Official Freewing 80mm A-4E/F Skyhawk Thread

[Bobaroo]

Micro servos on each side? Would you mount them forward of the SB or aft?

Forward !! cg dependent of course, The Linkages would work either way. There will be considerable Force applied to these when Open (Even on that little 50mm SA A-4F) Soooooooo, a set of strong Servos is required on these. I ended up using servo Over-Centering in the Deployed position on the LittleGuy to 'Lock' them out when opened !! They stayed there and took the Force without a problem They are of course Reinforced with PolyPly Fiberglass Sheet, and rigidity is essential in this business (You don't want one side collapsing on you in flight) where Aerodynamic Stability can be dramatically altered by a structural failure back there !!

A great Mod really, and it looks cool. GL should you give it a try. Cheers

[Bobaroo]

I have been "on the fence" about the A-4 for months and my greatest concern was the tall nose gear. After the long consideration, I finally ordered the A-4 last Friday. Subsequently, I found Alpha's post on the subject of the nose gear. I'm resting a little easier now and anxious for the big brown truck to deliver my A-4 Tuesday.

I do not have the luxury of a paved runway to the larger wheels are a bonus. I have been watching videos of the A-4 landing silky smooth and nose high. I am looking forward to practicing landings until I can get them right.

As I mentioned, subsequent to my purchase I have been reading posts about the A-4 on the Hobbyquawk thread, I'm up to page 5 and still reading. I will pay close attention to the balance and error on the nose heavy side for early flights.

Bob DeGood

My NoseStrut/Connecting Pin took a beating early on. Very Soft Aluminum up there. I had a rearward cg too on the Jet and it Flew great ! Just hard on that Strut. It got all messed up and the pin is still loose on that one. On the next one, I'm gonna add a Brace and Reinforcements up there to keep it from getting destroyed. GL

[fastforward]

For those worried about the tall nose strut, it's actually the same length from the ground to the retract plate as the Avanti... reputed grass king... so. I wonder if because much if the strut is exposed under the fuse that to the eye it appears significantly longer, but in reality, it's not. It's the same total length as the Avanti.

In terms of wheel size, the A-4's wheels are the tallest of all Freewing's 80mm jet's wheels, and in fact the A-4's wheels are taller than the big F-14, MiG-21, 90mm F-16, 90mm F-15, 90mm F-18, 90mm Venom, etc...

A-4 = 50x15 Nose and 65x17 Mains

By comparison, most of our big 80 and 90 jet's wheels are slightly smaller: nose is 45x15 and 60x17 or so on most aircraft mentioned above...

If any of you are operating the aforementioned aircraft on your grass, by these numbers the Scooter really shouldn't be massively less capable.

I have been "on the fence" about the A-4 for months and my greatest concern was the tall nose gear. After the long consideration, I finally ordered the A-4 last Friday. Subsequently, I found Alpha's post on the subject of the nose gear. I'm resting a little easier now and anxious for the big brown truck to deliver my A-4 Tuesday.

I do not have the luxury of a paved runway to the larger wheels are a bonus. I have been watching videos of the A-4 landing silky smooth and nose high. I am looking forward to practicing landings until I can get them right.

As I mentioned, subsequent to my purchase I have been reading posts about the A-4 on the Hobbyquawk thread, I'm up to page 5 and still reading. I will pay close attention to the balance and error on the nose heavy side for early flights.

Bob DeGood

[thmprusmc]

Micro servos on each side? Would you mount them forward of the SB or aft?

[Bobaroo]

Thanks guys! Having fun building and detailing this bird. Any good ideas on how to build scale speedbrakes?

Yes,. I do.
It'll be easy on this one because it is larger, and the bulk of the Hardware can be housed within the thickness of the Engine Hatch on the FW A-4. I plan to get into one of these and do it.

https://www.rcgroups.com/forums/show...??

https://www.rcgroups.com/forums/showpost.php?p=41301605&postcount=3706

[thmprusmc]

Thanks guys! Having fun building and detailing this bird. Any good ideas on how to build scale speedbrakes?

[e4dragongunner]

Nice... Welcome Marine! :-)

[EA-6B Geek]

I designed vortex generators for the wings.

Welcome aboard Marine! Those vortex generators look great.

[thmprusmc]

I designed vortex generators for the wings.

[thmprusmc]

My latest project.

[Evan D]

Thanks for the clarification.

[Radar-Guy]

Looks like he is putting the sharp edge on the rear of the inlet splitter just before the inlet air hits the fan spinner/blades. If you look at well designed EDF flow paths both inlet and exhaust flow paths are optimized --- see Bob Violet's models.

That’s what I was trying to say. Thanks!

[brk6188]

Looks like he is putting the sharp edge on the rear of the inlet splitter just before the inlet air hits the fan spinner/blades. If you look at well designed EDF flow paths both inlet and exhaust flow paths are optimized --- see Bob Violet's models.

[Radar-Guy]

The last three don't have split exhausts, what are you doing and what is "significant"?

Correct, but this is about the intake section. The mods to the Lippisch (incl. closing cheater holes plus wing spar fairing) resulted in about a 10% higher top speed. For the others, the term “noticeable” is probably more appropriate. Please excuse my poor English!

[Evan D]

No tests with the A-4 yet. But I made a similar mod on the FW F-4, F-22, Lippisch, Avanti and L-39. On the last three, I did a ‘before and after’ comparison, and there is a noticeable higher top speed (GPS measured on the Lippisch). The question regarding the sound is hard to answer, I feel it sounds smoother at top revs.

I’ve no idea, why the intake ducts are designed with the “high-turb” rounded splitter. Just google “skin friction drag”.

If you look at well-designed wooden or composite EDF models with bifurcated inlets, you will always find such a design.

The last three don't have split exhausts, what are you doing and what is "significant"?

[Radar-Guy]

Thanks, those look very useful !

Have you done any tests, does your "low-turb splitter" seem to produce better thrust? Does it change the sound?

No tests with the A-4 yet. But I made a similar mod on the FW F-4, F-22, Lippisch, Avanti and L-39. On the last three, I did a ‘before and after’ comparison, and there is a noticeable higher top speed (GPS measured on the Lippisch). The question regarding the sound is hard to answer, I feel it sounds smoother at top revs.

I’ve no idea, why the intake ducts are designed with the “high-turb” rounded splitter. Just google “skin friction drag”.

If you look at well-designed wooden or composite EDF models with bifurcated inlets, you will always find such a design.

[themudduck]

While exchanging the stock fan with an FMS unit, I discovered the blunt joint of the inner walls of the intake ducting. Such design creates a lot of undesired turbulence. I made a simple 3DP part to create a sharp joint to improve the airflow. In addition, a nose gear brace was made. Both stl. files are attached.

Thanks, those look very useful !

Have you done any tests, does your "low-turb splitter" seem to produce better thrust? Does it change the sound?

[WrightBrosRC]

While exchanging the stock fan with an FMS unit, I discovered the blunt joint of the inner walls of the intake ducting. Such design creates a lot of undesired turbulence. I made a simple 3DP part to create a sharp joint to improve the airflow. In addition, a nose gear brace was made. Both stl. files are attached.

Great ideas, both! At this stage of our technology with batteries and such, efficiency is the name of the game. I see more clam shell type construction these days with wood and plastic components sandwiched into the foam mold process. If I were involved with design I would consider a one piece, smooth, plastic/laminate or similar thrust tube from beginning to end with an appropriate space to insert your fan shroud, etc. I know there would be issues with cheater holes and the attached consideration for power systems, short vs long field ability, and all of that stuff... not even suggesting it would be the way to go. Just saying it would be an avenue I would investigate thoroughly. I'm not a scientist and have no data to even suggest the increase in efficiency would be enough of a benefit to outweigh the change in design and manufacturing costs. If anyone has done thorough thrust tube testing it would be cool to see the data. I tend to agree with your idea that every little bit helps. :Cool:

[Radar-Guy]

While exchanging the stock fan with an FMS unit, I discovered the blunt joint of the inner walls of the intake ducting. Such design creates a lot of undesired turbulence. I made a simple 3DP part to create a sharp joint to improve the airflow. In addition, a nose gear brace was made. Both stl. files are attached.

[WrightBrosRC]

Thanks for the explanation WB. Must be a very nice lens to pick up all of that. Obviously the way to go if you want an first class video instead of those dots in the sky, non edited, crap -- yes I know I don't have to watch and I don't any longer than the five seconds it takes to realise what is coming. Nice F-15, sold mine as thought it marginal on 6S and I am not an 8S guy. Can you post pics/facts of your camera and its mounting set up ? It looks like it could pan but is that just your editing? Thanks.

No Prob, Happy to tell you what I know. I have only had the camera for a week though, so I'm still learning on the fly (see what I did there LOL), and the weather has been limiting too. Many have asked and I should probably make a how to vid. I'll take that up shortly as I discover how to wring all of the goodness out of it.

There are 3 ways to record video with this cam:
1.) Make initial recording while live stream (viewers can actively move and select the camera view)
2.) Make initial recording, download video direct to internet.(viewers can actively move and select the camera view)
3.) Make initial recording, download to editing software, choose each fixed camera angle with options of other industry standard editing for stitching, picture quality, color, etc. (viewer cannot move the camera view)

I am still figuring out how to live stream, but even as a retired automation engineer, I have struggled at times to understand what the %^$@$%%^*%$ I am doing wrong. :Silly:

6S for me too. I can only guess that all stock power systems are not created equal. You are one of many to feel the F-15 was under powered to them. Mine has been so strong that it was my first camera ship with the Mobious, AND it has added servos for controlled drop tank release in flight. It is otherwise bone stock so I have no explanation??:Thinking:

-Den