ballasting a paddle steamer

[Alasdair AllanParticipant @alasdairallan37423]

Hi – I realise I have been a regular correspondent of late! I know that model paddlers are murderous to try to trim ballast on. I thought I had everything sorted when, all of a sudden, the boat developed a completely new problem – sitting at a list in the water and not righting herself. The problem is the same whether the boat is prodded to post or starboard – the list adjusts accordingly. I checked to see that there was no water or other shifting ballast on board.  Have tried taping lead to both inside and outside of keel. I suspect the boat is now over- ballasted, and I need to strip back the ballast and start experimenting again, but any top tips much appreciated!

[Colin BishopModerator @colinbishop34627]

Alasdair,

What you describe sounds like ‘loll’. The boat will float but leans either side or the other which is a stability issue.

Brief description here:

https://www.wartsila.com/encyclopedia/term/angle-of-loll

Paddlers like yours with their shallow slim hulls are particularly susceptible to this which is why I chose Bilsdale for my prototype with it’s much fuller ‘chunkier’ hull.

From my experience with Bilsdale, there are two main factors with the model. Firstly the paddles need to be properly immersed and the plans should show the waterline to be aimed at to achieve this.

Secondly, the ballast must be as low as possible to achieve maximum stability. Sometimes this is not possible within the shallow hull so alternative measures are needed.  Even with Bilsdale’s high displacement hull I found there was an issue and the solution was to add ballast to the bottom of the hull. This can be done by adding a weighted false keel or simply by attaching ballast to the bottom of the hull where nobody will notice it. I went for the latter solution using self adhesive motorcycle wheel balance weights with a waterproof resin coating. See photo below.

You can run a test on this by suspending a steel or iron rod/bar immediately beneath the keel to see if this improves stability,

When I motorised my Revell Queen Mary 2 Kit I had exactly the same problem and the boat needed a substantial external keel to keep it stable whilst maintaining the designed waterline. See other photo.

Colin

[Alasdair AllanParticipant @alasdairallan37423]

Many thanks Colin. With lead taped to bottom externally she is a bit better. In fact she rights herself when moving. Mainly lolls now when not moving.  I think I will try  the motorbike wheel eiight solution, as I dont have a lot more ballast I can add without reducing freeboard.

[Alasdair AllanParticipant @alasdairallan37423]

Interestingy (although infuriatingly) the loll problem only happens with the funnel on, though thatt is not too heavy. it must, as you say though, make the difference in terms of centre of gravity.

[Colin BishopModerator @colinbishop34627]

Yes, paddlers are particularly critical in terms of stability. You have a long slim hull then hang a couple of substantial wheels on the side. I did think I had sidestepped the problem with Bilsdale with her much fuller hull form and by building the upperworks as light as possible but stability was still initially marginal. Fortunately she was still riding a bit high in the water so there was scope to bring her down to her marks with weight on the bottom which I had not expected to be necessary. It’s all literally a bit of a balancing act.

Any chance of fitting a lighter funnel? I used lightweight electrical conduit.

Colin

[John W EParticipant @johnwe]

hi there I dont think the problem of listing is just confined to narrow beamed hull paddlers – as I have the same problem with my Forceful Paddle Tug.  My first initial thoughts were, it had been caused by the paddles being non-feathering & they were trying to pull the hull into the water.  However, as I discovered, at rest the hull still maintains a list.  So, like everyone else, I added more ballast.  The ballast did nothing really – it just made (if anything) worse.  Due to the fact the paddles were then sitting too deep into the water then.

So, I just really added sufficient ballast to the hull to bring it to the water line and left it at that.  I live with the problem of listing.

I just say – well the skipper has had too much to drink and he is standing on the wrong side.

John

 

[Alasdair AllanParticipant @alasdairallan37423]

I am keen to solve the problem if I can, so thanks for this advice.  Having been a helmsman on an actual paddle steamer in the past, I can confirm it is very difficult to go in a straight line unless both wheels are fully in the water! I think the best bet is going to be the weights stuck to the bottom, as there is very limited scope for reducing weight up top.  I now understand the benefit of deepening the hull a wee bit beyond scale to allow for lower centre of gravity. I don’t think this is too serious a problem as, from bath tests, she seems very keen to right herself once the wheels are moving, but Isuspect this is a boat for taking out only in fairish weather.

[Alasdair AllanParticipant @alasdairallan37423]

The only other solution that I can think of , off the top of my head, would be to invent some device that gave her a small nudge from afartright her. No idea what such a device would be!

[Colin BishopModerator @colinbishop34627]

There is no doubt that paddlers can be tricky subjects to model which is why we see so few of them. Stability is often an issue and model engineering skills are needed to build feathering floats, I don’t have much in the way of these so it would be beyond me which is why I am using the Glynn Guest fixed float design. They do generate plenty of thrust.

I am hoping to meet Ashley on Sunday at Bushy to photograph My Greek fishing boat and I intend taking Bilsdale along so we can have a bit of a play with her. On initial trials there was a bit too much wind which caused the lee side wheel to dig in.

John,

on looking at the Director class body plan the hull does seem to be heavily round bilged, maybe to help with handling, so it might not be as intrinsically stable  as it first appears. My Bilsdale is based on an earlier paddle tug design, has a much squarer bilge and therefore the hull has a higher block coefficient than the Forceful.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Strip ballast under the hull on the centreline is my go to

Weight where you want is assisting self-righting and also it acts as a bilge keel, dampening down rolling.

Ashley

[Alasdair AllanParticipant @alasdairallan37423]

Thanks for advice – I have tried all these options at distributing ballast, and the one that looks like it is going to work is a short weighted keel hanging about three inches below the boat.  I mocked up one of those and it cured the loll and stability problems right away. I am not going to drill a hole in the boat but instead will try to make a removable keel that i can bolt on and off some mecanno type brackets cemnted to the bottom of boat about the mid-length of actual keel.

[Alasdair AllanParticipant @alasdairallan37423]

I think I can work out how to make this- main concern is that p38 or something similar will hold it successfully to bottom of the hull.

[ashley needhamParticipant @ashleyneedham69188]

Letting a couple of stainless steel nuts into the hull would allow some bolts/set-screws to be screwed into them securing the keel to the hull. Unobtrusive when the boat is out of the water…?

Ashley

[Alasdair AllanParticipant @alasdairallan37423]

Thanks Ashley. You mean fixing the nut into a hole in the hull? I would probably feel happier drilling it into bit of plywood which i then m38d  onto the bottom. Actually that  might be an elegant solution.

[Tim RoweParticipant @timrowe83142]

Sailing yachts generally have long slim hulls and extreme angles of loll (LOL) without a keel.  Why don’t you paddlers build a slot in the hull into which you can plug a ballasted keel.  The additional weight would not have to be great due to it being much lower down and it would be far less obtrusive in display mode than bits stuck to the bottom on the hull.  The keel would also dampen the tendency to roll and therefore help with equal paddle immersion

Admittedly might be a bit tricky to retro-fit but for a new build it would be a doddle.

Here is the keel box on sailing yacht Galileo.

Here is the keel box before gluing together for Eventide. Note that it is very important to seal the internal surfaces before final assembly.

Tim

 

 

[Alasdair AllanParticipant @alasdairallan37423]

Thanks Tim. Yes retrofitting into a fibreglass hull would I think be possible but a bit squeamish about trying it. Instead i think i will try to fit a small plate and nut to bottom of hull. Not ideal, but possibly best compromise here!

[Colin BishopModerator @colinbishop34627]

You could consider making an external slot using aluminium angle. Bolt a couple of lengths to the underside of the hull and close together and seal the bolts on the inside. Before doing this, drill some holes in the other face of the angle sections so they match up and then you can hang whatever you like beneath the hull using horizontal bolts through the sides of the ‘slot’. This sort of mounting means that you can experiment with different types of ballast. Also you only need to drill four small holes in the hull rather than undertake major surgery.

https://www.screwfix.com/p/rothley-aluminium-angle-1000mm-x-20mm-x-20mm/462jp

As Ashley says, any mountings attached to the bottom of the hull are essentially invisible.

Colin

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