|Aug 02, 2011, 01:12 AM|
Hello chaps - been lurking for a while but my micro F-86 arrived today and thought it was well worth making my first post to mark the occasion!
Ordered from Hobbyking and just about two weeks shipping time to NZ I thought wasn't bad. Impressed with the packaging, instructions and little airframe so no complaints from me with HK so far (first order with them)
It's been interesting and beneficial to an edf novice reading this thread but it'll be a while before the maiden flight. I want to build some more flight time with my Twinstar and micro warbirds (nine eagles 3ch P-51 and 4ch P-47) before unleashing an edf but I had to have one to tuck in the back of the hangar ready for when my ability matches my ambition!!
Great forum - look forward to gleaning a lot more knowledge from here!!
|Aug 02, 2011, 05:43 AM|
Even if its straight thru - just to smooth out that silly large exit area behind the case. Best stuff is the slippery face plastic sheet.
I ask all this because mine flew quite well on 2S and the only difference was the tailpipe. Strike3 barely managed to stay up on 2S but he had no tailpipe. Mine was only reduced about 4mm in diameter to the models exit hole.
|Aug 02, 2011, 02:41 PM|
tailpipe or thrust tube mod
Need to know more about this tailpipe mod. Is it strictly Mig? Or F-86 as well? How about a little write up about this. With drawings, suggested materials etc. Weight? Or if it's already well documented previously, we need a link to that. Thanks! It may be just what I need.
|Aug 02, 2011, 04:46 PM|
A thrust tube or tail pipe is always better because it smooths the air on exit and with the correct opening it gives you more thrust... all these little jets will be better with them.
Go to the top right corner of this page and use the search functions... plenty of info on it, sorry I haven't got time to do it for you now... work beckons!
|Aug 02, 2011, 05:54 PM|
Thrust tube should be a straight line from the rear of the fan to the outlet, preferably about 10% smaller at the outlet. This model swells out after the fan, then reduces down to the tail. This is a big no,no. Intake should be about 10% larger than the inlet area of the fan too. These are just rule of thumbs, or is that rules of thumb. Also ducts should be smooth as possible. Those little molding dimples aren't doing any good either. Anything to keep the airflow as smooth as possible is a help.My first ducted fan was in 1955 with an English freeflight Vernon kit. Looked like a MIG 15 but different mfg. I remember now, it was a Lavochkin or LA 15. All stringers and covered with silkspan paper. Fan was bent up of aluminum with an Allyn Fury 15 glow for power.
|Aug 02, 2011, 10:50 PM|
Need detailed thrust tube instructions
Thanks. I waded through these forums reports of assorted success with adding one of these. And saw youtube vid on making one for a larger model but I'm still confused. How about a "Making a thrust tube for 35mm edf's" or "thrust tubes for dummies" entry step by step with pics. You use lightest material possible I assume. Would be appreciated by a lot of us who are less experienced. Again thanks.
I guess I'll just have to figure it out on my own. Would appreciate some pics though.
|Aug 02, 2011, 11:03 PM|
My new lipo arrived this morning!
Some nice foam cutting in the battery bay to make it fit and we are good to go. It balances spot one, so what a guesstimate that was!
|Aug 03, 2011, 04:26 PM|
2 make as perfect a cylinder as u can that is as long as the exit length
of the jet..........tape the seam........ scotch or cellophane tape
3 remove the tube of paper from fan
4 reassemble fan to plane
5 shove paper tube up the jets arse attach to fan with tape
optional... cut very small wedges from tube opposite fan
to reduce dia. to about 27mm plus or minus 1.5 mm.... not rocket science..
only jet science....
the longer you make the wedges (and narrow) the better
shoot for 1 dia of fan in length ( science ) ( or 35 mm for this one +/- 5mm)
tape the seams together and apply per < 5 > above
suggest cuts for wedges be made one at the bottom or 2 at both sides.
working on this stuff ( all rc ) is for fun trial and error etc.
( rocket science- Bad -- jet science- fun)
|Aug 03, 2011, 06:17 PM|
Just got my Mig and Sabre about a week ago but have to finish another project before I tackle them. One thing I'd like to try is something that worked well on my old Kyosho T33. Called cheater holes. Many times you can't get enough air into the intake, more air= more thrust. On the Mig, going to cut holes just below the wing about an in. long and 3/4in. from the wing downwards. Then feather it in to duct cleanly it into the fan. May or may not give 'er more poop but only one way to find out.
|Aug 03, 2011, 06:55 PM|
cheater holes most likely not required or any good ......
as the scale freaks like to point out ( many times bless their hearts)
the inlets to these birds tend to be WAY big. to the point of absurdity
do some basic calcs and see if the inlets are close to the area of a
35mm dia fan.
and inlets too big and cheater holes will just slow u down.
or perhaps let the extra air out and thus give u some air speed at hi speed?
either way IMHO dont bother.
but have fun and let us know what u find
|Aug 03, 2011, 06:56 PM|
How To Make A Thrust Tube For Dummies
*******Take all measurements in millimeters*******
1) Measure the inside diameter of the fan shroud (housing)
2) Measure the outside diameter of the fan hub (motor mount)
3) Unzip FSA Calc.zip
4) Input the figures you measured from the fan shroud into FSA Calc
5) Write down on a piece of paper the 85% FSA calculation from the center column labled Exhaust Diameter (single outlet) This figure will be your exit diameter.
6) Google "Cone Layout" and download it. It's free for a limited time period. If you decide you want unlimited usage you will have to pay for it after the trial has expired.
7) Measure the distance from the fan to the end of the rear of the fuselage. This will be the approximate length of your thrust tube. Write this figure down on the same piece of paper you wrote the exit diameter.
8) Measure the outside diameter of the fan shroud. Also, write this figure down on the same piece of paper you wrote the other two figures; thrust tube length and exit diameter
9) You now have your dimensions for the thrust tube.
10) Input the three figures from the piece of paper into the Cone Layout program. Diameter 1, Diameter 2 and Lengthh. Change all figures for angles in Cone Layout to zero to create a straight cone. Left click on "file" and print. You now have a template for a thrust tube.
11) Measure the inside diameter of the fuselage exit tube. Write this figure down. You might as well write it on the same piece of paper that contains the other three figures
12) Make a thrust tube centering ring. With a mechanical drawing compass draw two concentric circles using the fuselage exit diameter and the thrust tube exit diameter on a piece of 3mm foam sheet.
13) Cut the outer circle from the foam sheet and then cut the inner circle from the disc. This donut will be the centering ring for your thrust tube
14) Cut the paper cone template from the sheet you printed and tape the ends together down it's length forming a cone
15) With the fan housing cover removed from the fuselage temporarily curl the thrust tube down it's length , being careful not to crease it, and insert it from the rear of the fuselage large diameter end first all the way to the fan assembly. Ideally, the end of the thrust tube will fit over the fan assembly OD. If you were lucky the thrust tube will fit over the fan assembly and extend slightly out of the back of the fuselage. If not add a few mm to Diameter 1 and the length inputs in Cone Layout and keep making adjustments until it fits over the fan and extends out the fuselage exit.
16) Once you have a suitable thrust tube that meets all the criteria you can either use the paper one or more preferably transfer the shape to a clear plastic sheet, like notebook dividers, anything light and rigid, and use it for the final product. Attach it to the fan housing with tape or *PVA glue ( Elmer's ) and use the donut made in step 14 to center the tube at the exit and glue it in place as well
If I've left anything out or have otherwise been unclear in any way, my apologies.
* I suggest the use of PVA glue as it's water soluble in case removal becomes necessary.
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