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  #21  
Old 08-09-2017, 01:02 PM
TS Flightlines TS Flightlines is offline
 
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I do agree with Ross on the in tank pump location. We have done a few in the wing roots, that helps the situation some. Plumping is a pain.

Tom
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Teflon Hose Assemblies for Experimentals
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Ridgeland, SC
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  #22  
Old 08-09-2017, 01:14 PM
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airguy airguy is offline
 
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Quote:
Originally Posted by Norcalrv7 View Post
Do we know first hand of someone who has had vapor issues with a high pressure fuel system? I flew my plane to 115F+ Redding CA a few times while running 87 E10 in the Subaru. This was done while using the same fuel system as now. In my case the only difference I saw was maybe an extra second to prime the system when I first turned on the pumps. I'm certainly not saying it isn't of concern, Just curious.

Caleb
Prior to cleaning up my inlet-side plumbing, I had a couple instances of a pump refusing to pick up its prime while cruising at 16,500 and 17,500 while running 91E10. I run dual pumps, one pulling from each tank, so running on one tank at altitude for a while allowing the fuel in the other line to slowly vaporize in the lower ambient pressure at altitude and then when it was time to switch tanks it wouldn't pick up the prime to pump.
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  #23  
Old 08-09-2017, 08:06 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by rlmccarter View Post
Hi Guys,

I'm aiming for a simple design with margin for worst case (mogas at high ambient temp and altitude) - may never do that, but I like margin.

In the -8 there is enough room for SDS' mounting recommendation (low, horizontal, straight inlet) with 90 degree outlet and a service loop to the firewall.

My tech counselor is dropping by tomorrow to put a second set of eyes on the design before I finalize. I'll post pictures in a few days in case it helps others.

Cheers,
Bob

How about a straight outlet off one of the side ports (aiming toward the aircraft centerline) with a 270 loop to a 90 degree bulkhead fitting at the firewall?

Its been a while since I plumbed the -8 (and I moved the firewall fitting to the center anyway).
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  #24  
Old 08-10-2017, 09:39 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Your installation seems to have plenty of margin. That's good that you've tested at the extreme temps. Yikes. You fly at 115F?!!!
Vapor pressure of mogas blended for Canada and northern California may be different, just as winter and summer blends are different.
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  #25  
Old 08-10-2017, 09:55 AM
Canadian_JOY Canadian_JOY is offline
 
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I must first admit that I haven't built an -8 so I can't visualize the challenges of pump location vis a vis the firewall. I'm reading in several comments here the need for a 90 degree fitting and a service loop on the outlet between pump and firewall.

Would this perhaps be a situation where a stainless braided conductive Teflon flexible line might be the best solution? It would perhaps eliminate the need for a service loop. I'm also thinking if clearance is the issue driving the need for a 90 on the outlet of the pump, perhaps a "swept 90" fitting on the end of the aforementioned flex hose might be a better option to reduce flow restriction?

I know aluminum hard line is cheap, light and often highly reliable. This particular locale might be one where adding three or four ounces of weight might bring significant payback in improved performance and ease of maintenance.

Again, I have no direct experience in this exact installation so my question is an opportunity to learn more about the peculiarities of this installation.
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  #26  
Old 08-10-2017, 11:12 AM
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rv6ejguy rv6ejguy is offline
 
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You can see in the first photo in this thread that the pump module has 1/4 NPT plugs on the sides. If fore/ aft clearance is an issue, I'd just plug the center outlet and use one of the side ports for the discharge. As Toobuilder mentioned, the pump is reversed in the photo. The Larger hex fitting houses an inlet filter.

Dan is correct, mogas formulations vary widely and so does their vapor pressure. Our goal with plumbing is to minimize the chances of so called "vapor lock" before the pump inlet by following best practice.

It should be noted that the ID of a -6 90 degree fitting is much larger than the bore of the pump spigots. I don't believe one 90 before the pump would have any impact of flow restriction if the pumps are floor mounted. Adding a couple more possibly would. Be aware that these pumps flow around 40 gph at all times.
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Last edited by rv6ejguy : 08-10-2017 at 02:47 PM.
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  #27  
Old 08-10-2017, 02:27 PM
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rmartingt rmartingt is offline
 
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Would a pair of gradual bent 180s cause a problem, in your experience? I'm thinking of fitting fuel filters in the wing roots and the only way I can figure on doing that is with some bent 180 degree tubes. Don't think I'll need hard 90s anywhere though.
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  #28  
Old 08-10-2017, 02:38 PM
TS Flightlines TS Flightlines is offline
 
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Yes, 180*'s work well in the roots. Its tight with some planes, but it works well.

Tom
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Teflon Hose Assemblies for Experimentals
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RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com
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  #29  
Old 08-10-2017, 02:54 PM
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rv6ejguy rv6ejguy is offline
 
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If you do need some custom braided hose assemblies to plumb your pumps, Tom is the best source for these.

I think Goodridge came out with some braided hose which you could do very tight bends on with no little or no collapse of the hose cross section 10+ years ago. Amazing stuff. Maybe Tom could comment on that.

Braided hose is a lot easier to route than rigid line and you have less concerns about vibration induced failures over the long term.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 417.4 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 08-10-2017 at 03:06 PM.
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  #30  
Old 08-13-2017, 01:46 PM
TS Flightlines TS Flightlines is offline
 
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Default Just for the sake of discussion---

there is a MAJOR Aerospace fitting manufacturer that makes block or forged style angled fittings for all of their crimped teflon hoses from -3 to -8. This manufacturer is very well known, and has this type of hose ends flying on litterally millions of hoses worldwide. So, I'd defer to them to find out the actual flow loss of their forged style fitting, vs a bent tube design, thats used.

Gee---maybe we'll take a couple of fittings up to AirFlow Performance, and have Don flow them so we'll have real data.

Tom
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Tom Swearengen, TS Flightlines LLC
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com
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