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Top-rc F-4

Old 02-15-2024, 02:21 AM
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Thanks very much for those helpful comments. I m going with inverting the tanks for now. Its not ideal but I d feel happier flying that way and will use a brass tube section in the tygon pick up line to keep it from twisting. If the model flies nice, then as I said it will deserve some better custom tanks, access is easy to swap out the tanks at a later date. I m not impressed with the manufacturing quality of the glass fibre tanks as supplied, and can see long term problems, in partcular the seams and glued joints.

I m using a MAP bubble trap for twin tanks, so each tank has a direct feed to the trap.
Old 02-15-2024, 05:17 AM
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Originally Posted by Edhamp
Thanks very much for those helpful comments.

I m using a MAP bubble trap for twin tanks, so each tank has a direct feed to the trap.
Ed, you need a center tank plus the UAT. Iíve seen and been involved when saddle tanks independently go direct to the UAT. If one tank draws the fuel faster than the other, or the clunk sucks air. The UAT will still empty for the flame out, with as much as half or more fuel left in the opposite tank. The other issue I have experienced is that when fueling and the jet isnít level, one tank fills faster than the other. And when done, one tank will siphon from one tank through the UAT to the other tank and into the overflow tank, or onto the ground. Once the siphon starts, the only way to stop it is to plug the overflow, or pinch a line.
Off of saddle tanks, you always need a T with equal lengths of fuel line to the center tank or the UAT.
If you donít believe me, you can do an experiment on the bench with the tanks. Use your 5 gallon fuel can and pump to suck the fuel out of the UAT engine out line to the engine fuel pump. Even with equal lines, elevate one tank when filling. One tank should fill faster than the other, and once pump pressure is off, it should siphon from high tank to lower tank and into the overflow tank.
Best wishes!
Old 02-15-2024, 06:00 AM
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Yes I do have some concerns as you have observed but this set up was suggested to me by someone who should know what they are talking about. I had planned to use a Tee with a single fuel feed to UAT fuel inlet (its worked well on my F16). I will test the set up first as you suggest to see how it behaves, and change it if no good. The tanks need to fill and drain equally in simulated conditions to pass the first test. All lines feeding the UAT will be equal length. Thanks very much for the heads up.

Last edited by Edhamp; 02-15-2024 at 09:04 AM.
Old 02-15-2024, 02:03 PM
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Mine is plumbed in series to a 24oz header tank then to a UAT.
Old 02-15-2024, 02:31 PM
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Originally Posted by tp777fo
Mine is plumbed in series to a 24oz header tank then to a UAT.
Another safe option. I know itís a very small amount, but on the high performance aircraft, I donít like the longitudinal imbalance and can tell in the roll axis. Itís as much of an irritant to me as the lateral balance changing when burning off fuel.
Old 02-16-2024, 04:16 PM
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The saddle tanks fitted inverted. It did need about a 1/4" wood removing from the former that the bottom of the tank sits on, which I re-enforced with a ply doubler just in case. There is just enough room for the top engine cover to clear the top of the tank at the front. The tank is secured with an aluminium L bracketts attached using hysol.
You can also see how much forward the engine can be moved and the stainless steel extension piece I made to the thrust pipe which makes use of the existing nut and bolt screw fixing holes on the bell housing end and is pop riveted at the other end. This mod should save quite a bit of nose weight with minimal effect on performance but can be reversed easily if required.
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Old 02-16-2024, 08:37 PM
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Default Tank set up

My Skymaster F4s use similar set up with low area backside. They are plumbed from top down and have worked great for years of flying. If your tanks have hole in front, I would just seal and drill new hole from top!!
Old 02-19-2024, 12:51 PM
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Thanks for your tank plumbing suggestions. I did some tests today and the MAP dual inlet UAT that was reccomeneded worked well as a bubble trap and header tank combined. In my set up , with one tank empty, fuel was still being drawn from the other tank into the UAT rather than air from the empty tank.

With the engine and tanks fitted, I can work towards final installation. I fitted some Unilight afterburner lights (the model comes with an arrestor hook but I ve left this off for now). A Phantom withpout afternurner lights just is not right!

My model did not come with the nose battery cradle shown in the manual. I do not know if this is a later change or not. I make my own solid battery mounting tray in the nose cone for the turbine battery, using 3s 3500mah on this one, the radio and gear batteries are as forward as possible in the nose. To ensure a secure fit, I attached the nose cone to the nose with an additional wing type nut and bolt arrangement . Coupled with the factory fitted locking system and pin which is well thought out, the heavy nose , which also carries some lead to balance the model, is properly secured. Also it a quick job to put together in the field without any tools.
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Last edited by Edhamp; 02-19-2024 at 02:00 PM.
Old 02-19-2024, 01:00 PM
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Afternoon Ed,

Iím glad that you did a fuel tank test. Did you happen to take any pictures of it? How it all connected together? To help figure out why we had the siphoning issue. Itís been a few years ago, and I think it was an interico dual UAT. But truly donít remember. I just remember T fittings fixed the problem.

Thank you Ed for sharing your experiences and findings!
Dan
Old 02-19-2024, 01:22 PM
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Some pictures of the assembled model. Still some installation to do internally and the main legs need some shims to correct the angle, but most items in place if not connected yet. Really that is about all I have to add to this thread. Final balanced model weight, dry without the drop tanks is 17.8kg which I am very pleased with. I have a suspicion the factory cg (358mm from leading edge) stated in the manual, which is just about the centre of the wing tube, may be a bit nose heavy (the tanks as located result in virtually zero cg shift full or empty). I balanced gear down and no fuel. The control throws suggested in the manual seem a reasonable starting point. I suspect that elevator will be very effective.

Anyone who has flown this model would be great if you could chip in with thoughts on cg and your set-up.

Overall,subject to flying I am really pleased with this model. It looks fantastic and as good as if not better than many costing twice as much. Replacing the current gear drive with Electrons looks an easy swap if proves necessary and my only real complaint is the rubbish manual and poor fuel tanks design/quality.

Ed
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Last edited by Edhamp; 02-19-2024 at 01:26 PM.
Old 02-19-2024, 01:46 PM
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Originally Posted by RCFlyerDan
Afternoon Ed,

I’m glad that you did a fuel tank test. Did you happen to take any pictures of it? How it all connected together? To help figure out why we had the siphoning issue. It’s been a few years ago, and I think it was an interico dual UAT. But truly don’t remember. I just remember T fittings fixed the problem.

Thank you Ed for sharing your experiences and findings!
Dan
Thanks Dan. Each tank is connected to a UAT dual inlet direct. The tank vents are connected to a t-piece with a single exit. All pipe runs equal length. All lines are at least 4mm ID. The MAP has high-flo nipples almost 6mm diameter. I did not take pics but I guess the MAP trap seems to work well here. I also beleive that that you must uses high flo felt clunks.
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Old 02-19-2024, 02:47 PM
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Show us how you attached your main gear doors.
Old 02-19-2024, 02:50 PM
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Originally Posted by tp777fo
Show us how you attached your main gear doors.
See post 21.
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Old 04-21-2024, 02:54 AM
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Any updates from anyone? Final thoughts on the kits and flight characteristics?
Old 05-06-2024, 04:31 AM
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MLG strut broke yesterday during test flight taxi test. Top RC is aware of this problem and will provide new struts for V1 owners.
Old 05-06-2024, 04:40 AM
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Ouch.

That thing going to be at Nall by any chance?
Old 05-06-2024, 09:34 AM
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Originally Posted by tp777fo
MLG strut broke yesterday during test flight taxi test. Top RC is aware of this problem and will provide new struts for V1 owners.
hey amigo how did you break an F4 strut? Those things are beefy!!! Any other damage to framework?
Old 05-06-2024, 04:57 PM
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Design flaw known to top rc and being corrected. They are providing V1 owners new struts. Mine broke during taxi. Yes, I will be at JN. The F4 may be there for sale.
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Old 05-06-2024, 05:23 PM
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Is this truth that top Rc is owned by the FEJ former partner and part owner? Thatís what I heard .
Old 05-07-2024, 03:50 PM
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Originally Posted by tp777fo
MLG strut broke yesterday during test flight taxi test. Top RC is aware of this problem and will provide new struts for V1 owners.
Do you know what are differences between version 1 and later models. Got a photo?

Found another video of this thing flying, much better display than the earlier ones I seen. Looks to fly well and nice landing, certainly able to fly slow and tight with the P47s in the circuit at the Prowing show in Germany.

Old 05-08-2024, 07:37 AM
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No
Old 05-10-2024, 07:03 AM
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Judging by the lack of input into this thread I wonder just how many there are out there. Certainly TopRC F4 seems more popular in Europe looking at various forums, videos and the many dealers that carry them. A dealer in Italy had been advertising a V2 version for some time. He said they had modified the rudder set up and UC mounting geometry but was not specific. I had no trouble fitting my UC so I am hoping it is a V2. On one you tube video mentioned earlier the wheels are facing outboard, on another it looks like the owner opted to fit Electrons, neither of which are a good look scale wise even though Electrons are generally rock solid.

Last edited by Edhamp; 05-10-2024 at 07:11 AM.

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