Thames Sailing barge

[Bob Abell 2Participant @bobabell2]

Paul

I have replied to this post, which must have been via Email about 30 mins ago

Had a message saying it couldn`t be sent……..I`ve had a few messages not sent lately……Similarly

Have you received it, please?

It was about my mast being 54" tall and some bumf about full size barges not needing a keel weight etc

Bob

[Paul TParticipant @pault84577]

Hi Bob

Not received any emails from you.

If your 4ft barge had a 54in mast then it stands to reason that an 8ft barge would have a 108in (9ft) mast, but don't give up on building the 8ft barge because of a tall mast as, just like the hull, it can be split down into smaller pieces.

I don't believe that this little challenge would put you off building this iconic model (and it would look great as an 8 page special in MB)

Paul

BTW I appreciate that full size barges wouldn't need keel weights as they had the mass of the hull / cargo to maintain stability.

[Bob Abell 2Participant @bobabell2]

I`ve not got over the shock yet!

What`s the keel weight?

Right then….

Full size barges don`t have a keel weight……We all know that

Model boats do……..We all know that

Had this argument many times in the past

At one twelth scale, could the hull carry enough ballast so that a keel weight would not be required?

Get this mystery!……The hull rotates about the waterline…..The hull is symmetrical. so where is the required counterbalance effect coming from?………That`s a good one?

Capt Bob

[Bob Abell 2Participant @bobabell2]

I've given the above mystery some thought and have twigged it!

Any suggestions out there?

Bob

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Good Evening Bob.

Consider this. When a yacht is sitting up right, the centre of gravity is directly below the centre of bouyency. As the boat heels, it pivots around the centre of bouyency, not the hull centre line. As the hull goes over the c of b moves out board, away from the hull centre line. The c of g goes the other way, creating a power full righting moment.

I would think that an 8' long barge could be made to stand up to her ring with out a deep ballest keel, she is big enough. I would go for a scale depth on the hull, forget about any sort of water ballesting, build the top sides light, the bottom heavy, then use a thickish lead shoe on the out side of the bottom. The thames barge has a very stiff hull shape, once ballested down. At scale draft she would have enough lateral resistance to sail on a close reach, the motor will take care of the windward side of things!

Aj

[Bob Abell 2Participant @bobabell2]

Hello Amy J

You are very well informed regarding the subject!……..I am really impressed and I think we all are!………When I set the poser, I misled the readers by saying the hull was symmetrical, letting the readers think there was no righting moment!

But the righting force comes from the fact that the full size barge pivots about the outside edge of the hull!…And therefore has the full weight of the hull is acting downwards!….ie….I've, twigged it!

I really am impressed with your nautical knowledge, and is nice to read the way you describe things in such a technical way

I was a bit disappointed that nobody jumped on me!…..Including someone I won't mention!

The response has been so poor, I'm beginning to think that scratch building is on it's way out?

Having thought about the madness of building a one twelfth scale barge, I can't face the look of horror on my wife's face when she found out!….I will have to find a way of softening the blow!

Hello Paul. Draw the typical frame and I'll make a sample and we'll take it from there?

Thank you, Amy….Call again

Bob

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Hello again Bob, indeed I shall call again!

The response has been so poor,I'm beginning to think scratch building is on it's way out?

A few theories.

1) No body knows the answer, (highly unlikely)

2) People think that we all have to learn things the hard way (I hope not)

3) No body cares (that would be very sad)

4) Every one is too modest (shame)

5) People think they are being set up, and don't want to look silly. (also sad)

I waited a while, hoping some one else would reply to your question, (don't want to come a cross as a know it all, I'm not, and will only reply if I'm pretty sure of what I'm saying)

This is a forum, it's all about sharing information, for the benefit of a great hobby! I've said this quietly before, so , with my apologies, now I'm going to shout it.

If you know the answer to some one's question, please, please, please, post it! The more the better!

Any one agree with me?

(I'll shut up now)

Amy jane.

[Bob Abell 2Participant @bobabell2]

Hello Amy

I've said this many times before…..

Our club has about 140 members and only three members will post a message!

The majority of members are over 60 and shy away from new fangled computers, I think this is the main reason

Then there is the Website construction itself! I find it straight forward and easy to navigate, but many struggle for some reason?

On the other hand, I visit websites and find some of them difficult to fathom out too!

I've posted pictures and interesting reports concerning the local clubs activities and it's the norm to get no response!

I have noticed that we get a good response when a controversial subject is mentioned!

I wouldn't be surprised if we get a deluge of comments now, concerning our latest posts?

Another major obstacle is the posting of pictures!

We'll wait and see what sort of reaction we get now

Bob

[Andy CParticipant @andyc56856]

Hi Bob

I have read all the way through this thread now, no mean feat. Could i suggest some sort of ballasting system as used in submarines. Some kind of pumping system to allow the water in then pump it out when sailing is finished. Also the sloshing can be damped down by adding baffles, the way they do it in fire engines.

Would that work?

Andy

[Bob Abell 2Participant @bobabell2]

Thank you Andy

At the moment, we are still only talking about building a one twelth scale barge

The water idea has been discussed at great length and at the moment, I still prefer the flooded hull idea

But the keel weight was showing to be far too heavy to handle also

The hull idea without a keel may be possible, similar to full size practice, but may require 200lb of lead or even higher than this and a reefed sail?

This is why we are only talking at the moment!

Bob

[ashley needhamParticipant @ashleyneedham69188]

Bob, dont expect any posts from deepst Surrey, i know nowt about Thames barges.

HOWEVER, at this size you will need a trailer and it will be heavy even without ballast. I would go for an overscale deep hull and use water ballast as suggested, get a pump, arrange sealed compartments to flood fully to stop the slop. If this is not enpigh. use concrete and treat the whole thing like a sailing dingy.

Ashley

[Bob Abell 2Participant @bobabell2]

Hello Ashley

Don't forget, we are only talking…..And talk's cheap!

An eight foot hull can be made in two pieces…..No trailer required and it's half the weight already!

I said something completely daft last week……So what's new?….I said we could fit thrusters or props in the keel to act as a counterbalance to the wind?

With a big lumber barge, this may be worth a rethink?

Still only a pipe dream……I'll wake up soon

Bob

[Paul TParticipant @pault84577]

Bob

'I said something completely daft last week'

You will have to give us a bit more to go on as you said quite a bit

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

You've already poo poohed my idea, as being too feeble and slow

And it was a daft idea actually

Bob

[Andy CParticipant @andyc56856]

been digging into water ballast. Found this article

**LINK**

very interesting read.

Andy

[Bob Abell 2Participant @bobabell2]

Thank you, Andy

Got to admit, I don't understand the diagrams at all……Do you, Paul?

It states that CZ is the righting force?

In the article, CZ is shown above the C of G……How can this be a righting force?

The righting force can only come from the keel weight, surely?

I can't believe the article is incorrect…….So where am I going wrong?

Bob

[Andy CParticipant @andyc56856]

Questions, question. Gets the brain matter going though.

Andy

[Bob Abell 2Participant @bobabell2]

Had another look and I've twigged it….I think

The vessel rotates about the C of G and the righting force is the offset of the C of G from C of B

This applies to round bottom hulls

A flat bottomed barge rotates about the outside edge and the C of G has more effect

I think I'm right there, no doubt someone will advise otherwise?

Bob

[Paul TParticipant @pault84577]

Bob

Yes I understand it.

The righting force is a combination of buoyancy and mass (not just the keel weight)

Paul

[Bob Abell 2Participant @bobabell2]

Paul where is the C of B of a plank?……Is it the outside edge?

I'm thinking about a plank again as the hull version was confusing the readership!

The plank will need to be hollow to support the mast and gear etc

Thinking about it….A barge is really a thick raft and has the stability of a catamoran

A raft is also a plank!

I think we've learnt something today?

Bob

Bob

[ashley needhamParticipant @ashleyneedham69188]

Two of my boats have plank bottoms, and in both cases I had to cut a well out of the centre to put the battery as they were very unstable otherwise. A very thick plank of the sort you were proposing would be even worse. It raises the c of g too much.

However, as a base it would be fine providing the middle was removed to put ballast in. You could then use very cheap and durable material for the hull sides!

Ashley

[Bob Abell 2Participant @bobabell2]

Thank you, Ashley

I forgot to mention that we are still using the weighted keel

While I'm on….More thinking out loud…..

A plank barge would probably sail quite well, with the wind behind it

In a cross wind, the wind would tilt the hull over, but would it actually lift the windward side of the hull?

If the wind was very strong, then it would do, but if the sails were let out by the servos, then it may be controllable?

Just another crazy idea

Bob

[ashley needhamParticipant @ashleyneedham69188]

Bob. Not if you are using a weighted keel, the bottom of the hull would be underwater just as much as any other sort of hull and so the bottom would remain wet..or have I got the wrong end of the stick?

This is reminding me of a possible project, one on the list…a Drakkar. I have one for my Viking soldiers and this was made by cutting a one in plank to a fat hull shape and then cutting off either side a strip 1/4 wide and sticking this on the sides to be the..er..sides. A figurehead and tail was added and the whole lot shaped on the belt sander. A bit of dark varnish completed and it looks ok. Not meant to sail of course but it does float ok and is fairly stable. I am sure I have mentioned this ages ago. If the sails were net or muslin/gauze (so as not to create too much wind resistance) then a small motor and the gear could be housed in the typical centre tent and Bob would be my uncle!

Ashley

[Paul TParticipant @pault84577]

Bob

To answer your many questions

I'm thinking about a plank again as the hull version was confusing the readership! This member of the readership wasn't confused.

The plank will need to be hollow to support the mast and gear etc A hollowed out plank is called a hull.

Thinking about it….A barge is really a thick raft and has the stability of a catamaran By necessity a barge is hollow but a raft is not so the two craft are different, a raft has the stability of a plank whereas a catamaran has far greater stability by virtue of its two hulls.

A raft is also a plank! I agree that a plank could be a raft.

A plank barge would probably sail quite well, with the wind behind it, Without a counterbalanced keel it will just capsize and with a weighted keel it would sail like a plank with a sail (i.e.not very well)

In a cross wind, the wind would tilt the hull over, but would it actually lift the windward side of the hull? Yes it would

If the wind was very strong, then it would do, but if the sails were let out by the servos, then it may be controllable? No because the servo reaction time would be to slow.

I'm quite enjoying this.

Paul

Edited By Paul T on 05/05/2014 19:47:16

[Bob Abell 2Participant @bobabell2]

Paul

I've composed an extensive reply to your post, but the MB website had an error at the time and the post was lost

The post is still on my Ipad and will forward it shortly……Some good ideas in it

Bob

[Author]

Posts