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Sep 10, 2016, 08:02 AM
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Build Log

F-15 Eagle - 64mm/70mm 1000mm(L) - Tian Sheng

Wow, this is an OLD jet of mine! I think I bought it as a kit 5 years ago, but never finished building it! Or it might have even been a PNF, with a pathetic 64mm 3S setup.... as per my F-18 had been.

When I got it I started building it up, but seeing the F-18 was anemicly powered I decided to change the 64mm fan to a 70mm CS10 setup. Plus add retractable landing gear.
This delayed things so much, and caused so many pauses "to think how to do things" that I lost interest, but still did a BIT now and then.... never finishing it.
A few weeks ago I decided to get it out and finish it!

It is a very old generation foam model... one of the very early designs. In foam terms that is still ok, but it is a very basic foamie jet.
I don't think you can even find/buy them anymore, but there are other better F-15's around now anyway!

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Sep 10, 2016, 08:08 AM
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Fan and ducting

When I first put a 4S CS10 setup into the F-15, the output thrust was WEAK. A fan capable of about 1.5Kg thrust gave out 600g from the F-15! This was due to the highly restrictive exhaust outlets.

I sanded those right out to as large as they could be, which is close to just right for a CS10 as it turns out.
I also cut and sanded bevels onto the inlet duct openings.
The thrust was then a bit over 1.1Kg... which is not bad seeing you will always have SOME losses anyway. I also need to re-test that in its current shape/state....

Instead of gluing in the fan as per stock, I added some plywood rails to mount the EDF onto.

In this recent resumption, I changed the ESC to a 80Amp YEP and mounted that right ahead of the fan using velcro and a clamping plate.

Sep 10, 2016, 08:11 AM
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Battery area

Seeing the jet is made to carry a 3S 2200mAH battery, which is pretty light, there was a big problem in getting a 4S 2650mAH 40C+ to ever have the CofG set correctly!! By a LONG way!
So I modified the battery area to allow the battery to go way more rearwards - which is also why the ESC was put right ahead of the fan. To be more rearwards and also to allow the battery to come more rearwards.
Even after doing that it is very nose heavy!

Sep 10, 2016, 08:20 AM
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All Moving Tailplanes

One thing I had done when I first got it, was to remove the FIXED Tailplane and Elevator setup it came with, and set them up as All Moving, Horizontal Stabilisers. I had made up a plywood block pivot system, but it was not really adequate.

Now that I have some 3D printers, I could design and MAKE a proper pivot block!

The HStabs have a 3.5mm fiberglass shaft fixed into them now, so that is the pivot rod. This runs into a pivot block in the fuselage. To keep the HStab in place there is a 4mm wheel collar that sits within the pivot block, thus the pivot rod cannot move outwards.

The control horn for the HStab is an alloy plate that is epoxied onto the HStab inner face, but it also has the pivot rod passing through it which means it is very well affixed and ends up sort of being an extension of the pivot rod too.

I also made some servo mounting trays so that the servos are easily removable. The servo is put into the tray and then a screwed on cover plate clamps the servo down into the tray.
The servo extensions coming from the front RC/RX area are locking tab types, so you plug in the servo and feed it into the fuselage, for future disconnection ability.

I used the HobbyKing alloy clevis at the HStab control horn - and a Z-bend at the servo. With all pivot points perfect fits so that there is virtually zero freeplay in the HStabs.

Sep 10, 2016, 08:29 AM
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EDF cover, Ordinance rails, and Retracts

You might have noted in some pictures here that I REMOVED the retractable landing gear and filled all the openings with balsawood etc.
This was because the added weight was too much, AND seeing I fly from grass the retracts on such small jets rarely work well, or last well. So out they came again.....
I will be bungee launching this jet!

With the mods to the fan area, the stock EDF cover screw system cant be used, so I made a plywood plate/strip to glue onto it and those bolts do up into internal plywood plates with captive nuts.

You might also have noted my F-15 is ALL grey. That is because I primer/undercoated it in Enamel spray paint. I was intending to paint it to the more common mid/light grey, but I might not do that scheme.
The problem with that scheme is that it is ALL grey! Not a good colour for orientation or longer distances!

One option to help break up that "same colour on top and bottom" was the idea to add the ordinance rails with a few (4) AIM-9 Sidewinder missile fitted. Thus adding some WHITE to the underside.

I made those up. Balsawood rails and 3D Printed AIM-9 missile.
I would fit the rails as permanent, and the missiles as removable. Though the rails would be the same colour as the whole jet, so you really need the WHITE missiles there.

Sep 10, 2016, 08:37 AM
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Almost ready to fly....

To balance the F-15 it needs 80 grams of lead weight right at the tail end!
The AUW, with the lead and also a 4S 2700mAH 65C Nanotech battery, is 1250g.
That is OK.... possibly a little bit heavy if you ever wanted to hand-launch it - or you better be able to give it a very good FAST throw!
Thus why a BUNGEE launch setup is much preferred!

I used a FRsky X4R RX, seeing it only needs 3 channels anyway, and that is a very light full range RX.
I just to work out where and how to affix the lead weights efficiently, and make some hatch hold down system, and then it is ready to test fly.
I will not paint it until it FLIES.... maybe it would be destroyed on the maiden, or first day! lol

It was a long drawn out project, and even probably a bit more effort than it is worth.

You might see I have the Tian Sheng F-16 listed in the blog somewhere... it is heavier and uses 6S! But I do not like the way it flies!! That was also modified for All Moving Tailplanes, and I think they way they operate in the airflows off the wings is what makes the plane act 'weird' when you do pitch changes. Something like they are 'weak' in their centre area range, but then pitch forces exponentially increase as they come out of that airstream. Whatever it is, it makes it hard to fly nicely - or to feel comfortable flying it!
The F-15 could very well fly that same way...

(more pics of the final state to come)

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