Shaun Evans

Tom,

Agreed. Good luck with the build, and let me know if I can be of any help.

Shaun Evans

Hey,

I ended up cutting spar channels into the wings aft of the gear mounts and capping them with 1/4" hard balsa, leaving a slightly oversized 1/8" gap for the spar. This spar will go a bit deeper into the wing since I'm building this one for turbine use. I sanded the balsa caps to the contour of the wings. Strips of masking tape are great for keeping yourself from accidentally sanding through the balsa sheeting.

k_sonn

My Feedback: (32)

Cool Shaun. I built one a few years ago. AUW weight was 10 pounds.

Here's some video:
http://www.youtube.com/watch?v=v4LI3SQlo1c

Kirk

Shaun Evans

Kirk,

NICE! 10 pounds? Really?? What did you do differently? I see you have no struts on the mains, so that saved you some weight, but what else? That's lighter by 2 pounds than the lightest I've ever built. What did you do for an inlet? What mods did you do for that build?

k_sonn

My Feedback: (32)

Shaun, the fan, motor, controller, and batteriesweighed 4.25 pounds. The rest of the airframe weighed 5.75 pounds. I glued the wings on instead of using the plug in hardware, that saves about a pound of weight. I also used light weight glassing and painting techniques I learned from a localpylon racer. The trick to getting a light weight glassed finish is to use a slow setting epoxy to give yourself time to scrape off as much of the resin as possible from the first coat and then mix micro ballons into the second coat of resin until it is a thich slightly runny paste. Then scrape off the excess resin. As you're scraping off the excess resin you're also filling the weave with the micro ballons. This is the lightest way to fill in the weave of the cloth and get a nice smooth finish for priming and painting. Other things I did to save weight is use Spring Air retracts, wire struts on the mains, no brakes, foam wheels on the mains, and a simple radio setup (nopower box). When I built the A-4 I also added a lot of detail and weathering.

Kirk

TJK

My Feedback: (69)

Kirk,

What brand of finishing epoxy did you use and how much time does it give you before it starts to set?

Nice weathering!

Tom

invertmast

My Feedback: (23)

Kirk,
I've heard the micro-balloons trick before, but everyone i asked about it had either never heard of it, or never tried it. I think i may have to try it on the U-viper. So any tips you can give would be great.

k_sonn

My Feedback: (32)

Thanks Tom.  I use the West System epoxy with the 206 hardener.  Here in the Pacific Northwest the 206 hardener has a 30 to 40 minute pot life during the summer (mid 70's to low 80's temps).  In the winter I use the 205 hardener (low 30's to mid 40's temps) .  When I lived in Hawaii, I used the 209 hardener (20 to 30 minute pot life in 80 to 90 degree temps). 

Kirk

k_sonn

My Feedback: (32)

Hi Thomas,When you're ready to apply the second coat of resin, mix the epoxy and hardner together first. Then add the micro ballons until the mixture is a slightly runny paste. Spread that out over the structure and scrape off the excess like you would do for the first coat of resin. When it's dry and ready for sanding, wet sand with 320 grit using a block until the surface feels smooth to the touch. Next, prime and fill in any imperfections. Then wet sand with 400 grit, again using a block. This will leave you with a good, smooth base to work with. If you have any questions, feel free to give me a call anytime.

Here's a photo of the A-4 wings. The left wing has gone throught the process described above and the right wing is at the first primer stage and needs to be sanded with 400 grit.

Kirk

Shaun Evans

Nice.

Kirk, what inlet are you using? Which version of the kit is that?

Mark 5

I have reached the point where I need to choose my powerplant. Electric-TJ100,stumax,turbax, or turbine-Kingtech80,p70,Super Bee,Wren54. I fly off thick sod grass so I need a very light and powerfull motor.What do you guys reccomend?

k_sonn

My Feedback: (32)

Thanks Shaun. It is the latest version of the kit with the larger fan compartment cover. I started out flying with the Yellow intake with the BVM intake adapter. Then I was talked into switching tothe little guy's (if you need to know who I'm referring to send me a PM)120mm intake so I did. Plane lost power with that intake so I ripped it out and went back to the Yellow intake with the BVM adapter.

Kirk

k_sonn

My Feedback: (32)

If you go electric, of the three fans you mentioned the Stumax fan would get you off of grass and the Turbax may get you off of grass, don't think the other one would get you off of grass. Other options you didn't mention would be the BVMEVF-2 (10S or 12S version), Turbofan 4000 with a Neu 1912 1Y motor (for 10S) or Neu 1527 1.5Y motor (for 12 S), and the Dynamax with a Scorpion motor. Of these fans, the BVMEVF seems to be producing the most power with the longest flight times as witnessed by many at jet events across the country.

Here's video of the BVMF-86 flying from a grass field with the older, less powerful EVF 5612fan and older generation batteries:
http://www.youtube.com/watch?v=9ts4h_jNbfs

Here's video of gunradd's Yellow F-16 flying from a grass field with the Stumax fan:
http://www.youtube.com/watch?v=7dwLExT5AEo

Both planes weighin the17 pound range. I haven't seen any video of any of the other fans flying a from a grass field.

I'll leave the turbine suggestion to others.

Kirk

Shaun Evans

Hi,

To add to what Kirk said, the other consideration (which may or may not be important to you) is the sound. Of the three, the TJ sounds the least 'jet-like.' It's a good fan, but it sounds like a toy compared to the others. Kirk mentioned the EVF, and it turns out that BVM makes inlets for their old A-4 that will fit into the Yellow A-4 with very little work. I've tried it!

dbateman

My Feedback: (31)

This is all good stuff and informative minus the BS i'm used too on other forums. I am doing my second Yellow and 5th A-4 (3 JHH). I want to do the Blue Angel scheme. I have the "sport" version wing. The Yellow arf looks very good color wise. I have seen many that have off shade blue and yellow. I think i have found a spray can option that is very close and that's Rustoleum Dark Blue Navy, and Duplicolor school bus yellow. I have purchased the Yellow stick on decals but may end up using them as paint stencils. I have been told they are not dense enough color wise to prevent the blue from altering their appearance. This will be my second Yellow A-4 EDF. First was with Aeronaut T/F 4000 120mm fan, 1912-1y Neumotor, castle hv-110 in tail-cone running 25C 5000 packs. Jet took off if 70 feet-no bull-no flaps. Flew very well with very good power for climbing maneuvers and high speed flybys. Jet is still in our club. Having been sold on the sound of the Stumax i am weighing both that fan and Tams 90mm 7 stator/midi rotor unit. The 90mm sounds pretty good from what i have heard and since i am installing one now on my Savex L-39 i will know soon. The cut down Dynamax's (90-100) don't seem to be going anywhere from what ive seen. Everyone's doing one but where are they? Will be posting as i get into build. Doug

Shaun Evans

Doug,

Thanks for the input. I'm sorry you're perceiving BS....I'm only doing what I always do which is to call 'em like I see 'em. Re your comments, I agree that the yellow nomenclature isn't opaque enough to go on blue paint.

SDCrashmaster

I don't think he was perceiving BS...he was congratulating y'all on NOT bringing BS into it Shauno.
I'm callin' "wire gear pass" on this one!

Shaun Evans

Oh,

My bad, Doug! Wire-gear pass! I love it. One of those unforgettable memories with jets, friends and the kids....

dbateman

My Feedback: (31)

Wire gear pass?

gunradd

My Feedback: (9)

Doug glad your building another one the last one you had was very nice.

gunradd

My Feedback: (9)

I love the EVF but I dont see how you can go wrong with a Stumax.

dbateman

My Feedback: (31)

Of these fans, the BVM EVF seems to be producing the most power with the longest flight times as witnessed by many at jet events across the country.

I'll bet if you powered the Stumax or the T/F 4000 with 12S 6500 40C packs they would really hustle also. I am leaning toward Stu's rig, but as i said, i want to see how the Savex sounds with the 90mm. I plan on designing my own plug in wings using carbon fiber flat stock.
thanks gun, and your F-16 sounds nice and flies great.
Read more: http://www.rcuniverse.com/forum/m_98...#ixzz0tWPHExY0

Shaun Evans

Hi,

Well, a long time ago, a bunch of us drove up to Fresno for the jet meet. Paul, as you know, is world-famous for his landing gear dressups. He always expects jet pilots to at least make an ATTEMPT at respectful treatment to their landing gear on scale planes, and was dismayed to see so many 'scale' planes with wire gear. He mentioned this in frustration several times. Well, we happened to have a bull-horn with us because my nephew Mark was flying the noontime helicopter demo for JR, and Paul announced him.

Later during the day, some guy was flying a Rafale (or something) and as the flight got long, he came by and dropped his gear. What happens next? You guessed it.....Paul Reese cries out, "WIRE gear pass!" over the loudspeaker. I was like, "Dude. You're gonna get our *****es kicked." It was pretty funny, though, had you been there.

Ron101

My Feedback: (22)

I have to throw in my vote for the Stu Max SM110-52 it's just a sweet heart of a fan.. I'm nearing 100 flight in my Stu Max powered Spark and it's been rock solid in the california heat.
Stu also has a new 100mm and 90mm just about ready... and it very close with the new high power 120mm and 110mm

here's a video of Neils yellow A-4 with cheap 12s 4900 hobby city rhino packs... image good packs with this setup...
I run thunderpower 11s 30c 5000 in my spark and it's off the hook..... there really is no other fan for this plane in my book


[youtube]http://www.youtube.com/watch?v=hnzVZRx4Qvc&feature=related[/youtube]

Shaun Evans

Wow,

That thing REALLY sounds like a jet.