Lateral Stability Problem

[Walter Snowdon]

Hi Daryl, I used carriage wheels sold by HOBBYS LTD. for my wheels on bohemia. they were the right diameter and by removing alternate spokes i got a nice set of wheel frames which are very strong and run true without any wobble and are VERY cheep.( £2.99 for four wheels). As you say, the wheels in the kit are an abomination. Onto the PHANTOM wheels- I think the big problem is the solid disc Glyn Guest  uses as the inner face of the wheels. this works like a scoop and the water can ony escape via the front face of the wheel. Enlarging the plan meens that an even greater amount of water is lifted. Add to this the leaning tendency in a turn means that the floats are immersed even more deaply, thus lifting more water adding to the problems of escaping from the box till you reach a point where the water lifted is greater than the area for it to run away thus you get into a hydraulicing situatin where a paddle box is always full of water. I also think that on PHANTOM the floats need to be narrower and wider. Regards, Walter

[Peter Webster]

Walter,
           As usual your explanation makes total sense but do you mean narrower floats and wider paddleboxes. as this, along with a redesign of the wheels would be making sense.
Peter ( with the problem) Webster.

[Daryl]

Hi walter,
Thats exactly the problem we had with Bohemia the paddles acting like a scoop. We solved it by making new ones and having a 3mm gap between the paddles and the hub of the whhel thus allowing the water to escape and not get carried around the wheel like a scoop.

Daryl

[Walter Snowdon]

Hi Peter, sorry for the confusion. Thr length of the blade is the  horizintal blade across the paddle frames. Blade width is better described as the depth of the blade!. Long narrow blades are generaly more effective than wide blades as they generate good drive without lifting too much water. Also blades do not need to run deep, in fact, they are probably most effectve with the top edge only just immersed , or even above the meniscus of the water.  Sorry if this sounds like gobbledygook!!. My usual rule of thumb is that only three blades should be touching the water, One just immersing, one immersed and one lifting out of the water. All the best, Walter.

[Peter Webster]

Walter,
           I have just posted a photo of the Phantom and from what you say it is the floats  causing the problem so my next job will be a new set of floats as you stated ie long narrow blades and I will also make a second set with less floats per wheel and see if they show any marked improvement.
Peter Webster

[Roderick Smith]

Reading Walter's advice reminded me that I had this photo, which Sean sent me as a mystery quiz.
How do real-world clearances compare with the advice given so far to solve model problems?
Some real-world aspects do scale directly to models; others don't.
High-school science, explaining why giant monsters from outer space won't exist: mass increases with the cube of size, but bone strength increases only with the square of size, to large monsters can't support themselves (which is why dinosaurs lived in swamps).  Perhaps water drainage is one of these?

After only a few days of running the replica Lady Augusta, the operators trimmed the floats to make it cruise better.  I don't what the problem had been.

I was chatting with F05's builder at Echuca, and he discussed paddles on some of his earlier boats, and which boat had the most efficient ones.  When comparing two particular ones , the lower-powered one cruises faster than the higher-powered one, simply because of better wheels/floats.  This was enough to make me realise how difficult it is to get the proportions right, and not enough to help me go out and designe the perfect paddle.

Regards,
Roderick B Smith
Rail News Victoria Editor

[Roderick Smith]

Knowing that I would be in western-suburban Melbourne today, I arranged with Peter W to visit his group's operating session this afternoon.  There were three paddleboats on the lake today, plus a fast planing launch.  The paddleboats were:
* The long & lean Phantom, gliding at realistic speeds and with stability which pleased the builder.
* Pevensey: an earlier boat by Peter, with wool bales (and not a pitched roof of canopy), providing a convenient housing for equipment.
* A partly-finished Industry (no superstructure yet) from a different builder.
The whole session was very educational: my 180 questions in 90 minutes were answered very clearly.  I was able to see practical demonstrations of all of those diagrams and ballasting hints and floats which I have been reading in this forum.

I enclose a photo taken on the picnic table, giving some idea of scale and size.  All of these boats are powered electrically.
After seeing Peter's news of the project, I have added a couple more.

Thanks to the group via Peter,
Regards,
Roderick B Smith
Rail News Victoria Editor

[Peter Webster]

Eddy and the gang,
                            Last night I made one more alteration to the Phantom.
I changed the batteries from 2 x 6v 4.5amp standing upright in the hull to 2 x 6v 2.3amp laying on their sides behind each other thus lowering the ballast even more and also not requiring the bags of lead shot that I previously had to use to statically ballast the model. It is now super stable and even moving the rudder side to side rapidly has no effect on stability.
More photos coming soon and also it was an enjoyable time, albeit short, that we spent with Roderick. My next task is to get him to build something that floats instead of running on rails and I will probably need any help from other members to.
Till next time
From very wet Melbourne
Peter Webster