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Nov 29, 2012, 02:26 PM
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Gravity Drop Arm Foam Cutter


I built a Drop Arm Gravity Foam Cutter from an old issue of RC Soaring Digest.

http://www.rcsoaringdigest.com/pdfs/...SD-2008-11.pdf

all kudos goes to Curtis Suter, the author of the how to article, thanks for sharing your knowledge.

The instructions are very good and easy to follow. Explaination of the Drop arm pully setting for a tapered wing is very good too as well as now to test the setting before you cut foam. You can make a cheaper setup but this design looks to be durable.

I'm no expert so I cant debate one design over another, wire size, power supplies or defects. I've only played with EPS from from Home Depot with swing wire templates so far. But I'll post what I did and how it works.

Place holder for links and photos.

Supergee build thread.

https://www.rcgroups.com/forums/showthread.php?t=545273

Tips

https://www.rcgroups.com/forums/show...ds#post2741007

Photos are of the Cutter I made using the plans.

I deviated from the plans in these ways:

1. Suspended the bow vice using a wheel. The bow is suspended at the Bow Center line.

2. I replaced three of the pully wheels with eyelets. This keeps the pull string in place better than the pullies.

I tried using the power wires to the bow as pull strings but the wire I have is too stiff. Might try again if I can find very flexible 18-20 ga wire.

The templates must be very smooth. I sanded the edges with 220, 400 might be better.

Things I learned.

1. Templates must be very smooth.
2. Templates must rest on the table. Do not expect the pins to hold the templates in place on the foam with the bows weight.
3. Do many test pulls to ensure the bow pulls out evenly at the completion of the cut.
4. Make sure the bow is free to move.

More to come once I get some hi load 40. Test EPS cores will be used to practice bagging wings.

Still want to try suspending the bow under the table ala Joe Cormier.
Last edited by rockbus; Dec 04, 2012 at 03:03 PM.
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