The New F86D Dog Sabre
#976
Regards,
Gus
#977
My Feedback: (6)
Back in the old ducted fan days I had a similar tank installation on a Zone 5 jet. I made the tubing on both sides of the "T" identical b ut still one tank always had more in it than the other at the end of a flight. I always meant to vary the line lengths to even it out, but was too lazy. It worked just fine.
#980
My Feedback: (3)
Tank plumbing
OK, I'm going to Joe Grice's place tomorrow to get his take on the tank plumbing situation. HOWEVER, my son, who is working on his full scale instrument rating right now, brought up a good point. With "series" plumbing, the clunk of the tank closest to the VAT would still have a full tank to swim around when the flight is 1/2 over, making aerobatics safer. 3/4 of the way thru the flight, there's still going to be 1/2 tank for the clunk. This seems safer to avoid a flameout than series, where each tank would only be 1/4 full, increasing the danger of sucking bubbles near the end of the flight. Comments?
#982
The UAT should take care of momentary situations of negative 'G' in aerobatics. If you keep positive 'G' as in an inside loop, there should be no problem. All I can say is that the parallel system I described in my .jpeg drawing worked (at least until I stalled it on a downwind turn when I couldn't see the jet very well) and I tend to put a lot of faith in 'what works'. BUT - it is your jet and you can do what you want.
Regards,
Gus
Regards,
Gus
#984
My Feedback: (25)
Right Jetflyr, the rounded opening is riveted. Took the words right out of my bell mouth. Even the if bellmouth WAS bolted, can you imagine trying to put the screws back in and tightening them working down and aft in that little hole? With the P1 former and the thrust pipe in your hands, it's not immediately apparent that you CAN slide the pipe through the former since the hole in P1 is smaller than the pipe diameter. It deforms the pipe and you have to force it through. One doesn't want to ruin the pipe, and the instructions don't say the pipe will pop back into shape like it apparently does.
Countryboy, thanks for sharing your wood alignment jig photos from the 3-14-2010 Jet Legend F-4 thread, post #163. The idea was new to me, anyhow. Question: Does your plug set just the alignment and not set the gap from the end of the engine to the beginning of the exhaust tube? Mine bottoms out flush with the thrust pipe bellmouth so it sets the gap automatically(notice it's tapered). This is needed on the Saber Dog because there's no access to the area to measure it. Your F4 has amazing access to the area in question compared to this Saber Dog where one is working not only down in the access hole, but offset aftwards one set of formers.
Countryboy, thanks for sharing your wood alignment jig photos from the 3-14-2010 Jet Legend F-4 thread, post #163. The idea was new to me, anyhow. Question: Does your plug set just the alignment and not set the gap from the end of the engine to the beginning of the exhaust tube? Mine bottoms out flush with the thrust pipe bellmouth so it sets the gap automatically(notice it's tapered). This is needed on the Saber Dog because there's no access to the area to measure it. Your F4 has amazing access to the area in question compared to this Saber Dog where one is working not only down in the access hole, but offset aftwards one set of formers.
#985
My tanks have a solid brass vent line going to the top of the tank. My fill/clunk line extends about 2 inches inside the tank, then Tygon to length allowing full swing of the clunk.
Since there is not a neck to worry about splitting on the tanks, I just used a Dubro cap and gas/kero bung. It hasn't leaked yet.....
As I mentioned, I plumbed mine in series - which is also the way the CARF Lightning and Flash is plumbed - the pump really doesn't care if the correct fuel line diameter is used.
The tanks are just secured to the fuse sides with a dab of silicone - you don't need much.
There was a lot more in my submission - but Jay edited it down for space in the print edition.
Hysol 9462 is VERY different from JB Weld, or 30min epoxy. Each has its place - and really shouldn't be substituted for each other. Micro-balloons do nothing for strength - and in fact make the joint weaker. Search the archives of JPO's Contrails for the article Lance Campbell (of the big SR 71) did on strength and compatibility of epoxy resins.
My guiding principle is KISS - and each aircraft has its own issues. I have yet to run a check valve on the vent since it vents outside the plane ... if I get fuel inside, it is from another source, not the vent.
My 2 cents -
Greg
Since there is not a neck to worry about splitting on the tanks, I just used a Dubro cap and gas/kero bung. It hasn't leaked yet.....
As I mentioned, I plumbed mine in series - which is also the way the CARF Lightning and Flash is plumbed - the pump really doesn't care if the correct fuel line diameter is used.
The tanks are just secured to the fuse sides with a dab of silicone - you don't need much.
There was a lot more in my submission - but Jay edited it down for space in the print edition.
Hysol 9462 is VERY different from JB Weld, or 30min epoxy. Each has its place - and really shouldn't be substituted for each other. Micro-balloons do nothing for strength - and in fact make the joint weaker. Search the archives of JPO's Contrails for the article Lance Campbell (of the big SR 71) did on strength and compatibility of epoxy resins.
My guiding principle is KISS - and each aircraft has its own issues. I have yet to run a check valve on the vent since it vents outside the plane ... if I get fuel inside, it is from another source, not the vent.
My 2 cents -
Greg
#986
#987
Gus (Mtnflyr), thanks for the great photos, and the plumbing diagram. Interesting divergence of thought on how to plumb the tanks! Have any of the folks in the parallel school of thought had any issues with uneven fuel usage between the two tanks? If parallel, it seems like it would be best to locate the Y connector between the two as close the the tanks as possible to minimize any differences in flow rate. Also, the Greg Moore review didn't offer any info on tank plumbing. I know Joe Grice, he lives near here. I'll shoot him an email about plumbing just for kicks. Lots of people recommend Hysol 9462, which just seems like structural epoxy. How do you say JB Weld??? Anyway, seriously the cost is TEN TIMES what 30 minute epoxy is. Add microbaloons for viscosity if needed. The Greg Moore article says that goop is ok, too. Or even plain old silicone caulk.
For the vent, on gasoline engines I've always terminated the vent line with one of these TME check valves. They completely prevent leaks inside the plane, and take no pressure at all to draw fuel through because they contain a flapper reed valve. It's not the ball-and-spring affair where the fuel draw has to overcome the spring tension. Does anyone see any issue with using these for turbines, to terminate the vent(s)?
For the vent, on gasoline engines I've always terminated the vent line with one of these TME check valves. They completely prevent leaks inside the plane, and take no pressure at all to draw fuel through because they contain a flapper reed valve. It's not the ball-and-spring affair where the fuel draw has to overcome the spring tension. Does anyone see any issue with using these for turbines, to terminate the vent(s)?
#988
My Feedback: (3)
Yes, notice in the second photo that I posted that the end of the jig in the pipe is at the location of the pipe opening and not at the face of the bellmouth . This is the distance I have come to understand that the correct turbine exhaust nozzle to pipe distance should be gauged by. Right or wrong, the stock Jet Legend pipe in my F-4 has shown no evidence of heat related issues after 30 flights and numerous ground runs. Granted, you did have a much smaller area to work in as compared to my F-4. I just think I might have done it a little differently, however you got the job done and that's what counts. Good luck on your maiden.
#989
My Feedback: (3)
The TME high volume check valves are sold at Horizon. http://www.horizonhobby.com/webapp/w...pe=productgrid
You can also get them on Amazon.com and Ebay has them too. Hope that helps.
You can also get them on Amazon.com and Ebay has them too. Hope that helps.
#990
My Feedback: (3)
My tanks have a solid brass vent line going to the top of the tank. My fill/clunk line extends about 2 inches inside the tank, then Tygon to length allowing full swing of the clunk.
Since there is not a neck to worry about splitting on the tanks, I just used a Dubro cap and gas/kero bung. It hasn't leaked yet.....
As I mentioned, I plumbed mine in series - which is also the way the CARF Lightning and Flash is plumbed - the pump really doesn't care if the correct fuel line diameter is used.
The tanks are just secured to the fuse sides with a dab of silicone - you don't need much.
There was a lot more in my submission - but Jay edited it down for space in the print edition.
Hysol 9462 is VERY different from JB Weld, or 30min epoxy. Each has its place - and really shouldn't be substituted for each other. Micro-balloons do nothing for strength - and in fact make the joint weaker. Search the archives of JPO's Contrails for the article Lance Campbell (of the big SR 71) did on strength and compatibility of epoxy resins.
My guiding principle is KISS - and each aircraft has its own issues. I have yet to run a check valve on the vent since it vents outside the plane ... if I get fuel inside, it is from another source, not the vent.
My 2 cents -
Greg
Since there is not a neck to worry about splitting on the tanks, I just used a Dubro cap and gas/kero bung. It hasn't leaked yet.....
As I mentioned, I plumbed mine in series - which is also the way the CARF Lightning and Flash is plumbed - the pump really doesn't care if the correct fuel line diameter is used.
The tanks are just secured to the fuse sides with a dab of silicone - you don't need much.
There was a lot more in my submission - but Jay edited it down for space in the print edition.
Hysol 9462 is VERY different from JB Weld, or 30min epoxy. Each has its place - and really shouldn't be substituted for each other. Micro-balloons do nothing for strength - and in fact make the joint weaker. Search the archives of JPO's Contrails for the article Lance Campbell (of the big SR 71) did on strength and compatibility of epoxy resins.
My guiding principle is KISS - and each aircraft has its own issues. I have yet to run a check valve on the vent since it vents outside the plane ... if I get fuel inside, it is from another source, not the vent.
My 2 cents -
Greg
OK, on to jets. I pressure tested my tanks to 1 psi and submerged them, one leaked and the other one did not. So I've been busy fixing it. I laid up fiberglass all around the seam hole and retested. It still leaked....the air just traveled to the side. This time, I pulled a vacuum on the tank and dribbled thinned resin over the area. The hope was the liquid sucked into the passageway. Then, I laid up a 2nd round of glass & resin over it. This time it held just fine. I ramped it up to 5psi and it still held. So, I'm past that little issue.
Greg, I need to clear up one thing. You've mentioned both you routed your tanks in series, but you also said you had vents in your tanks(S). Plural. so, I'm thinking a series tank setup should have one vent in the last tank? Otherwise, there's nothing to draw the fuel from the last tank into the first one. Was that just a typo? Or am I still missing something? Thanks for all the help and comments.
#991
Each tank has a vent line - the atmosphere goes to vent line in Tank 2. Vent line in tank 1 is connected to the clunk line of Tank 2. Vent line from UAT is connected to the clunk line in Tank 1.
Sooo.... each tank has to have the vent line bent to reach the top of the tank.
Greg
Sooo.... each tank has to have the vent line bent to reach the top of the tank.
Greg
#992
My Feedback: (3)
Got it. Just a confusion of terminology is all. I was defining vent as going directly to outside. You're still calling it a tank #1 vent even though it's serving as the feeder line between tank #1 & #2. What do you think the effect would be if the vent (feeder line) in tank #1 went to the bottom, bathed in fuel, vs sitting on top like tank #2? Thanks.
Rick
Rick
#994
My Feedback: (3)
I've only used it for gasoline. All my 2 stroke gassers use this check valve on the vent line, and they have never failed. The original application for this check valve is in smoke systems, and since many smoke systems use kerosene based fluid, it would be a good assumption that it is compatible with kero. However, I've contacted TME via email to ask that very question. If I hear from them, I'll post it here.
#995
Got it. Just a confusion of terminology is all. I was defining vent as going directly to outside. You're still calling it a tank #1 vent even though it's serving as the feeder line between tank #1 & #2. What do you think the effect would be if the vent (feeder line) in tank #1 went to the bottom, bathed in fuel, vs sitting on top like tank #2? Thanks.
Rick
Rick
Greg
#996
My Feedback: (3)
You made me think about it a bit harder, Greg. I think If Tank#1's vent (feeder line from #2) is down in the fuel, it's simply another way to do a parallel connection. The fuel would be consumed in (presumably) equal amounts from each tank, negating the aircraft's unusual attitude advantage of sequential drainage during flight. I'll make a model of this with some junk sullivans I have lying around to see if this is true. Great discussion. I bet you guys can't wait until I move on to batteries. ha ha ha ha!!!!
Update: I made a dual tank mockup and tested with water. See the pic below. I was only partially correct. With tank#1 (nearest engine) having it's vent (feeder line) bathed in fuel pointed down, all fuel fills to the last tank (#2), completely bypassing tank #1. Obviously an untenable situation.
When Tank#1's vent is pointed UP as suggested by Greg, the fuel first fills Tank#1, and then sequentially tank #2. During flight, the fuel first drains tank#2, and only starts draining tank #1 after #2 is empty. Good for aerobatics later in a given flight. Thanks to Jetflyr for giving me the incentive to try this on the ground rather than airborne. Here's a pic of the test rig. It's in the drain mode, you can see tank#1 is all full, and tank#2 is already half
empty.
Update: I made a dual tank mockup and tested with water. See the pic below. I was only partially correct. With tank#1 (nearest engine) having it's vent (feeder line) bathed in fuel pointed down, all fuel fills to the last tank (#2), completely bypassing tank #1. Obviously an untenable situation.
When Tank#1's vent is pointed UP as suggested by Greg, the fuel first fills Tank#1, and then sequentially tank #2. During flight, the fuel first drains tank#2, and only starts draining tank #1 after #2 is empty. Good for aerobatics later in a given flight. Thanks to Jetflyr for giving me the incentive to try this on the ground rather than airborne. Here's a pic of the test rig. It's in the drain mode, you can see tank#1 is all full, and tank#2 is already half
empty.
Last edited by Pull Up Now!; 12-31-2013 at 04:09 PM.
#997
How you do your tank setup is entirely up to you, but I think you are making this too hard based on "aerobatics later in a given flight". Most aerobatics are done in positive 'G', in which the pickup clunk is at the 'bottom' of the tank all the time regardless of the orientation of the aircraft. I guess if you want to do inverted (negative 'G') passes very late in the flight, then maybe you are concerned about the pickup clunk being bathed in fuel. BUT - you also presumably have a 4 ounce UAT that should take care of momentary fuel flow issues. Like I said earlier, the scheme I posted worked for me with no problems, and I like what works. Up to you; my last post on this topic.
Regards,
Gus
Regards,
Gus
#998
My Feedback: (3)
Happy New Year everyone!
#999
sounds like you're getting tired of this discussion. That's fine, but remember every product you use was the subject somewhere of exhaustive meetings and debates to get it right. This discussion rocketed this thread to the top 10 RCU at one point, which means front page billing and more exposure for Modellbau and more education for everyone. Not a bad thing. I'm not sure if you mistook the discussion for arguing. If so, not my intent. My tanks are installed and set up just the way you recommended. I just took the time to verify it all, including my side trip with that Tank #1 vent position. It's not just about flying inverted, etc. Tygon hardens after a while, sometimes leaving the clunk above where it should be. Sometimes hard landings or carrying the plane kink the clunk, too. Your recommended setup makes sense on several levels.
Happy New Year everyone!
Happy New Year everyone!
Regards,
Gus
#1000
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Join Date: Mar 2009
Location: Dudelange, LUXEMBOURG
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Hi Pull Up Now!
I never had problems with different fuel levels in parallel fuel cells (On many planes). If one fuel cell has a lower level, the hydrostatic pressure on the other cell will be higher.
I never had problems with different fuel levels in parallel fuel cells (On many planes). If one fuel cell has a lower level, the hydrostatic pressure on the other cell will be higher.