HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Sep 27, 2011, 10:15 PM
Registered User
cutty01's Avatar
Bay Area, CA
Joined Apr 2008
295 Posts
Mini-HowTo
How To Design a Custom Thrust Tube (Tailcone) for your EDF

I bought a HobbyPartz EDF/Motor combo that was supposedly 64mm for my Phase 3 F16 and have been challenged with how to make a custom thrust tube. After some research, I thought I would share my experiences and findings. This information is probably scattered in various other places on RCGroups but I thought I would create a "one-stop" thread that had everything in one place.

It takes a lot of trial and error to create a cone from a rectangular piece of mylar/transparency film because when laid flat the longer sides of a cone shape should be angled and the front and back edges should be slightly curved.

The easiest route if it works is to use a drink or coffee cup shown in this YouTube Video

I wanted something a little more durable and I need a longer thrust tube than the cups I could find.

The next best option is to see if one of the DonRC templates works for your particular application that is a sticky on the DonRC forum.

While he had a template for 64mm fans, I found out the outer housing of my fan was actually 67.5mm and could not use one of Don's templates.

The option I finally chose was to use a cone layout program called Cone Layout v2.0.5. It is shareware so you only need to pay for a shareware license if you use it past 21 days. The nice thing is that it will create a flat cut-out plan that you can print onto paper for a template or directly onto your mylar/transparency film. Then you just need to fold and tape/glue the piece(s) together.

A few things about the program
  • I could not get it to print on paper larger than 8.5x11. There is an option to print to larger paper but it kept reverting back to the 8.5x11. You can also play with the margin settings. For my application I needed to print to two 8.5x11 pieces of paper and tape the two halves together before folding into a cone and taping again.
  • Enter in the diameter ("Diameter 1") of the EDF housing. Be sure to add extra for overlap for taping.
  • Enter 0 for "Angle 1"
  • Enter the exit diameter ("Diameter 2") that produces 80 ~ 100% FSA. See the above youtube video for the math. Dont forget to add for overlap.
  • Enter 0 for "Angle 2"
  • Enter the "Length"
  • Print the template on paper first to test that you have the right fit before you waste your mylar

UPDATE1: Please see "ApexAero" post below to print onto larger paper and accounting for overlap by importing your template into a AutoCAD program. Thanks

UPDATE2: Please see "effluxRC" post below to see pictures of one way of how to assemble the tube after you have printed your template. Thanks.

Hope this is a useful reference should you need to design and build a custom thrust tube. Please add to this thread if you have other ideas or suggestions.
cutty01 is offline Find More Posts by cutty01
Last edited by cutty01; Sep 28, 2011 at 11:31 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 28, 2011, 01:07 AM
Registered User
LuvEvolution7's Avatar
St.Catharines, Ontario
Joined Jan 2009
10,377 Posts
I use the "cone" program that you just mentioned and it prints out on multiple sheets if you have the cone large enough. it even numbers them so you know how it fits. simple. it'll make a thrust tube any length, any diameter and any angle of entrance, exit you wish. best program out there IMHO. I don't remember it ever resetting itself though. perhaps it's a computer issue, rather than a program issue?
LuvEvolution7 is offline Find More Posts by LuvEvolution7
Reply With Quote
Old Sep 28, 2011, 01:11 AM
There was a crease in the plan
Steve Haynes's Avatar
Joined Jun 2010
1,332 Posts
Many of us have been using the cone layout program for many years, but every now and again its worth mentioning as new guys who want to experiment a bit may not be aware.

Some good tips on how not to waste material, well done and thanks for posting.
Steve Haynes is offline Find More Posts by Steve Haynes
Reply With Quote
Old Sep 28, 2011, 02:16 AM
efflux RC's Avatar
United States, CA, Santa Clarita
Joined Aug 2009
8,194 Posts
cutty01.

Good idea, posting a "how to" for thrust tubes.
Every EDF should have one. Foamy or composite.


Here's few pics I had to go along with your description.
efflux RC is offline Find More Posts by efflux RC
Site Sponsor
Latest blog entry: Updated blog Jan 2014
Reply With Quote
Old Sep 28, 2011, 04:50 AM
There was a crease in the plan
Steve Haynes's Avatar
Joined Jun 2010
1,332 Posts
Quote:
Originally Posted by efflux RC View Post
cutty01.

Good idea, posting a "how to" for thrust tubes.
Every EDF should have one. Foamy or composite.


Here's few pics I had to go along with your description.
Good idea to put some strong tape where the motor wires come out to stop the mylar splitting.
Steve Haynes is offline Find More Posts by Steve Haynes
Reply With Quote
Old Sep 28, 2011, 06:09 AM
Aka: Tom Jenkins
ApexAero's Avatar
Palm Beach County, Fl.
Joined Aug 2008
4,255 Posts
As far as printing on any size paper etc. The cone program has the ability to save a layout as a DXF, then import it into auto cad and do what you need. Offset a line for overlap, offset the big end for the overlap on the edf housing. I like to size the mylar to fit my printer, I print directly on the sheet then cut out with scissors or a razor knife. Auto cad has the ability to print on to any size if you have the printer. Plus the cad file can be saved rather than opening the cone program to make a duplicate.
Tom
ApexAero is online now Find More Posts by ApexAero
Reply With Quote
Old Sep 28, 2011, 06:26 AM
Da' Cajun
Boogie_'s Avatar
Lake Charles, Louisiana
Joined Jun 2009
2,843 Posts
Are y'all just taping the mylar together?

I've always scuffed the over lapping edges and glued them together with CA. Going on two years of hard flying with one of my tubes, so far so good.

If taping holds up well that really simplifies things.
Boogie_ is offline Find More Posts by Boogie_
Reply With Quote
Old Sep 28, 2011, 08:56 AM
Xtreme Power Systems
Lake Havasu, AZ
Joined Jun 2005
15,492 Posts
CA won't glue true mylar (which is not clear, it's more of a opaque white). In fact, it takes a special two part epoxy to bond it fully, and then there is no flex. I have found that Shoe-goo works well though. Other types of pliable adhesives might also work to hold the overlap in place. I use a single strip of clear package tape the full length of the tube, on each side of the overlap (inside and outside).
JimDrew is offline Find More Posts by JimDrew
RCG Plus Member
Reply With Quote
Old Sep 28, 2011, 11:48 AM
Registered User
Doug Bateman's Avatar
Swarthmore, PA 19081
Joined Dec 2004
2,832 Posts
I do mine by hand. I cut a piece of 1/16" sheet balsa the diameter i want at the exhaust exit. This is based on a % of FSA. I then measure overall length from fan to exit and add 1" extra for fan overlap and fudge factor. I roll the mylar tube tight around fan rear and tape it at outside seam just at fan location. I then roll rear end tighter so it has slight taper. Small piece of tape holds this also. I install in fuselage with tube pushed forward to seal around the mounted fan tightly. I can now make a mark at exact location of tube end where it exits the fuse. Remove mylar tube and drop balsa diameter former down into tube. Locate it at mark made for exit location. Make sure the template/former is squared up. Loosen exit tape and roll tube so it is tight around former. You can now make reference marks for cutting inner and outer overlap at seam. I use 1/2" You can now make minor trim adjustments on ends to square it all up. I do outer seam then lay the tube "seam down" on table and extend a piece of tape through the tube with a dowel or such. I grab both ends of tape and position it over the inner seam while pulling moderate tension. Works like charm.
Doug Bateman is offline Find More Posts by Doug Bateman
Reply With Quote
Old Sep 28, 2011, 11:58 AM
Registered User
Tumbler's Avatar
New Jersey
Joined Feb 2003
7,903 Posts
I use a dowel the length i need and cut 2 plywood discs....1 the same diamter as the fan and one the diamter of the exhaust exit. i tack glue them to the dowel so that I can remove them and change them if I need to. then I roll the mylar around the discs and mark where they overlap and cut so I have about a 1" overlap. I use clear packing tape to hold themtogether and I tape the inside and outside(forgot to tape inside one time and it blew up). taping the inside with out wrinkles is the hardest part if you have a long thrust tube.
Tumbler is online now Find More Posts by Tumbler
Reply With Quote
Old Sep 28, 2011, 01:43 PM
Registered User
Joined Mar 2011
72 Posts
I just built a Sapac viper and the thrust tube they had went together very well. It was glued with thin ca and worked very well. What type of material is it?
airraptor is offline Find More Posts by airraptor
Reply With Quote
Old Sep 28, 2011, 01:44 PM
Registered User
Tumbler's Avatar
New Jersey
Joined Feb 2003
7,903 Posts
The Sapac planes I have had had plastic thrust tubes. not Mylar

Quote:
Originally Posted by airraptor View Post
I just built a Sapac viper and the thrust tube they had went together very well. It was glued with thin ca and worked very well. What type of material is it?
Tumbler is online now Find More Posts by Tumbler
Reply With Quote
Old Sep 28, 2011, 01:44 PM
Registered User
Doug Bateman's Avatar
Swarthmore, PA 19081
Joined Dec 2004
2,832 Posts
I use packing tape on outside, 3/4" scotch tape on inside. Packing tape on inside is hard to do without wrinkles as mentioned.
I mentioned mylar but it is thin sheet plastic from Tamjets, that i use.
Doug Bateman is offline Find More Posts by Doug Bateman
Reply With Quote
Old Sep 28, 2011, 02:16 PM
My project: FAIREY DELTA 1
Erik v. Schaik's Avatar
Uden Volkel, Netherlands
Joined Dec 2003
4,968 Posts
Cone program works great for intake tubes as well.
For not round intakes just tape around the former and measure the lenght of tape Dia=lenght/3.14 which can easely be used for cone program which is pretty accurate. Importing a pic into CAd to measure FSA is a great tool as well.

Wiring the leads the Ralf Dvorak method prevents cracking the mylar which should give max strenght to the thrusttube. if this is not possible I always add a wiring hole in the overlaps where is more strenght. I use dremel tools to dremel round holes so there is no corner for cracking.

good luck on your builds!
Erik
Erik v. Schaik is offline Find More Posts by Erik v. Schaik
Reply With Quote
Old Sep 28, 2011, 06:20 PM
Da' Cajun
Boogie_'s Avatar
Lake Charles, Louisiana
Joined Jun 2009
2,843 Posts
Quote:
CA won't glue true mylar (which is not clear, it's more of a opaque white).
Probably right, I think I'm using Duralar(?).
CA loves it.

Good stuff Erik.
Boogie_ is offline Find More Posts by Boogie_
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Equation for figuring the thrust tube on an edf?... FSA?! turbored21 Don's RC 23 Aug 24, 2013 03:54 AM
Idea Found easy thrust tube for HET 6904 soundguy63 Electric Ducted Fan Jet Talk 2 Jul 31, 2011 02:16 PM
Discussion What to use for EDF thrust tube? profilefan Foamies (Scratchbuilt) 0 Jan 22, 2010 01:24 PM
Yippee! Thrust tube for EDF... Mike_eee Electric Ducted Fan Jet Talk 1 May 08, 2009 06:45 AM