Eagler's Nest
Airframes => Single Seaters => XL => Topic started by: dz1sfb on February 26, 2016, 10:11:37 AM
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While I am chomping at the bit to get started, I was thinking about the possibility of a fuselage mounted fuel tank. The obvious advantage to the wing tank is the gravity feed. So, here comes my question;
How much space is between the wing root ribs? I have noticed the wing center fairing and am thinking there might be enough space for a fuel tank of sufficient volume to take up the gap. Kind of like a motorcycle fuel tank that straddles the frame. Maybe I am just dreaming too much, but you could have a nice airfoil shaped aluminum tank there that would not necessitate opening the fuel system to remove the wings and have the benefit of gravity flow.
A second question is; if the space is too tight to sufficient volume, what about spreading the wings apart just a skosh more to get the volume?
This may be all purely academic, but I can see this one in my minds eye.
Ken
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I plan on doing the same. You can fit 5 gallons in there between the wing mounts front and back and between the wings without modifications.
My aircraft will live in a trailer for part of it's life. Anything I can leave hooked up and on the fuselage is time saved.
tom xl-7
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I plan on doing the same. You can fit 5 gallons in there between the wing mounts front and back and between the wings without modifications.
My aircraft will live in a trailer for part of it's life. Anything I can leave hooked up and on the fuselage is time saved.
tom xl-7
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Tom, where are you getting this much volume? what width are you using for your calculations? and are you using just between the attach points or using space fore and aft as well. I am not saying this can't be done, but rather my calculations of using tank the shape of the wing, and 1" in between the fore and aft attach points, with width of 4" was giving me only 3.3 gal.
Of course adding slightly in height, or lower (head clearance) or somehow adding ahead or rear of attach points can make a big difference very quickly. or even the width. ( every .500" wider gives me .4 gal more space)
Am curious in the calculations used.
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Scott , Ken
Did some calculations and yes my statement "with no modifications" is full of something and it is not fuel. Page 53(XL) shows 10 inches for a gap cover so I may have allowed as much as 8 inches width if I needed it. Page 7A shows the mount 2.5 inches wide and page 35 shows the root fitting sticking out of the wing 2.75 which I have changed to 2 in red ink.
2 root fittings plus wing mount should yield a 6 inch gap. Assumption time: rib drawings not in hand-28 inches overall length.
231 cu inches in a gallon times 5gallons needs 1155 cu inches of volume. 1155 / 28 / 6 =6.875 height which I don't have easily. Ken suggested a motorcycle type tank which would hang beside and below the top fuse tube. I would rather not go that route (more fittings -two sumps) but one side lower could act as a useful sump.
I sketched it long ago just as a proof of concept. I would not extend the root fitting but have little problem lengthening the wing mount.
If I had used the original numbers on page 35 that would have given me 7.5 inch gap which reduces needed height to a more workable 5.5 inch average height.
I probably used 8 inches and that is what memory was coming up with. 8 wide 28 long.
Good catch - doable regardless.
Tom XL-7
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Maybe not so bad after all If I did use 2.5 for wing mount plus two root mounts at 2.75 (which was the original drawing) that does equal 8 inches. Stock dwgs.
That may be where I came up with 8 inches to begin with. The power of another cup of coffee!
tom xl-7
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Well certainly good talk on this subject... I'm going to have to sharpen my pencil and calculate a few of my measurements as I am basing my calculations on one set of numbers and Tom is using others.
So first I will compare mine with with Tom's- As the old saying goes, I have certainly been wrong once. :emoji_u1f601: if I took my present calculation of max width of 6.2" and go out to Tom's 8" I would easily have enough gal/space.
As present I am still under 5 gals.
Now for the sump/style/motor cycle way.. If I am understanding this correctly..the tank being slung saddle style over the top frame frame bar where the wing attach points are. this would create two low parts of the tank. Easy enough for all to picture. Under low fuel levels, (Just in these two lower cavities) one would need a sump hole each side- and front and back. For landing and take off- to keep from un-porting. This has always been the problem with long narrow tanks with flat bottoms with the long axis in direction of travel. (think climb out angle and decent angle and where the last gal would be) And of course we would certainly fall into this. I don't know if this would warrant a cross over tube, if so, it would be needed front and back. This of course could reduce sump requirements to one in front and one in rear..but your still adding an extra hole for the cross over..unless done with fittings alone- all about the same for matter of work.
That being said, this is still well worth considering. I will keep working on it, to either prove or disprove the idea. Presently I would estimate this a 80%+ possibility.
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Hi, Guys.
I've finished the ribs and am waiting for things to warm up here in Minnesota. I had this idea a few months ago. If my math is correct, (no promises here) a FOUR gallon airfoil shaped tank can be built to the dimensions of 24" L, 6" W, 6.4"H. I built to the inaccurate rib drawings provided in the plans, so I gain a bit in the height dimension. A ONE gallon header tank is placed in the forward fuselage. From what I've read this should allow for a cleaner routing of the fuel line and minimal CG issues. Is it worth the trouble and extra complexity? Maybe not... A 5 gallon fuselage fuel tank doesn't seem to be problem on Sam Buchanan's XL. Les Homan says in a video that there is trim change but his plane seems to fly fine. I have no idea how this would be mounted to the airframe, also, I am in no way an engineer so take this all with a grain of salt.
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Hi, Guys.
I've finished the ribs and am waiting for things to warm up here in Minnesota. I had this idea a few months ago. If my math is correct, (no promises here) a FOUR gallon airfoil shaped tank can be built to the dimensions of 24" L, 6" W, 6.4"H. I built to the inaccurate rib drawings provided in the plans, so I gain a bit in the height dimension. A ONE gallon header tank is placed in the forward fuselage. From what I've read this should allow for a cleaner routing of the fuel line and minimal CG issues. Is it worth the trouble and extra complexity? Maybe not... A 5 gallon fuselage fuel tank doesn't seem to be problem on Sam Buchanan's XL. Les Homan says in a video that there is trim change but his plane seems to fly fine. I have no idea how this would be mounted to the airframe, also, I am in no way an engineer so take this all with a grain of salt.
Just thoughts Terry-
- one gallon header tanks- certainly easily do-able and if you use the Tube method of building, very easy to make.
- Cleaner routing of fuel lines- Cleaner than what? Leonards way vs the top center tank or Sam's tank? Sam's would be far the simplest, after that, there is not much difference.
- Trim change- a few seconds of work per gal of fuel burned off, no problem.
- No idea how mounted to airframe- To which are you referring? Sam's tank used the under lying frame work of the main frame and a few easily made tabs. And the top center tank can easily use the front and rear wing attach bars. They are there and handy. Pretty easy to use/make these tabs as well.
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- I have checked my rib jig and the 28 inch length is wrong. 27.5 between the spars. General clearance needs plus one has to leave space for bolt heads or nuts, tools will reduce that a bit.
The idea of a header is something I have been interested in. Would it solve the problem of a rear drain losing fuel in a descent. I realize your not to plan on running out of fuel but if you saw air in your fuel tubing it would be nice to know the fuel was in the header.
How many times has that reserve position on a motorcycle petcock come in handy.
Don't know where that No. 1 that starts this post came from but I can't get rid of it.
Tom XL-7
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The idea of a header is something I have been interested in. Would it solve the problem of a rear drain losing fuel in a descent. I realize your not to plan on running out of fuel but if you saw air in your fuel tubing it would be nice to know the fuel was in the header.
Tom XL-7
Tom,
Leonard had a small header tank in the prototype LE for a while. I don't remember why he took it out... Probably to save weight. A header tank is basically a wide place in your fuel line...
He had the zenith carb on there for a while too but changed to the dual Mikunis. I don't know if that had anything to do with getting rid of the header tank or not.
You got the 1. in your post by clicking the "ordered list" Icon in the editor above your post box.
To get rid of it put your cursor just to the right of it and hit the back space key, as I did when I trimmed your quote above.
Attached is another tank possibility. Looks like an aftermarket dirt bike tank.
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Hi, Scott.
I think the way Sam mounted his tank is the simplest and I like to keep things simple. I haven't abandoned the idea of a center tank but I do favor the location used by Sam B. and Les H. A header tank would not be difficult to install but no matter how easy to install, it does complicate the matter.
Cleaner fuel line routing... I could have been clearer. I'm not a fan of the fuel line suspended in the pilot's line of sight to the right, it just bugs me. It's just a matter of opinion, I've never flown a L.E. and it doesn't appear to be a problem with anyone who has completed and flown their A/C.
Again, I should have been clearer about the CG. I was concerned about flying qualities of a plane without a trim system. A quick and dirty trim system from days gone by was a small independent tab located above or below the stab. A simple retrofit if required but I doubt that it would needed.
Yes, it would be easy to mount the tank between the wings or on the fuselage diagonal as Sam did. I just hadn't put any thought as to how it would be done.
I've been reading your posts, much good information!
Best regards, Terry.
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If you are looking for another tank location - the Sam Buchanan fabrication will challenge you skills... His fus location is about the lowest you can feed the dual Mikuni's with the (large orifice) gravity flow carb float inlet valves... IIRC Les has a tank that is a little less than 5 gallons... On a big tight 1/2 motor you can see nearly 3 gallons an hour consumption with a rich mixture... Fly away from the home field down wind and find you are too far out when you start grinding your way back...
If you want to fly soon put the Team ready made tank in the wing... A tank over the tube between the front and back wing mount is a head room limiter, a bear to fabricate and the first thing your head rams in a roll over... An inch clearance between head and wing is common, the shoulder harness has to be really cinched to maintain that clearance... Carefully mock up the wing tank clearances if you are determined to go this way... The wing tank is a safety measure and a few minutes work to drain into a 5 gallon can when u take the wings off... Unlike the plans; put the tank in the right wing half and enter the cab from the left - no pilot fuel line interference and you can watch the evil fuel line air bubbles if they develop...
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If you are looking for another tank location - the Sam Buchanan fabrication will challenge you skills... His fus location is about the lowest you can feed the dual Mikuni's with the (large orifice) gravity flow carb float inlet valves... IIRC Les has a tank that is a little less than 5 gallons... On a big tight 1/2 motor you can see nearly 3 gallons an hour consumption with a rich mixture... Fly away from the home field down wind and find you are too far out when you start grinding your way back...
If you want to fly soon put the Team ready made tank in the wing... A tank over the tube between the front and back wing mount is a head room limiter, a bear to fabricate and the first thing your head rams in a roll over... An inch clearance between head and wing is common, the shoulder harness has to be really cinched to maintain that clearance... Carefully mock up the wing tank clearances if you are determined to go this way... The wing tank is a safety measure and a few minutes work to drain into a 5 gallon can when u take the wings off... Unlike the plans; put the tank in the right wing half and enter the cab from the left - no pilot fuel line interference and you can watch the evil fuel line air bubbles if they develop...
Hi, Steve. Thanks for the great site.
I've looked into the center fuselage wing tank because I'll most likely be removing the wings fairly often. I too don't like this position in the case of a nose over but I guess the fuse is not a lot better. The fuel line is a small issue, looks more than function. I think my best bet for improving trailering will be procedural, such as attaching wing bolts with an electric drill/wrench, some type of wing support attached to the trailer. Or... I'll probably pay hanger fees.
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Well this certainly stirred some response. I like the idea of a small header tank. If you have some welding skills, you can fabricate from aluminum, or mock up in foam, fiberglass it, then put in some gas to eat out the foam and viola`.
Having sumps on each side of the top tube it would be good to have a crossover. Also you could go above the wing profile some ala Tiger Moth and maintain the headroom below.
Ken
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Okay, after seeing Charles Deboer's LE here (http://www.eaglersnest.com/forum/index.php?action=dlattach;topic=1091.0;attach=1817;image) , there would be no need or desire to have the center tank saddle over the top tube. This further supports the possibility for ample fuel volume.
Ken
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never considered hitting my head on the underside of a center wing tank. That top fuselage tube would give my head a.75 inch warning. This isn't anything I have to concern myself with at this time and it is always reversible.
I have been more concerned with the wisdom of storing fuel directly overhead. I guess a ruptured tank wouldn't be a good thing whether it was overhead or in your lap. At least, overhead is not adjacent to the hot "ignighty" parts. It very well may be safer in the wing. Although it is mighty close, just over a shoulder.
William Wynne of flycorvair fame was involved when his pietenpol was stalled and spun directly into the ground. Fuel from the center wing tank leaked and caught fire. This was a high speed auger - nose into ground. He was not in command but was a passenger. The engine quit and the pilot decided to turn the piet into a sailplane.
His story focuses on pilot skill -lower the nose and maintain airspeed rather than the fuel tank location, but I have always thought of it when considering the center wing design.
Not so sure a J-3 type tank would have been better , very likely worse.
If you can predict what type of crash you are going to have perhaps you shouldn't fly. But we should always look for any safety edge we can find . Just like those ounces and grams you can leave off.
Tom XL-7
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never considered hitting my head on the underside of a center wing tank. That top fuselage tube would give my head a.75 inch warning.
Tom XL-7
Tom:
There is a material difference in wing attachment arrangement between the LE and the XL... Vertically it amounts to inches in difference... Only an inadequate tank can exist above the fus tube on the LE... On the XL are you planing to take take the fuel out at the front of the tank with no sump?... There might be some lost (any) fuel availability in a sustained climb... Sump at rear of tank takes you below the fus tube with plumbing and into the pilot's head territory...
Again, I mention that fuel system glitches are one of the higher frequency fails in home-building and they happen to many people across the engineering skill spectrum... Build a proven fuel sys design and enjoy flying the airplane - you will be thrilled with your achievement...
Steve
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I think a sump would be prudent and the rear location would support climb out best. But I get your point. While running out of fuel in an initial climb out is the worst time to happen one should not be leaving an airport empty. But running low on fuel does require a landing. so a front port might seem a good idea. I was thinking of rear sump but yes my head has a similar address.
Luckily while I like the idea I am not committed to a center wing tank. There will be time to mock one up and sit in the seat. Use a spike to represent the fuel petcock. That will get my attention. No way.
Maybe a better use of time than making airplane noises.
Good point - as I said I had never considered it a problem. Now it is another constraint that has to be solved.
Thanks
Tom XL-7
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Tom:
I think you are completely ready to have a peek at Pat Main's[slowride] run at building a metal Spratt 103 - those wing halfs are just a tad over 20 lbs - no ailerons ofcourse... Pat and builder/flyer friend have matching XL's and they did the total conversion of the 1/2 engines cutcase method including the crank adaptions - you should see their prop duplicator machine - a rework of Pat's Dad's axe handle making machine... Are these guys gear heads or what!...
My message, build your dreams!...
Steve
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So after all that on center wing tanks, there is one heck of a convenience of fueling a fuselage mounted tank. The weight of 5 gallons of fuel seems to be variable because there seems to be a range of 5.8 to 6.5 pounds per gallon. So we can compromise to approx 31.25 pounds. The center wing tank is mostly centered on lift, so is not an issue.
I never read Sam or Les complain about the changing balance. Much easier to keep an eye on fuel levels as well.
Swivel head
Tom XL-7
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So after all that on center wing tanks, there is one heck of a convenience of fueling a fuselage mounted tank. The weight of 5 gallons of fuel seems to be variable because there seems to be a range of 5.8 to 6.5 pounds per gallon. So we can compromise to approx 31.25 gallons. The center wing tank is mostly centered on lift, so is not an issue.
I never read Sam or Les complain about the changing balance. Much easier to keep an eye on fuel levels as well.
Swivel head
Tom XL-7
Tom,
You mean 31.25# in weight, yes.
Yes, if you have a "centered wing tank" the CG will change the least. Though in right or left wing, has not been an issue as it is pretty close to the center LONG axis of the aircraft.
Yep, filling a fuselage mounted tank, is easier than a wing tank.
Yep, if you have a tank right in front of you, you can watch the fuel level on your fuel float (bobber rod) vs looking slightly up and observing a clear line that you have barred line behind.
attached is a center tank photo of 5.3 gal. before the center tube notch. With a 6'2" pilot below.
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I modified the original post from 31.25 gallons which was wrong to the corrected 31.25 pounds
good catch Scott
Tom XL-7
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... attached is a center tank photo of 5.3 gal. before the center tube notch. With a 6'2" pilot below.
So to make up for the loss of volume across the top tube, the tank could be extended fore and aft above the wing mount to some degree. This also means there are sumps on each side of the top bar where one would want some kind of balance tube fuel pickup.
I could see mounting bosses from underneath the extensions to the wing mount posts.
Great work Scott! What CAD system/s do you use?
Ken
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Yes, exactly Ken!
And very simple angles, (bosses-attached to the tank) resting on the fore and aft wing attach squares- Keeping in mind, the tighter this location gets, the harder it will be to install wing attach bolts. But many planes are done, with much tighter conditions than these.
AS for keeping fuel even, between sides- yes I think is a must- can either be done by two sumps fore and two aft. Or the simple sump with a cross connection to the other side. And yes, there are those that say they will never take off with 1.5 gals of fuel left- But then you will also have to say you WILL NEVER LAND with 1.5 gals of fuel. To that I will simply say, never say never! When the fuel flow becomes unported, it is a bit late for wishing for more fuel, or to get level and hope it will restart by magic. To run out of fuel with the tank empty-is much acceptable to me. though still not a good thing.
SolidWorks '16 is the CAD
cheers
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Thanks Scott,
Certainly want to leave enough finger and plier room for wrenches and cotter pins install/removal. I still like the addition of a header tank as well.
I'm a Unigraphics NX (day job), TurboCAD, and SketchUp (home business) user.
Ken
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So what exactly are the pros and cons for the fuse tank? is this correct so far?
Pros:
1. Easy to fill
2. easy sight fuel level
Cons:
1. CG gets pushed forward
2. have to manufacture a tank
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So what exactly are the pros and cons for the fuse tank? is this correct so far?
Pros:
1. Easy to fill
2. easy sight fuel level
Cons:
1. CG gets pushed forward
2. have to manufacture a tank
Con: Trim change as fuel is burned off
Con: Very low head pressure
Con: Tank volume (See S. Kiblinger post below)
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I believe Les and Sam have both mentioned that landing is more challenging when the tank is full. Perhaps they can weigh in on this.
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have to manufacture a tank
I don't think we could/should list this as a con- as to get "any" tank the way we really want it to fit the space, we will or would have to mfg it.
And if your capable of welding the frame, building the wings or tail feathers, the tank is easy.
Of course there are easy and hard ways to build the tank. So a bit of R & D goes a long ways in this area. But a little creative welding, and tab making can go a long ways to building a alum, tank in a few hours.
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I believe Les and Sam have both mentioned that landing is more challenging when the tank is full. Perhaps they can weigh in on this.
I never made that statement and it doesn't reflect how my plane flew.
There was negligible difference between full and partial full load on my plane because of the limited about of fuel used and it being located fairly close to the CG. If there had been a difference in handling, landings would have been easier with full tank because pitch would be less sensitive.
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This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.
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This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.
Ok, being we are calling out exact dimensions, lets do some quick math.
you have tube bolt centers called out at 4.5 inches- yes
and wing rib edge is 2" to center of strap hole (sheet 35) -yes?
So we add these and get 8.5" MAX space between centers- yes? for a 1/4" tank gap (outsides)
And if we use the 1/2" radius also called out on sheet 35 for the wing straps this would consume 1" fore and aft of tank- yes? or a 1/4" distance at least past your tank sides.
And using the strap distance of 27" spread, this also gives you 1/2" for your nuts to fit in.
While tight, I guess things have been in tighter places. And there are tools for holding nuts for situations like this.
Now for strength calculations- Someone, somewhere probably knows how to do the difference. I don't.
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Scott, My intention is to leave my wings attached after I first install them, then add the tank. The tank is just a simple rectangle. Should be easy to make. If I wanted to remove the wings so I could trailer it, I would shorten it just a little and add the upper shape of the wing to get my volume correct. I like the idea of having the tank right over the CG. You could add a rollover valve from a dirt racing supplier to the vent on the cap to keep the gas in the tank in case of a tip over. They are very cheep and they do work ( been there, done that ). Just weld aluminum angle to each end to fasten to the square wing cross tubes. As far as the outlets, one in the right front and one in the right rear with a fall of about 6 inches back to front and a tee where they meet at the front. I know this would have it's pros and cons. Just thinking out loud right know. I would like as many people to share there input as possible. Thank you. Randy Q.
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Scott, My intention is to leave my wings attached after I first install them, then add the tank. The tank is just a simple rectangle. Should be easy to make. If I wanted to remove the wings so I could trailer it, I would shorten it just a little and add the upper shape of the wing to get my volume correct. I like the idea of having the tank right over the CG. You could add a rollover valve from a dirt racing supplier to the vent on the cap to keep the gas in the tank in case of a tip over. They are very cheep and they do work ( been there, done that ). Just weld aluminum angle to each end to fasten to the square wing cross tubes. As far as the outlets, one in the right front and one in the right rear with a fall of about 6 inches back to front and a tee where they meet at the front. I know this would have it's pros and cons. Just thinking out loud right know. I would like as many people to share there input as possible. Thank you. Randy Q.
Not sure about the height of your rectangle, but having the top profiled to the wing, looks good and is not hard to do. Wind drag would be far lower as well, that XL has plenty of drag already.
Yes, on the CG thing
Yes, you could on the rollover valve as well.
The angles for the support/attach areas are done just like you said.
Not sure where the 6" of fall comes from, as the angle is about 2" if you are talking the center fuselage tube, but if you meant where you would combine the front and rear outlets, then yes I follow you.
On the fuel flow/ simple ground test, at max climb and max decent angles should tell the story.
All sounds good.
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I realise this is an old thread, but i have thoughts on this.
What if a person were to angle the rear of the tank forward on the bottom, perhaps it would move the rear sump parts away from the person’s head an inch or two and also give better access to the wing hold bolts? Ive been thinking seriously about a center tank that holds 4 gallon or so and maybe a 1 gallon header tank. Id make the top airfoil shaped and use a windshield like putt putt to cover up the front part of the airfoil (like a cub sort of has). Thoughts?
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I built an aluminum tank to drop in the wing panel. The top of the tank is airfoil shaped and serves as top of wing in that location
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It appears that the top also doubles as the mounting flange in addition to being the top of the wing? Very cool.
I love the pressure test balloon too :emoji_u1f646:
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Very nice, Frank.
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Thanks fellas ,
Steve, yes that's the plan with the flange.
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Hi:
First ... I want to say that looks like very very nice work, Frank. Congratulations.
I have a J3 kitten, which has a heavy fiberglass tank between the panel and the firewall. I'd like to move the tank up top ... preferably between the wings, but I'm not sure of the headroom there. I'll have to measure tomorrow. Your idea is excellent, and I'll be doing something similar to that.
A few questions:
1. What grade of AL did you use? What thickness?
2. Will you add internal baffles?
3. What did you use to seal the tank?
4. How do you plan to seal the upper joint ... where the top of the tank joins the sides.
5. What will you use as a filler cap? Any links to where I can get it?
6. How did you attach the filler cap to the top of the tank? Is it a problem to attach a flat filler cap to a rounded surface?
7 Do you intend to mount the upper flange to the tops of the ribs? Or will you add additional bracing to the ribs first?
Thanks.
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Check out Bob Hoover's website, (no, not that Bob Hoover), on aluminum tanks https://bobhooversblog.blogspot.ca/2006/12/av-yo-fuel-tank.html (https://bobhooversblog.blogspot.ca/2006/12/av-yo-fuel-tank.html)
Also if your an EAA member...
How About An Aluminum Fuel Tank? By Tony Bingelis (originally published in EAA Sport Aviation, December 1986)
It's an easy search.
Good luck.
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http://www.eaglersnest.com/forum/index.php?topic=1636.0 (http://www.eaglersnest.com/forum/index.php?topic=1636.0)
MontanaMan- Here is my thread for the XL fuel tank.
It should have the answers to your questions. and several photos, i will be adding a few edits to update it soon too.
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Thanks for the help. Frank ... your work is really good. I just finished reading your entire XL thread. Can't wait to see how that 3VW motor performs!
-Robert
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This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.
Ok, being we are calling out exact dimensions, lets do some quick math.
you have tube bolt centers called out at 4.5 inches- yes
and wing rib edge is 2" to center of strap hole (sheet 35) -yes?
So we add these and get 8.5" MAX space between centers- yes? for a 1/4" tank gap (outsides)
And if we use the 1/2" radius also called out on sheet 35 for the wing straps this would consume 1" fore and aft of tank- yes? or a 1/4" distance at least past your tank sides.
And using the strap distance of 27" spread, this also gives you 1/2" for your nuts to fit in.
While tight, I guess things have been in tighter places. And there are tools for holding nuts for situations like this.
Now for strength calculations- Someone, somewhere probably knows how to do the difference. I don't.
My plans show mounting hole centers on fuselage at 2.5” center to center. Is 4.5” acceptable?
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Ah wait, i see where 4.5” comes from now.
Is that ok to do if one uses 5/8 steel tube and a wider gusset?