Paddleducks
Paddler Modelling => Construction => Topic started by: Peter Webster on March 27, 2005, 07:57:13 PM
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Can anyone help,
We have recently r/c'd an old static kit called the "PS Ailsa Craig" but have a problem of it listing from the slightest wind puff and will not recover. We have opened the paddleboxes and added a keel but to no avail. See the attached photos
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I have one of those, it's a kit that used to be available (I think?) PBM 'Edwardian Paddlesteamer'. I bought mine as a completed static model and changed most of the original details and layout to make it look more like a south coast ship and also make it easier to handle (for example, replaced the plastic railings with brass ones as they get broken too easily...)
(http://www.btinternet.com/~mjt60a/ubb_link_images/connaught02.jpg)
I too find it very unstable in even a slight breeze despite using the lightest possible motor/speed control and making up all the ballast in a lead bulb type keel 3" below the hull. I've also found that when it 'lists' the paddle seems to expel all the air from the paddlebox which then sticks to the water surface, openings in the vents (which are actually just depressions in the surface) should allow the ship to right itself if/when the wind drops, though I haven't tried it yet....
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hi Peter - seems like one of the things we cannot control is scale placement of mass in a model & it reminds us only too well of PJ's comments years ago about building light, but looking at the snaps a number choices appear possible [although a little radical]
1) the new keel in it self not right the vessel from a list but will assist in maintaining the vessels attitude or angle of list when @ speed - so we need to increase the hull displacement by a % of new keel [foam & fiberglass all blended & contoured to the original hull proportions], then collapse the foam internally & add lead ballast to compensate for the greater displacement - by installing the lead this way will naturally have a pendulem effect & will minimise the tendency not to self right from windage or a turn
2) reduce top side weight, however if she was kit built I could not see too much reduceable weight in the kit components, but the funnel looks thick walled or is it just a funnel topping?
3) reduce windage - open up the windows beneath the funnel & above the paddel wheel axis
So - 1) may seem radical, but will work - a helpful calculation method is to fill the bath then use a set of kitchen scales & press down on the vessel until you achieve a unit [say 10 mm] of greater displacement & record the force required to achieve this - from this you can get a correlation of the mass required to get the vessel [by the same unit] lower in the water - Derek
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This model is the old EDWARDIAN PADDLE STEAMER issued by PBM models from HA BLUNTs model shop in Mill Hill London for a very few years between I think 1978 and the earely 80s. It was a very good kit for its day and to my mind superior to the "plasiky" offerings of today.
I have built two of them and have a third unstarted which I got off ebay ( I have a very soft spot for this kit which can be altered to resembly a great many UK paddlers).
MODEL 1. I built as per kit with, you guessed a permanent limp after every turn!. As the sponsons are very close to the water, any list means that the gap between the box and the surface is too small for the box to "breathe" causing the box to fill with water and lifting the opposite paddle out of the water so that it cant lift any water to counterbalence the other side! (Phew). my partial remedy was as follows: cut out the paddlebox slats, allowing some air to enter
the box low down. Remove the walkways on top of the box and drill 2 small holes in the box top (about 1/8 ") Replace walkway making sure that air can get to holes. This allows some air to enter the box top, breaking the Hydraulic effect.
If you still get some listing, stop engines and gives a short burst astern, this should allow the water to drain from the box.
Add a small removable bulb keel as per model yachts , about 3" deep about the weight of 2 AA batteries. Use smaller reciever batteries to compensate for weight increase.
MODEL 2. As above, with the following alterations. Remove large areas of the bottom plank which allows batteries etc to be placed lower down and add a 1/2" balsa sheet to the bottom. This has two effects, lowering the weight assists stability and the extra plank increases stability so that ballasting can be added, in my case, a1/4" square strip of lead let into the new plank on the keel line. Result perfect stability.
MODEL 3. Will have much of the wood replaced by thinner section and some of the internal structure deleted as in some respects the kit is over engineered. This is a really pleasant kit to build and results in a very pretty model. Best of luck, Walter.