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        Discussion foam cutting highly tapered tips

#1 GaryO Oct 02, 2008 02:53 PM

foam cutting highly tapered tips
 
I've been trying to cut some highly tapered foam cores on a new hlg. The tip panel is 2" wide, inner airfoil is 3.5, tip is 2".

Can't get it to work well with my gravity cutter. Anyone have any techniques that might work?

#2 Tony Hallo Oct 02, 2008 03:53 PM

Here's some information that I posted some time ago on another site, might be helpful.
http://www.rcuniverse.com/forum/m_39...tm.htm#3951812

#3 blewis01 Oct 03, 2008 12:04 AM

Gary - if you have a Feathercut, look in the instructions for the pivot method. Basically, one end of the wire is fixed, and the 2nd end is attached to the drop arm. PM me an email address if you need a scan of the instructions. I use this method to cut DLG tails.

Bruce

#4 Harpye Oct 03, 2008 03:13 AM

The burn effect depends on the Mateial you want to cut ( for EPP there is an recommended spline length ratio of about 2 - the shorter spline is minimum the half of the longer! Of course you might expand this a bit but results go worse...

I did several tapered parts but used EPP for material which had been cut very slowly with low current ( and is also more resistand against heat) but you also could include folds in the spline you have to grind away afterwards or another posibility is that you cut not tapered but dual spline ... which lowers the precision of your cut!! ( what you may compensate when designing the endplates you cut on...

Mine is truely tapered but cnc ... - I also had this problem many times ... ;) dont give up


EPS 40 styrofoam prototype

http://people.freenet.de/Modellbauwahn/MIGEPP/2.jpg

RG30 EPP Final
http://people.freenet.de/Modellbauwahn/MIGEPP/12.JPG

#5 Harpye Oct 03, 2008 06:18 AM

Hot Wire Cut Video of Tapered And Straight Cut Combination
 
I attached a little video which is to show how it works...


DIY Hot Wire Cut (1 min 13 sec)



Hansjoerg

#6 ThermalThief Oct 03, 2008 10:47 AM

Gary,

I would guess you will radius the corner on the tip. I would hand craft the entire tip section...or cut with much less taper as you will modify the leading edge when you radius anyways.

Ken

#7 GaryO Oct 04, 2008 03:34 PM

Ken,

You might recall at Pasco both Tim and Jonathan and maybe Phil has versions of Jonathans "Dolly".

The purpose of the highly raked tip is to get an accurate airfoil and it seems to work well. Anyhow, that is what I'm trying to do. They are cutting it with the wire pivot method and that's what I'll try.

Another question for anyone:

When cutting a panel with both LE and TE sweep with a Feather Cut type cutter, how are you positioning the blank on the table?

TE paralled with the table edge
Blank adjusted so the middle of the blank (span wise) is parallel to the table edge
Or something else?


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