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Design => Stunt design => Topic started by: Kim Mortimore on September 17, 2007, 09:50:47 PM
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I'm considering flying at the Brodak next year, and I checked out the events on the Brodak website. In Profile it says 3/4" maximum fuselage width. Does anyone know if that is just from the trailing edge back, or does it include the front end also? I gather that rule nitpicking is not exactly job #1 at the Brodak LL~ but it is a long way there from the left coast, so....
Thanks,
Kim Mortimore
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according to AMA it ust be 3/4" from trailing edge back. ahead of that doublers are allowed and as far as I can see no restriction is placed upon thickness. Only exception being engine must be completely exposed from lugs to head. Now as for Brodaks, I think as long as you werent trying to gain some untoward competative advantage,,,,, but then who knows really.
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I am *Ivory Soap* positive that Brodak's uses the AMA rule for *Profiles*.
Plus, the engine restriction for Profile Stunt follows the AMA rule, also. Up to .91!
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This is an interesting issue. The intent of profile was to create a simple event where you just use a piece of 1/2" sheet balsa for the fuselage. Now it's grown up to 3/4", which panders to more rigid, hollow structures the are basically just a "narrow full built-up fuselage". Where's the simplicity in that?
I expect that you could build a body a full 1" thick and get away with it, given the lax enforcement at most contests.
What's the harm? Welllll, no real harm, I guess, expect allowing a simple, lower-cost event to creep into a second chance to fly Modern CLPA.
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From the current AMA Rulebook, CL General,
10. Profile Definition. The fuselage of a
profile model resembles that of a
conventional airplane in the side
(profile) view and appears as a thin flat
sheet in the plan (top) view. The engine
shall be completely exposed from the
mounting lugs to the cylinder head and
shall not have any type of fairing.
Additional reinforcements such as
plywood nose doublers and cheek cowls
on the opposite side of the engine (for
side mounted installations) are
permitted. Cheek cowls may extend
from the prop drive washer to a point 25
percent of the root chord back of the
leading edge at the root, and may be
faired in. In the case of an inverted or
upright engine installation, the engine
mounts may protrude from the fuselage
sides but may not be faired in.
(Underlining added.)
On the previous page, there's a chart of widths allowed by specific events. Can't copy that in, but its specs are:
1/2A Proto...........1/2" fuse width ......3/8" mx cheek cowl
Scale Racing.........5/8"......................? possibly as 1/2A Proto
Slow Combat.........3/4"......................3/4"
Carrier..................3/4"......................? possibly as Slow Combat
Slow Rat and.........3/4"......................? possibly as above
.. Rat Racing
These are most likely AMA "safety specs" local contests can't tinker with, for these events at an AMA Sanctioned meet, anyway.
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Very good, so that answers it.
3/4" is the ultimate limit, with additional width to the first quarter of the root chord, NOT the trailing edge.
I would interpret the 3/4" to be a generous tolerance to allow thick covering and painting of a 1/2" fuselage and allow no further slack beyond that. A limit is a limit.
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I would interpret the 3/4" to be a generous tolerance to allow thick covering and painting of a 1/2" fuselage and allow no further slack beyond that. A limit is a limit.
Paul,
I've never seen anyone come even close to the 3/4" width. Some folks laminate 1/64" ply to the wimpy 1/2" balsa slab. This helps keep tail wiggle down to a manageable level so you can trim the beast out for a decent pattern. But you can build up some serious tail weight if you're not careful, so I would never expect to see a "thick" finish.
Take care,
Ron