New CGRCjets super scale A-10
 

Ok, here we go again! I have decided to remold my 1/9 scale A-10 warthog kit and add a few bits to it. I will be posting here what i have learned over my past kit, machining, plug making etc. to help those in need of any insite on the process. I have endured much trial and error, as i am self taught. Some may do the process differently and have better suggestions. This is how i do it. Hope it helps.

Chris

RE: New CGRCjets super scale A-10
 

First off, here are some new additives for ver. 2

Initially i was going to update the same airframe with better detail, but thinking of all the things i can make better, i decided to start from the ground up.

1- 3 piece wing for easier transport
2- decelerons
3- true fowler flaps
4- one piece elevator
5- all panels/panel lines, raised and flush rivets
6- removable front canopy
7- more accurate airframe
8- scale cast struts

If i forgot anything, i will add it here. If anyone has any other great suggestions , i will take that into note as well.

thanks
chris

RE: New CGRCjets super scale A-10
 

First set of business on the list was some 3d scanning, with my structured light 3d scanner. I see quite a bit of model makers working off smaller scale hobby models to get there measurments to duplicate it in a larger scale. The model i used was an older monogram version of the a-10 which was the most accurate one i could find but i decided to take a short cut by scanning and bringing it into cad for editing and then to the machine.


Chris

RE: New CGRCjets super scale A-10
 

Wow, your first version is so nice.... good to see you are pushing it even further!

will your new version still be a good candidate for EDF or will you keep the old one around for EDF?

lighter is better fo us e power guys :D

RE: New CGRCjets super scale A-10
 

For the second go around, i want to produce the airframe with true accuracy. Something i will never question myself again. Unfortunately there is not one A-10 on the market, being small model or large scale r/c that duplicates the A-10 in every way. With the passion i have for the A-10, i decided to throw out my scanned high density polygon model and pay some good money to have it proffesionaly duplicated for my cad needs. This will also allow for easier editing in the software.

Chris

RE: New CGRCjets super scale A-10
 

Hey Ron. Hows things been going?

The new version will be a tad larger, only by 2", but will still make good edf.

I like to challenge myself a bit and in my eyes there is always room for improvments. I was going to do a 1/7 scale but decided to try my new tricks on the 1/9 first. All good fun!

chris

RE: New CGRCjets super scale A-10
 

Heres a sneak peak at one of the plugs i am working on and the detail it will have. I have never tried the flush rivets before but they definately go on much faster than the raised. I machined a little jig for these. These flush rivets only taken me a few minutes, where as the raised take a few hours for both sides. The panel lines i have decided to scribe this time instead of using chart tape.

Chris

RE: New CGRCjets super scale A-10
 

Chris,
The vertical fin looks good. One thing i have learned, make sure to over-exaggerate the flush rivets. If not, they will nearly disappear very quickly during the finishing process. Granted, you may have figured this out already :)

RE: New CGRCjets super scale A-10
 

Yes. Definately. I thought about that and had a concern, so i applied extra layers of primer to make sure i was able to get a little more depth on them. I am actually using the paint i do my Arfs with as it seems more stable than regular can primer. Works out good as i can lay it thicker or add the reducer to thin it out. On the fiberglass plugs i use duratec high build primer then i will add the final coats of paint. I tried riveting into the vinylester primer and it does not work well.

chris

RE: New CGRCjets super scale A-10
 

For alot of the smaller plugs, i have decided to machine them from resin as the surface comes out very nice. I do a stepover of .005 on the cnc router which leaves me just about nothing to sand and ready for primer. Better to let the machine do the dirty work. For the resin, i will machine out a fence that is bolted down to 1" polyethylene and cast the resin in the fence. The resin will not stick to the polyethylene, so when its finished machining, the part can be lifted out, small amount of prep and then primer. Works out better than foam (which would need fiberglassing) or mdf that would need to be sealed. Here is a pic of the one piece elevator being machined.

Chris

RE: New CGRCjets super scale A-10
 

This is fantastic news! And I'm glad you're going to try it on the 1/9 scale. Any thoughts on what size turbine?

RE: New CGRCjets super scale A-10
 

Good man, just working, building and flying when I can

I always think about your A-10 and really hope someday I can do one.... I loved watching Tam fly it at California jets

Keep that baby light! do you forsee weight gain with the added details? if so would you consider doing your old version as EDF still?

I'm thinking in the future because my F-18 and P-47 projects have me broke :D

I will follow your build as always... you do amazing work!!!
big fan

RE: New CGRCjets super scale A-10
 

Hi tulz

Although most people lean towards edf, most people chose the wren 44 for turbine power.

thanks
chris

RE: New CGRCjets super scale A-10
 

Hi Ron

There may be a small amount of weight gain because of the new wing design but i dont see much, plus the airframe is slightly larger. Can always lighten the layup as well. With tj90 setup, i lightened layup and structure and was able to get the weight down to 20 pounds. 5" setup averaged about 27-28 pounds. I think 110mm would be ideal.

thanks
chris

RE: New CGRCjets super scale A-10
 

For the larger parts, such as the fuse, engine nacelle, wheel nacelles etc. i will be machining them out of foam and fiberglass them. I have in the past machined the wheel nacelles out of foam then coated the foam with bondo and machined it again to get a hard surface. This works out very well as the bondo eats away the top layer of foam and all thats needed is to re machine it. I have found that this does not work well with deeper parts as the bondo will become thinner on the sides and perfect thickness on the top. I am guessing this is due to the forces of gravity and the way the bondo eats at the foam. This did work out well on the wheel nacelle. I tried this with the fuse and learned the hard way.

The main wing will be built up of ply formers on a jig and filled with expandable foam and finished out. On my last kit, i used my hotwire machine to cut out foam cores to finish out. Its a bit tougher to work with foam and be as precise as the way i am doing it now. The flap and aileron bays will be very accurate and with the way i am doing the new flaps i will need the accuracy for the flaps because they will be riding on 1/4" bearing on an attached piece of machined g10. All the wing bays will be fully enclosed and layed up. The g10 guides will be screwed and glued on the inside of the bay for faster building. Flap bays will have separate enclosures on the top and bottom, like on the real A-10. I am hoping this will make for faster layups with less trimming as well as faster and easier assembly.

Chris

RE: New CGRCjets super scale A-10
 

Here are some pics of the wing in cad. I am using booleans operation to pull out my structural formers and will be using these to build up my wing plug. These will all be layed out on a jig for accuracy.

Chris

RE: New CGRCjets super scale A-10
 

Here is the wing structure in the jig. After filling it with expandable foam, i trim off the excess and float it out. Being in the drywall business for the last 16 years, i tried using 5 minute hotmud to get the fill i needed. Worked out very well. I thought about using bondo for the fill but the hotmud was much easier to use and does not smell like stinky polyester. I made sure the ply structure was sealed. I just sealed it with the wood glue i used to assemble the structure. The hotmud has moisture in it and i did not want any chance of it warping the ply. I did this over a period of 2 weeks to allow all moisture to evaporate before glassing. I applied 2 layers of 2.4 oz. glass. For less finish sanding, i used paper towels to dab off the excess resin like you would do on an open mold layup. After cure i continued with duratec high build vinylester primer to smooth out any low or high spots. I used a piece of aluminum angle iron with with 120 grit sandpaper attached to get my flat surfaces. I marked the low areas and only sprayed those spots with each pass of primer.

Chris

RE: New CGRCjets super scale A-10
 

Chris

Great to see you back.

Dont throw away the old fuselage..................

Best wishes

Mark

RE: New CGRCjets super scale A-10
 

Hi Mark
Still have the molds. I will await your readiness. In other words, just let me know when your ready for your new one, lol.


thanks
chris

RE: New CGRCjets super scale A-10
 

“GULP”! If your plane has a 12 inch average wing cord and weights 25 lbs that would give it a wing loading of over 66 oz per sqft. I have a hard time imaging that on a plane of this size. REALLY?

It sure does look sweet.

RE: New CGRCjets super scale A-10
 

Hi Chris

It was good to talk with you on the phone. I'm looking forward to your new A10. It will be my first effort at serious scale. I'll be using two Stumax SM110-52's for power, they're his older versions but the sound is the most jet like I've encounted.

Thanks for your talented work and committment to quality,

Joe

RE: New CGRCjets super scale A-10
 

I'm in Chris...Put me down for one...

RE: New CGRCjets super scale A-10
 

Hi Joe
No problem. The 110's will be great in this airframe. I look forward to building you one.

Ty
I look forward to building you another one as well. If you get the kit again, it will be much faster to build this time around. You made me wait 8 mths last time and teased me with your maiden. I think we should be able to knock off a month or so on your build. Be easier on shipping now that im only a few hours from you. Sorry i missed you at Florida jets. I was looking forward to meeting you.

thanks
Chris

RE: New CGRCjets super scale A-10
 

Another thing i will be adding to make things go together more quickly, are pylon profiles on the wing. I always hated measuring out the locations for these. Every little thought will add to time savings while building these. Like i say, if you guys have any other thoughts on design, i will take that into account. I want to make this kit as efficient as possible while still in the design stage.


Chris

RE: New CGRCjets super scale A-10
 

I would like to see you make it “lighter.” I live at 7200 feet above sea level. A RC plane with a 6 foot wing span, a 12 inch wing cord at a weight of 25 lbs has a wing loading of 66 ozs per square foot, “that’s over four pounds per square foot”. I’m afraid to say this but it would need around 80+ mph to get off the ground and 60 mph to land. I build heavy too but I would shoot for 13lbs ready to fly [electric] minus the bombs and rockets and I would pull my hair out trying to keep it under 15lbs. This would slow it down for landing, shorten its take off run and give it much more vertical performance with a wider flight envelope.

At fifteen pounds with a 12 inch cord and six foot wing span the wing loading would be 40 ozs per sqft.

“Much better.”[8D]

RE: New CGRCjets super scale A-10
 

Would this larger airframe still be suitable for twin wren44 gold?

RE: New CGRCjets super scale A-10
 

13" cord 75" wingspan. I can always lighten the airframe but its all dependent on your power system. The twin power system can add quite a bit of weight to the airframe. What power system were you thinking?

Chris

RE: New CGRCjets super scale A-10
 

Hi Yann

Wren 44 gold would still be the ideal size turbine for this airframe. Although its a bit early to get the actual weight I dont think it will be a big difference. I do like my airframes a little more on the sound side but I will adjust accordingly.


chris

RE: New CGRCjets super scale A-10
 

Thanks,
I've been eyeing on this plane for quite some time, and I may jump into it when the new airframe becomes available.
I'm not a big fan of EDF, so it will be turbine powered for sure.
Yann

RE: New CGRCjets super scale A-10
 

No problem Yann. Im hoping to have it available sooner than later as i already have some orders and deposits for it. The design process can be the worst part of it. That can consume alot of time in itself. I will try to make short work of it as we will also still need to do testing on the new airframe.

thanks
chris

RE: New CGRCjets super scale A-10
 

One of the design challenges, is the deceleron. Trying to find a small and strong enough servo for the application without bringing it out of spec.

chris

RE: New CGRCjets super scale A-10
 

Is the Deceleron meant to open all the way only or is it supposed to have partial settings like regular flaps?

RE: New CGRCjets super scale A-10
 

On the real A-10, i believe they can be adjusted to any point. At least thats what i have observed at airshows. They are never fully open in flight, only on the ground. Fully open is shy of 90 degrees, im guessing about 80 degrees. 80% is the max open position in flight. I know a crew member on the west coast demo team. Maybe i can contact him and see if they can be opened to any range of motion. I would think they have set settings with all the other stuff they have to think about.

thanks
chris

RE: New CGRCjets super scale A-10
 

FYI on the decelron, as per the book "operators manual" that i got off ebay i believe that the max INFLIGHT opeing is set for 40 degrees. I will check and post later tonight after i find it in the book again. This is for the A model but i assume its the same on all. I think your right about the max open being 80 degrees

RE: New CGRCjets super scale A-10
 

The A-10's speed brakes are proportional........selectable by a switch on the right throttle quadrant. We described the amount of speed brake deployment in "degrees", just did it by how it looked.....no indicator gauge.
Interestingly enough, the airplanes roll rate is fractionally faster with just a little blip of open. Maybe a 2" split.
How do I know this? I flew the "Hog" from 1978-1981

Be careful with the idea of working speed brakes, there was at least one incident of a Mibo A-10 fitted with them that suffered catastrophic aileron flutter. Managed to bring it back using rudder.
Cheers,
Mike


PS: Hi Chris, no not built yet, divorce has gotten in the way.......http://www.rcuniverse.com/forum/js/f...ngry_smile.gif

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RE: New CGRCjets super scale A-10
 

Thanks guys, I'm not used to such competent feedback :D

Chris, as you work through your design are you able to develop fairly accurate take off and landing mph specs? I plan to have full telemetry and knowing the real boundaries would be great. (I know the final weight is the critical component which you don't have full control over, but something based on min/max values)

RE: New CGRCjets super scale A-10
 

Hi Mike

Sorry to here about that. Was not because of the hobby was it? I know my wife has threatened me because of it but this time around she seems a bit more at ease. I will admit, i spend more time on this stuff than she can handle. I just appreciate the fact that she stuck it out. Ofcourse we moved from California to Florida and with the big price drop with housing and the beaches, its like vacation.

Thanks for the insight on the A-10. I knew you would come around. I think i still owe you a wingtube.

thanks
chris

RE: New CGRCjets super scale A-10
 

Hi Joe

I would not know until testing is complete. The Flaps will be different than the older version. They should have a bit more lift on the newer version as they will extend out further. On the older version, too much flap would act as an air brake. Almost learned that the hard way with the first test. I was not there for it but they said it almost stopped in mid flight.


chris

RE: New CGRCjets super scale A-10
 

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[/quote]
Hi Mike

Sorry to here about that. Was not because of the hobby was it? I know my wife has threatened me because of it but this time around she seems a bit more at ease. I will admit, i spend more time on this stuff than she can handle. I just appreciate the fact that she stuck it out. Ofcourse we moved from California to Florida and with the big price drop with housing and the beaches, its like vacation.

Thanks for the insight on the A-10. I knew you would come around. I think i still owe you a wingtube.

thanks
chris
[/quote]

Hi Chris!
Moved to Florida? Big change!
Yea, need to get that wing tube and buy your set of weapons pylons.

How about PM me your latest contact details. Thanks
-Mike
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RE: New CGRCjets super scale A-10
 

Yes Florida. I lived in Cali my whole life and was use to the high cost of living. Now that i am in florida i have less stress. Only thing i am worried about here is the humidity when i go to pull the molds from these plugs. I use pva in mold and was having a hard time with it fully drying. Im not sure if i want to use it on these plugs, especially with all the detail that will be in them. I may have to just wax them 100 times. Dont want all the work to go down the drain.

chris