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Building Tips and technical articles. => Building techniques => Topic started by: Leester on May 14, 2008, 01:05:32 PM

Title: Molding Balsa
Post by: Leester on May 14, 2008, 01:05:32 PM
All the previous times I molded balsa I soaked the wood in plain water. Today I used Ammonia and water mixed HO-CHI-MAMA that stuff stinks and burns the eyes. Good thing I'm single or ... well you know. mw~ mw~ mw~ mw~    LL~ LL~ LL~
Title: Re: Molding Balsa
Post by: Will Hinton on May 14, 2008, 02:19:41 PM
A very loooooooooooooong time ago I used to always use the ammonia because those who wrote about molding balsa said to.  No more, I've not used it for the last 15 or more years and have molded balsa on every stunter I've built except for the profiles.  It just ain't needed!
I have also found that soaking the balsa for no more than a half hour is sufficient.
Blessin's,
Will
Title: Re: Molding Balsa
Post by: Mark Scarborough on May 14, 2008, 04:31:15 PM
IMHExperience, I have just ran hot water from the tap over my balsa, typically on the side that will become the outside. Granted I havent done complex shappes but its working so far
Title: Re: Molding Balsa
Post by: Jim Thomerson on May 14, 2008, 04:43:09 PM
Ammonia softens lignin and subrin, which balsa has little or none of.  The problem is getting the balsa whetted.  A tiny bit of simple green or similar will help in the process.
Title: Re: Molding Balsa
Post by: steve pagano on May 14, 2008, 07:35:25 PM
Hello guys

Not to redirect the thread But for those of you who mold, How would one go about molding a top block of an aircraft in which the plans do not show top block formers, In other words when the plans say carve. How does one make a mold buck of the top block shape with out having formers on the plans to show you the exact shape of what the mold should be?

                                                          T.I.A.
                                                        Steve
Title: Re: Molding Balsa
Post by: Leester on May 14, 2008, 07:50:38 PM
Steve: The best way is to get Windy's DVD's on molding Balsa. He shows how you carve the top block then mold balsa around it.
Title: Re: Molding Balsa
Post by: RC Storick on May 14, 2008, 08:10:54 PM
Steve: The best way is to get Windy's DVD's on molding Balsa. He shows how you carve the top block then mold balsa around it.

Or Robins view from Bob Hunt. Thats how I leared. Great stuff!
Title: Re: Molding Balsa
Post by: steve pagano on May 14, 2008, 08:24:59 PM
Or Robins view from Bob Hunt. Thats how I leared. Great stuff!

That's what i got. But in the video the plans have have formers for molding the top and bottom blocks.
Title: Re: Molding Balsa
Post by: RC Storick on May 14, 2008, 08:40:42 PM
That's what i got. But in the video the plans have have formers for molding the top and bottom blocks.

If you have the video for advanced molding techniques you can see how to loft out formers. If not start at the front and make a former to fit. The go the back and make another one. String a piece of wood across the two and measure where the other ones go (lofting). Do a search for my Tbolt molding and see the buck.
Title: Re: Molding Balsa
Post by: L0U CRANE on May 15, 2008, 12:10:38 PM
Agreed. Lofting is the best method, whether by the old historic methods, modern CAD methods, or whatever... (As I learned it about 50 years ago, the term 'lofting' was related to laying out - full-size - the curves of boat and ship hulls. BIG pieces: needed to work in a big open space, like a loft? Also used later for early aircraft full-size layouts...)

To Reply#4, Steve - a 'practical' way might be to build the forming buck with the intended formers in place at the desired positions (if the plans don't locate them for you.) You could tack-glue the formers with a dot of, say, SIG Cement, which acetone or dope thinner softens to let you separate them from the blocks. Or, you could 'build' the buck onto a keel, with the separate short blocks between the bulkheads securely mounted to the keel. Then carve away, just as you would have from solid block in the first place.

Remember to make the buck width and height undersize by the thickness of the wood to be formed... of course.
Title: Re: Molding Balsa
Post by: Kim Mortimore on May 16, 2008, 01:08:11 PM
If you have the video for advanced molding techniques you can see how to loft out formers. If not start at the front and make a former to fit. The go the back and make another one. String a piece of wood across the two and measure where the other ones go (lofting). Do a search for my Tbolt molding and see the buck.

I read the search instructions, then tried searching:  storick thunderbolt molding.  Both basic and advanced search.  No matches, but a suggestion for struck rather than storick.  Tried without the name.  No cigar.  Anyone know what I am doing wrong?   n~

Thanks!
Kim Mortimore