Four * Forty modification?
 

I have a Four Star Forty that I dearly love and am looking to build another one. My question is whether or not anyone has tried sheeting the wing from the leading edge back past the main spar? That would obviously add a lot of strength to the wing but at what cost? Would it adversely affect the flight characteristics of the airplane?

RE: Four * Forty modification?
 

The additional weight that such a modification would add would be marginal in the overall scheme of things, and the benefits derived would certainly outweigh any possible negative.

Karol

RE: Four * Forty modification?
 

I agree. I don't think you are going to gain enough benefit to justify the added weight you are going to get. The best mods for a 4-Star, in my opinion, are cutting a couple bays off the ends of the wingtips and take out some of the dihedral out of the wing. Doing those mods will really wake this bird up and make it fun to fly, but still keep it tame enough for newer pilots<div>
</div><div>Ken</div>

RE: Four * Forty modification?
 

Ken, how close to flat would you make the wing?

RE: Four * Forty modification?
 

Most of it!! The sheeting of the wings LE I have done several times. Strength added, not much, people not sticking fingers through the covering and breaking stringers priceless. Removing a couple of bays outstanding roll rate!!

RE: Four * Forty modification?
 

Yeah, Gene, that was what I was concerned with more than anything else. Handling a wing with a sheeted leading edge is a lot easier than handling a wing with only shrink covering on the front third of the wing. Also, what would be wrong with making the wing totally flat? The Four Star doesn't have all that much dihedral to begin with.

RE: Four * Forty modification?
 

I've always built D-tube wings. That sheeting will most likely be in front of the balance point, which will be a good thing in most cases. The added strength and ease of handling is worth every gram. Weight? Maybe an ounce. The best thing to do is throw that lite ply in the trash. It is heavy, weak (for plywood) and usually warped.

RE: Four * Forty modification?
 

I always leave in a little dihedral, I'm not an aircraft engineer but the next kit I build like an Extra or Kaos that has no dihedral will be the first so I figure if they have it then who am I to remove it. Even if I lay one side flat and add a block of about 1/2 inch to the other that adds a little. I block both tips though so you do the math.
I have a sheet of 1/32 door skin I use for the LE and turtle decks on the 4*s but also use contest grade 1/16 balsa. Both are light weight but the sheeting is thinner.
Do a search here on RCU, Ed Moorman has posted photos of one of his that he bashed to look like a warbird, perhaps the coolest one I have seen.

RE: Four * Forty modification?
 

I have also made a wing with a sheeted LE. Then I applied capstrips to the tops of the spare from the sheeting back. Looked good. I didn't shorten the wing. If you like, you could inset a couple of T-nuts into the inside of the wingtip ribs so that later you could attach a couple of wingtip plates, just to experiment. That's what I'm going to do with my next 4*40

Just my $.02

Bob

RE: Four * Forty modification?
 

OK, here's my plan. I am going to build the wing with sheeting on front 1/3 of wing. I am going to shorten the wing by at least one bay. I am going to remove most of the dihedral. I am going to put servos in both wing halves for the ailerons. Will it fly?

RE: Four * Forty modification?
 

Your not doing anything new at all. What is it that would make you wonder about flying?

RE: Four * Forty modification?
 

I asked the designer, Bruce Tharp about the wing, and if the stringers were intentionally designed as turbulators. He said that wasn't considered. Weight and simplicity drove the wing design.

RE: Four * Forty modification?
 

I did notice a bit of a difference with a sheeted wing LE. Had to enlarge the wing opening in the fuse to compensate though.

I also bought another kit and made an identical plank wing but used a S8036 airfoil. There was a difference in that too - of course, sheeted LE on that as well.

Bob

RE: Four * Forty modification?
 

Has anyone shortened the wing by 2 rib bays?

RE: Four * Forty modification?
 

As long as you're modifying it, I'd suggest these: make a hatch for the fuel tank and use a real tailwheel (Sullivan is good, but there are lots of others, too). These take very little time to add and will likely simplify your life somewhere down the line.

RE: Four * Forty modification?
 

I do it all the time on the 60 but I haven't built a 40 in several years and don't recall a lot about it. I know I removed a bay but can't recall how many. I use the 60 to teach building and have made mods with almost every one. Last one I did was last year and it was with an older fellow and left completely stock.
Two bays on the 60 really helps with the roll rate and doesn't seem to harm the floating of the plane at all. They do have a huge wing on them and I understand they are still a trainer but two bays on the 60 works just fine. The 40???

RE: Four * Forty modification?
 

One of the things I did to mine as to add some 1/4" tri stock to the leading edges of the ailerons, rudder and elevator for two reason. One, so I didn't have to sand that bevel in the trailing edges and two, just to add a little more area to the control surfaces. And then I used a canopy from a SSE. It was an awesome plane until the covering took a dump. :(

RE: Four * Forty modification?
 

GB, thanks. Tip plates should help the roll rate even more. Itwould make a good trainer. I've used a Sig Somethin Extra for a trainer.

RE: Four * Forty modification?
 

L.G. mount could use a little 'shoring up'! I had a 'V' tail, 'barn door' and static balanced ailerons with slots in wing L.E. and a 'fast back' turtle deck to replace aft portion of bubble canopy and shortened wings with end plates on mine. Oh... I powered it with a ST90, too!

RE: Four * Forty modification?
 

I second the point about LG mounts. Also,l as I recall, the kit wing hold down plate (where the wing bolted into the fuse) was braced with balsa. I'd recommend a couple of pieces of pine cut to the same size.

Just my $.02

Bob

RE: Four * Forty modification?
 

Yep. Pine and 1/4" nylon bolts.