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[geoff p]

I'm building a model of Frederic Mistral steam tug.  Today was my first time on the water and she sits a bit low by the bow.  I need to remove some ballast but....
The ballast is steel balls  ::) and, foolish youth, I poured two-part resin glue over them, to keep 'em in place y'know.  Seemed like a good idea at the time while I had her in the bathtub.  Of course the resin ran down between the balls, making a very strong job and, perhaps rustproofing the steel.

Now I need to remove a fair bit of the ballast to allow for larger batteries.

So has anyone a good idea for destroying the resin bond, without destroying the boat?

The hull is 1mm ply planking over bulkheads, covered outside with nylon-reinforced resin.  I don't really want any oo-nasty to soak into the wood. :(

Geoff,
Taiwan

[GaryM]

Hi Geoff - I'm only a novice but if the balls are more than one level high, could you carefully drill the resin around the top ones?
I would guess the ones next to the hull wouldn't for fear of damaging the hull.
The other guys should have a better method - all the best.

regards
Gary :)

[Alastair_I]

A google search suggests the following options..

• MEK
• Methylene chloride based solvents
• Possibly hexane/acetone
• Something calling itself "BIO-SAFE 1025  Epoxy Resin Remover"

I suspect you'll need to experiment as it may depend which epoxy was used.

Other than that, as Gary says.. drill or dremmel between the balls and try and cut them out (or experiment with pouring various solvents into the drill holes.  Solvents might risk damaging the outer skin though.

Al

[das boot]

Been there, done that with U-117...I had to drill holes in my lead ballast which I'd overdone. I don't think I'd go down the solvent route personally...just in case something nasty happens where you can't see it. Try the drill first, it should be easy enough to remove enough resin around your balls[hmm... ::)]to be able to remove enough of them.

Cheers,

Rich

[djrobbo]

Likewise...been there done that.........personaly i would use the " take a drill to your balls" ::) approach , i dont think i would try the solvent method incase it did more harm than good , having said that i have never tried the solvent method , so if anyone else has perhaps they can put you wise.

              regards....bob.

[mike_victoriabc]

I'd be very cautious using the chemical removal and certainly not do anything with them inside.

I've had good success putting the weight in zip-lock bags - can be shifted around and removed if necessary.

[djrobbo]

Just a thought , but if you reposition your balls , why not set them in silicon , i.e...bath sealant etc.......that way if you need to move them again its not the end of the world to get them out........

           regards......bob.

[Martin (Admin)]

GOOD IDEA Bob! 
Must remember that for my next build.

Just a thought , but if you reposition your balls , why not set them in silicon , i.e...bath sealant etc.......that way if you need to move them again its not the end of the world to get them out........

          regards...... Bob.

[Alastair_I]

Another idea.. line the area where the ballast is to be installed with an inert liner (plastic shopping bag? thicker type).. pour the ballast and resin.. then lift out the ballast when cured.. it's now formed to the shape of the area and can be non-permanantly secured, eg with velcro.  PVA makes a viable alternatove to resin as a matrix for the ballast block if your balls aren't too big.. I'll get my coat..

[geoff p]

Thanks, guys,
I've tried drilling and the drill bit skids over resin patches 'til it finds a nice gap between two balls and jam!

I'll try solvents next, if I can find a Chinese translation that works: Google translate's results are not necessarily understood by the locals here in Taiwan.

Cheers,
Geoff

[tobyker]

This could be dodgy, but ... If you cut top and bottom out of a tin can to make a flame shield, what would be the effect on the epoxy of a fine blowlamp flame? Would it soften the epoxy enough to let you prise out some of the top layer of balls with a small screwdriver? Once you could put the flame on a ball, it would conuct the heat through itself and soften the epoxy arpund it (maybe).  If you do try this, a well ventilated area is recommended and a fire extinguisher handy! (SWMBO with a bucket of water?)

[nhp651]

epoxy resin and polyester resin are two of the most flammible of modelling materials that you can use........combine this with a timber hull and the results could be...........   well err!.  ...............CATASTROPHIC  ???????
I would try and persevere with drilling out with smaller bits, as even though you can use a solvent, that same solvent gets into the little parts you can't see from above and it continues to work and desolve the resin long after you have stopped where you think you want to be and in the end you have a very gooooooy mess in the bottom of your model that is a real task to clean out.
 believe me, been there and done that.
the other way although dirty and dusty ( and is an out door job ) is to get hold of a Black and Deckker power file and grind it all out. laborious but it can be done.
neil.

[Bradley]

Seeing Neil's mention of a power file - would it be possible to get an angle grinder with a cutting disc at your 'balls'.  Even, if necessary, removing the shield from the angle grinder - desperate problems require desperate solutions .  If you value your model I would stay well away from solvents :(.
Derek.   

[dreadnought72]

Geoff - it might be "good for morale" to work out how much ballast needs to go.

Tape a block of expanded polystyrene under the bow, sized to give you the trim you want.

Measure the volume of the polystyrene (submerse it in a filled measuring jug).

Divide that volume by 5 for a reasonable idea of the volume of ballast needing removed. (5g/cm3 is approximately right for the overall density of steel bearings in a tight spherically-packed array).

It might be less than you think.

Andy

[John W E]

Hi there

Picture this scenario, after taking literal advice; from Derek   ' would it be possible to get an angle grinder with a cutting disc at your 'balls' '  ::)  How many of us are now rolling around the floor in agony at the thought of this and then at the accident and emergency department trying to explain this to the Doctor and Nurses - well Dr someone on the model forum suggested I take an angle grinder to wedding tackle  :'( ::)

Seriously though, PAIN OVER....

Have you access to a hot air gun, the type which is used for paint stripping?    Soak a towel or some cloth in cold water and sit your hull on top of this.  Then with the hot air gun, begin at the centre of mass of your epoxy mix - playing the heat back and forwards, softening the epoxy.   As the steel balls heat up, they will retain the heat and you will possibly be able to, with the aid of a screw driver, start to dislodge the offending 'balls'.

As has been suggested, we try and avoid using chemicals, because they do have a tendancy to soak into the timber and in doing so, they can cause more trouble than they are worth such as breaking down the glue bond on your hull.   The reason for the hull sitting on a wet towel is to absorb any heat as transferred through the hull sides/and bottom to try and minimise any distortion caused by the heat.

Aye
john e
bluebird

[geoff p]

Hi Guys,
Wow!  Your ideas are coming faster than I can try them out.  Many thanks :)

Last night, I tried a splash of acetone on the ballast in just one bay.  It did soften the resin a bit, enough to prise out some balls with a screwdriver.  After an hour or so I weighed the (small) tub of removed balls - gosh, a whole 150 grammes, out of the 3 Kg in the boat.

It got me to thinking - at last! - so I weighed some of the other bits-n-bobs as well:
The original Nicad pack : 600g
6V 4Ah accumulator : 800g
2 x 6V 3Ah accumulator : 1800g
and, of course, while doing the ballasting in the bath, I used the Nicad, set about midships.
but for 'sea trials' I used a pair of 3Ah accumulators set a bit further for'ard (cos they couldn't fit midships), never giving a thought to the  ballasting situation. 

Since the duration I got with two accumulators far exceeded my hopes, I think I can safely go down to just one, and that will position midships.

So it should be 900g accumulator midships
instead of the  600g Nicad,
              less  150g of ballast already removed from a for'ard bay.

Perhaps I'll try her out again this weekend.

And never again will I set my ballast in resin direct against the hull,  Promise  ::)

Geoff

[kiteman1]

If it's any consolation, Geoff, I once did the same thing.

I once made a very stand off Dreadnought model, brushed the shell with two-part resin and then poured hot lead into the hull. The net result was a pretty good imitation of an underwater sonar dome and a big brown patch caused by the heat.  The only good thing was that the hull remained sound....We live and learn, don't we? 

It's worth bearing in mind that if no one made any mistakes no one would be able to give the solutions....That's what I tell myself anyway.....

[geoff p]

Hi Folks,
I am very pleased to tell that the small amount of ballast removed, together with changes to the battery positioning have made a massive difference to how she sits on the water.  Had a good sail/motor/steam around the lake for a couple of hours on Sunday.

So on to 'fitting out'.  May get this done, sort-of, eventually.

BTW, how does one upload photos to go with these messages, please?

Cheers,
Geoff

[Roger in France]

Geoff,

UPLOADING PHOTOS:

You may need to resize, if so have a look at the list of options on the Site Home Page (a list on the left of your screen on a yellow background). There you will find some help.

Here, in the Forum, click on the words "Additional Options...." at the foot of the message drafting box to the left. In the blank box marked "Attach:" enter the location of your photo or choose "Browse" and search for your photo. If more than one, click "(more attachments)".

Roger in France