I'm really looking forward to finishing my Sledge 540... but I did see some things I think should be considered when building the wing (and Jeff maybe some manual changes)


Jeff was wondering why wgeffons shear webs (Jeff calls them I-Beam pieces) didn't go full across the span between ribs....wgeffon told him because the material wasn't wide enough.

To elaborate on this, the manual shows placing the shear webs with the grain running horizontal (or from root to tip) this is INCORRECT. Shear web grain should run vertical (from spar to spar). Their reason for being isn't necessarilly to "shore up" the spars, but to keep all the entire assembly from collapsing like a cardboard box without a top or bottom. Horizontal grain simply can split and fold, while vertical grain is like ripping a phone book in half...

Now while a funfly design may not put enough stress on this area to really be concerned, simply orienting the grain vertical will increase the shear strength of the wing immensely with no weight gain. I used some VERY light 6" wide 1/16 sheeting...


Secondly, I really dislike the leading edge setup. There simply isn't a way to get a nice round LE on the wing without seriously weakening the sheeting at the leading edge. (see pic) I'll probably lay another piece of 1/4" balsa on top and round it around too... The wing is very light and another ounce wouldn't hurt it.

Lastly, the wing is built (basically) in two halves. The design does not allow for any spars to cross the center of the wing. Even the spar doublers and leading edge are "seamed" at the center of the wing. No joiners, nothing. This creates a weak wing prone to folding. While again it may not happen with a funfly (I really put some twists and spins on mine) it would be easy to modify the design without adding any real weight.

I plan on sanding 1/4 slots in the ribs (top and bottom) across the center 5 ribs W1's thru W3'w and laying a 1/4" balsa spar in to tie across those ribs. It'll add MAYBE 1/4 oz.


Now I don't mean to sound like I'm bashing Jeff and his design... It looks like it'll come out light and probably will fly great... but these are some basic design things that shouldn't be left out.

My kit has very good wood except the 3/8"... I replaced with medium hardness and saved 1.2 oz over 3 sticks!!! ... they were LOGS. And they left out the plywood hatches ( I called and am sure they'll send em a set out). It also didn't come with a tailwheel... the plans show a skid but even Jeff shows in the manual he went with the optional skid.

Alright... 'nuff said... back the the workshop...