Jeff Quesenberry 's Boyington Corsair Project


This Corsair will be built from 60 percent enlarged Ziroli plans, with a wingspan of 152 inches, and a projected weight not to exceed 75 pounds. I have Likes retracts, I will be making a home brewed fiberglass cowling, and I have actually found a 1/3 scale canopy mold. I also have a 1/3 scale full bodied pilot. Final scheme will be Pappy Boyington's Corsair F4U-1A, Bureau Number 18086 "Lulubelle"
Center Section Construction Details

The wing is framed with 3 main spars of 3/16 4 ply. These spars are all one piece, cut from the full spar front view supplied on the plans. I did not feel comfortable cutting spar valves and joining them with doublers. All the ribs, except W3 and W4 are of 3/16 aircraft 4 ply, and all are lightened, except for ribs 5 and 6 that the gear mount to, and rib 7, which attached the outer panel. Ribs 3 and 4 are of 1/8 aircraft 5 ply. Flaps will be mounted on the wing. The ribs fit very tightly on the spar, and there was a concern toward getting a good glue joint. Any glue I used, would be squirted out when I slid the ribs on the spar. So I decided to install all of the ribs and wick them with thin CA. I then use triangle stock to reinforce all of the joints. Where the ribs meet the front spar, this is a butt joint. So to increase strength, I use 1/2 spruce triangle stock utilizing Elmers Pro-Bond exterior wood glue. This glue is weather (water) resistant, so should hold up to the cold, humidity and temperature changes. Wood glue also provides a glue joint that is as strong, if not stronger, than the wood.....very strong stuff. I did the same on the rear spar where the ribs meet the aft spar. I also used triangle stock on the center spar/rib joint. Since there is so much surface area here at the center spar, I opted for 1/2 balsa triangle stock, and applied it with the same wood glue in all 4 corners (both sides of the ribs and front and back side). I am not as concerned with strength here, but rather a good surface area glue joint to hold the rib in place.

The design of the Corsair center section is, such that, everytime to land, the stresses are wanting to break the wing at the top of the spar "W" where the wing meets the fuse. With this in mind, I added the doublers that would be otherwise used on the 2 piece spars and glued them using T-88 Structural epoxy. I then added 1 inch Spruce triangle stock at all of the W1/spar joints glued with T-88 Structural glue. T-88 is a very stable epoxy that is used in the building of homebuilt airplanes. It does not soften up in the heat, nor does it become brittle in the cold. ASTM test provide information that a lap joint using T-88 has a shear strength of 2800 psi, resulting in substrate failure. Therefore, the wood failed before the glue. This glue is available from Aircraft Spruce and Specialty and is pretty inexpensive. All square stock spar insert pieces are of 3/8 aspen pine. The center section, framed up, weighs 11 pounds without the gear. Gear are from Likes with 13 inch struts using 9 inch compressor tires.

Stab Construction Details
The stab is built up with 3/16 balsa ribs, with 3/8 square aspen pine spars. It was sheeted with 3/32 balsa. There were no major deviation from the plans, but I did make some changes. Because the size of the stab is 63 inches, which is equivalent to a 60 size plane's wing, I shear webbed the spars with 1/16 balsa for rigidity. The trailing edge was also capped with 1/16 ply to stiffen and increase strength. The stab will be glued (epoxied) to the stab saddle. In addition, I will utilize a dowel pin in the front, and will bolt it in, with the bolts encapsulated in epoxy, using 10-24 cap head bolts. It will basically bolt on like a common RC wing attaches to the fuse. Since the stab was so large, I figured the stresses involved left it questionable as to whether or not simply gluing the stab to the saddle, and relying on the balsa sheeting/stab glue joint, would hold up over time.


Wing Panel Construction

The wing panels were framed using 3/8 x 3/4 Aspen pine from a 1x2 board purchased at Menards and ripped on a band saw to fit. Aspen pine is a great medium weight, straight grained wood that is very clean and really soaks up the glue. It is also strong and rigid. The inboard rib is made of 3/16 4 ply, and will be face glued to the outboard rib of the center section. The next 2 ribs are of 1/8 5 play and was chosen to help support and strengthen the wing joint brace attaching the outer panels to the center section. The remainder of the ribs are of 3/16 balsa. The tip spine piece is of 1/8 lite ply. All of the ribs were glued on using medium CA from Balsa USA. I really like this glue, it seems to be the best out there from what I have used.I shear webbed the front and back of the spars using vertical grain 1/8 hard balsa with medium CA. This is a wing panel that could be walked on. The only thing stronger than a boxed spar, would be an I-beam spar...but that is a lot of work and not necessary.

The inner most rib bay was shear webbed with 1/8 5 ply glued in with T-88 epoxy for its' strength, and was gusseted with 1 inch triangle stock with this same T-88 epoxy. This area is where the wing joiner brace will attach to the spars. I will then fill the are between the top and bottom spar with a piece of hard wood. This will act as a continuation for the main center section spar and should never fail. The inset sub leading edge is of 3/8 square aspen pine with a 3/16 balsa leading edge sub cap. After the wing is joined and sheeted, I will cap the leading edge with 1/2 inch balsa. There was no design deviation from the plans...only material choice was changed.

Wing panel nearing completion

After the wing is joined and sheeted, I will cap the leading edge with 1/2 inch balsa. There was no design deviation from the plans...only material choice was changed. Each wing panel measure 52 inches from inboard rib to tip edge.


Motor Box and Firewall Construction

In this pic, you can see former F1 made of 1/2 inch 9 ply. The slots to the side are to clear the 3/16 ply inner wing/fuse saddle. You can see that the motor box sidewalls and the firewall itself is also from 1/2 inch 9 ply. They are mortised into their adjacent structure and will be pinned with 1/4 inch aluminum pins, and gusseted with spruce tri stock as well. Once finished, this set-up will be bullet proof. T-88 structural epoxy will be used throughout.

I have all of the formers cut out. I spent most of the night setting up the firewall mount. I deviated from Ziolri's plans slightly. Former #1 was cut from 1/2 inch 9 ply. I will be bringing the inner wing/fuse saddle, made of 3/16 4 ply up through the firewall, but it will stop 1 inch forward of the firewall instead of continuing on to form the motor box. I will gusset it front and back side with 1/2 inch spruce tri stock.

In case any of you hate cutting those 1/8 notches in the formers, a friend of mine came up with a slick idea. We always trace the formers onto the wood using carbon paper. Just mark the center of each notch and make a tick mark 1/4 inch deep from the edge of the former (I use a compass set to 1/4 inch and just run it around the perimeter of the pretty good). My buddy came up with the idea of putting a 1/8" wide dado blade in his table
saw and just running the former in, back to the 1/4 inch tick mark. The dado blade taper inward at the base of the cut, so you get a tight fit with a squeeze at the base of the notch...almost don't need any glue. I notched all the formers in about 15 minutes.

Husky 240CC

Here is a pic of the Husky 240CC sitting on the firewall with the 34x12 carbon fiber prop.


Fuse Construction

Started the crutch. Built up of 3/8x3/4 aspen pine with 3/16 hardwood cross braces back to former #7, then 3/16 balsa reminder. The inner wing saddles are from 3/16 4 ply and that is former #2 made of 3/16 4 ply as well.

Second picture is the fuse up on the crutch jig. Formers F1 through F11 are on. F1 is of 1/2 9 ply and will have the engine box attached. F2 is of 3/16 ply with a 1/2 ply doubler around the big dowels. Formers 3 thru 7 are of 1/8 5 ply and will have the inner ((installed) and outer wing saddle attached to them. F8-F11 are of 1/8 lite ply. F12-f14 are 1/8 5 ply and will have the tail retract installed on F12 (currently fitting). The wing saddle will go between F12 and F13 (I will get a close up of this are when installed). F-14 is the last former that ties everything together and will have the balsa tail cone attached.

Here is a snap shot of the outer wing saddle. This piece was cut from 1/8 5 ply and was quite a task to bend it down and around the body from F6 to F7. Adding big gussets here to take off some of the load from the formers. In this pic, you can also see that I have gussetted all of the front end formers around the wing saddles to strengthen this area since I plan on hoisting the plane within this area. Excuse the table mess...I am running out of room.

Here is a shot of the stab saddle. To try and lighten this area, yet make it strong, I laminated 1/4 balsa between 2 pieces of 1/6 ply. In this pic, you can also see that I did not cut out former 12. I left it solid and drilled a 3/8 hole that the stab leading edge dowel will go thru. Look closely, and you will see that I added a 3/8 x 3/4 piece of aspen pine to the outside of the stab saddle and crutch. The stab was centered and two 8-32 holes were drilled down between the outside of the wing saddle and this aspen piece I added. There will be a T-Nut at the bottom to bolt AND glue the stab to this saddle, just like a standard wing attachment. Once there, always there

A shot of the elevator being laid up. The core is of 1/8 lite ply, with a balsa leading edge and 3/16 balsa false ribs top and bottom. Where the elevator is cut out on the back side there, I plan on installing fake trim tabs, but operational balance (boost) tabs a-la full scale. I have not decided yet, but I may add lightening holes every other rib bay indicated by the pencil marks you see. I will be using some of Sierra Precisions new 1/4 inch thick aluminum pin hinges. These things look tuff.

Been doing putzy work. Finished off the elevators and added the lightening holes every other bay. Also made up the trim and boost tabs. Built the vertical fin/rudder yesterday. Here is the assembly. i built them per the plans, only I added a 1/16 ply backer to the rear side of the vertical fin post for rigidity. Now, the only thing left to do is to fit the retracts, figure out the servo installation and start sheeting

Top of fuse front and top rear turtledeck have been sheeted. The fin is installed. Fuse stringers are 1/8x1/4 aspen pine. Sheeting is 1/8 balsa. I should have the whole top half of the fuse sheeted by the end of the weekend

Well, I was able to get the tail feathers mounted and the fuse to all sheeted down to the wing saddle. That is all the farther I can go on the crutch jig. I will be removing it, adding all the radio gear and sealing up the fuse bottom this week. Here is a 3/4 profile shot of the tail end. The horizontal stab was mounted with a dowel through former F12 and two 8-32 bolts and T-nuts in the rear. The whole lot was epoxied down, never to be removed again. IF you look at this photos, you will see the big black blob on the rudder front, top air balance. This is the lead added to balance the rudder. 4.5 oz.

Here is a close-up shot of the tail bottom. You can see the T-nuts that hold the rear of the stab in. Also, just forward of the 1/2 former F13, you can see the aspen blocks I have installed. I opted to put the servos in the back, under the stab so that I could go with short, stiff control rods and have everything out in the open for daily inspection. Small price to pay since it is pretty well hidden under the stab. Hard to notice

I have the tail feathers all on. Here is the spring I use to help hold pressure off the servo (for taxiing, etc.). I also mass balanced the elevators

Here is a picture of the rudder attached to the airframe. It has been fabric covered, scale pinking tape applied and doped. The elevators are also on and I have them fabric covered. I am in the process of applying the pinking tape now. If you look at the elevator, you will see the mock trim tab on the left elevator, and the functional boost tab on the right elevator. Everything is reversed on one horizontal tailplane half. Vought made one horizontal stab/elevator and used them interchangeably on either side of the tail plane. As such, you will also find that access hatches are located on the top of the left horizontal stab, and the bottom of the right horizontal stab. A good idea for repairing battle damage.

Fuse is now all sheeted, except for under the front end....until after I fit the wing center section. Here is a shot showing the carbon fiber arrow shaft rods for pull-pull on the rudder. Fitted with 4-40 ball link fittings from Rocket City. The fiber rod on top is attached to an air cylinder and the retractable tail wheel. The dowel rod you see poking through the former is mounted into the stab, which is bolted to the stab saddle/crutch

Here, the fuse has been removed from the crutch jig, and placed upside down on some dense foam blocks to work on the internal linkages and fitting of the retractable tail wheel. The top of the fuse has already been glassed, and I have just finished adding the bottom stringers.

Here, the fuse has completed sheeting, except for the very front, under the wing leading edge, which will wait until I have fit the wing to the fuse. All up weight as you see the fuse is just shy of 19 pounds.


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