Models by Design Cygnus 33 1:16 scale

[Paul FreshneyParticipant @paulfreshney24971]

One or two of you are aware that this new model of mine had an unfortunate maiden voyage in mid-July when it capsized. This was in spite of it being ballasted correctly to the scale waterline and although a bit roly-poly in the test tank, had recovered well enough to remain upright. On our Fishers Green pond it proved quite a handful on the maiden voyage, until it drove the port freeing ports underwater and the resultant volume of H2O) on the deck meant it did not recover to a vertical position. Thanks to prompt action by fellow members, it was speedily recovered and indeed was undamaged with nothing lost at all, so that was the first bit of luck.

Analysis at home concluded:

It was top-heavy, which is obvious really.

The 950kv Turnigy brushless motor, although turned-down to 35% of its maximum speed was still far too powerful and torquey.

The propeller was perhaps too big.

It certainly needed a liferaft for the non-existent crew!

Well, by 5pm on that fateful day, this inshore trawler was ready for sea again (although still awaiting the liferaft), but these pictures are from 2 weeks later.

3.5lbs of ballast had been added, making it float deep by approx. 3.5mm, but more important the C of G is now much lower.

A 300kv motor from Alistair Engel (the German submarine guy) has been installed which on a 7.4v LiPo produces just 2220 rpm max.

A smaller propeller has been fitted.

A four man liferaft container for the non-existent crew was made using dimensions ex-Internet.

Not in these pictures from 28th July are the trawl boards and minor additional rigging.

Yes, it floats slightly deep now, but that doesn't notice when on the water and I can always add a 5mm boot topping if I get the urge. Performance on the water is now perfectly fine and controllable and a subsequent continuous 2 hour sailing session resulted in no water inside, no significant rolling on turns and a dry boat in average conditions.

So, the point of this little homily is that we (I) don't always get it right first time, but on the first ill-fated voyage, as soon as the problems became evident, about 5 seconds after leaving the pond's bank, it should have been recovered rather than pressing-on for another 10 minutes with an ever more poorly handling model. The safest place for a model boat in such circumstances is on the stand!

Paul F.

[Paul FreshneyParticipant @paulfreshney24971]

[Bob Abell 2Participant @bobabell2]

Hi Paul

Could the instability be a timely warning for the full size craft?

Bob

[Colin BishopModerator @colinbishop34627]

I wouldn't have thought so Bob. Scaling down inherently results in a loss of stability compared with the full size version plus the materials we use as modellers to build superstructures and most fittings are proportionately greater in weight than their full size counterparts. That is why while big cruise ships are stable enough, trying to make a model one poses a lot of practical problems.

Colin

[Paul FreshneyParticipant @paulfreshney24971]

Hi Bob

It perhaps explains why some full-size craft of various types capsize easily. On this model the hull is very 'round' and as I said with the extra ballast it is fine. In hindsight I should have raised the waterline by 5mm before painting, but there we go,

Paul.

[Bob Abell 2Participant @bobabell2]

Thank you, Colin and Paul

One final point……..When Paul first decided on his waterline…….Did he decide on a laden waterline or what?

Any idea what the waterline difference is, between laden and unladen?

I`ve got a similar problem with Silver Mist…..

Very round hull

Very light ballast…..Predicted by others!

Using Designers waterline as on drawing……….Surely, we`d like to know the waterline range available?

It`s very rare for a model to capsize, but it certainly caught Paul F out, with his trousers down!

Bob

[Colin BishopModerator @colinbishop34627]

As a pleasure craft, the difference in draught between light condition and fully laden for Silver Mist would be pretty small, basically just the weight of the crew and their sandwiches. It would be different for a commercial fishing boat which puts to sea light and hopefully returns with a full fish hold!

One feature of these types of hull is that as they float deeper the immersed hull gets wider so you can add significant extra weight without affecting the waterline very much.

A further comment on stability: fishing boats have to have good reserves of stability as they are intended to haul heavy nets full of fish out of the water. This is particularly critical if they are hoisted over the side, less so if over the stern but the C of G must still be adversely affected in either case.

Colin

[Bob Abell 2Participant @bobabell2]

Thanks, Colin

Are Trawlers fitted with Plymsol Lines?

I read somewhere that Great Eastern had several paddle diameters to cater for cargo and coal variations

Bob

[neil hpParticipant @neilhp]

some of the larger 100 mtre purse seiners operating from Peterhead, Aberdeen and Scalloway and Lerwick in the Shetlands which double as factory freezers do have to Bob……….but the smaller ships and near water boats don't carry the marks.

[Bob Abell 2Participant @bobabell2]

Thank you, Neil

Nice to know you are still around

All the best…….Bob

[Paul FreshneyParticipant @paulfreshney24971]

When staying at Sutton Harbour in Plymouth recently, that part of the docks has the fishing quay. There were numerous fishing boats of varying sizes and although there did not seem to be much activity at the weekend, on the Monday morning there were lorries and vans suddenly all coming and going. Some of the fishing boats were pristine and some well-weathered. Many had extra (after-build) panels on their hulls either on the sides or stern quarters, presumably to protect or reinforce their hulls against the nets and ropes etc.

Not all had boot toppings, and some that did had distinctly non-straight ones surprisingly. Some were floating well below the marked waterline, i.e.. were very light and others were more or less on it. Some were deep at the stern, but light at their bows.

Most had huge amounts of cordage and nets piled on their decks,

This Cygnus 33 of mine is a generic version, that is to say it represents something typical. It could probably do with a rope hauler and some other fittings, something to think about once the chore of decorating has finished.

The Engel 300kv brushless motor is fantastic. It can turn the prop' at next to no rpm and on another two hour continuous sail today, consumed just 1.6 amps from the 4000mAh 7.4v 2S LiPo battery. It is not geared and is intended for Engel's submarines. I have not seen such motors elsewhere.

Paul F.

[Bob Abell 2Participant @bobabell2]

Thank you, Paul

You are are wealth of Trawler information!

A Plymsol line would be nice to see and give the viewer something to ponder?

Your model looks extremely clinical

I have an pet theory on that……….In a show case……Prestine is the order of the day, but in the water, working boats need to look like workers…………eh?

Your predecessor liked his models well and truly weathered, in fact his weathered models had a big impact on me

It was a shock to the system……..Was he called John Cundall?

Bob

[Paul FreshneyParticipant @paulfreshney24971]

Bob

Some fishing boats at Sutton Harbour were quite pristine and some were quite tatty. What I was trying to say was that in practice either option is okay, or even in-between, and floating perfectly on the marked waterline, something that the MPBA were keen on in their scale competitions a few years ago, is not always correct either. Mine has weathering that becomes clearer if examined closely, but fades when viewed from a distance – that is my style as is the satin finish.

John Cundell – still going strong but heavily into Croquet now, Indeed he has written a book on it and has (is?) been a member of the UK's top team.

Paul.

Paul

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