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Old Jul 04, 2009, 12:21 PM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
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Philip Avonds F-15 twin SM110-52 Stumax fan

Hi there,

I woud like to tell few words about the subject but, first...
I ask apologies for my english, I'll try my best!

Following the suggestion given by some members here on RcGroups, I am starting this thread to share and receive help from all of you willing to give!

I have finally decided how I want this thing done, now that big EDF are proving what they are capable of, bigger and bigger airframe will be seen around, I just hope it will not take too much time for me to finish this up.

It has been a while that I have it in the corner of my workshop actually, but never been really convinced about its original propulsion system (single Ramtec fan and OS-Max 91 VRDF with JMP System II pipe), so I just kept it there for better time...turbine or ???!
My friend (Arfio) wanted to convince me to go turbine but I rejected the idea for semplicity of use (electric is still the easiest way)!

Actually my friend 'Arfio' has an Avonds F-104 perfecty UN-built that should be treated just like my F-15...with an electric cure , but he is hard to be convinced ehhh!!!!
Maybe we can send PM to his box all together asking him to take this route???
...it would be nice to see an Avonds F-104 pushed by a Stumax or Dynamax fan, isn't it??

Well, I initially thought to convert my F-15 to EDF by using a Ramtec or Dynamax and keep everything that was supplied with the kit just like it was in the original project (ducting, wood, landing gear, all...) but I shortly realized that even if the performance would be increased... this won't make me really happy performace wise so, after some mails, posting and chatting I started to think that a twin could really be what I want...except for the involved!

The power available will fly it with authority and should also allow enough throttle back in flight to extend the flight duration to a decent value!
Browsing the web I took inspiration from Jet Hangar Hobbies that is still offering the original Avonds F-15 twin (winner of the W.M. long time ago) with different propulsion systems: twin E-Turbax or IC and of course turbine!
After looking around a little bit more I thought that two SM110-52 would match the airframe well, match the JHH ducting (120 mm diameter) with minor adaptations and of course add the benefit of the sweetest sound I ever heard to the package!

Also because the two intakes must provide enough air to each fan, I thought that going with the smaller SM110-52 could perform better!

Right now I placed my order for the two Stumax, plus the ducting from JHH, but at this point my Spring-Air retracts (originally used) are no longer usable with the twin onfiguration since the space for the gear retraction will be taken up by the ducting, so I ordered two main rotating retract from Tam Jets to allow the wheel to seat flat under the ducting!
I really hope everything will match one another when I will have all in my hands!

That's all for now guys, there's nothing else I can say...just patiently wait to receive all!
Of course I am more then happy to answer questions that will come!

Gianluca
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Old Jul 04, 2009, 12:29 PM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
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LOL

Just have seen all the encouragement received in the Stumax fan thread about this one of mine!

Thank you guys I will keep going!
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Old Jul 04, 2009, 01:56 PM
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Signing on. I have an F-22 coming that is about the same size as your F-15.
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Old Jul 04, 2009, 02:13 PM
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it should fly good with a pair of stumax fans.
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Old Jul 04, 2009, 02:40 PM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
Joined May 2004
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Thank you Ron,

I wish that your F-22 will arrive soon...are you thinking to twin as well or single Dynamax maybe?

The Avonds F-15 is 1:9 scale and the specs are:

Length is 85" (2,16 m)
Wing span is 57" (1,45 m)
Weight (D/F) 16lbs (7 kg dry) as per instruction

Now I would like to guess the predicted weight of the model by following some simple considerations about D/F stuff.
I did the math an this is what theoretically should be the weight of the components I can get rid of

Ducted Fan stuff:
3 fuel tank system (all included) = 235 g.
1 Ramtec ducted fan = 600 g.
1 OS 91 and JMP System II pipe complete = 950 g.
TOTAL = more or less 1,8 kg

This mean that from 7 kg I am going down to 5,5 kg without the list above.


EDF system:
1 Stumax fan complete with motor is 700 g.
1 Phoenix 110HV is 150 g.
1 12s Lipo 5000 is 1,5 kg (more or less)
Total for twin is 4,8 kg, so make it 5 kg

This will bring the weight up again till 10,5 kg

Then there will be other things to be added, for example I will have another duct installed for the second fan, then also scale retracts and struts, then some other things around that right now I can't compute precisely but all them together will probably bring the weight up till 11,5 or maybe 12 kg...this is my guess work till now...so we are talking about 25 1/2 to 26 1/2 lbs!

What I really hope is that my calculation of the D/F stuff is wrong, so I will be able to lower the predicted airframe-only weigth a little bit more.

Gianluca
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Old Jul 04, 2009, 05:27 PM
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Quote:
Originally Posted by felix72
Thank you Ron,

I wish that your F-22 will arrive soon...are you thinking to twin as well or single Dynamax maybe?
F-22 has those two big motor housings on the back just like your F-15, so it has to be a twin. Interferance with retracts???

Oh, Felix, one other thing. Your english is as good as any, better than most.
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Old Jul 04, 2009, 05:52 PM
GRX
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Quote:
Originally Posted by felix72
LOL

Just have seen all the encouragement received in the Stumax fan thread about this one of mine!

Thank you guys I will keep going!
Keep up the good work and keep us posted, I've got a StuFan based project currently in the works. That F-15 is gonna be really sweet sounding on the twin setup.

Goulet, where are you on the twin TJ powered Mig?
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Old Jul 04, 2009, 06:13 PM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
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Quote:
Originally Posted by Ron Pogue
Interferance with retracts???
Ron,

the Avonds F-15 designed for a single Ramtec in the center allow the two retracts to go up and rest each sides of the fan.

Now with the two ducting running on each side of the fuse the space will surely be in the center (where I have idea to put the batteries) but no longer on the sides.

In the JHH version of the Avonds F-15 (made for twin turbax and not for single ramtec) they were using rotating retracts like for example the one you can find on F4U corsair or P-40. Unfortunately no more retracts available from JHH so I had to look around to find suitable substitute and I believe the Tam Jets will do the trick.
I have not seen the Tam's retracts yet (USPS is taking care of their journey to me), nor I have seen the ducts (JHH have to fabricate them after my request), so I don't really know how they are going to work together.
What should happen is that the retracts will rotate 90 while retracting, leaving enough space above them to allow the duct to pass!

I cross my fingers!

Gianluca
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Old Jul 04, 2009, 06:19 PM
Jets fly goooood!
felix72's Avatar
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GRX,

I am very curious as well to know, see and hear how the two Stumax are going to sound together...resonance wise and also the resulting compounded sound!

I am starting to be scared by the recharging time considering that I will have to use 4 6s pack of about 5000 mah!

If the R.T.F. weight will really end up lower I could consider an 11s instead!

Gianluca
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Old Jul 04, 2009, 06:58 PM
Xtreme Power Systems
Lake Havasu, AZ
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Our Skymaster version weighs 27 pounds and uses only tailerons. The flaps, ailerons, and rudders are glued in place. So, this reduces the weight by a pound or so due to not having the servos and supporting hardware for these surfaces.

We flew the last one on tailerons only and I think it flys better this way.

The Stumax fans sound GREAT!
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Old Jul 05, 2009, 02:06 AM
Jets fly goooood!
felix72's Avatar
Italy, Lazio, Ariccia
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Jim,

the Avonds F-15 is working just the same way, only tailerons!
I will not add ailerons on mine, not needed...but I want the rudder for sure and maybe I can consider to add flaps, even if the model doesn't need them, for scale apparence and also to change the AOA in approach, but I still have to decide on them!
You know the F-15 has a short distance between the two mains, I will use rudder and gyro to have full control over the yow!

I don't know how much che Skymaster F-15 weight naked, but you are starting to make me think that I could easily hit 12 kg on mine, and I don't like it!!!

About the retracts, I don't know if the picture is showing exactly the rotating version, but they look cool!

Gianluca
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Old Jul 05, 2009, 12:15 PM
Xtreme Power Systems
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You don't need rudders or a gyro. Take offs and landings are quite easy without either.
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Old Jul 05, 2009, 01:07 PM
Jets fly goooood!
felix72's Avatar
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Normally yes...I do agree Jim!

but in windy condition the F-15 is easy to overcontrol and touch the runway with the wing tip, and then also...
how could I do my knife edge flight all the runway long???

Gianluca
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Old Jul 05, 2009, 06:51 PM
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Quote:
Originally Posted by felix72
Actually my friend 'Arfio' has an Avonds F-104 perfecty UN-built that should be treated just like my F-15...with an electric cure , but he is hard to be convinced ehhh!!!!
Maybe we can send PM to his box all together asking him to take this route???
...it would be nice to see an Avonds F-104 pushed by a Stumax or Dynamax fan, isn't it??
Gianluca,

I have the Avonds F104 kit as well and was thinking about the Dynemax for it. I'm waiting to see how it goes in the F18 I'm building currently.

The Avonds F15 is a wonderful model, and the few that I've seen fly have all flown very well. Also, Philip is fantastic to deal with which is a very nice bonus.

Looking forward to watching your build thread.
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Old Jul 05, 2009, 09:04 PM
Xtreme Power Systems
Lake Havasu, AZ
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Quote:
Originally Posted by felix72
Normally yes...I do agree Jim!

but in windy condition the F-15 is easy to overcontrol and touch the runway with the wing tip, and then also...
how could I do my knife edge flight all the runway long???

Gianluca
You can't knife edge the Skymaster F-15, even with huge deflection of both rudders and 100+mph, it just slowly falls. You can see in the video from San Diego there is a long bananna pass... that is without any rudder.

Even on very windy days, you don't have to worry about not having rudders. We have 3 huge F-15's here (two that are 9' long, and the Skymaster @6') for a reason... they are absolutely a pussy cat to fly. No bad habits, easy to take off, and easy to land. In fact, it's a bit embarrassing when people come up to you after a flight and tell you how good you are. LOL!
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