EJF Composite A-10 Construction

[Arthur Knowles]

Hi all,

Since I could not find one when I searched previously, I thought I'd start a new construction thread. Assuming someone else is going to want to build the Electric Jet Factory Composite A-10 kit. :)

In any case, mine arrived today. Kit contents include:

Composite Fuse
Composite Nacelles
Foam Wings (wire cut)
Balsa Spar, LE, and TE
3/16" Balsa Tail
1/32 Balsa Wing Skins
CD with instructions/pictures

Componets I will be adding:

2 Mega 16/15/3
2 Wemotec 480 mini fans
24 ET-1200 LiPoly batteries in a 4S6P pack
3 gear EJF Retracts
Robart Retract Kit (pump, tubing, air tank, fittings, etc.)
Hitec Electron Rx
4 Hitec/RCD HS-81 servos
Servo rods
Wing/Motor mounting bolts
Triangular stock
1/8" plywood
Carbon fiber
1"~1 1/4" Aluminum landing gear (used for mounting motors)

Art

[Arthur Knowles]

Fuse, Nacelles, and Wings

[Arthur Knowles]

Tail Section & Wing Skins

[Arthur Knowles]

I'm still working through the instruction manual. The instructions are 13 pages, and not for novices (i.e., not a series of step by step instructions). There are no printed plans. You can print the manual, but the primary plan sheet is too large to fit on a 8.5" x 11" page. If you scale it to fit, you can't read the text. Luckily for me, I have a plotter in my office so I was able to print the plans in a readable size (36" wide, so I had to scale them down a bit, but still it's much better). You can review the image files using a JPEG editor at 100% size and read the text or view the detailed images on the plans if you don't have access to a plotter/large format printer.

I do have a couple of questions for the more experianced out there:

1) I've never worked with foam wings before. The instruction state to use 3M77 spray for the wing skins. If I recall, this spray has changed and is no longer foam friendly. So, if I go this route, what should I use?

2) The instructions also suggest that instead of wing skins, I could just glass the exterior. What do you think? I am planning to paint the aircraft.

3) The plans show a balsa spar and a plywood diheidral brace, but no plywood was found in the kit. No triangular stock for retracts, carbon fiber for bottom of wing, wing/motor hold down bolts, etc. Is this a case of just using your own materials?

4) The wing shows a balsa spar 2" from the leading edge. Do I cut the wing at this point and insert the spar between the two wing pieces? Or do I carve the wing out to fit the spar?

5) The tail is composed of 3/16 balsa. Has anyone considered rebuilding the tail out of 3/16 stick? Or hollowed out the existing pieces?

I'm sure I'll have more questions as I go, but this seems like a good enough start.

Thanks for any help you can give me...

Art

[JANSSENM]

"1) I've never worked with foam wings before. The instruction state to use 3M77 spray for the wing skins. If I recall, this spray has changed and is no longer foam friendly. So, if I go this route, what should I use?"

I use the new 3M77 with the foam core for my EJF F18. It work out fine, you just have to spray it lightly on the cores and sheeting.

I notice that EJF kit is not so complete. you have to use your own stuff if you already have them or buy what you need. sorry I can't help you more. I never got to finish my A-10. I give it to my brother.

jans

[Herb]

I won my EJF A-10 inc fans & motors at a raffle :) . The wing on mine was weak. Too weak. I would suggest you have a nice good sized spar, reinforce the wing joints, skin the wings with balsa & probond or epoxy, and glass the whole thing with 3/4 oz ultralight glass cloth, reinforcing the joints. If you do a careful job it will add very little weight. The glass will provide you with a smooth final surface ready for primiing.

Picture of mine from three years ago, twin edf 400 units, loudest edf ever :D

http://aeneas.ps.uci.edu/edf/a10/a-10_mine_4.jpg

[RickG]

"1) I've never worked with foam wings before. The instruction state to use 3M77 spray for the wing skins. If I recall, this spray has changed and is no longer foam friendly. So, if I go this route, what should I use?"

Count me among those who've had less than satisfactory results fron 3M-77. I just tried ProBond and am impressed with the results. You need very little of it though, and because of the way it penetrates into the smallest spaces, you can skip pre-joining the wing skins. Just tape them together as if you planned to glue them. Works great.

[Arthur Knowles]

OK, well I have started to work on the composite parts. Sanding off the mold lines and in general just cleaning it up a bit. I've also purchased 5 meters of 3/4 oz cloth and some carbon fiber for the wings. While I was at Hobby People, I picked up some 1/8" plywood and a couple of different maple engine beams for the retracts. Not sure if I'll use 1/4" or 3/8" sq. yet.

I've also printed and read the instructions for the all balsa A-10. That cleared up a few questions, but left a few as well.

I could not find any probond, but do have epoxy. I have some pacer finishing epoxy that I was going to use for the external cloth/epoxy when I glass the wing. The main question I have is shuld I use the 1/32" wood sheeting at all? I could do as the instructions suggest and just apply the cloth directly to the foam with carbon fiber reinforcement. If I use the wood, I need to attach it using epoxy as well. Or the 3m77/probond that I don't have. Any suggestions where to find probond locally?

[Jim Phelps]

Lowes, Home Depot or any good hardware store will have the Pro Bond. There are other brands as well, the original polyurthane is called Gorilla Glue. I just started using Pro Bond and it works great. I had been using 3M-77 and thought it was too, but the PU glue makes a much stiffer wing.

Jim Phelps

[bruce ryan]

Arthur,
Just happened on your question,
my opinion is that glassing over foam is very difficult to make a good looking wing. I would use the 32nd balsa and then a light glass cloth.
Although, My first choice for foam cored wings is 1/16 balsa and then .5 oz or .75 oz cloth just for the finishing aspects. There you could use epoxy or dope, though I read people like the water based poly coatings too. If you go this method you might feel more secure with a reinforced epoxy bandage over the wing joint.
good luck
Bruce

[Ed Waldrep]

My 45" scratch A-10 has 1/32 sheeting over foam cores....it's plenty thick enough. 1/16th would work but is kind of overkill for a model this size unless you use contest weight (3-6 lb/cu. foot) wood, and glassing the entire surface will add more strength.

[hoser]

Arthur sorry I did not get to respond earlier I was out of town visiting the Mouse.


1. sheeting the wing is pretty easy I used the 3m 77 spray as recommended on some of SIG manuals for their kits use a light spray on both surfaces let sit and get tacky and then bring both surfaces together, I have also used sheeting epoxy which is very watery (use sparingly though. use the model the foam came in to sandwich the hole think flat and smooth.

2. I recommend for the retract version trim the spar so you can glue to the top and bottom some 1/4" wide hardwood strips and create a sort of "I" beam. at the wing joints definitely use a 4" strip of glass after you epoxy the 3 piece wing together and if your neurotic like me after sheeting run two 1/4" wide carbon fiber strips on the bottom of the wind from tip to tip.

3. don't forget to make al of the holes for servo leads and pneumatics prior to gluing the wing together.

4. for finishing you could use the whole wing, or use silkspan ( for non gloss finish or even clear monokote and sand lightly to accept paint


5. for the spar carve out 1/4" of foam, I forgot and mine flies fine :) I just move the CG back 1/4"

6. the carbon fiber and other items are up to the builder to provide, they are only needed when making a high performance set up. same issue with the retracts, the basic kit is for fixed gear and stock 480bb motors

7. I don't think you would get too much savings from building up the tail section

hope these help

[hoser]

and this

[Arthur Knowles]

I stopped by Home Depot today and bought a small container of Probond. It's a wood glue with "real" wood fibers. Looks similar ro Elmers wood glue. Is this the right stuff? Or should I be looking for something else?

[Arthur Knowles]

Hoser,

Thanks for the input. I just purchased a 9" band saw from Sears (for $70) so cutting the wing is going to be easier than originally planned. So, I have the spar thing covered.

The retract installation though is a bit different. I have ABS covers for top and bottom for the wheel covers. If I understand why these ABS pieces are in the kit. I noticed the picture you have shows balsa covers for the retract area. Is this because you have the balsa kit, or because you choose to make balsa covers over the ABS ones?

In regard to the wing, I've decided to use two servos (HS-81s). One in each wing. I'm going to run an extension from the center to the outboard panels where the airleron (sp?) will be installed. I have to check the depth first to make sure it will fit properly. This is an option on the plans so I can also use flaperons for landing.

Art

PS: Today I am going to start on the wing section (cutting and fitting of parts).

[Arthur Knowles]

Hoser,

I cut down an aluminum landing gear to 1 1/4" wide so it fits in the saddle area. But I see from your pictures that the motor mount has specific dimensions. If so, what are the correct dimensions and angle? Or was it just guessing for the length and angle for attachment?

Art

[hoser]

Arthur I did not use the ABS covers and built my own out of scrap.

I recommend the flaperons for the heavier set ups 3/8" max down on the ailerons and mix with 1/8' up elevator

the HS-81 are fine for the wing, I have a ton of pics I wrote the composite manual ;)

GOOD LUCK !!!

[hoser]

the motor mount on mine was a suggestion to Robert at EJF and was not part of the kit so it will not look like yours, i just cut up some alum gear i found at the hobby store :D

thrust angle should be the parallel to wing, you can glue the motor mount, I used nylon screws an put a ply piece in the fuse so I could remove the nacelles if needed.

this kit is very flexible so go with what looks good to you :)

[Arthur Knowles]

Hoser,

Well I had planned to go with the aluminum motor mount and plywood in the fuse. I wanted to make it removable for maintence. I'll have to fudge around a bit then and figure out the overall width and angle on the mount to get it set right.

I've got the wing frammed up with the balsa spar and LE. Tomorrow I'll add the trailing edge. Then some carbon fiber and finally the wing sheeting. After that I'll glass it and cut out the airlerons. Of course, before I put the wing sheeting on I need to cut holes for servos, retracts, wires, tubes and install the framework for the servos and retracts. I suspect that'll take as long as it takes to build the entire wing. Wish I had a router! Guess my flex shaft dremel will have to do.

At least cutting the wing was easy. I got to use my new Sears bandsaw. Makes it very easy to cut wood or foam. Almost too easy.

While I was waiting for glue to dry, I decided to work on making some LiPoly assembly tabs for a 4S pack. I used a Radio Shack circuit board kit and made some boards with copper pads to assemble the pack. The circuit board is slotted so I can just slide the tabs of the cells into them and solder. I need to make 6 of them for a 4S6P pack. If I get a chance tomorrow I'll post a pick of the wing assembly and pads.

[Arthur Knowles]

Well I sheeted the top of the wing panels last night and today. Just to make it easier to work on and more ding resistant. Tomorrow I'll cut out the slots for servos, retracts, and plumbing and sheet the bottom.

In regard to sheeting. The kit came with 1/16" sheeting but the plans stated use 1/32. So, I bought some 1/32" wood to sheet the wings. Instead of following the plans (I did, but wouldn't next time) and sheet over the leading edge, I suggest you leave a small lip on the LE and sheet up to it. It'll be much easier than trying to bend 1/32" wood over a tight curve. Even in the foam beds.

[Arthur Knowles]

Here's a pic of the assembled 4S6P battery (14.8 v nominal @ 7200 mah) with a 8 cell 3000 NiMH pack next to it for size comparision.

Note: I still need to wire it up for parallel output and add connectors.

[Arthur Knowles]

Side View

[Ed Waldrep]

Arthur, I've never really looked at the plans for this kit as I don't own it but on all the foam wings I've ever done I've had a leading edge piece of balsa glue to the wing. It butts up to the sheeting on both top and bottom, and is shaped into the leading edge shape after attachment. On my scratchbuilt A-10 I used foam core wings sheeted with 1/32" balsa and after I trimmed that flush with the leading edge of the core (which was about 1/4" tall not counting the sheeting), I glued on the the leading edge "cap". After it dried I shaped it to the proper airfoil shape. You could use leading edge pre shaped balsa but that stuff rarely matches up to what you are doing.

I guess the EJF kit doesn't use a leading edge piece from what you are saying but that doesn't sound very ding resistant. Maybe they did it for lightness, but the first time you bump it on a table or a door jamb you'll get a dent. Maybe it is fine like it is, there's more than one way to skin a cat as they say (although why would you want to skin a cat...can't be too tasty).

[Herb]

I think you need a hard balsa leading edge for durability and strength...

I am curious to hear how many Amps and Watts you are pulling full throttle out of you Lion cells. I suppose you need about 400 Watts to fly the A-10 decently.

[Ed Waldrep]

My A-10 which is similar in size to this one (45" span) is pulling about 400 watts in the Kyosho nacelles and the performance is quite satisfying. I'm at 4 lb 2 oz so I'm at around 100 watts/lb which isn't super high for EDFs but it scoots quite nicely, 100 foot loops are no problem. I'm probably pulling about 43 amps off of a peaked battery, the one time I put on the wattmeter the battery had been sitting a few days. I'm using 10 x 2600 NiMH so I'm a bit fat ("I'm not Fat, I'm BIG BONED"...Eric Cartman from Southpark).

[hoser]

I use a pre-shaped trailing edge and a square leading edge that I installed AFTER sheeting the wing, I cut it with a straight edge and then epoxied the leading edge and carved out smooth and filled any gaps with light wood filler.

BTW congrats Ed i did not know you went flying allready !!! my plane is 4.25 pound and my watts are 420 the plane could easily handle 1 more cell and increase permormance so im thinkin of 13 faup 1950's since i only pull 35A on 12 cells

[Arthur Knowles]

The leading edge on the wing is a balsa block shaped before sheeting. If I were to do it again, I'd either add the balsa block after sheeting, or line it up behind the balsa LE.

As for the watts, well Motocalc predicts 44 amps at 11.8 volts (under load), but that's assuming the LiPoly cells have a .015 IR as the Thunder Tiger packs do. That's just a guess. The 4S6P pack is rated at 14.8 volts nominal (more like 15~16 with no load) and good for a max of 44 amps at 6C. I may add one or two more 4S packs and make a 4S8P. That would be good up to about 60 amps.

At it's current configuration (estimated weight) I'm looking at 130 watts per pound in and about a 30 oz/in wing loading. For a total of 520 watts. It should fly well if I can keep it within this range.

[Herb]

Originally posted by Arthur Knowles
... and good for a max of 44 amps at 6C. I may add one or two more 4S packs and make a 4S8P. That would be good up to about 60 amps....

Sorry I thought you had already tried out this setup. How many flights can you get out of the Lions at 6C? Just curious.

[Arthur Knowles]

Originally posted by Herb
How many flights can you get out of the Lions at 6C? Just curious.

Good question. The ET cells are LiPoly not LiOn and are rated at a max draw of 7C. The Aircraft World info pack (http://www.aircraft-world.com/prod_datasheets/lipoly.htm) states:

4C – The rate for highest capacity and very long life
5C – The "standard" rate at which most are using E-Tec cells
6C – The peak rate for aerobatic models using throttle management
7C - A possibility for models like ducted-fan jets - using some throttle management
.
.
.
Although many users are reporting excellent results at higher peak rates, to maximize the capacity of the pack 6C is the target to shoot for when calculating peak discharge currents in high-powered models, or 5C for longer flights.

So, I'm basing my calculations on 6C and do expect to use throttle management to lower the average rate to 5C. Although, according to Motocalc, my current power systems falls in the 5C rating at full thottle at the maximum airspeed. It's only 6C at takeoff/stalled.

I'm hoping to get long life out of these cells. At least a season of flight at a minimum. I spent about $350 on the pack. If I need to, I will increase the pack size to a 4S8P for a max amp draw of 57 amps @6C and 67 amps @7C. Of course, I can't tell if I'll need the exttra cells until after I perform some preflight testing with my wattmeter.

[Arthur Knowles]

Well, I routed out the foam 3/32 for the plywood mounting plate for the retracts. But creating the 1.25 x 1 x 3/8 hardwood for the main retract installation was a major pain. I used my bandsaw to cut the wood, but it has a tendency to creep toward one side when it cuts. I built a rip fence from some Sears parts for a scrool saw and that works really well, but still the bandsaw creeps when it cuts. I'm not sure why. Doesn't matter how slow I go or anything.

I finally created the pieces I needed by cutting oversize and sanding the excess using my new Sears sander ($88 on sale). So, now I'm ready for the assembly and mounting. Before I do, I wondered about the best way to mount the plywood to the foam to prevent it from ripping out on a rough landing.

My initial plan is to pin the 1.25 x 1 x 3/8 landing gear blocks to the 1.5 x 3 x 1/8 (I think that's the plan size, but could be off) plywood. I'll still epoxy the gear blocks, but thought pinning it with 1/8 wood dowels would make a stiffer & stronger join. But what about gluing the plywood to the foam?

Should I just glue it with epoxy? Or should I also pin in with the 1/8 dowel. I've got plenty of down and adding 4~6 pins should make it a stronger join. But maybe there are downsides I haven't thought about.

So, what do you suggest?

Art

PS: Do remember that I fly off of a dirt field. It's not the smoothest field either. :)

[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 :eek: 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 :D

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.

[hoser]

that looks perfect Arthur

[Arthur Knowles]

Here is a picture of the wing after fiberglassing with .75 oz cloth and Z-Poxy finishing epoxy. I've brushed it down with 80 grit sandpaper to knock some of the high spots/overlap and will hit it later with 220, 400, and 600 before I prime it.

[hoser]

how does it fell in strength ?

[Wof]

Slow down Art i am tring to keep up with you,are you going for the curly wingtips with carved balsa?

[Arthur Knowles]

Originally posted by hoser
how does it fell in strength ?

Much stronger than before the FG. There used to be more give in it. Now it has a hard inflexible shell. I'm sure I could break it if I tried, but if that's going to happen I want it to happen in the air!

[Arthur Knowles]

Originally posted by Wof
Slow down Art i am tring to keep up with you,are you going for the curly wingtips with carved balsa?

I haven't decided yet. I don't have a good picture of the wingtip to base a carved balsa tip on. I thought about using the kit tips as a template/guess. If I go with carved balsa tips, I'll have to hollow out the block when finished.

Do you have a picture of the tip you can share? If you can't post it, you can e-mail it to me direct at Art@NT-Guru.Com.

As for slowing down, don't worry. There is still a LOT to do. Mostly sanding & filling. Once I have the wing finished the way I want, it's retract and servo time. I just ordered some servo mounts and covers for the plane from Hobby Lobby (used for sailplanes and include a hood for the servo arm/linkage).

I'm also debating reworking the EJF retracts. The mounting ears are very wide. So wide I think the wheel covers I'll make out of balsa will look rediculous in width. They'll have to be 1.5 ~ 1.75+ inches. I can cut at least 1/8" off each side of the mount and redrill it for closer spacing. That would drop it to 1.25 ~ 1.5 inches wide. Possibly more.

[Wof]

I do have a close up of a wingtip at home i will send it to you

[JANSSENM]

This is what I did for my RBC A10. It is close to scale and light, I think.


jans

[JANSSENM]

another....

[Ed Waldrep]

There are some great web resources out there with info and pictures including detail shots of full size aircraft. It can really help during building to see how the real thing looks.
www.aircraftresourcecenter.com Go to walkarounds and pick Jet Aircraft...there's like 7 listings for the A-10 with lots of pictures.

They also have a reviews section where they have pics of built models that are helpful, and also articles on aftermarket decal sets. I'm using decals from CAM that are 1/32 scale and i had to blow them up 2.06 times to fit. This homemade decals stuff is harder than I thought, the decal sheet has a light blue background and the decals I got made on a color copier have the same background...oh well, guess I'll need to keep trying.

Here's a nice A-10 model on the same site
http://www.aircraftresourcecenter.com/Fea1/601-700/Fea692_A-10_Spitaels/fea692.htm

[Wof]

Art try this view

[Wof]

There must be some aerodynamic reason for this Hoser can you help?

[Wof]

http://www.a-10.org/
Try this link hundreds of A10 pictures videos etc etc
Jans you must have a few planes on the go now i will have to call you Jans twelve kits on the go the same as me,i must finish one before i start the next.
A10 pictures to follow later.

[jperch]

Wof,

I thought those were known as "Horner Tips". I vaguely remember seeing an article in a modeling magazine many years ago. I could be way off base but I thought they reduced drag by changing the way the vortices developed on the wing tips.

Does this sound right?

Joe

[Wof]

Sounds good to me Joe.
I am no expert but there are various shaped tips to do the same thing, i seem to remember that there was a jet airliner that changed the shape of its tip increased wing performance by some 5% less fuel burned = cheaper flights.
Art i have just thought this is your building thread sorry to diversify.

[Arthur Knowles]

Thanks to all for the links and pictures. Wof, I wouldn't worry about the diversification, all threads spread around a bit. :)

With he pictures available, I guess I'll have to go with the rounded tips now. At least I won't have to cover them as I plan to paint it. Those tips would be no fun to cover with film.

[drksyd]

Arthur
What kind of lithium cells are you using? According to your calculations the cells are 950mah? The chart you're referring to is good only for the Etec cells, Kokams will only handle 5C in short bursts. If you have the new high output Kokams then they're good for 8-10C. The life of the pack should be good as long as you don't drop it below 10volts in the current config now, 4S6P.

[Wof]

Art do not forget the tip lights He He

[Ed Waldrep]

Originally posted by Arthur Knowles
Thanks to all for the links and pictures. Wof, I wouldn't worry about the diversification, all threads spread around a bit. :)

With he pictures available, I guess I'll have to go with the rounded tips now. At least I won't have to cover them as I plan to paint it. Those tips would be no fun to cover with film.

Arthur, I thought I should pass on my experience covering my A-10. I ran out of Utralcoat grey so I bought some Ultracoat lite clear since I was going to paint it anyway. The stuff is thinner than regular Ultracoat and it will shrink more. I covered my curved horner wingtips with it and got it to stretch around the whole perimeter and shrink with no wrinkles! Amazing! I've never seen an iron on covering to that with the exception of fabric.

The key is to have two hands to pull on the covering while you heat it. A actually had my heat gun between my chest and my chin trying to hold it at the right angle and that worked somwhat. I kept heating and stretching the stuff and got it to shrink enough. This worked better than an iron I guess because the heat was spread out more evenly.

The Ultracoat lite takes paint well, I used Testors Model Master sprays and didn't even rough up the covering first, I was in a hurry. Some paint did come off when I was masking with newspaper but I only uses small doubled up tape loops to hold the paper off the surface a bit to get a soft masking edge. Sanding with steell wool or 600 grit might have prevented that.

[Arthur Knowles]

Originally posted by drksyd
Arthur
What kind of lithium cells are you using?

They are E-Tech 1200 mah cells. 1200 * 6 = 7200 mah (that.s for the 4S6P pack). NipponDave has stated that others have pulled up to 10c in burst from the ET cells without damage. So, it looks like the 4S6P pack will be OK to use.

Based on the data provided for IR for single cells (.035) my motors & fans will pull 52 amps at full throttle - static. That's about 7C. In flight the motos & fans will pull 35 amps. That's 5C. I don't expect to fly at full throttle all the time. That's estimated at 90 mph.

All these calculations are based on Motocalc values and are just estimates. I'll firm up values as the plane is built and I can adjust the weight and wing loading accordingly. As it stands now, I'm going to put about 175 watts per pound into it.

[Arthur Knowles]

Ed,

Thanks for the input. As I have glassed the wing, there is no need to cover it with film first. I'll think about doing this with the elevator and rudder though. That may be better than glassing it as well.

Wof,

Lights. Hah, that's a good one. :)

On the serious side though, if the plane flies well I will be adding scale details to the fuse and wing. Lights (non operational ones) may not be too far fetched.

Art

[Wof]

The stage i am at excuse the poor building area no space

[Wof]

The fuse

[Wof]

Picture 1 just to make sue all flat and correct washout,picture 2 just drying

[Arthur Knowles]

Wof,

So, no operational rudder, huh? I've been thinking about that a lot. I have one HS-81 servo I could use for the rudder. If I could figure out a good way to make them operational without making it too ugly.

I thought about using a pull-pull cable with a tie between the two movable surfaces. I could mount the cable on the external (outside) surfaces. Maybe use fishing line (clear).

Or maybe use a pull cable on the inside surafaces with the external surface under tension. Though that one bothers me is the line snapped (i.e. the tension would pull the rudder out and possibly cause a crash). I think a passive system would better.

Anyone have any ideas they'd like to share?

Art

[Wof]

This will be quite a simple version no operational rudders you can just see the bungee hook on the fuse,the sites i fly from are grass with a nice long tarmac runway but i cant guarantee i can always land on it.
It maybe easier to have a stearable nose wheel i assume it will only be used for take-offs?
Mark

[Arthur Knowles]

Wof,

I will have a steerable nose gear. I will only use it for takeoff, landing, and taxi back to the pits. Unless it has problems taxing on the dirt runway we have.

I'll be using a micro servo for the steering. If I have functional rudders, it'll use another servo with a Y connector.

I just haven't decided on the rudder because of the complexity. Most likely, I'll skip a functional rudder. If I do, it means no stall turns. No snaps. No knife edge or 4~8 point rolls.

Art

[Wof]

I must get used to the fact that electric flight has advanced so much from when i got into it a good few years ago,it was an achievement to have a EDF that could fly let alone do a roll.
My first plane that surprised me was made by an english company called MFA it was the first plane that i had that could do a loop and a roll from level flight cant think of its name.
I am just getting back into electrics got quite a few planes ready for our two week summer when it arrives.

[hoser]

Arthur no need for rudders the plane is small enough that it only becomes and issue in severe crosswind conditions, where the nose gear can't correct the force of the wind on the rudder planes.

Wof, the plane hand launches pretty easy depending on the weight, for those who use a bungee like DR jet and jepe have uses fixed wheels in the nacelles like if the real ones were retracted and a tail wheel (I think) this would allow for landings on paved surfaces.

also this model will roll loop, fly inverted, split S and (by accident) do a hammer head) :D

[Wof]

Art more curly tips to see,got the wing 1/32 balsa covered now been sanded reinforcing the servo wells then to glass we go.

[Wof]

I will never fully understand computers, i tried to attach a picture that i saved off another thread tried to post it it was to big ?
how can that be so i have shrunk it.

[Wof]

Any colour schemes in mind yet getting close now

[Arthur Knowles]

Originally posted by Wof
Any colour schemes in mind yet getting close now

Yes. I'm going to use one of three schemes. All are camo version.

1) Forrest greens. This one is basicaly green with brown and black blotches.

2) Desert tans. This one is basicaly tan with brown and black blotches.

3) Artic blues. This one is basicaly white with grey and green blotches.

I like the idea of the desert tan, but seems like everyone is using it. I'd like to be a bit different. So, most likely I'll go with the artic scheme. Here's a picture of it. I have a pattern for it too. I found this on a web site for a plastic kit A-10 (http://www.arcair4.com/Fea1/401-500/Fea455_A-10_Nagle/Fea455.htm).

Art

PS: Painting is still a ways a away. I have a lot of work still to do on the fuse (canopy assembly, retracts, servo mountings, etc.) as it is just a FG shell. It need some reinforcement with bulkheads and the like before I can do real work on it.

[Wof]

One for the printer and a steady paintbrush.

[Wof]

Art if you can can you post a picture of the bottom of the fuse so i can see if i am shaping it properly
Regards Mark

[Arthur Knowles]

Mark,

Sure. I'll get one up here tonight.

Art

[JasonJ]

Originally posted by Wof
I will never fully understand computers, i tried to attach a picture that i saved off another thread tried to post it it was to big ?
how can that be so i have shrunk it.
For some reason when you save a pic off the zone, its saves as a bitmap, .bmp file. You have to open it with a pic view or editor and resave it as a .jpg . Nice hogs!

[Arthur Knowles]

Wof,

Here's a picture of the fuse. Bottom and side view. Minus the canopy as I've already cut that part out, but not assembled it yet.

As you can see, it's mostly just a box with rounded corners.

[Wof]

Thanks Art i also need to think how to reinforce the front of the fuse its a moulded part,i will probaly glass inside.
Glassed the wings tonight need to do some serious sanding,also need to think if i will cover the foam parts on top of the fuse with glass or not.
Decisions decisions.
Regards Mark

[Arthur Knowles]

Wof,

Well if it is any consolation, I will be glassing all the balsa parts. Wing, elvator, and rudder. The fuse is already glassed. :)

But that's mostly because I am going to paint my plane and I want a consistent finish on all the parts. Anything not glassed would have to be sealed. That's just as much work & weight as glass so...

Tonight, I'm working on my new HDTV setup. The TV arrived today, but I have an AV rack to assemble and connect. So I'm not going to work on the wing until tomorrow. It needs additinal sanding. I filled some low spots with putty and need to sand it down to smooth it out. I used 80 grit initially to knock down the high spots and epoxy overlaps. Then 220 & 280. After that, it's 400 & 600 before I prime it.

Art

[Wof]

Have been doing some more stuff on the Hog have sanded the styro fuse top parts then filled with ultralight filler,have covered with ultralight glass cloth (as well as my A4 wing as you always mix up to much epoxy) the tailplane has got re-inforced corners.

The wing is now fully covered with ultralight glass(favorite word of the reply ultralight) looks like yours without the retract plates wont bother with the picture just needs loads of sanding as well.

Picture of fuse if it will upload.
Regards mark (13 kits on the go )

[Wof]

Two more pictures the first one the tailplane is fixed for good.

The second is being filled with filler.
Art you must be watching that HDTV no posts for a while ?

[Wof]

"Ultralightweight filler"

[Arthur Knowles]

Yes, I was watching some TV & flick on my new HDTV. But I also had a choir recital to film and a few other items to finish. Saw X2 this weekend as well.

My wing has also been filled. I used green putty filler to hit the low spots. It's worked really well. I also received my servo covers/mounts last week. I need to trim my servo wells a bit more and install 1/4" wood dowel as a hardmount for the servo cover/mount.

I also attempted to create some FG skin using a sheet f glass and some 2 oz cloth. Didn't work, the epoxy stayed on the glas, but the FG came off. In cleaning the glass plate, I broke it. So I need a new piece of glass, some PVA or mold release wax, and some 4oz or better cloth. Either that or I need to cut up my carbon fiber sheet. I need it to mount my canopy. You can see what I mean in Steve's thread here (http://www.rcgroups.com/forums/showthread.php?s=&threadid=112764&perpage=15&pagenumber=1). It's a neat way to attach a FG canopy on a FG body.

Art

[Arthur Knowles]

Here's a picture of the right (empty) and left (covered) servo wells. Notice that I had to remove all the foam in the wing to mount the cover. There is just enough room to fit the cover flush if I want to route off 1/16" off the top skin. Notice also the hard points (1/4" dowel) for the servo cover screws. I epozyed the hard points in place then drilled them out.

PS: The green stuff is Squadron Green Putty sold at Hobby People. It's a great filler. Harder than the light weight filler but just as easy to sand.

[Arthur Knowles]

Well the retracts have been installed. Last night I decided that the EJF retracts mounting flange was just too wide for this airframe, so I cut it down about 1/4" on each side and drilled new holes. I also had to make new mounting plates and bearing blocks. The glue is drying on them now.

Tomorrow I will add balsa wheel covers. The ABS ones supplied with the kit are still too small to cover the retract. Even after cutting the flange. Only about an 1/8" though. But that's OK, I think the balsa version will look better.

After the covers I'll take a few pics to post. I will also buy some balsa blocks tomorrow to make the wing tips out of. Once I finish those, it's priming and painting time.

[hoser]

your right on the flange and wheel covers.

The wheel covers that come with the kit will not work with retracts and are not very scale either.

the retract flanges are a little wider than they have to be, but in a normal wing application or fuse applications it makes no difference, but I can see how on the A-10 they could be too wide. I had My A-10 before the EJF retracts came out so I used the spring air 600 which have a narrower flange.

have you started on the nose gear yet ?

[Arthur Knowles]

Hoser,

No, I have not done much with the nose gear yet other than cut out some bearing blocks. I figure to leave the nose gear flange as is. It is fine for the fuse, but the wing was something else again. It would be look funny with wheel covers almost 2" wide. :)

Art

[Wof]

I wont have the retracts problems gone the easy bungee route,
had a bit of peace and quite tonight the wife went out with the girls so did some more building.
The curly tips which will have flashing lights (not)

[Wof]

Another tip (no not a better way of doing things)

[Arthur Knowles]

Wof,

Those look pretty good. Looks like you had to dig out the foam for the servo well also. As for mine, well I got the retracts installed and picked up the wood today for my tips. So, tonight or tomorrow I'll add them and FG them.

Art

[Wof]

Next step is to hollow some recesses where the wing bolts go for some hard balsa blocks so the bolts do not crush the wing, and some extra layers of glass at the wing dihedrals.

[Arthur Knowles]

Wof,

Did you FG the entire wing? Or are you just going to FG the seams?

Art

[Wof]

The whole wing a bit more on the dihedral parts,

[Wof]

Art you still building or watching that new TV ?