F-15 (Jetset44 ) 70mm EDF Conversion - Page 2 - RC Groups
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Feb 01, 2013, 06:33 AM
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Thanks CoolerByTheLake,

You guys are so inventive and creative… seriously inspired!
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Feb 06, 2013, 05:10 AM
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Hi all,

Talk about a steep learning curve!

Main design changes Ė
  • The system now has a Constant Area Inlet at @100% FSA.
  • The inlet profile remains the same for as far as possible, only transitioning on the straight before the fan - 2nd pic.

I have also carried out fairly crude flow simulations to help tweak the design ref. keeping the velocity through the inlet constant for as long as possible.

Gery (Gdimonte) is going to make a start on the fibreglass ducting as soon as we are happy. This is fantastic as he will be able to test the system before the design is complete.

Flow simulation on YouTube -

F15 EDF Ducting Flow Simulation Std1 (5 min 0 sec)
Feb 06, 2013, 05:21 AM
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Great work really impressive.
Feb 06, 2013, 02:02 PM
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jetset44's Avatar
Wow, Steve, your design and 3D CAD skills are amazing! Great work! The ducting drawings, especially.
Feb 08, 2013, 09:10 AM
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meerkat13's Avatar
Thanks Steve & Dennisp_sq,

I'm defiantly one of those people who learn by doing... and making those all important mistakes.

Hand on heart I can say that I have learnt more in the past couple of weeks then over a year of flying RTF models.... scratch building rocks

Hopefully get the ducting design finished over the weekend. We want to change the exhaust slightly to be more in-keeping with clausxpf fantastic thread - Ducts for EDF's

Its scary to think how long it would take to get to this same point without the shared knowledge and experiences given freely from everyone.

Cheers, have a good weekend.

Feb 08, 2013, 09:40 AM
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Weights & Wing Load Estimates

Hi all,

I have done my first estimates for weights & wing loading and would really appreciate anyoneís thoughts /comments on the results.

Geryís Configuration ( 34Ē Wingspan )
  • Wing Area : 403.318 sq in
  • Estimated All up Weight : 1545.5 gm (54.52 oz)
  • Wing Load : 19.46 oz/ft^2
  • Cubic Wing Load : 11.63 oz/ft^3
  • Thrust to weight ratio 1.1 : 1

SteveJís Configuration ( 34Ē Wingspan )
  • Wing Area : 403.318 sq in
  • Estimated All up Weight : 1765.5gm (62.35 oz)
  • Wing Load : 22.26oz/ft^2
  • Cubic Wing Load : 13.3oz/ft^3
  • Thrust to weight ratio : 1.39 : 1

The attached PDF details the weight estimations for 2 configurations.

Cheers, SteveJ
Feb 08, 2013, 11:08 AM
Registered User

If you search on "FSA Calculator", you should find a calculator that does inlet and exhaust parameters. It's all based on inside shroud and rotor hub diameters. It not only does single exhaust, but also bifurcated exhaust. You may find this very useful, as it provides diameter of the exhaust based on the FSA% you prefer. I also read Clausxpf's info on ducts. Great work your doing!!!

Update: Check out SteveC68 blog for two useful calculator's. These are excel spead sheets that do the work (number crunching). Just provide input parameters.

Last edited by ksqm; Feb 08, 2013 at 11:20 AM.
Feb 08, 2013, 02:54 PM
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Thanks ksqm for the links.

We actually used SteveC68's FSA calculator (thanks Steve) which worked great.
Feb 09, 2013, 05:13 AM
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Just finished the revisions to the exhaust duct design.

The velocity is still a bit slower towards the outer most area but much improved with the new exhaust nozzles. The nozzles also sorted out the inward vectoring problem.

Itís going to be interesting to see how this performs in the real world. Gery is going to do the physical testing of the system before we get too far into the design. At least this way we will have a good idea of what thrust we have to play with.

The PDF just shows the before and after results.

Cheers, SteveJ

FlowExpress F15 EDF Exhaust Std2.mp4 (3 min 10 sec)
Feb 09, 2013, 05:24 AM
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Amazing work, the video is very impressive.... Well done.
Feb 09, 2013, 06:59 AM
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meerkat13's Avatar

Fabrication methods for Exhaust

As I know very little about fibre glassing or mould making I thought I would put together some thoughts on how we could build the exhaust part of the ducting.

CoolerByTheLake posted me this link which has some great techniques in by AIR SALLY (start at page 605).

F15 Exhaust Mold Options (5 min 39 sec)
Feb 09, 2013, 07:33 AM
Do it Right, the first time!
CoolerByTheLake's Avatar
"As I know very little about fibre glassing or mould making I thought I would put together some thoughts on how we could build the exhaust part of the ducting."

Try not. Do or do not, there is no try.
-- Yoda
Mar 07, 2013, 02:46 PM
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Just a quick update.

Gery is having a go at prototyping the exhaust as a lightweight glass fibre assembly. After several adaptations the Inlet ducting is almost ready for drawing up.

While Iím waiting for my bits to come from HK I thought I would have a play with some Depron. For the 1st trial I drafted the front section of the F15 in a fairly traditional former & stringer interlocking method. I nested and printed the profiles, cut them out in 3 & 6mm Depron and have just finished gluing them up.

Once dried I will skin the frame in the 3mm Depron and then have a go at finishing in fibre glass Ė a first for me.

The main point of the exercise is for me to get a feel for the material and also trial different design approaches. Also it will allow me to test the my SolidWorks material setting, both for weights and for my material bending / rolling allowances for Depron.

Iím really enjoying the whole experience and itís been great doing some actual building.

Mar 07, 2013, 02:57 PM
Do it Right, the first time!
CoolerByTheLake's Avatar
Here's a little something on intake design.

Mar 07, 2013, 03:19 PM
Registered User
meerkat13's Avatar
Thanks Cooler,

How is the foam forming going?

I have just got the book you recommended on building with foam - a very good easy read.

Another good book I have is - Radio Control Foam Modelling by David Thomas and has a good section on skinning and vacuum bagging.

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