Misc fuselage Const Photos

here are some mixed fuselage construction photos. All of my airplanes use stab alignment jigs. several are shown in these photos.

man all the laser cut parts for snaggletooth 2 look good

Interesting construction photos, see you still have your "slave labor" to assist you. The plans for Snaggletooth II looked great, can't wait to see the real thing in action. What size engine are you installing?

"Slave labor" is building his own airplane. The airplane is reworked to use the RO-Jet 65/PA 65 rear exhaust.

I've got a couple of minutes. I'll add a few thoughts on fuselage construction of semi-scale airplanes. This information may be of use in the construction of classic stunters, but, I couldn't say for sure. I don't build classic stunters.

I use all 3/32" sheeting for my fuselages, some molded, some flat. the Critical Mass and Snagletooth 2 have mostly flat fuselage side skins. To obtain the necessary strength of a finished fuselage, I use, typically, four to eight 1/8"x1/4" longerons. They look heavy but weigh about 2 1/2grams each. These stringers could be lighter but, for strength, I strip them out of 1/4" sheet, 10lb balsa. So, even on the Bearcat, which has eight longerons, there is less than three quarters of an ounce of stringers in a very powerful four stroke stunter. In the Snaggletooth there are only 3 full length longerons and a couple of shorter ones.

My bulkheads are all laminations of 1/32" ply and 3/32" balsa. The bulkheads ahead of the wing leading edge are typically made up of a 3/32" balsa core and a 3/32" ply lamination front and back. Excepting the 1/8" ply engine mounting floor, bellcrank mount "hard spot" and leadout guide, there is no ply in the airplane thicker than 1/32". Even the bellcrank mount is the same 3 layer lamination as the forward bulkheads. The engine mounting floor is a light 3 ply birch. Kyle has difficulty laser cutting 5 ply aircraft grade which is stronger and heavier but needlessly strong and heavy for the application. The design allows for the weaker, lighter birch. Bulkheads aft of the wing leading edge are typically one lamination of 3/32" balsa and one 1/32" ply for a total thickness of 1/8" but very strong and light. The engine bearers are never more than 3/8"x3/8" maple, even in the larger four stroke airplanes. The engine mounting system depends on distributing loads from small maple engine bearers the the birch ply floor and through the laminated bulkheads to the longerons and skins. Laminated bulkheads vary in weight depending on their size and number of laminations but are probably lighter and stronger than you might expect. The larger 3 ply forward bulkheads may weigh 8 to 15 grams. They are much lighter than plywood bulkheads and strong enough. The 2 ply bulkheads may weigh 3 to 5 grams. The net result is that, while I may use a lot more pieces of wood to build my fuselages, the finished weights are probably no more that a typical stunt ship fuselage, and in some cases maybe lighter. Take a look at the photo of the aft fuselage of the Snaggletooth in its jig with the curved doublers for the radiator bottom. that is all of the structure there is excepting the 3/32" sides, molded 3/32" top and 1/16" bottom.

Building the fuselage from the inside out on a jig is fun. The jig takes almost no time to build as the pockets are laser cut on the same sheet as the bulkheads. The pockets are simply laminated and glued to a jig base centerline at spacing dimensions shown on the plans. An interesting aspect of jig building fuselage construction is, after the front three bulkheads are assembled in the jig with the engine bearers for alignment, the sub-assembly may be removed to complete the interior structure of the forward fuselage conveniently in hand. One of the photos above show a fat, bald-headed guy (me) working on a Snaggletooth fuselage with a forward fuselage sub-assembly laying near the fuselage jig.

This construction method stresses using wood weights and sizes tailored to the anticipated loads which might be imposed on the completed airplane structure. So far, it hasn't been pointed out that a jig built fuselage will necessarily be very straight and accurate with no tolerance for pitch errors in the engine mounting.

Without laser cutting, the jig built fuselages of the molded Mustang series was a labor of love. They were fun, but took an awfully long time to build. The goal, of course, was always to build a reasonably good looking and realistic semi-scale airplane without sacrificing competition capability. History shows that I managed that then. I think the designs are still aerodynamically sound in design. They should still be competitive with modern engines and updated labor saving construction techniques. To this end I updated the Snaggletooth molded Mustang design with modern rear exhaust engines, larger removable fuel tank, and modern construction methods. May a Snaggletooth once again reach the winners circle.

Ah, for the good 'ole days when the engine was canted to get the muffler inside (no rear exhaust engines) and the tank had to be glued in to save weight and give the fuselage necesary strength.

Al,

Looking at photo #2, it appears that you're using JB Weld as an adhesive for a number of joints. Am I correct in my observation? If so, why? Thanks for sharing your series of construction photos. They are highly instructive and very much appreciated. Gary

Gary,

Yes, it is JB Weld. This stuff is a very good epoxy which I occasionally use on critical joints on higher power airplanes. Usually though, I just go with CA because of the way my engine compartments are designed. I probably wouldn't use JB anywhere except the engine bearers.