Anyone here actively flying with the wingtanks.com poly tanks?

[C5Engineer 1170]

One of the things left on my to-do list with my new bird is to find out how much useable fuel I have and to mark the tanks for quantity. Depending on where you look they hold somewhere between 5 and 6 gallons and there are 4 tanks total. The filler neck is in the outboard tank and they gravity drain inboard through two separate tubes. I am currently deployed with too much time on my hands to think this out so bear with me as I “rocket science” analyze this as Leni would say. 

Step one of my master plan is to start with the tanks dry and level the plane for Level Flight attitude. I plan to calibrate a jug in one gallon increments and pour fuel in until I see it come down the line and start to fill the header. This should give me a rough estimate on the unusuable.

Next I’ll fill them one gallon at a time until full making marks as I see fit. I’m curious how quickly they will drain inboard. My concern is that if at a pump I will have to go back and forth wing to wing topping the outboard tank back off. 

Like my other bird this one has had the oil injector removed. My other concern is how I’m going to mix the fuel while going cross country. In my other one I just shut off the tank, put in a known quantity from the pump and then do the math and pour the oil in the tank and mix it right in the tank. (Gets great stares from the spam cab drivers at the pump btw) That’s obviously not going to work with fuel transferring around tank to tank. Thinking of purchasing one of the collapsible jugs but then the question arises how much to mix up at a time. Going back to injection is too much work since I plan to 912 swap this bird eventually anyways.

I’d love to hear from someone running these (calling on you Mark) and to hear you guys who are smarter than me thoughts on this. 

Edited 14 Dec 2017 by C5Engineer

[fr3dcat 0]

I have them in my left wing of my Subaru powered Mark IV.  I dont like them.  They don't seem to feed well when they are below 1/2 tank.  In fact i had them quit feeding on me and the engine quit and I landed in a hay field.  When I rolled to a stop the engine started up.  That happened at about 300 hrs.  I put that tank in at about 285 hours.  

 

It reminded me of fuel venting problems I sorted out in the first hour of initial flight test with the original Avid fiberglass tank.

 

it seemed like that the two tanks have about a gallon each unuseable.  

Tim Morris

s/n 1492

 

 

 

[C5Engineer 1170]

Thanks Tim this is the info I was looking for. Did you have both tanks vented or just the outboard one? Based on a recommendation from Stace I put the 90 Degree forward facing vents on all 4 tanks. On the fiberglass tanks the outlets are in the very back corners and on these they are further forward closer to the middle of the tank. 

[dholly 718]

Joey - the poly tanks from (now defunk?) www.wingtanks.com vs. those sourced from Stace Schrader at Rocky Mountain Wings (http://www.realflying.com/) are two different designs. My buddy Russ, who's Mk-IV is pictured on the wingtanks.com website, also mentioned the poor fuel cross feed setup used with those tanks. Also took forever to fill as he used only one filler neck per wing. Regardless which poly tanks you use, might want to come up with a better system for connecting the two tanks in the same wing. I remember Mark and others commenting about dealing with leaks there due to the rubber slip-in grommets. Perhaps a separate fuel line from each wing tank to a header would be something to consider. 

[edit] FYI - during the model 4 production, KF also changed the outlet location on their f/g wing tanks from the rear to the center to help avoid un-porting during extended nose down/low fuel flight attitude.

Edited 14 Dec 2017 by dholly

[Av8r3400 1177]

When did the they change the outlet position?  Mine are brand new and the outlet is in the back...  ?

[C5Engineer 1170]

Doug these ones are from Stace. Looking at these old pics it appears there is an outlet on both tanks. I’ll have to research this system closer when I get home. 

Edited 14 Dec 2017 by C5Engineer

[fr3dcat 0]

The wingtanks.com tanks I had had a vent on the single filler cap.

[fr3dcat 0]

The wingtanks.com tanks I had had a vent on the single filler cap.  Let me clarify.  The vent on the cap is a 90 degree tube pointed into the relative wind.

 

My tanks also took a long time to fuel as well. 

Tim

[EDMO 1078]

fr3dcat,  If you want to add to your post, or change it, just click on "edit" at the bottom and you can rewrite or add to your post.  FYI  I do that most of the time - guess I think slow?  But, I keep on thinking!  ;<)  Just did that too.  No one else can change your posts.  EDMO

Edited 15 Dec 2017 by EDMO