mechanism for the Lürssen effect in my S38 but that is not the Wal 1.
I would have attached a photo of the Wal, but for some reason the 'add image to post' and choose file options do not work.
Thank you to all who took time to respond.
-
Strange no one appears to be on deck. :}
-
Perhaps this works.
-
Old Topic here: https://www.modelboatmayhem.co.uk/forum/index.php/topic,63782.msg674898.html#msg674898
-
I've been working on a similar system which I have trialled to moderate success on a Glynn Guest Type 21 which was suffering from too much top weight. It's still very much work in progress so I won't go into too much detail but essentially it is a low hanging weight within the hull, positioned via a servo, controlled by a microcontroller & accelerometer / gyro. The weight by default sits as low in the hull as possible and as it tries to lean the servo rotates the weight the opposite way exactly as a person balancing themselves with their arms does. I had quite a time finding a servo that was fast enough to ‘get ahead’ of the movement so it wouldn’t just wildly amplify it. What also didn’t help was the physically tiny size of the model I was working with.
My conclusion so far is that it can work but any kind of passive system is far superior… I had much more positive impact with much less effort by reducing the top weight and adding steel bilge keels.
I’m still planning to progress with it as I think now I have fixed the underlying issue and the model has natural stability, it could rather than stopping the roll, it could modify it so that the small model could sit in choppy water with the presence of a much larger ship. Also the heel angle on turns can be controlled to look ‘correct’
I also tried controllable trim tabs to pacify a model I had put way too much power into and became terrifying at high speeds but that didn’t show much promise. Lowering one trim tab and raising the other either didn’t have enough effect to counteract the torque from the prop or was just like dropping an anchor on one side and would cause the boat to career off wildly at 90 degrees to the intended direction. I just couldn’t find a sweet spot for that system.
Anyhow if people are interested I could do a bit more of a write up with photos, videos and schematics when time allows.
-
Strange no one appears to be on deck. :}
.
Port 30, Hands to dinner, was a common occurrence on the Grey Funnel Line🙄