Eagler's Nest
Airframes => Single Seaters => Topic started by: PropMan on September 25, 2017, 05:19:58 PM
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I'm workin on the fuel system for the XLR an thought i'd share what has been learned so far. Hope those who know better than me jump in and help straighten out any screw ups.
Going to post several pictures of progress.
After reading the plans i decided to build a tank from aluminium, similar to my RV6 wing tank in technique(rivets and pro-seal).
The tank will reside in the left wing, additional support has been added to the upper ribs where the tank will attach. (and to the right -Just In Case(-: )
Plan is to form ribs that have the upper rib shape and the top of the tank will be upper wing skin in that area.
I first read what was available on experimental fuel systems , then sketched out what i thought would work for My installation.
edit: you will notice I have a header tank in the design. that is due primarily to the type of carburetor on the Scarlett 3VW. it is a Walbro 37, and has no bowl.
my thought process is to make Sure i have fuel at all times, and to limit chances of air in the fuel lines.
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I then made form blocks to fit the rib bay, where i wanted the tank to reside. calculated to make sure i had 5 gallons of Usable fuel.
Cut my aluminium sheet and formed a couple ribs.
The forming causes the rib to have a curve, it needs to be fluted in the proper spaces, rivet spacing is determined the flutes are done to straighten the rib.
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Ribs complete, so i cut a sheet the proper width and took it to the brake.
Carefully measured and made my bends.
The flanges will be trimmed and top fabbed up after i sort out plumbing.
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Ribs complete, so i cut a sheet the proper width and took it to the brake.
Carefully measured and made my bends.
The flanges will be trimmed and top fabbed up after i sort out plumbing.
N i c e !:emoji_u1f60e:
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Propman
Looks great. What is your rivet spacing? Do you apply the proseal during the construction or after the tank is complete?
Jim
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Propman
Looks great. What is your rivet spacing? Do you apply the proseal during the construction or after the tank is complete?
Jim
The rivet spacing is 1 1/8" , rivets are AN470-3 and AN426-3, of proper length for the application. The top skin will use the flush rivets(AN426). The proseal is applied liberally along the rivet line during assembly and I will also form a fillet on the inside of the seam. i'll post photos when to that stage of assembly.
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Frank, that will be a slick installation. Will you have any support for the top panel to keep its shape, or will the curve take care of that? I know from welding tanks that the panels will get distorted, but have not done a riveted tank.
I'm sure you have it planned, but your sketch does not show a main tank vent. Maybe part of the filler cap?
We have the Verner on LEU Treehugger, nea, Three Jugger, fed directly from the wing tank. Starts and runs fine. We plan to do a fuel flow test into a container to verify adequate fuel flow, especially in a nose high and/or low fuel level condition. Then we plan to do a full throttle run-up when nose high to simulate a worse-case (or, maybe it is best-case with that awesome prop) climb condition.
When you eventually test it, it will be good to know if the Verner will run with a low mounted header tank, like you have, with worse case low/no fuel in main tank.
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Looks like Frank is doing excellent work there. Some may wonder about a NO pro-seal method using welded over rivets and that can work to, but takes perhaps what might be considered special skills on the welding side… It is simply a learned “skill” Just like many other aspects of the aircraft build.
That being said, many ways to skin the cat, and Frank’s sure looks good!
Frank, did you calculate volume? I could always do that for you, with a few measurements, doesn’t take long.
cheers
Scott
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Prpoman
Thanks for the info. I am keenly interested in the outcome of your tank. Looking forward to more pictures and progress.
Jim
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Tom- if all goes to plan the top skin will be supported by the ribs and possibly a strip of angle down the center formed as the ribs were with the curve. And, Yes, the cap has a vent, pic to follow.
Scott- I have all the tools to weld , just haven't had time to acquire the skill. so opted for something i knew. One day i will tho.
Yes, i calculated the volume ,old school way. i may send you the dimension just to check my work, Thanks.
And Scott hit the nail on the head, many ways to skin this cat. just pick one you are comfortable with and go. the basic fuel system stays the same, just lots of ways to build it.
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Here is a shot of the fuel cap.
I want to keep things as aerodynamic as possible, read drag reduction. and my way is not always the best. just how i decided to do it. I purchased the cap from ACS- UD-3-C Fuel Cap with Contoured Adaptor. drilled and installed vent tube and a few vent holes inside cap assembly.
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Had a little time to work on the fuel tank today.
Drilled the ribs to the bottom skin and drilled a couple stiffeners to the tank bottom to give a bit of support.
Also test fit the tank in the wing to determine where trimming needs to be done.
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N i c e :emoji_u1f62f:
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Looking good Frank! I see you are using 2024-T3. What thickness are you using?
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Frank,
Looks really good, what is your estimate on weight?
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Thanks fellas.
Poormam- I used 2024T3 cuz I had some, would probably be better to use 0 instead of 3 for forming.
Bottom skin is .032
Ribs are .025
Top will be .040
Bob- I hope to come in under 3lbs. Once my ACS order comes in I will dril and fit the top skin, then rivet together. Then it can be weighed
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Frank,
Sounds great. did you consider baffles to reduce sloshing as well as for bottom support? I was thinking of going the baffle route. More holes to seal maybe but not too bad.
Keep the info coming, great project. Seems like a 5 lb savings over the Team Mini max plastic tank.
I went to solid struts, and no paint to make my weight. Thinking of redoing my tank so I can paint!! The struts are not a big deal I flew with them both and without, and seemed to me if I came in hard I would bend metal either way!! The solids are just fine. Keep the speed up[!!
Bob
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Thanks fellas.
Poormam- I used 2024T3 cuz I had some, would probably be better to use 0 instead of 3 for forming.
Bottom skin is .032
Ribs are .025
Top will be .040
Bob- I hope to come in under 3lbs. Once my ACS order comes in I will dril and fit the top skin, then rivet together. Then it can be weighed
A FEW words on tank building..for those that have never built with Alum.
you have to be a good metal worker like Frank, to make 2024-T3 work in this situation. The reason is simple- if you don’t pay attention to bend radius, the alum can and will crack in the bends. By doing it right- you have a mighty tuff tank, but doing it wrong, you could have cracks that haunt you. There are bending rules for each thickness (same rule, just different radius mins. - for each thickness)
And most know- there is zero welding on 2024-T3, so that is not a fix option or add a tab option before filling the tank.
Lots of ways to skin the cat, these "outside flange- wing profile tanks"- have a lot going for them.
cheers
scott
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A few more details done while waiting on my ACS order.
Fittings made and drilled for the fuel line, vent and sump.
The fuel line/finger strainer attach is 1/4 plate tapped for 3/8" pipe thread drilled for rivets, then drilled to the tank in two locations (i tried to determine the lowest for and aft position for fuel pickup that would allow the most usable fuel from the tank). The finger strainer is from Wicks pt#FS375-125. These are also on the outside of the tank skin to allow more usable fuel(see pic).
The Fuel sight gauge and header tank vent are on the inboard rib. The attach plate is made of a piece .20 material i cut from some angle, could have used the .25 but saving as much weight as possible and the 1/8" fittings have plenty of thread contact on the .20. These are drilled for 1/8 pipe thread, tapped, drilled for rivets and drilled to the inside of the tank. Installing them inside allows for the fittings to fit close to the rib and makes tank install to the wing easier.
To assure the header tank is vented properly back to the fuel tank an AN fitting was installed in the upper front rib wall(next to upper sight gauge fitting), then the fitting is drilled out to accommodate a 1/4" tube which is secured and routed to a high point near where the fuel fill will be.
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Frank,
Sounds great. did you consider baffles to reduce sloshing as well as for bottom support?
Bob- Yes, i decided against baffles, hope its a good decision. Trying to save weight. the bottom of the tank has two .020 strips of angle for stiffeners. My thought process on both of these decisions were: 1) 5 gallons Usable will only be in the tank for a short while and shouldn't slosh around enough to be a problem. 2) the thin bottom skin .032, definitely needed support. plus i referenced my old RV6 fuel tank drawings and it had stiffeners between ribs on the tank bottom.
These stiffeners will be trimmed to save weight where possible also.
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Regards baffles on a Legal Eagle XL 5 gallon fuel tank, the only sloshing around that will take place is when taxiing. My tank is made of .032 and it has never been a problem.
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Finished drilling the top skin. And test fit to the wing.
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Frank,
Looks absolutely Fantastic.. Wonderful fab work.
Scott J.
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Ditto on what Scott J said!!!!
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Hi Guys,
If you fly a carburetor that has no bowl be sure to turn off the fuel in a engine failure as the fuel will keep flowing and a fire can be the results. I have seen this. Leonard
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Thanks for the complements everyone!
Started proseal and riveting the tank together. I have broken this task up in a few nights, don't think i could handle this in one session. wayyyyy to much mess!!!
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A few shots of final drilling the skins and fitting
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This looks beautiful. I may skip the center tank idea in favor of this
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Any idea what the final weight ended up being after proseal and all?
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Got pics of the finished tank. And it weighed in at 5.2 lbs. That's complete with all fittings, fuel sight gauge, cap and vent.
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It's looking good man! You can always spot the RV builder in the bunch.
Mark.
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Love this tank! Great job! You've convinced me, this is the way I'm about to build mine! Anything you'd change if you were going to build again? Also I got a question on the corners, what steps did you take to really seal the corners? just concerned the point of corner will leak!?! Did you/can you seal from the inside using a tank sealer?