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Old Dec 02, 2002, 10:49 PM
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Rootbeer fix!

yes, I was in Philadelphia and yes, I did break down and drink a bunch of Hires Root beer this weekend while I was working on the F4 .
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Old Dec 02, 2002, 10:51 PM
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Outside of Dyer, Tn. USA
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Looking better and coming along! Hate to see the heat on foam problem.
Don
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Old Dec 02, 2002, 11:11 PM
I fly Army UAVs!
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West Saint Paul, MN
Joined Aug 2002
566 Posts
I have to say it looks good so far and I cant wait to see your completed F-4.

Right now I am to the point of putting the duct work in. I chose to make the ducts completely out of the overhead plastic film and I have to say it sure looks nice and I hope it holds up once I begin covering.

Now after thisplane is finished I will need to go out and get myself a camera so that I can post my picon here also.

Harry
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Old Dec 03, 2002, 05:15 AM
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Lilburn, Georgia, USA
Joined Nov 2000
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Wings

I wished I had caught you before covering the wings. My recommendation would have been to sand them smooth and:

brush on water/glue mix OR light spray of B-I-N Primer sealer (foam safe paint)

THEN, after throughly dry,spray with black paint

The water/glue/paint finish is quite smooth

Sheeting the wings makes her too heavy......
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Old Dec 03, 2002, 12:24 PM
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raleigh, NC usa
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wing painting

Hey fanman

thanks, I was actually ready to use the paint method with 10% white glue and hot water then decided on the Litespan after much diliberation.

If I had not been so overzelous about my covering job it would have been fine. I have used the litespan on open frame work and foam in the past but just got my underwear in a bunch because I wanted it - perfect --

The burn is not as bad as it looks, the covering stuck to the foam when it startedd to burn and I caught it before it had a chance to really deform the airfoil . . should be OK in flight but the black covering just makes every deviation stand out . . I did not think it would be as bad as silver - - but it is! Shows every imperfection!

Lite span is th way to go though, no fuss no muss, bends to the compound curves nice and it doesnt stick to itself as you are trying to bend it around the corners like that lite weight film stuff does . .

The bottom hatch is a big one to me - - dont want to over engineer and dont want to add more than I need . . how did you go about accessing the radio and battery - where was your hatch and how big??

Also need a basic idea of the throws . at least where to start. I can always program in dual rates but - is 1/4" up and down for 1/2 " total throw a good starting point??

thanks

Phil
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Old Dec 03, 2002, 12:31 PM
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raleigh, NC usa
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transparency material for ducting material

Hey guys,

In so far as the applicability ofthe LASER PRINTER style of transparency film for ducting goes. It works well and it is almost as light as the 24# paper sugested earlier.

The biggest difference I have noticed is that when you spool up the fans, the paper duct material does react to the vaccuum and distorts while the transparency material stays perfectly shaped - no distortion, no warping nothing - - perfect!

The only cuation I could suggest is this - - make sure you use the LASER printer verion of the transparency material as the non LASER paper or inkjet version will react to the heat of the heat gun while you are covering it~~~

again . . . . .HP LASER TRANSPARENCY PAPER has been tested and works to my satisfaction to render a perfectly round duct not effected by the heat of a heat gun while covering normally.

Phil
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Old Dec 03, 2002, 01:08 PM
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Los Angeles
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For the prototype the bottom was sheeted and then a hatch was cut - the middle stringer on bottom was removed where the hatch opens up and then I just used some "CA" plastic hinges - I mage the hatch large enough to fit the battery in roughly the same location as shown in the plans and still access the rear to fit the radio equipment - as for the throws - very little is needed - to say an exact amount would be presumptuous on my part as they have changed almost everytime I have flown depending on the wind - again because it is a taileron controlled plane turns will need very little control on your part - with too much throw and over turning on your part you will "spin" - while this is a great move down the road it may not be at first!

John
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Old Dec 03, 2002, 01:39 PM
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Charlotte, NC
Joined Dec 2002
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hatch

Maybe I looked at the plans wrong, but the plans show the batteries on top of the fuse doesn't it? And your saying you put a hatch in the bottom yet kept the batteries in basically the same place? I'm missing a piece of the puzzle!
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Old Dec 03, 2002, 01:43 PM
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Charlotte, NC
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Servo mount

Phil,

Any chance things are still open enough to get a close-up shot of the servo mounts? Both to the fuse and to the tailerons. I'm a little nervous I'm mounting these wrong.

Great follow through Phil! Its made my first model much easier
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Old Dec 03, 2002, 01:47 PM
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raleigh, NC usa
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starting point

Ball park -

are we talking 1/8" in either direction or 1/4" in either direction - as a starting point.....

Give me some lovin here!!!!! I need somewhere to start . ...from what you have expressed already in the post last week, we are talking very little movement for turn - - but more for up and down....

I am of the belief that I need to set this up in my 388 as a delta palnform (flying wing) but does the throw for pitch need to be greater than the throw for roll??

thanks

Phil
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Old Dec 03, 2002, 05:30 PM
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I would say 1/4" is about right. When it comes to control it's better to have too much then not enough!

John
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Old Dec 03, 2002, 11:18 PM
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Charlotte, NC
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my ducting experience

Well I started my ducting today. Let me say, pval3 is not exagerating at all about how tedious a task this is. I made 3 complete ducts, each of a different material to see what the weight difference was and to see if there was any noticable difference in maintaining duct shape under power.

First off I used:
1. Ink Gel paper : 6g
2. 24# paper : 6g
3. Overhead transparency : 8g

On the transparency I tried both the laser and regular and both seemed to withstand a sufficient amount of direct heat but for safety sake I used the laser for the test as they weighed the same.

The Ink Gel paper is a little rougher then most 24# paper, but it is black and I liked the idea of the ducts being black It performed exactly the same as 24#

First time I connected the battery the plane almost launched off the table (had the esc on wrong channel) and threw paper everywhere. Definitely a bit of thrust there and that was only 1 motor going.
The second time I had the front ducting installed and no rear. At mid throttle everything was fine using paper, but when I moved it to full throttle the front-most duct collapsed a bit...then tore from the former. Once secured properly there was still flexing with the paper, and none with the transparency.

Personally this worries me. If the paper is being sucked in that much wouldn't that suggest the EDF isn't getting sufficient air flow? Doing a simple test there seemed to be considerably more thrust without the front ducting in place. Obviously you can't run like that so I am going to get a more sensitive scale tomorrow and try adding "cheater" holes.

Contrary to pval3's experience, I found the paper a dream to work with compared to the transparency! The main reason is because the transparency is so darn slick! For the paper all I did was use the cut-out balsa pieces from the formers, wrap the paper around them tight, then tack it in place with a small piece of tape while the glue dried. This was especially easy for the frontmost duct. First I did the round end, wrapping it around the cut-out balsa then tacking it in place with one small piece of tape - no glue. Then on the other end I slowly wrapped the paper around the cut-out, actually taping the paper to the cut-out as I went so it was exactly flush with the cut-out. Also keep in mind I had about 1/4" extra paper on this end. My hope was to tape it to the cut-out...then pull it through the former (definitely add the CA like pval3 suggested) and pray it matches up...this should leave a 1/4" too much still taped to the cut-out. Glue it to the former. One dry cut off the extra.

I still haven't decide which to go with yet, I like the black paper and how easy it was to assemble, but I don't want flex...[gah]

Oh I also had problems gluing the transparency. I just reread what pval3 used, so I will try the glue stick tomorrow.

Happy ducting!
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Old Dec 03, 2002, 11:46 PM
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Charlotte, NC
Joined Dec 2002
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duct picture

A picture of me using the cut-out to form the duct. Use small pieces of tape so your sure you will cut it all off in the end. Also note that using this way, your duct is completely glued and dried before you even get it near your plane.

Oh and I opted for making the rear duct go on the outside of the EDF unit. It probably wont make a lick of different but I was worried about over time the paper could get pulled away from the EDF with all that wind blowing over the edge all the time. Probably wont matter...but I did it anyway!
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Old Dec 04, 2002, 02:25 AM
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Great Idea about using the cutout from former F2 as support for the duct while it glued! I think you find the intake percentage to be correct once you get it all in. I would suggest putting all the ducting in as is and then powering up. The F-4 has more than enough power with some to spare. Adding cheater holes would definently increase the thrust but I don't think it's needed.


John
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Old Dec 04, 2002, 03:18 PM
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Lehi, Utah, United States
Joined Dec 2001
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I've been watching this with great interest. I have a couple of questions about the model constuction and flying.

1 - Which battery pack was the proto flown with? I saw someone mention an 8-cell NiMH AAA pack, but I couldn't tell if that was an intent to use or a report of success.

2 - How can the EDF motors be changed? They look awfully inaccessable from the pics, but maybe there's something I'm missing. My experience with those little GWS jobs is 30-50 flights between changes.

3 - Has anyone flown these at high altitude (5000' +) yet?

4 - I assume these are 2030 impellers, is that correct?

I'm not a big F-4 fan but I'm really looking forward to the Eurofighter and F-22 from AERC. Great work!
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