EJF Composite A-10 Construction

[gregg f]

a couple of thin ply ribs (on each side of the retract unit) to spread the load.................gregg

[Arthur Knowles]

Originally posted by gregg f
a couple of thin ply ribs (on each side of the retract unit) to spread the load.

Hmm, that's a good thought. More difficult to do than a few pins, but possible. I'll have to think about it.

Art

[hoser]

I used epoxy on everything and used no dowel I just roughened or scored the surfaces to hold the epoxy well.

then I used a router dremel and routed out 1/8" out of the wing right where the mount goes so it fits flush it will become part of the spar.

rough landings not sure you can make it strong enough for all landings just use a low bounce wheel and make sure you use the struts with the coil.

DIRT FIELD, your on your own I never have ROG of dirt... never tried.
but I've torn the gear of a couple of times

make sure you test fit the gear in the mount before glue in everything


ALSO to lighten things I drilled holes in the 1.25 x 1 x 3/8 hardwood pieces.

[Arthur Knowles]

Well, for those of you planning to use the EJF retracts, you'll need to modify the plywood mounting plate. Instead of 1.5 x 3 x 1/8 it needs to be the width of your retract gear. In other words, make a 1.75 (or a tad wider) x 3 x 1/8. Otherwise you will be unable to moung the hardwood landing gear blocks.

You could also use thicker langing gear bloacks. Instead of 1.25 x 1 x 3/8 consider 1.25 x 1 x 5/8 (or wider) blocks. That way you could have the blocks contact the side of the retract housing and still have enough wood for the mounting screws.

PS: My blocks are curing now. Once the epoxy has cured, I plan to drill though the plate and pin the landing gear blocks to the landing gear plate. I may add a bit of trianguler stock on the inside face as well to help spread the load better.

[Arthur Knowles]

While waiting for my langing gear mounts to cure, I decided to work on the fans. I have one fan assembled. Still needs just a bit of sanding on all the blades for that perfect no touch fit. Seems the shroud is not 100% round and there is a flat/low spot that all the blades touch.

Is there something I should do to unstress the shroud before assembly?

Also, while the fan intake ring fits on the nacels perfectly. The fan does not fit in the nacel. The nacel is mush wider (10cm or so) than the fan. There are no directions for assembling the nacelles with 480 size mini fans. Just a picture for the wood kit that does not apply to the composit kit.

So, what do I do. Do I have to make an inner ring out of plywood to hold the fans? Do I need to build thrust tubes? Or do I just hack up the epoxy nacels (not something I'd want to do)?

I gotta be honest. For the $200 I paid for this kit, I expected a lot more. I expected a full kit with much better instructions. All the parts required to build the model. This is a "short" kit and it's short of a lot of things. Not a kit I'd recommend to even an experienced builder (I've been doing this stuff on and off for over 30 years).

The good news here is at least I have people that can help out on the e-zone. Hoser, that means I appreciate your help a lot too. But this kit could use some work and I hope Robert can do something about it for future builders.

PS: If I could have looked at the instructions online, it may have warned me, but the links don't work. Maybe that should have told me something.

[Ed Waldrep]

From looking at the pics of the kit and know what the MF480 looks like, I'd say you have the right idea. Cut two rings of lite ply to serve as bulkheads. The inner diameter would be the outside diameter of the MF480 housing and the outher diameter of the bulkhead would be the inside diameter of the fiberglass nacelle. To insert and later remove the fan if necessary, you could remove the fan from the front, and hold the intake ring in place with a couple of plywood tabs glued to the intake ring that extend rearward into the nacelles and held in place with #2 srews. Keep the intake ring removable (don't glue to the fan). Once the intake ring is off, the fan could be held in place with small plywood tabs glued to the outter housing of the fan. These tabs would rest up agains the first nacelle bulkhead, and you'd drill thru them and secure the fan with #2 screws. I guess a diagram would help, I might draw one later, need to work on my A-10 for the jet rally.

The exhausts could me made form posterboard or mylar sheet. Cereal box cardboard would work. It could be attached to the rear of the fan with tape or make another ply bulkhead and attach the exhaust to that and the rear of the nacelle. When the fan is inserted in lines up with and maybe slides into the exhaust a bit, forming a tight fit.

[bruff]

The way I have done it is to mount the fan to the metal mount. The other lug is cut off. Cut hole for the fan mount to fit through the nacels and split the nacel from the hole to the front edge.This will allow it to to slip over the mount. Then fit the inlet lip to the fan and nacels front. I use drafting mylar for the thrust tube with double stick tape to keep it together. The inlet lip can be glued to the fan and nacells. Hope this helps.
Bob Ruff

[Arthur Knowles]

OK, let me see if I can lay this out properly. The MF 480 intake ring has a diameter of about 68 internally and 90 mm externally. The nacel has a diameter of 90 mm front and 60 mm at the rear. That means:

1) I need to make a thrust tube 68 mm in diameter to go from the inner ring of the intake lip to the MF 480 shroud.

2) I need to make a thrust tube 68 mm in diameter tapering from the shoud to the exit hole at 60 mm in diameter.

3) I need to mount the fan to the aluminum support using one set of mounting lugs on the MF 480 fan.

4) I can use a set of split rings (have to be split so I can assemble/disassemble the unit) around the MF 480 to support the nacel.

Sound right?

PS: Where do you find drafting mylar?

[Arthur Knowles]

Just as an FYI, if you use the EJF retracts, you cannot use the lighter ABS plastic wheel covers supplied with the kit. They are not wide enough to hide the retracts. I plan to follow Hoser's methodology and build balsa versions.

I wish I had of known before I spent the time grinding the excess flash off of the ABS pieces. Ah, well live and learn.

[Arthur Knowles]

OK, I have assembled the mini fans and installed the motors. One required just a few passes on the rotor with a sanding stick for a perfect fit. The other required quite a bit more work. Hope they both work as well.

I'm currently installing the TE on the wings. Once that is done I will make dihedral braces & join the wings. Then I plan to install the wing servos & retract lines and sheet the wings. After sheeting I need to glass the wing. After all that, I should be able to cut out the airlerons.

This kit is definitely going slower than planned, but I think it wil be worth it in the end. I just hope it flies well & I don't crash it.

[hoser]

I don't know your flying experience but the plane is a very nice flier, just remember its not a prop plane and you need a god roll before you pull up, sharp maneuvers require you to get back on step.

I flew my balsa one in my back yard for hours without motors and gear as a glider. it would go for over 100' with a light toss, if there were any slopes in Florida I would of used it as a slope plane.

just make sure you generate enough power from you lipolys and the weight is not to high.

for the retract version 2 pounds min. thrust is required

[Arthur Knowles]

Hoser,

If MotoCalc is accurate, or close to it anyway, I'm looking at about 3.25 pounds of thrust. I'll actually measure it using my digital fish scale (good to 1/10 of an ounce) before I fly it.

I've got the wing assembled now. The last bit of epoxy is curing. Tomorrow, I'll cut out the servo openings and route wire and retract plumbing. Then I'll sheet the bottom and glass it. After the glass cures, I'll cut out the airlerons and servo openiongs again.

It is finally looking like "real" plane parts.

Art

[Wof]

Arthur looking at the problems you have faced during this thread i am glad i went for the full wood kit,i have ordered two kits from EJF one F18 MF480 and the wood A10 both kits were short,and i had to chase delivery for two months.
This was one year ago so i hope things have improved,i am not knocking anyone but if i was a newbie it would have put me off EDF.
Mark (England)

[Arthur Knowles]

Here's a picture of the wing showing the top and bottom structures. The bottom has not yet been covered so you can see the wood spar, LE, TE, and cutout for the EJF retract mounting plate.

[Arthur Knowles]

Here's the wing. Covered with 1/32 balsa. Retract tubing and servo extensions installed and all cutouts. Next step is to glass the wing and install the servos and retracts.