Jett in a CBM F-16

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Goggles -> Jett in a CBM F-16 (4/30/2002 5:00:29 AM)
Gotta love support from the manufactureres. I have a Combat Models F-16 I'm building and was thinking of putting in a Jett .50 RE. What type/brand of pipe do I need for the engine? Also I have read that when you place the order for the engine you tell Jett that it's going into a CBM F-16 it will be set up for you from the factory. Is this the case also? In the CBM F-16 will I need a pump to pull the fuel from a mid-mounted fuel tank or will just a hopper tank at the engine and engine pressure be enough? What RPM will it turn out and what kind of speed do you think it will achieve? Thanks for your help. Kelvin.

bob27s -> Jett in a CBM F-16 (4/30/2002 9:42:49 PM)
Kelvin, The SJ-50 has been used in the CM F-16 very successfully. Infact, I believe there was an RCM review of the kit in November 1998 in which the Jett 50 was used. Its a great powerplant for the application. I think this link still works http://members.aol.com/cbmjets/homepage/rcmf16n.html If you are going with the FIRE engine and pipe combination, have JETT tune and test the pipe for you. Dub makes a few small modifications to the pipes, and you get a welded assembly. You can use a small U shaped return to exit the exhaust backward. Unless you will be doing long vertical manuvers, you will not really need a pump. The pipe arrangement will provide solid tank pressure. The small header tank is probably worth while, as long as you ensure that the fuel system is leak-free and it stays filled. RPM you can expect from a FIRE 50 will be around 17,000 rpm or better. The pipe set-up will determine what RPM range you will have to maintain. Be sure when you order the engine to identify which pusher prop you will be running, so he can set up and tune the pipe for that prop. I hope this is helpful! Bob

TopShelf -> Jett in a CBM F-16 (5/8/2002 2:08:21 AM)
Bob, I am putting a Jett 50 in my CBM F-16N and am planning on using a header tank. Will a one ounce tank be big enough? Thanks.

bob27s -> header tank (5/8/2002 2:46:09 AM)
[QUOTE]Originally posted by TopShelf Bob, I am putting a Jett 50 in my CBM F-16N and am planning on using a header tank. Will a one ounce tank be big enough? Thanks. [/QUOTE] Yes, a one oz tank will be more than sufficient as a header tank for the F-16N. :) Bob

Craig-RCU -> Jett in a CBM F-16 (6/8/2002 9:25:57 PM)
[QUOTE]Originally posted by bob27s Unless you will be doing long vertical manuvers, you will not really need a pump. The pipe arrangement will provide solid tank pressure. The small header tank is probably worth while, as long as you ensure that the fuel system is leak-free and it stays filled. [/QUOTE] If by "vertical maneuvers" you mean +- 2 degree attitude maneuvers then you don't need a pump. If you want to climb or dive at more than +-2 degrees for any length of time, then you need a pump. I have tested the Jett FIRE 50 without a pump in my CBM F-16N and it can only handle about a 2 degree attitude change operating on pipe pressure alone before the engine quickly either starves or is flooded (pipe pressure cannot stop the weight of the fuel in the 3 ft lines from rushing into the engine in a nose up attitude). The tanks in the CBM F-16N are 3 feet away from the engine. This is the furthest distance between a tank and engine that I have encounterd in a R/C model. If the CBM F-16N doesn't need a pump, then nothing does. Pipe pressure and a header tank will not substitute a pump. It is enticing to think that having a header tank close to the engine will cure any fuel draw problems but, fuel is an incompressable fluid and thus is subject to the laws of hydraulics. This means that, when the fuel tanks and lines are full, no fuel can be drawn from the header tank unless it is also drawn into the header tank from the main tanks three feet away from the engine. The header tank is essentially just a "bulge" in the fuel line and will not help you break the laws of hydraulics. So, the only benefit of a header tank will be to trap air bubbles from the main tanks. A pump is not optional on this plane unless you move the main tanks to within 6" of the engine, then you will have ballance problems instead. Have Jett engineering set up your FIRE 50 with the VP 30 regulating pump and an APC 10x6 pusher prop. They guarantee their setups to work I believe. I did not have them set mine up and am having overheating problems. I did not specifiy that I needed to turn an APC 10x6 pusher and it was set up with a Bolly 10.5x5 tractor prop. The Bolly prop is not as much of a load as the APC and I think the overheating is caused by the pipe being too short for the APC. I am going to try retuning the pipe myself before send it back to Jett for setting up-- just to warn you Bob27. :D

bob27s -> F-16 feedback (6/10/2002 6:13:00 AM)
Craig, It is always good to have various feedback on installations like this. Helps build a good data log to work from. Some guys have run pumps, and the installtion works well. Others have managed without them. I guess some of that had to do with whether they chose a side exhaust or rear exhaust engine.... apparently that affects where you can install the fuel tank within that aircraft. The jett SJ-46 powered F-16N I flew last summer had only a header tank, and the engine ran quite well Dub's pipe set-up is a bit of a modification to a standard Mac pipe. He does a few tricks to improve fuel draw and performance. If you call, you can learn if you can simply tweek your exisiting pipe installation, or if something more involved is in order. If anyone has any sort of concerns at all about any application, feel free to drop Dub an email [email]jett@jettengineering.com[/email] or simply call. Dub or Dennis are always willing to help their customers. Bob

Craig-RCU -> Jett in a CBM F-16 (6/10/2002 8:29:30 AM)
Bob, Did you mount the tanks in a different location than up by the nose gear in your SJ-46 powered F-16N? Is that how you are able to run it without a regulating pump? I have not had any engine reliability what-so-ever without the pump in my '16N but, I have not tried moving the tanks back by the engine. I also, have not heard of anyone moving their tanks to a different location. I guess that could work if I balance the '16N with the tanks full. The CBM F-16N instructions also list a pump or an engine with a pump as a necessity. Unless... we are not talking about the same plane. CBM makes two F-16's, the F-16N and the F-16T as they call it. The F-16N is the scale, pusher prop version and the tanks are 3 feet in front of the engine. I tested the 'N without a regulating pump and it flooded or leaned with the smallest change of AoA. Since the tanks are 3 feet away from the engine, there is no interference possible between the tanks and whatever pipe you have side or rear unless you mount the tanks in a different place than the instructions call for. The F-16T is the nonscale tractor prop version that looks a lot like the electric, Kyosho F-16. It could also take a Jett 50, but the side exhaust version instead of the FIRE version would be the most convenient.

TopShelf -> Jett in a CBM F-16 (6/10/2002 7:53:28 PM)
Craig, Bob, Man, I am just so confused by this whole issue. Dub, Bob and the guy from RCM say it's no problem to use the Jett un-pumped. Some bench testing I did seems to say it should work Ok. Several like you Craig say it won't work without a pump. I guess I'll just put in in un-pumped and see what happens. In case I need a pump, what is a VP-30? Is that a Perry model number? Kent

bob27s -> Jett in a CBM F-16 (6/10/2002 8:35:40 PM)
Craig, the plane I flew last summer was not mine, but I do seem to recall that the gentlman had the fuel tank located near the CG of the plane. He did this because he was concerned about a tail-heavy aircraft when the tank was empty. From what he told me, this had been a problem on his previous F-16 with the tank mounted further forward. I am not sure exactly how/where the installation was done, but I can try and find out. Kent, the perry pump details can be found at http://www.perrypumps.com

Craig-RCU -> Jett in a CBM F-16 (6/10/2002 8:58:16 PM)
Kent, I am equally confused. As I said in an earlier post, if the CBM F-16N doesn't need a regulating pump with its tanks 3 feet away from the engine, then no model aircraft needs a pump. All engine manufacturers recommend keeping fuel tanks as close as possible to the carb for consistant fuel flow and 3 feet is as far as I have seen on any model. You mentioned that you did some bench testing with success. My bench tests in no way indicated that engine realiability was adequate with the tank three feet away from the engine unless regulated. Did you test with the tank 3 feet away from the engine? Did you then lift and lower the tank from carb height? I found that changing the height of the tank even a little would cause the engine to quit either from leaning when the tank is low or flooding when the tank is high. All I can think of is that I am just too picky about consistant engine performance and should be content with the engine quitting if I climb or dive for more than a few seconds or the guys who say they do not need a pump are actually talking about the F-16T and not the F-16N. I have had some problems with my Jett 50 FIRE, VP-30 regulating pump setup that I am not sure are caused by the pipe not being tuned for the prop I'm using. A tuned pipe that is too short for the prop being used can cause similiar throttling and overheating problems that I have experienced with the Jett 50 FIRE and VP-30 but, I have also had the same problems with the VP-30 and RJL Conquest 15 and Sport Jett 50 engines (both with correct props for their pipes) . The Specific problem that is consistant with these three engines that I have tested with the VP-30 is that fuel delivery at full throttle is not adequate while the midrange remains rich. The similarity among all three of these engines is that they all turn over 16.5k rpms. This leads me to wonder if the VP-30 is not efficient for rpms over a certain amount similiar to how a human heart in "fibrilation" (very fast quivering of the heart muscle) is very inefficient at pumping blood. The VP-30 does work quite a bit like a human heart as designed and must have a "sweet spot" of rpm range that it works best in. This incompatability of the VP-30 and high rpm would also be a good reason for Jett Engineering to say that the VP-30 is not needed in the F-16N since fuel flow consistancy is not greatly improved with a pump that is incompatable with high reving engines.

Craig-RCU -> Jett in a CBM F-16 (6/10/2002 9:12:51 PM)
[QUOTE]Originally posted by bob27s Craig, the plane I flew last summer was not mine, but I do seem to recall that the gentlman had the fuel tank located near the CG of the plane. He did this because he was concerned about a tail-heavy aircraft when the tank was empty. From what he told me, this had been a problem on his previous F-16 with the tank mounted further forward. I am not sure exactly how/where the installation was done, but I can try and find out. [/QUOTE] Bob, That would move the tanks almost a 1.5 feet closer to the engine and fuel flow consistancy would have to be much improved. I am considering moving the tanks back even further than that just because I have found setting up the VP-30 with high revving engines to be such a headache. Moving the tanks well aft of the C.G. should not be a huge problem if I ballance with the tanks full as I mentioned earlier.

TopShelf -> Jett in a CBM F-16 (6/10/2002 9:37:22 PM)
Craig, For my bench tests, I hooked up the tanks with the full length of fuel tubing provided by CBM so I guess that's like 42 inches away and raised and lowerd the tanks. While the engine rpm did change as I moved the tanks, the engine continued to run under most conditions. The main problem I have is at tanks high and low throttle i.e. landing confuguration. However, my estimate was that this was a higher AOA than one would normally land. At higher throttle positions, the engine did not flood. While it is not perfoming perfectly, it was close enough to move on with construction as one cannot duplicate exactly how the engine will react in the model. My set up is a Sport Jett 50 using a 1oz header tank and a YS check valve between the header and the engine. I tried the check valve on the exhaust side but that seemed to flood the engine. I understand your point about header tanks but it did seem to make the set up work better. Kent

Craig-RCU -> Jett in a CBM F-16 (6/10/2002 10:30:48 PM)
Kent, I guess I am just too picky about how consistently my engines run and that is part of the discrepancy between the pump vs. nonpump reliability issues. Your comment, "the engine continued to run under most conditions," would be a reliability concern for me. As they say... "Reliability issues don't get better in the air". If your engine quits at low throttle and a high tank position, then pulling G's and/or a bump of turbulence at low throttle will cause your engine to quit for sure. I don't mean to rain on your parade, but it would sure suck to loose your '16 because of an engine out in a tough situation. I kind of like the throttle stick to just function as a way to control engine rpm and not have to be concerned whether current flight attitude will cause the engine to quit with a change of throttle setting. I am not that great a pilot and that is just too much to think about for me while I'm flying. Maybe not for you. I would at least move the tanks as far back as the C.G.. If you move the tanks back further than the C.G., then you will have to start adding nose weight. How far you move the tanks back is sort of a compromise between more consistant engine operation and keeping the nose weight added to a minimum. The CBM F-16 is very light and could easily handle 1 lb of nose weight if needed but, then vertical performance would be affected. Best of luck.

TopShelf -> Jett in a CBM F-16 (6/10/2002 11:05:17 PM)
Craig, I did intend to say that I would fly the plane with the engine running under "most conditions." I agree that things don't get better in the air. Bench testing is only an approximation of what will happen in the plane. Once I get the engine mounted in the plane, I will do final testing and tuning to determine if I need a pump or not. While it's no one's fault but my own, I'm ticked that this is even a concern. I thought I had reasearched this model thoroughly before selecting my engine. Primarily based on the RCM review, I selected the Jett. The guy made no mention of a pump or any other fuel flow concern. Of course well after I purchased then engine did I start to find posts about fuel flow issues. I am currently running the engine in another plane it it is a great engine. I just hope I can get it running as well in the F-16N. Best of luck to you too.

Craig-RCU -> Jett in a CBM F-16 (6/10/2002 11:52:07 PM)
If you have your Jett in another plane right now, then you are not really out any money. If you can't get things working to your satasfaction in the '16, then you can always put the Jett back in your other plane and go with the Y.S. 45 in the '16. The Y.S. has it's own pump/regulator right on the engine and it worked flawlessly in my '16. It's just not as powerful but, still a great engine for the CBM '16. I have my Y.S. in a different plane right now or I'd reinstall it in the '16 and use the Jett in a more conventionally setup plane. I have been tripped up by a couple "oops I forgot to mentions" too. I found out about using the Jett 50 from Jerry McGee's article in RCM too. I emailed him and found out that he used a VP-30 and that Jett engineering set it up for him. Although he didn't mention a pump in the article, he does mention an inflight mixture control. Was that a clue of fuel flow problems?

TopShelf -> Jett in a CBM F-16 (6/11/2002 12:06:06 AM)
Craig, I think we should take this to PM as our conversation no longer pertains to Jett support. Kent.

bob27s -> Jett in a CBM F-16 (6/15/2002 7:48:06 PM)
Guys, thanks for the info on the F-16 installations. I get several questions about this installation each month, and as you have discovered there are a bunch of variables involved. Hopefully this thread can help others making the same decisions. Bob Brassell

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