stunthanger.com
Design => Stunt design => Topic started by: Avaiojet on October 22, 2011, 03:54:09 PM
-
How thick are the fuselages on profile kits? I'm actually referring to the larger models and I'm not concerned with the thickness at the engine.
My interest is the fuselage balsa wood thickness.
Please, name the model and the thickness?
Thanks,
Charles
-
Typically, 1/2" slabs. The Flite Streak was odd, at 7/16", at least the original TF kit. Most designers that use a "built-up profile" use 1/2" for the edges and wing/engine/stab area, 3/32 x 1/2 diagonals (or foam core) with 1/64" ply outer sides, or perhaps 1/16" or 3/32" sheet balsa.
Some "Profile Stunt" rules may specify maximum fuselage thickness, often using the same specs as CL Profile Scale, which is apparently 3/4". I always wonder if there is any + tolerance on stuff like that, to allow for paint and such. ??? Steve
-
I don't recall seeing any magazine plans that call out more than 1/2" wood.
I just built a Flight Streak fuselage that's 3/32" over a 1/2" hollow core. It's way stiffer than solid 1/2" (the math says it's 60% stiffer), although probably not as crash worthy.
-
Tim,
I see you're still up?
OK, does that mean I shouldn't build my original Flite Streak? What kit is yours or scratch?
CB
-
OK, does that mean I shouldn't build my original Flite Streak? What kit is yours or scratch?
If my friends are to be believed, it is altogether too over the top.
http://stunthanger.com/smf/index.php?topic=22001.0 (http://stunthanger.com/smf/index.php?topic=22001.0)
-
The old J. Roberts kits for Carrier were 3/4" wide, 1/2" longerons with 1/8" sides. I think 3/4" is still the max.
-
How thick are the fuselages on profile kits?
As thick as the engine bearers usually, and with 1/2 x 3/8" and 1/2 x 1/2" bearers in common use I think that 1/2" would almost be universal.
-
If you are looking to build a larger model with a 46-60 engine, figure on using a 3/4 in. fuselage. That fits the rulebook definition. The bigger motors need the extra thickness to get a stiff enough front end. I use 3/8 x 3/4 in motor mounts that go right to the surface of the fuselage. The doublers are fiberglass or carbon fiber, at least 8 oz/ sq.yd for glass. Carbon fiber could be less, 4 oz/sq.yd. You can use 1/16 in. ply and 5/8 in. core wood for more stiffness pm a 60 powered plane.
For a stunt stick type plane(~3 in. tall fuselage), nice, light 3/4 in. wood all the way back to the stab should be OK and not make the plane tail heavy. If you are going for something more scale, the fuselage should be built up behind the spar, either using a foam core and 1/16 in. sides, or some kind of geodetic 1/16 in. strip core. Rather than using 1/64 in. ply for the sides, go with solid medium balsa and .2 or .5 oz. cargon veil applied with epoxy for added sitffness.
-
I have been designing a lot of profile planes using a 1/2" balsa core. The balsa core has the edge/rim thinned to a 3/8" thickness. A 1/2" foam core is inserted and the whole thing is sheeted with 1/16" plywood and balsa. The 1/16" plywood doublers stop at the normal place and the 1/16" rear skins butt up flush to the doublers. The result is that the doublers do not stick out and the whole fuselage is smooth. This produces a very light and rather stiff fuselage. Usually a 3/8" balsa left side nose doubler in installed to give the off-side from the engine a little nice shaping. It also stiffens the nose a bit. Not a bad thing. My last plane, the Mako Jet, used this technique and at 600 squares came out at 45 ounces and flies wonderfully.
I'll attach a set of fuselage plans for an example.
Pat Johnston
Mad Design Studio
Skunk Works
-
If you are looking to build a larger model with a 46-60 engine, figure on using a 3/4 in. fuselage. That fits the rulebook definition.
(Deleted)
Overall, Phil's post has some usefull information. However, the comment about what "fits the rulebook definition" needs some clarification.
There is no specified "rulebook definition" for a profile fuselage or a specification for a profile stunt fuselage minimum or maximum thickness. There are no AMA official rules for any CL Profile Stunt event nor is there any unified unofficial rules for CL Profile Stunt. Different contests might have their own defined fuselage width allowances for such contests, but my experience is that many do not.
The rulebook does contain paragraph 10, CL General, that gives a profile definition that outlines certain aspects of how the fuselage of a profile model should appear. The CL General section also gives a table for the maximum fuselabe width for the several official CL Profile events - 1/2A Proto, Scale Racing, Slow Combat, Navy Carrier, Slow Rat Racing and Rat racing. That table table also gives the maximum width "with additional reinforcements" for each of these events as provided for in this section of the rulebook.
Then, in the CL Profile Scale rules, a maximum fuselage and engine nacelle(s) width of 1 inch is specified with an allowance of a total width 1 1/2 inches for a cowl or cowls.
Otherwise, most of the the information provided in this thread is useful with the exception of the wrong specification in another post about Profile Scale.
Keith
-
Dave Gardner was the head scribe writing the NW Profile Stunt rules http://flyinglines.org/rules.profilestunt.html (http://flyinglines.org/rules.profilestunt.html). When I asked, Dave told me (by phone, as I recall) that the 3/4" spec came from the AMA CL Profile Scale rules. The rest was based on Profile .40 rules used in other Districts. Doesn't matter, this thread is not about Profile Scale. D>K Steve
PS: I recall lobbying against allowing pipes on profile, but there are several flying around here, and I'm building one myself. If you allow electrics, you pretty much have to allow pipes to give IC's a fighting chance. I still don't like it, but it's only fair. This isn't your casual Ringmaster event anymore. That's life.
-
Here's a typical West Coast profile stunt plane: http://s1213.photobucket.com/albums/cc469/JimAron/Current%20Projects/Hydra%20B36/?albumview=slideshow
-
Howard,, now that is a rather misleading post dont you think?
I mean really, letting on to the rest of the world that our west coast profiles are that simple is pretty misleading dont you think?
n~
-
Here is something a little more normal for the Profile event in the Northwest.
Pat Johnston
-
Ty!
Right you are. Thsi would be a really cool profile carrier plane. I also have a MKIII version drawn up with a straight wing in the "normal" location for a profile. This lowers the wing about 2" so the tail is raised up to be under the fin in a very conventional placement. The controls stay more normal this way. I'll attach a PDF of the plans.
Stop by "Taterville" sometime and stay with us.
Your old buddy,
Pat
-
Here's a typical West Coast profile stunt plane: http://s1213.photobucket.com/albums/cc469/JimAron/Current%20Projects/Hydra%20B36/?albumview=slideshow
I hope everyone realizes that this link is a double slide show. The part showing Jim's rebuild is a must view. Thanks for posting, and yes, I'm interested in the profile fuselage responses, but have nothing to add there.
SK
-
I've gone to a 3/8" thick balsa fuselage core for Mo'Bests; the single piece engine crutch is cut from 3/8" birch plywood. This is clad in a 1/64" plywood fuselage skin sides. From the nose aft to the wing high point are 3/32" birch plywood doublers. On the outboard (engine) side of the nose is an additional 3/32" birch ply tripler (spacer under the engine) and on that is the 1/8" aluminum sheet universal engine mounting plate. On the inboard side of the nose is a 1/2" balsa tripler.
I hope this illustration makes it clearer.
L.
"Progress was all right. Only it went on too long." -James Thurber
-
My most recent is sort of a compromise, aimed at torsional stiffness. It's 1/2" medium balsa core, with some lightened trussed aft area. 1/16" ply doublers extend back to the high point, where they are butted against 1/16" balsa sheeting. Nose has a 1/2"+ balsa tripler, and all of the fuselage except the right nose is covered with a layer of 45-degree bias .56-oz fiberglass, applied with West Systems resin. The plywood under the engine lugs is cut away and replaced by aircraft aluminum tapered pads for about 1.5 degrees of out thrust. So the engine does not crush the plywood. It is actually pretty light - and very stiff.
SK
-
It appears that the "new" design profiles in the larger size are using 1/2" cores, a "built up" portion behind the wing for torsion resistance and weight saving, then covering with sheets up to 1/8" thick. Using 1/8th" ply on the nose, the 1/8th balsa behind those gives a smooth fuselage side. That's how Aaron did his latest, a Trophy Trainer.
Big Bear