Being as I am a kiwi, I am pretty confident you can find bondo even out on that dry rock you call a country! Bondo is god's gift to designers and shapers. Even in the biggest boat yards I worked in, Bondo (a generic term for any polyester filler) was still the putty of choice for forming and shaping. Syntactic typically uses an epoxy resin with a micro-sphere filling powder mixed in to give it more of a putty viscosity. The macro-sheres are little fiberglass or carbon fiber balls about a cm in diameter. The mixed product kind of looks like tabeoca pudding which I'm sure you're familiar with down there. I've only had a very brief play with using it from a free sample that Tom managed to swindle out of the manufacturers. The two five gallon pales of micro spheres and macro-spheres they sent him didn't appear to weigh any more than the empty five gallon pales. Crazy suff! The resin is what adds the weight to it so, just like in composite construction the lower the resin ratio, the lighter the finished product. However this can be taken to a disastrous extreme if you're too scottish with the resin (note: I'm also a Scotsman) Have I tried using Bondo and ping pong balls? No. Do I think it would be a suitable substitute to trust mylife to? No. Do I think it would be a suitable substitute to trust your life to? hmmm, Where did you say you were from again? That's your call my friend. It sounds better than paper mashe!!! I have done many many hours of shaping with bondo. It's not so good on the finished product but great for shaping plugs and making temporary molds. If I were going to do it. I'd make a cardboard former of the shape I wanted to frame in, line it with grease proof paper as a release surface, pour in the bondo (only enough to fill about half as high as the ping pong balls) of very lightly catalyzed bondo and then just place as many ping pong balls in as you can keep covered. Should look like a gigantic almond joy. Then when that layer's cured, repeat the process again and again until you have filled the void. Try it out. If it's a fantastic success I assume total credit. If it fails, we never had this conversation! Good luck, We'll make a bionic dolphin builder out of you yet mate! Good onya sport
Rob Innes
INNESPACE
>>p.s.. how long did the dolphin take to create..from paper to water?
Paper? What paper? They just kind of evolve from some "what if's" some "Oops, that didn't work's" and some "She'll be right mate's"
DISCLAIMER TO APPEASE THE MASSES
Seriously though, Much as I advocate the trial and error approach,
we are not building deep diving heavier than water, pressurized submersibles
and I do not pretend to know the first thing about calculating, designing
or building one or those inside out fish tanks. Our positively buoyant
bionic dolphins are not currently subject to the same design constraints
as a conventional "sinker". Our greatest concerns spawn from high speed
and low visibility rather than implosion or a one way ticket to the sea
bottom. We have learnt many of these new constraints (some the hard way)
and we have adopted a new appreciation for paranoid safety.
Erik Michael Muller wrote:
Hi Rob,
Interesting Idea. Have you tested this composition to any depth? Not
having used bondo before (or even knowing what it is...) and assuming
that it is similar to epoxy (surfboard) resin, I intuitively sort of
think that this mix might require quite a high ratio of bondo/resin to
ppballs.
in terms of volume, what do you think might be a realistic resin/ppbal
ratio? 2:1, 3:1?
Of course, testing is vital, but it is nice to have a ball-park figure
beforehand...
Also, could you describe bondo a little more? As I said, we dont have
it in Australia and surfboard resin is quite expensive (around
AU$20/litre). Will polystyrene foam dissolve in bondo, as it does in
sv resin? The sb resin also gets extremely hot while curing..hot
enough to melt parrafin wax, and almost burn if you touch it for too
long! (depending on the quantity and geometry of course)
E.M.p.s. how long did the dolphin take to create..from paper to water?
Thanks again,
E.M.-------------------
> Poor man's synyactic: Bondo and ping pong balls!
> Bondo runs about $10 a gallon and you can buy a thousand industrial
> ping pong balls for about $40. Bondo gets hot and cracks when set in
> large quantities but the ping pong balls would act much like the
> macrospheres in syntactic acting as a heat sink plus reducing the
> weight. You can also thin bondo with regular polyester resin. You
might
> want to check if the bondo melts the ping pong plastic though. You
could
> always dip them in wax before you set them in. Just a thought.
>
>
>
> Rob Innes
> INNESPACE
>
>
>
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