Re: [ATM] Cutting the sonotube for a dobsonian

["Mel Bartels" <mbartels@bbastrodesigns.com>]

>> I'm starting to look at building a dobsonian, and I've got a question. It
>> seems to me that one could put in substantial cutouts (expecially
>> longitudinally) before affecting the ridity of the tube. Has anyone cut 
>> out
>> any sections of the sonotube to make it lighter and to add ventilation? 
>> Any
>> experience with how much can be cut out before comprimising the rigidity 
>> of
>> the tube?
>
> I haven't actually tried it.  My guess is that Sonotube is just barely
> stiff enough as is.  Cutting substantial holes in it is liable to result
> in an unstable device.  A whole lot of the stiffness of a tube comes
> from its circular cross section.  Interrupt that and stiffness falls off
> rapidly.


That is indeed the case.  Cut out a regular pattern and you'll see the 
sonotube really start to sag.  It's not very stable structurally and will 
collapse when you try to handle it.

Mel Bartels 

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