Cut pieces of 3/4" dowel and glue them in place using a mix of epoxy and micro-balloons.

Scott,

You may already use this method, but I wanted to share something I learned about using the [link=http://www.houseofpylon.com/Tools/HoleSaw750.aspx]3/4" Hole Saw[/link] to cut holes in wings.

If you press the hole saw down so that the teeth are seated, then turn the saw backwards until you have a nice groove, then possibly work it back and forth, you will get a real nice clean cut.

If you try to start out turning it forwards, it tends to wander and tear up the surface around the hole some.

I recommend practicing on a scrap piece of foam with some balsa glued to it.

Initially I started a hole too far back and hit the carbon fiber. The hole was moved a little to miss the carbon fiber on the bottom of the wing.

The dowel reinforcement is located farther back on this wing to allow for tank installation.

I currently plan on removing about an inch from the leading edge to allow for the tank.

A 3/4" Forstner drill bit is the perfect tool to drill thru balsa sheeted foam core wings for
the wing hold down points. Put some masking tape on the bottom side, drill slowly and
chances of splitting out the wood on the back side are greatly diminished.
The cost for a Forstner bit is a little higher but it is a great tool.
brad

Next you make sure the dowels are flush with the bottom of the wing.

Some Skin It was mixed up and 3 layers of fiberglass were added on the bottom.

These were applied in the following order: 9" wide, 6" wide, and 4" wide

Some stretch wrap was applied over the top to provide a smoother finish.

Some tank installations require the removal of about 1" from the leading edge of the wing.

The 4 ounce bladder tank will be mounted farther back so that the fuel weight has less of an impact on flying trim.

A 6 ounce clunk tank (shown later) requires this modification.

A piece of 1/8" thick plywood was glued between the sheeting to reinforce the joint.

The sides were sheeted with pieces of balsa.

Both the 4 ounce bladder tank or the 6 ounce clunk tank are acceptable for this model when powered by Thunder Tiger Pro 40.

The bottom surface of the wing tips were fiberglassed with 2 ounce glass cloth and Skin It epoxy.

Use a sanding block to shape the leading edge of the ailerons.

At this point the wing can be covered with a film finish if you choose.

Ichose to fiberglass the wing with 3/4 ounce cloth and Skin It epoxy.

A piece of glass cloth was wrapped around the wing surface and laundry pins were used hold the cloth in place.

Two containers of Skin It were mixed. Each was about 1 ounce.

Apply the Skin It on the surface and use a squeegee to spread out the glue.

Set it away from everyone and let it dry overnight.

Use a sanding block to trim the fiberglass from the surface.

The fiberglassed wing weighs about 15 ounces at this step in construction.

Attach the wing using masking tape.

Insure that the wing is straight before going to the next step.

Drill and tap the wing and hold down for the nylon bolts.

The wing is counter sunk for the front bolts.

Some minor grinding (with Dremel) is required to get the hatch to fit.

Use a Sharpie to mark the approximate size of the cutout.

I used an earlier model (AJ-2) as a frame of reference for the cutout.

Adjust the size of the hole based upon trial and error.

After fitting the compartment should allow the installation of the Thunder Tiger Pro 40 and any other Q-40 engine you want to run.

My model will use the interchangeable Jett mounts. Either motor will fit with just minor changes.

Cut out the firewall and sand the edges to fit as needed.

It should fit relatively loose at this point.

Use a Dremel tool and/or sandpaper to roughen the fiberglass.

Install the motor mount, engine, and firewall.

Tap the firewall forward with a screwdriver.

Tape the spinner in place so that the motor is lined up.

Once aligned CA the motor mount to the firewall.

Use a long drill bit to drill the motor mount holes.

Remove motor and associated materials from the fuselage and drill remaining holes.

You can install an engine kill or install a throttle linkage for the Thunder Tiger Pro 40. I prefer an engine kill so that type of installation is being installed for both motors.

Reinstall the motor mount, firewall, and engine kill into the fuselage.

Install the motor, align as needed, and tape the spinner in place.

Mix about 0.25 ounce of 30 minute epoxy and apply to the firewall glue joint inside the fuselage.

Add some cut up pieces of fiberglass cloth to the epoxy inside the fuselage.

Let this dry as needed.

My Q-40 motor was removed and the other motor mount and Thunder Tiger Pro 40 (TT) were test fitted.

I ended up adding a 1/32" thickness piece of plywood behind the TT mount to bring the spinner farther forward.

Some epoxy was added on the surface of the firewall, spacer, and back of the motor mount.

The motor mount was then attached using 6 x 32 bolts. Some 6 x 32 bolts were installed on the front beams of the motor mount.

Fiberglass cloth and epoxy were mixed and applied to the front motor mount beams.

Apply fiberglass cloth and epoxy at the seam where the firewall attaches to the fuselage.

Looks good Scott. Since you epoxied the mount beams, I guess this means you will be using the TT40 in this plane? How do these fly with a sport engine compared to a Nelson?

I've flown my AJ-2 with both a Q-40 engine and a Thunder Tiger Pro 40 (TT).

With the TT it flies very well. These are faster than the 424 class Q-500. These fly nominally 125 to 140 mph (sentence edited 05/23/09). These are faster than the 424 class but not as fast as the 428 models.

These are fast enough to get the blood moving but they are still easy to fly.

I use a 4 ounce Tetra tank and have plenty of fuel for a race.

With a 9 x 6 APC prop they will take off a sheet of plywood, like is done for Q-500 racing.

My engines are equipped with an engine kill so it lands like a Q-40, dead stick. It keeps on gliding so plan accordingly.



FYI - I'm using mine as a step up tool to improve my flying skills. I still plan on flying the 422 class. This model will help me improve my flying and landing skills.