Grumman F-9F Panther for EDF-40

[Esprit440]

UPDATE 7-18-06: plans & build manual are attached below in .PDF format

Just got back from the successful first flight of my little nano-Panther. This was a model I designed in my free time while in Japan recently on an extended business trip - it was nice to get it in the air after a lot of daydreaming.

It's a kind of "profile plus" model with simple covers that hide the gear and give it a more three dimensional look.

Specs are:

WS 22"
AUW 4.7 oz.
EDF-40 with 5800kv Feigao
TP 3S 730 pack
CC Phoenix 10
4 ch Berg & Blue Bird servos, AET control

Took six (!) agonizing test flights to get the CG right, it was really tailheavy at first and I'm surprised it held up as well as it did. Damage at the end of the session was confined to a slightly crunched nose and a few weed-whacks.

Once the CG was right it flew really well, although roll stability was less than I'm used too. I took out the dihedral of the original for simplicity's sake and that might be the reason. I also want to try mounting the battery on the underside to see if that helps.

Next version will incorporate all the tweaks, and then plans will be along eventually.

-Matt

[Kevin Cox]

Hey!

Slick....good job.

[St. Martin]

Wow..what a neat little plane! What are the construction materials? Looks easy to enlarge for other size fans, also. I've got a few KY fans hanging around doing nothing.

Steve

[Kevin Cox]

Gregg F did one a while ago with a stock motor and fan fold.

[roccobro]

How cute! Could somebody bang out a kit like FTM does? :D

Justin

[uncljoe]

Matt
Outstanding!!! Like the way you cleaned up the airframe.
Semper Fi
Joe

[Esprit440]

The fanfold version from Gregg looks nice - we took a pretty similar approach to the component layout too.

I wanted to keep the fan hidden under the covers (which have a subtle "S" bend in side view that adds a lot of shape), and also locate is far rearward as possible for better performance.

Airflow from the fan blows back over the cross-shaped fuselage, which negates almost all of the torque effects from the overwhelmed stators in the EDF-40. This was a huge problem on my disastrous Su-27!

Materials are 3mm depron, with 1mm depron used for the fuselage covers. 2mm carbon rod for reinforcement, fiberglass tape for edge protection.

Still wondering about the elevator servo, mine sits right next to the fan and connects to the elevator with a wire pushrod. Seems to be the simplest way right now.

Scaling up - I have an ancient but unused EDF-75 on my shelf that would be just right for a 200% version. Thrust is probably less than the brushless EDF-40 though!

Plans will come but I want to build a second version to get everything just right - more test flying tomorrow I hope.

-Matt

[keven64]

That is SMART... ! ;)

Keven. :)

[Haldor]

Job well done! :)

[St. Martin]

Matt, I'm curious as to whether the exposed carbon rod, if moved to the top of the wing, might help performance? If in the correct place, might act as a "turbulator" and enhance performance? As a young boy(please don't ask when..) I made a lot of HLG's. A trick to improve performance, was to glue three lengths of heavy fishing mono in the first 1/3 of the chord, on the top surface.

Again, one neat little plane!

Steve

[roccobro]

Steve, I meant to say it is nice to see you back. :) I couldn't tell you before because the thread was closed. :(

BTW, how long ago was that? :p

Justin

[St. Martin]

Hi Justin! Not too long this time, my friend. In fact, the shortest "cooling off period" yet! I'll PM you. No need to take this thread off topic, on Matt fine efforts(smile)

Steve

[Esprit440]

Second day of flying went really, really well right up to the part where I drilled the model into the ground!

CG was right on this time and it was a dream to fly, really fast and maneuverable. The fuselage makes a cool whooshing noise at high speed. Got in trouble doing consecutive rolls, it slowly nosed over and I botched the pullout. Ugh.

Damage isn't so bad but I will just strip the gear out for the next one. I'm eager to fly this design some more!

-Matt

[Pilot44]

Matt,

Bummer mate, nice job on the Panther, waiting on the plans. Looks like it might be less expensive to get one together as opposed to the Aeronaut Panther..... :eek:

Jim

[uncljoe]

Matt
Look at all you learned with the "prototype". it also appears all the hardware survived for future developements on the next Panther.
Semper Fi
Joe

[King_Ice_Flash]

4.7 Oz, with the 5800KV motor? I bet that thing flew awsome!

[AirX]

Matt,

I guess I missed it when the electricity was out yesterday. Nice work again.

Eric B.

[Esprit440]

Flew the second version this morning with a break in the windy weather.

First flight was ok, but a little tailheavy. Moved the battery forward but stalled it on the next launch and landed vertically on the tail at full throttle - static thrust, save me now! Need to throw it a little harder and go easy with the elevator at low speed.

That landing cracked part of the rear fuselage and led to some strange yawing under power as the fan efflux was deflected. After I glued that back together everything was great!

I did my first rolling climb and had a big smile on my face through two packs. It's about as fast as I can handle in the space available but slows down nicely for landing.

Also tried out the 200% (44" ws) fanfold version powered by an EDF-75 that has been sitting on my shelf for years. Didn't get anything more than a long powered glide out of that which is no surprise. The EDF-40 version actually has more thrust!

I'll have the plans ready soon.

-Matt

[AirX]

Nice work and congrats, the Panther looks great.

Eric B.

[roccobro]

See's a beaut. Nice and simply elegant. Thanks for the maiden replay! :)

Justin

[Spitfireski]

Nice looking foamy, very scale looking! yeah those edf 75's in stock form are worthless, i haven't been able to find another use for mine until maybe they get BL's and a big fat 4s lipo to power a larger jet. Awesome panther, will we ever see some vid?

Chris

[Esprit440]

Thanks for the kind words guys, I spent some time finalizing the plans today so they should be ready this week. I have some video of the first version that I will try to edit together sometime - including the incredibly stupid crash!

Oh - I forgot to ask this morning, but I wanted to get some thoughts from the EDF gang on an unusual stall that I've gotten this model into a couple of times.

First version did this (slightly tailheavy) and so did the second version this morning (slightly noseheavy): when stalled at a high angle of attack, maybe 60-70 degrees, it starts to sink nose up in a spiraling turn. Throttle, aileron, and elevator have little or no effect at this point and the model just floats to the ground like a leaf.

I recovered from another one of these today but it was pretty violent; while holding some down elevator and goosing the throttle the nose suddenly "popped" down and the model shot into a dive about ten feet off the ground - yikes.

This stall has happened a couple of times, usually when snapping the nose up out of a loop or other heavy-handed pitching maneuvers. I have one on video but it's hard to see much.

Any ideas? It's kind of a fun trick but I'd like to understand what is going on a little better.

-Matt

[roccobro]

How close is the fan to the CG? Someone recently noted how a fan unit can act like a gyro when spot on the CG in a plane.

Justin

[AirX]

Sounds like High Speed Stall to me. I have experienced it before with DF not with propellor driven models where the thrust from the prop will help recover it.

Eric B.

[Esprit440]

Justin, the fan is back 9cm from the CG which is about a fifth of the fuselage - still pretty close though. The gyroscopic effect would explain some weird, ah, gyrations that I've seen in vertical maneuvers.

Eric - yeah it definitely feels "stuck" in the stall. I wonder if the t-tail has something to do with it?

Guess I will just have to start flying it with a little restraint! I'm really eager to see what a good pilot can do with this design since it is very fast and agile.

-Matt

[keven64]

Matt,

That orange tail scheme is a real looker ! ;)

Perhaps one only slightly bigger - for TWO brushless EDF-40's ?
One either side of the central keel and still hidden under the 'covers'...?
That is such a neat way of doing things...

( I MUST order more 3mm depron... :rolleyes: )

Keven. :)

[Esprit440]

Keven - yeah I'm glad I painted the tail orange because the dark blue is very hard to see! I think I will paint the next one drone red.

I've been working on a few of these "profile plus" style designs that add a little shape to basically flat airframes. It's fun to play around and find simple ways to give a realistic impression.

Gotta build, build, build this winter!

[Esprit440]

Gotta finish some of these...

[keven64]

that Sea Harrier is GEORGEOUS...!
( where's the 'heart' smiley when you need one ? ;) )

A Harrier was published as a free plan here in the UK some years ago - for an old 'Morley' fan unit - with a 540 buggy motor.
A profile fuselage - and batteries IN the wings...

Yours is just blummin' lovely ! :D

I'm rather fond of the odd Sukhoi types as well, like the Fitter, the two Fishpot variants... and your Flagon, which also appeals greatly.

Keven. :)

[AirX]

A-4 is my favorite...:)

Eric B.

[RCParkflyer]

I'm going to be hosting Matts Plans on my website, although I might want to start a different page, as all of the plans so far are full body designs. What do you guys think?

Tom

[keven64]

A new page would be a good idea... ;)

Keven. :)

[roccobro]

I would have to agree...

Justin

[RCParkflyer]

Parkjets Profile Pushers?

[keven64]

No Tom...

My reasoning being that the F-9F model featured in this thread ( and also the Harrier in the attatchment, as I understand ) are EDF-powered ! ;)

What about 'Parkjets Profile Foamies' - or 'Parkjets Profile Foamjets' ?

I've got it ! A simpler one...

'Profile Parkjets' ? ;)

Keven. :)

[Esprit440]

Yep they are all EDF designs. How about "Profile Plus Parkjets"? I wanted to combine the simplicity, easy building, and light weight of profile designs with a little something extra - hence the "Plus" part.

Anyway - I will be working on the Panther plans this week, no more designing for now!

-Matt

[RCParkflyer]

Profile Parkjets - EDF and Pusher, it is :) This is gonna be fun!!

[albireo]

I can't wait!

[keven64]

Nor can I... :D

Keven. ;)

[Esprit440]

Oh man, my eyes are spinning from an evening in front of the monitor!

I went back and set up all the servo arm, control horn, and pushrod locations in the Rhino model so the final plans will be nice and tidy.

I'm having a good time though - looking forward to getting these plans out there.

-Matt

[roccobro]

Thanks Matt for all your work.

Justin

[albireo]

Oh you're just stringing us along! :)
Reminds me of the new series LOST! Another cliffhanger...

Joe

[Esprit440]

Good show, but takes forever to get to the point - hey! How about if I have something done before they get off the island?

-Matt

[albireo]

No fair!
This isn't Gilligan's Island you know!
Besides, I NEED to know what happened to the little boy (Walt)...

Joe

[Esprit440]

Ok guys - the plans are DONE! RCParkflyer is going to host them on his site so stay tuned for the link - thanks again Tom.

F-9F plans (http://www.parkjets.com/F-9-F-for-EDF40-v1.pdf)

-Matt

[RCParkflyer]

Here is the link for the Plans and assembly guide,

http://www.parkjets.com/F-9-F-for-EDF40-v1.pdf This is just the PDF file for now, I still need to make a few web pages yet, Stay Tuned!!

Tom

[keven64]

Arrrggghhh !

More irresistable plans... :cool:
Whatever am I going to do...? :rolleyes:
I know - I'll buy MORE depron ! :D

Now- where's that spare EDF-40 got to...?

Keven. :)

[albireo]

Holy Flying Cat Batman! They're up!
I **JUST** cut the Depron for my F-15... (We got the kids in bed early and I stayed up and got 4 hours sleep) I gotta finish that one first...
You posted a MANUAL TOO! Yikes!
Thank you Matt!
Joe

[Esprit440]

Just uploaded a video (http://www.rcgroups.com/gallery/showphoto.php?photo=26754&sort=1&cat=500&page=1) of the original version's first flights. Some pretty sad launches I must say, but it survived and had a very brief life as a nice little flyer.

I'll put together another video of the later flights & demolition soon.

-Matt

[roccobro]

I really like how it flutters down like a leaf after a botched manuever! That option would save me hundered of hours of repairs in my life. That would be a cool channel option on a radio, "leaf switch". Takes the place of a real ejection seat. :) Great video Matt!

Justin

[AirX]

Nice video Matt. You designed a neat little plane. The first few tries on the video looked like what I went thru on the little F32 I did in depron. real tail heavy... :)

Eric B.

[Esprit440]

Yeah the leaf maneuver is pretty much the stall I was talking about earlier. The new version is well balanced but will still do it if you get careless at slow speeds.

It drifts down really slowly so it is more annoying that dangerous, although I almost landed in a trash can that way last weekend. Three points!

I'll get the next video together soon, where it was flying really nicely up to the point where I planted it. Pretty funny footage of my wife reacting, too.

-Matt

[jjbtlb]

I really like this airplane and thanks for the plans. But, I'm having problems printing page 11 the last page, how was it printed? or setup to print!
Thanks again for the plans.

Joe

[Esprit440]

Joe,

Sorry the last page is not tiled. Gotta get back to that.

For now, try this method:

- Set view to 100% scale

- Pan around on page 11 until something is in sight

- Print with the Print Range set to Current View

- Make SURE page scaling is set to None

- Repeat as needed to make the tiles, being sure to overlap each page a little bit.

- Refer to the 50mm scaling squares to make sure everything is correct

Alternately, you could go to a place like Kinko's and get the last page done in one piece.

Haven't had much luck finding a PDF tiler, any ideas?

-Matt

[Esprit440]

I uploaded the second video (http://www.rcgroups.com/gallery/showphoto.php?photo=26798&sort=1&cat=500&page=1) to my gallery, oh the humanity. If my lame underhanded tosses weren't enough, now you can watch me royally botch some rolls.

On the other hand it's pretty funny to watch! I like the flyby at around 1:15 too - whoosh.

-Matt

[AirX]

I plot from AutoCAD to PDF, using a grid to lay the plot windows over. Works great but can be time consuming when wokring with a large drawing.

Eric B.

[keven64]

Matt,

Take a look at the following page ;) :

http://www.blackflight.com/planes.asp?plane=tileprint

I just need to figure out how to use it... :rolleyes:

Keven. :)

[AirX]

I have that one, works great. Set a measurement on the pic that you want to enlarge and it will set the tile sizes to fit the paper you use. IIRC.

Eric B.

[Tres Wright]

Just found this thread linked from another one. Wow, the Panther looks fantastic! Nice work Matt!! I love the videos too, hilarious! :) That tail stall is really bizarre, I haven't seen anything like that before. Is #2 still flying?

[tbitz]

I ran a doppler using the pass at 1:18min

Freq approaching = 3.2kHz
Freq passing = 2.85kHz

speed = 19.6 m/s = 70 kph = 44 mph

If you run another video, make a high speed pass as close to the camera man/woman as possible (without chopping there head off). This gives the most accurate results using doppler.

Cheers,

Tony

[Esprit440]

Thanks for the kind words Tres. I have noticed that mishap/crash videos are a lot funnier a few weeks after the fact!

Yup #2 is still intact, last flight was a couple weeks ago when I maidened my Cox P-40. Winds started to kick up after a few minutes so I decided to land and call it quits.

The latest "sorted" version still does the stall trick; I think it is a combination of the t-tail and thrust line that makes it happen.

Also found a new trick where the model will hang in the air about 80 degrees nose up and waggle the wings indefinitely at full throttle. Right after discovering that, I discovered that it was impossible to recover! Luckily it will drift down fairly gently on its own when stalled.

-Matt

[Esprit440]

Hey Tony, thanks for the calculations. 44 mph seems decent, gotta build something with a thrust tube next.

What program are you using to calculate speeds? I tried the German doppler program (name escapes me now) but couldn't get it to display anything - maybe an issue running under XP.

I'll have to get my cameragirl/wife a helmet and then try some really low passes! It's for science, honey.

-Matt

[tbitz]

I used Goldwave. www.goldwave.com

It doesn't give speed. You need to look at the spectrum analyser read the aproach/pass frequencies and then do the math.

Speed (m/s) = 340 * (Fa - Fp)/( Fa + Fp)

Cheers,

Tony

[pacro]

lovely plane. gonna leave the computer to go build her

[pacro]

hey i already build one. have to go try it soon.

espirit when are you gonna put out the other plans

[Esprit440]

Got any pics Pacro? I think you're the first to build it - best of luck with the maiden.

Other plans will be available... sometime. These days I have less and less free time for this stuff, and recently I have been designing a lot more than building. Many more to come.

-Matt

[david_r2ese]

Matt,
Nice design. Thank you so much for offering this plan. I built this little bird in one night. She flies very nicely on a Medusa 5300. Once I moved the CG forward, I have not had any of the nasty nose high power stalls. I still get minor ones but I can thrust my way out of them with little loss of altitude. It looks to ballance about 1/4 inch ahead of what is marked on the plans. It looks very majestic in the air, even without paint. I can do loops from level flight at 75% throttle. The rolls are crisp and axial. It is my new favorite travel plane. I'll be sure and post more pics when I get her painted. And yes, I did bust off the nose on a power stall, but a little glue and tape.....

Dave

[Esprit440]

Looking good Dave! I'm really happy to hear it's flying well for you. Can you measure your CG sometime and let me know what works best for you? The CG on the plan was just slightly nose heavy for my model & seemed like the safe bet, particularly with the stall phenomenon.

Also, did you have any clearance issues using depron thicker than 1mm for the fuselage covers? Looks like they clear the fan ok.

Looking forward to seeing it painted, and reading more flying impressions!

-Matt

[david_r2ese]

Matt,
The CG floats between 5-10 mm ahead of the spar, depending on which battery pack I use. This design has got me thinking. I wonder how it would be with a actual built up fuse, along the lines of GGRN's skyhawk? I may just mess around with some extra foam.

Dave

[muntquist]

Hi Esprit440,

I am just finishing up an enlarged version of your Panther. I scaled it up to fit an Alfa fan unit and changed a few of the construction details. The main construction difference s that the fuse is made out of 3/4 inch pink foam that is covered in 1/2 once glass and WBPU. The span is 31 inches and the finished weight should be around 15 ounces with a 750 nimh 9-cell battery. I have painted it in the colors of the Blue Tail Fly, a Panther that my father worked on as an aircraft electrician during the Korean War.

I will post photos soon.

Steve

[david_r2ese]

I decided to start the experiment on the full fuselage F9F. Here are a few pics.

Dave

[david_r2ese]

More pics:

I'm kind of doing this by the seat of my pants, and I'm not looking for a super nice model. But I think it is a starting point and will hopefully show that she can be done as a full fuse. If she flies, I'll figure out how to make swept solids in SolidEdge, and build it as a solid model, and reverse engineer the panels.

Dave

[david_r2ese]

A bit more progress has been made. I think it is beginning to look like a plane.
As of now it is only 3/8of an ounce more than the original. :D
Dave

[david_r2ese]

I just got back from trying to maiden the full fuse version. I knew I was pushing the limit when I measured only about 90g of thrust. While she flew decently after the toss, she would bleed off too much speed in even shallow turns and slowly lose altitude. I think the design has a lot of promise. I believe it was my ductwork that was the problem. I had 5" of duct at 43mm dia. after the fan. My cheater hole was over 1.5 times the size of the FSA, so I don't believe the problem restricted intake air. I may try this again, but next time, move the fan back so there will only be a 1.5"-2" thrust cone after the fan. that should help the design a lot. I'd sure love to hear other peoples ideas on how to improve this plane.

Another bit of bad news is I broke the nose off of my profile version. I didn't double check my CG with the battery I chose, and had the CG too far back. in a low (4 ft.) turn, she went into a nose high attitude, but I couldn't recover and broke off the nose on impact. :eek: :censored: Luckily foam is easy to repair. I'll have her flying again in no time. :D

Dave

[AirX]

David,

The EDF40 even with a feigao in it will lose thrust with an outlet of 43mm. This is a divergent outlet and causes the airflow to slow as it exits the fan. The motor holder area must be subtracted from the outlet area if performance is to be upheld. This is simple physics.

Eric B.

[david_r2ese]

AirX, I was a bit misleading in my statement. The actual eflux tube was 3" @43mm, and the last 2" tapered to 37.5 mm FWIW. I just DL'd The 15 section instruction on EDF design. Hopefully I can make some sense of it, and rework things a bit.

Dave

[Esprit440]

Dave, nice work so far! I'm impressed by your work on the fuselage panels.

How about some pics of the latest? I'd love to see a "walk around" and detail shots of your intake solution. Are the scale intakes functional, or just the cheater hole?

One thing that steered me toward a profile version of the Panther was the beautiful blend between the rear fuselage and vertical stabilizer; I just didn't know how I could pull that off. I'm feeling motivated now though, great work!

-Matt

PS I read somewhere recently that Neil Armstrong had to bail out of an F-9F in Korea...

[AirX]

AirX, I was a bit misleading in my statement. The actual eflux tube was 3" @43mm, and the last 2" tapered to 37.5 mm FWIW. I just DL'd The 15 section instruction on EDF design. Hopefully I can make some sense of it, and rework things a bit.

Dave
Hi Dave,

Sorry but thougth it was 43mm in diameter thru it. If that is Klaus's manuscript it is good for understanding EDF.

Cheers,

Eric B.

[david_r2ese]

Eric,
I take it you have a decent knowledge of EDFs. I read through Klaus' document and wow, my head is spinning, not from the math, but from the volume of variables. WOW. I plugged away at numbers for several hours, and came away with unusable data. From what I saw it looks like a 36-34mm outlet would be the right size, as the effective inlet dia. is aprox 37.7mm. (40mm-13.5mm hub)the 34mm outlet would be 80% of the inlet area. I guess my question is, will 60 watts power an 8 oz plane to aprox 20m/s or 45mph? Those are all conservitive numbers. Actually, if anyone has a spreadsheet that allows you to just plug numbers into, that would be the best way for me to figure this out.

Dave

[AirX]

Well if you go further into Klaus's calculations you will find that the inlet needs to be at least 100% of FSA or as he defines it the anulus, the optimum is larger than 100% and nearer to 110%)( I prefer 120%). The outlet is supposed to be 80% of that anulus or as I define it the FSA(fan swept area). Here is a further description of duct from Klaus in a more descriptive form. From this diagram from ClausXPF you can see the progression of area change that is just about optimum thru a good duct design.

Eric B.

[david_r2ese]

Eric,

Another question. As the GWS shroud does not neck down to a dia = the FSA, does the >1:FSa duct have any ill effect as long as the thrust cone, or section that tapers at the end, is 80% of the FSA? With this design I have a cheater hole at over 150% of the FSA as well.

Thanks for the input.

Dave

[AirX]

Nice sketch of the area's for the system. Basically the cheater becomes ineffective once forward movement starts, it needs some ducting in from of the fan to get the airflow working. The reason cheaters become ineffective is the air has mass and it tends to follow Newtons first law of motion, "In the absense of an aplied force, a body at rest remains at rest, and a body in motion remains in motion with a constant velocity and direction", so the body of air or air mass will gain more force with increase in velocity and even though the aplied force from the fan is the same as it was at rest the air has to make a direction change and it will be diminishing returns from it as speed increases. In this case the suction from the fan is just not enough to change the direction of the air once it is moving.

Eric B.

Sorry to answer your question the outlet is defined properly but the inlet is where the problem lies I think, you can have many more losses in an inlet duct where vaccum is the driving force.

[david_r2ese]

Eric,

Thanks a bunch. So to make this design work with any decent efficincy, I need to have the intake ducted much as the original, but with a combined FSA x 120-130% to make up for ducting losses. Wow. Looks Like I might need to rethink this whole idea. What I wouldn't give for a decent workshop, or even an oven for forming the foam. Looks like I might need a completely hollow fuse from the wings back. Now if I get all my papers done early..... :D

Dave

[david_r2ese]

Here's what I've come up with for a layout so far. My inlets are @ over 130%FSA combined. Size wise, it is nearly the same as the original. I must be nuts for trying this. :eek:

Dave

[AirX]

Hi David,

That should be better. Do you have any way to measure the static thrust? What motor are you running in it?

Eric B.

[david_r2ese]

Eric,
This one is running a Fiegao 5300Kv. I'm not positive, but when I tested for static thrust with this same combo I was getting somewhere in the range of 110g of thrust. Any suggestions of what makes for good ductwork? If nothing else, I'll just use the 3mm depron. I also have overhead projection sheets. But that stuff is REAL flimsy.

Dave

[AirX]

Hi David,

On the outlet side the lighter the better on the inlet side there is a vaccumn to contend with and if you have 2mm depron it will be fine but try to keep as light as possible. 110 grams sounds light I have gotten 140 out of mine with the outlet duct on at FSA.

Cheers,

Eric B.

[Esprit440]

Some thoughts on the intake:

1 - the outer corners are very sharp and I wonder how smooth airflow there will be; fillets there would clean up the cross section nicely although the calculated area will decrease.

2 - to regain some of this area and possibly shrink the intakes to a more scale-like size, an indentation in the fuselage on the inner side of the intakes might be worth considering. My graphic is pretty rough but I'm picturing a nice smooth conical "dent" in the fuse just ahead of the intake and continuing inside.

-Matt

[david_r2ese]

Matt, not a bad idea. Now I'm thinking vacuum forming the foam might be the best way to acheave the desired shape. Has any hobbyist done this? I imagine it is how Fan-Tastic Models does theirs. If molded that way, the complexity of all the blending of radii (sp) on the fuse will be a peice of cake. Man what I wouldn't give to be working back in the pattern shop right now.

Dave

[Esprit440]

Vacuum formed sheet is the holy grail of foamie construction for sure. For a long time the process used by Fan-Tastic Models was a mystery, and I don't think anybody from the company has ever talked about it in detail.

I vaguely remember someone saying that the FTM process used virgin polystyrene sheet; depron is already foamed (with steam?) & extruded and more consequently difficult to reform.

People who have tried to vacuum form depron often mention that it's difficult to keep it hot enough to form since it cools off so quickly.

I think the final results would be very nice but it would take a long time to prep nice plugs - and a shame to build just one or two models at that point especially after the inevitable deluge of requests to make more!

Harpye has a nice technique for forming complex shapes that is a little simpler than vaccum forming, maybe a search for his builds could give some ideas.

Good luck!

-Matt

[scm]

Hi,

I posted information earlier (under the user name Muntquist) about my Alfa fan version of Esprit 440's design. Construction is 3/4 pink foam for the fuselage and 6mm depron for the wing and tail. There are 2 layers of 6mm depron for the leading edge of the wing. Thanks for the plans Esprit44. I will report back after flght testing.

[Esprit440]

Nice one! Good luck with the maiden,

-Matt

[muntquist]

Hi Matt,

I maidened my Alfa fan Panther last evening and it flew great! The hand launch was easy with no sag to get on step and it only required a couple of clicks of aileron trim. A couple of low passes, a few rolls and I was ready to land. It was easy to fly on approach, was very controllable using throttle, and had excellent low speed manners.

Thanks again for a great design!

Steve

[Esprit440]

That's great to hear Steve! I'm glad you are enjoying it. Got some flight time on mine recently for the first time since last fall and had a ball.

Got any more pics?

-Matt

[kdahlhaus]

Matt,

Any thoughts on how this would turn out if built with blu-cor foam? Based on densities of the foam, it would be heavier, the frame may even way almost 2x. It's a nice looking plane.

[Esprit440]

I think it could be done in the original size with Blucor although the parts would need to be modified to account for the thicker material. The fuselage covers would need to use a thinner material since they fit very closely over the fan and other components.

Anyway I'm pretty sure it would be perfectly flyable although somewhat heavier as you noted. Why not order up some 3mm foam and build a bunch of models from all the free plans around here? ;)

Good luck,

-Matt

[SNIPE_53]

muntquist,

what setup are you using with the ALFA fan?

[muntquist]

Hi,

Stock Alfa fan with the MPJet brushless that Hobby Lobby recomended. I fly it on a 9 cell 950mah nimh pack. Performance is ok. If I were building another one I would use a better fan/motor and go to lipoly.

Let me know if I can be of any more help,


Steve

[SNIPE_53]

Thanks for your response Steve. How did you find the glide ratio with the higher wing loading? Mine will be using a Wemotec Microfan and a 1300mA lipo so it will be a bit heavier than the GWS 40 setup :)

[FresnoJay]

I just found this thread and downloaded the plans for it. I have been wanting a cougar for a while but I hadn't been able to locate an arf kit in stock in a foamy range anywhere. All the arfs I did find were $300-$500 range and is well above my range for now. This one looks great and almost a no brainer not to mention a good beginner design for getting into scratch building.

Jason