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 Ballast questions please

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jarvo
BrianP
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BrianP
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Join date : 2020-12-04

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PostSubject: Ballast questions please   Ballast questions please EmptySun Jan 10, 2021 8:39 pm

Hi could anyone give me some guidance on using ballast please.

Here's the scenario:

I am building an aluminium hull tug boat.

I am at the stage where the hull is water tight .

It is sitting very high in the water at present.

I have loaded it with temporary ballast of steel blocks and water containers.
They weigh 33.7lbs/15.3kgs

I am quite worried that the hull is displacing so much water.

Could you any share thoughts on this amount of ballast for such a small vessel and can you suggest suitable ballast for the 
finished model please.

Here is the model tug boat. Thanks for any feedback and guidance.
Ballast questions please Img_4510

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jarvo
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Join date : 2015-02-19

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PostSubject: Re: Ballast questions please   Ballast questions please EmptyFri Mar 05, 2021 3:33 pm

Hi Brian, First you need to mark the waterline on the hull, then ballast down to the marks, that will give you the final weight to finish the hull and superstructure, motor, radio gear, batteries etc, with my tugs, i prefer to use batteries as ballast, removable to help transport.

Your worry of the weight of ballast, tugs displace a lot, so thats normal if you are on the marks, stern freeboard is quite minimal, make sure the freeing ports are clear, watch how the weight is being added to the hull, (balance) is also important

Hope this gives you a start

Regards

Mark
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BrianP
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyFri Mar 05, 2021 3:44 pm

jarvo wrote:
Hi Brian, First you need to mark the waterline on the hull, then ballast down to the marks, that will give you the final weight to finish the hull and superstructure, motor, radio gear, batteries etc, with my tugs, i prefer to use batteries as ballast, removable to help transport.

Your worry of the weight of ballast, tugs displace a lot, so thats normal if you are on the marks, stern freeboard is quite minimal, make sure the freeing ports are clear, watch how the weight is being added to the hull, (balance) is also important

Hope this gives you a start

Regards

Mark
Thank you Mark. Much appreciated.

I ended up using used lead balance weights from a car tyre workshop.
I bagged it up into convenient sized multiple food storage bags and distributed it evenly.
I am still shocked how much was needed to 'sink' the hull deep enough in water.
I learnt a lot about where placing ballast/ how high up affects stability.

Just waiting to go and try the tugboat now.
My youtube channel has all the build videos. f1pitpass

regards
Brian.
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Andrew Brown
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyFri Mar 05, 2021 4:08 pm

Hello Andy. the advice you have been given is sound , but if you wish to persue the sientific route you could find out the  block coeficient of the prototype boat and a relitivly simple calculation will get you the displacemant of your model . you will still have to distribte the ballast thoughout the hull. regards Andy.
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BrianP
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyFri Mar 05, 2021 4:32 pm

Andrew Brown wrote:
Hello Andy. the advice you have been given is sound , but if you wish to persue the sientific route you could find out the  block coeficient of the prototype boat and a relitivly simple calculation will get you the displacemant of your model . you will still have to distribte the ballast thoughout the hull. regards Andy.

i'm afraid my modelling skills don't extend to my tug boat being exact in scale...

Thanks for trying to help me tho'...

regards
Brian.
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Bob K
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyFri Mar 05, 2021 11:10 pm

Hi Brian;

Check your local sporting goods stores, and find one that sells shotgun reloading supplies.  You can buy 25 lb sacks of birdshot {size-wise I like #8 shot} for a very reasonable price.  You may not need the whole bag, but its nice to have some on hand for the next build too.

Last year I finished building a 76" offshore tugboat, "Nostromo".  After installing all of the running gear and 3 gel-cell batteries, it still needed a bunch of ballast.  I got 3 bags of shot and made up 5 lb bags from heavy plastic and 100MPH tape.  The tug needs all 15 bags to get down to its design waterline, so she ends up displacing almost 150 lbs!  Needless to say, launch and recovery is interesting and definitely not a one man show.

The other thing you can do with birdshot, is cast removable ballast blocks to fit into your hull.  Mix the shot with an ounce or two of epoxy, pour it into your mold, or, mold it in the hull with protection, and you'll have custom removable ballast that will not shift.

Good luck and have fun!
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BrianP
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PostSubject: Re: Ballast questions please   Ballast questions please EmptySat Mar 06, 2021 6:16 am

Bob K wrote:
Hi Brian;

Check your local sporting goods stores, and find one that sells shotgun reloading supplies.  You can buy 25 lb sacks of birdshot {size-wise I like #8 shot} for a very reasonable price.  You may not need the whole bag, but its nice to have some on hand for the next build too.

Last year I finished building a 76" offshore tugboat, "Nostromo".  After installing all of the running gear and 3 gel-cell batteries, it still needed a bunch of ballast.  I got 3 bags of shot and made up 5 lb bags from heavy plastic and 100MPH tape.  The tug needs all 15 bags to get down to its design waterline, so she ends up displacing almost 150 lbs!  Needless to say, launch and recovery is interesting and definitely not a one man show.

The other thing you can do with birdshot, is cast removable ballast blocks to fit into your hull.  Mix the shot with an ounce or two of epoxy, pour it into your mold, or, mold it in the hull with protection, and you'll have custom removable ballast that will not shift.

Good luck and have fun!
yep, tugs sit low and take a lottttttttt of ballast!
Yep, the finished model takes some lifting!
Good tip on the birdshot, thank you.
The 'project' seems an age ago but will soon be at the lake so tests will happen!
Thanks for the good wishes. 
Same to you Bob K!

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ivorthediver
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Age : 75
Location : Fulbourn Cambridge

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PostSubject: Re: Ballast questions please   Ballast questions please EmptyWed Jun 09, 2021 9:49 am

All sound advice lads , as for launch and recovery my Damion ASD had the same issues , and I ended up making a wheeled sub frame in which to launch and recover......
Ballast questions please 7821b810
Any new on the maiden voyage yet ?

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BrianP
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyWed Jun 09, 2021 10:00 am

that launch trolley looks great! Well innovated.

news on my maiden launch?
The project has taken a back seat ... but your launch trolley idea may help move it up the queue!
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ivorthediver
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ivorthediver

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PostSubject: Re: Ballast questions please   Ballast questions please EmptyWed Jun 09, 2021 10:11 am

Well it worked for me Brian , and was constructed with 1 1/2 pvc pipe as shown with wheels bought from B+Q on threaded metal bars for axels and strapping to aid launch and recovery , once afloat reverse out , when finished re-dock   and haul out again to drain off .

Necessity IS the mother of invention Brian ...DONT BE PUT OFF ..good luck
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Bob K
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PostSubject: Re: Ballast questions please   Ballast questions please EmptySun Jun 13, 2021 8:16 pm

I like your launcher Ivor!  I like it a lot!! Could you please post a picture of it out of the water??  I'm interested in copying your design for my Nostromo.  My old launcher needs serious updating.....

Thanks!
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ivorthediver
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ivorthediver

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Age : 75
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyMon Jun 14, 2021 8:36 pm

Well bob I have sent you two PM's which I assume you didn't get Rolling Eyes

If you send me your Email address I will send you some photos of it to aid you , as despite my best efforts I can not upload them as the forum sends an error code saying that they are to big to upload ! 

So I have done all I can mate its now down to you pale

My Email is " ivorthediver@yahoo.co.uk " so the balls in your court now Bob .
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ivorthediver
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ivorthediver

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PostSubject: Re: Ballast questions please   Ballast questions please EmptyTue Jun 15, 2021 3:20 pm

Ballast questions please 7821b811

This one is 3.20 MB but was taken on my iPhone 7+

and on my editing suite its:-

3.99mm f/1.8
3024x4032 
1.58MB

Hopes this all helps Barrie kind regards
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barriew
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PostSubject: Re: Ballast questions please   Ballast questions please EmptyTue Jun 15, 2021 6:34 pm

Ivor I've deleted some of the not very relevant posts - I am still trying to understand what's going wrong wityh you posting photos. In the meantime here are two taken from an email you sent to me. They are very small but hopefully illustrate your trolley.

Ballast questions please Ivorst10 Ballast questions please Ivorst11

Barrie
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ivorthediver
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ivorthediver

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Age : 75
Location : Fulbourn Cambridge

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PostSubject: Re: Ballast questions please   Ballast questions please EmptyTue Jun 15, 2021 8:21 pm

Thank you Barrie , be interested in what you find out please Thumbup
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