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Building Tips and technical articles. => Building techniques => Topic started by: Gordon Tarbell on December 22, 2007, 02:57:11 PM
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What is the legal limit for profile fuselage thickness in the profile class(P-40)? If the kit to be built is under that is it ok to add material to get that dimension? Is this in the PAMPA rule book?
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There are no legal limits.
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Beg to differ, but if you are using AMA definitions, it requires that the fuselage crossection be no greater than 3/4" at the trailing edge of the wing. Doublers and triplers are allowed forward of that as is IIRC mounting the engine veritcally or horizantaly. It does require the engine be exposed from the lugs to the plug. This is what our local Profile rules dictate, IE they refer to the AMA rules regarding profile definition.
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Without looing it up, my memory agrees with Mark. I do remember (at least at one time!) that the AMA rule book had the 3/4" spec in it. Without a printed book now, I wouldn't have a clue. A bone I would like to pick with AMA.... or is there a printed book available SOMEWHERE?? I have enough trouble, already, getting around the AMA web site.............
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After thinking about this, In all fairness to Crist, P-40 is an umofficial event, so I dont know about the exact implications. Only can speak from experience in the NW where our rules stipulate the AMA profile rules for the event
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After thinking about this, In all fairness to Crist, P-40 is an umofficial event, so I dont know about the exact implications. Only can speak from experience in the NW where our rules stipulate the AMA profile rules for the event
Gotcha, I didn't *think*, either. :-[ Apologises, Crist!
We just have "Profile". No rules, I guess! An Imitation can fly in our event, so side mounted isn't a requirement. No engine size requirement, either! I like flying it because there are no classes, all fly together, and I can fly with my friends who are Experts and get a (however slight) clue as to how I measure up that day with them! A very popular set up here is the TEOSAWKI w/LA 46. Uglier than homemade sin, but a true flying machine! I have to finish mine up for this season. (even if I do think it is uglier than homemade sin! LL~ LL~ ) A case of form follows function at it's highest level.
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. A bone I would like to pick with AMA.... or is there a printed book available SOMEWHERE??
Hard printed copies are available through AMA at $5.00 per copy. I ordered two copies when I sent in my dues.
already got them back.
Marvin Denny
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OK Bill, what is a Teosawki? I build ugly anyhow.
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The 3/4 inch thickness is for racing events. There are no legal limits for stunt. Look it up.
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OK Bill, what is a Teosawki? I build ugly anyhow.
The TEOSAWKI is a plane that Clayton Smith here in NC designed. It has a slight appearance of a very large Russian F2D plane, with lengthened fuselage. No flaps and 4 ribs per wing panel (IIRC) covered with mylar usually. Clayton sells them in ARF form, sorta. The End Of Stunt As We Know It is what the letters stand for. No matter how you build, if you build it stock, there is just no hope for the looks of one! LL~ LL~
But, one of the (if not THE) best flying profiles on the planet.
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As said, P-40 is not an official event. So check with the CD as early as you can. Generally--No, I don't mean generally--I mean in my experience, 3/4 in wide behind the wing and side mounted engine. If you build one like that, no one will complain (I'm pretty sure.).
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Thanks guys , good enough for me . I just would like to add a little rigidity to the rearend of a couple of profiles that I would like to enter in p-40 class. Most of my profiles flex too much back there.
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Profiles are notorious for aft fuselage flex. Twisting (tosional) flex can be reduced by adding stiffness to the surface, i.e. some sort of rigid or semi-rigid skin. Normally a layer of silkspan doped on will add considerable stiffness to the rear of profiles. More extreme measures are fiberglass or Carbon Fiber skins with epoxy. Think of the design of full scale airplanes most are a skin, aluminum or composite with supporting formers and stringers.
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As there are not even PAMPA official rules for Profile Stunt/P.40, the details are subject to local regs. It has nothing to do with PAMPA or AMA, so it's up to your local club, regional rules, or CD. Ask around your area is the best advise I can give. But I've never seen anybody actually measure a profile fuselage for thickness, either. D>K Steve
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:! As to the flexing of the fuse in the aft end I cover each side of my fuse with 1/64" plywood.
The fuse will not twist as the plywood doesn't strech or compress.
I must give Tom Farmer credit for this inovation, and since using it the fuse doesn't flex.
It adds about 1 ounce of weight to the fuse, but it works...FWIW... :!
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Here is the relevant definition (copied and pasted from the AMA CL General Section--so it at least should apply to all CL unless other specific rules supercede it), and as Crist says, there is nothing on actual dimensions. (That surprised me too!). But at least there is a definition. I suppose a profile contest which is AMA sanctioned, at least can have a definition of what a profile is!
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.
By the way, having the official version of the rulebook in electronic version actually makes it easier to find stuff like this. Since you are reading this on a computer, just go to the AMA site, click on the competition regulations, then do a search (in this case on "profile"). This is easier than a book primarily because this info is usually spread over a number of places in the rulebook, so manually searching makes it easy to miss these little "nuggets".
On the other hand, it is useful to download the sections, so in the future, when a new rule slips in or out, you will have some reference to know that you haven't lost your mind! At least as of this year, they put dates on the pdf files!
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Re: the files on the internet.
I have needed to have written copies at contests to answer questions. Sometimes easier, but now that I think of it a copy of the current rules filed on my laptop would work just as well. Since I have the laptop along at contests.