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Thread: Lowrider LSA

  1. #561
    Lowrider
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    Cub,

    Lesson learned...one of my Labs took a bite out of the family room carpet trying to "get" the dot...wife was not happy. Oh yeah...then there was the time he tried to climb the wall to get "it". With 2 dogs you can shine the laser on the one dog's paw and get the other to attack the dot...great fun!!
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  2. #562
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    noting tangible in the take off and i have 1100 hrs on this aircraft.

  3. #563
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    Beaver,

    What was the original thrust line off-set on your Cub and did you go back to the same after your less than positive experience with the zero thrust. Also, what is your HP and prop?

    I've heard of others who had a bad experience with changing from factory off-set to 0 degrees and I'm wondering if there is some common thing that makes them not respond well to the change to zero. I also wonder if the original off-set was 1.5 degrees or maybe much greater due to sag over time and the zero just brought it back to near factory and therefore an improvement in flight characteristics. I'm having a hard time with the exact measurement of "half degrees" on the thrust line of an older plane.

    Any ideas out there?
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  4. #564
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    Finished the tail wheel attach mount this morning and I'm getting ready for the doors. #2 son is doing some lathe work on the tail wheel at some point and I hope to have that done fairly soon as well.

    Found out that Airxraft Spruce is no longer carrying the parts for the H2AD engine mount ring kit. Anyone have any ideas who or where else I might find the parts? It almost certainly requires the use of some fairly precise bending equipment, otherwise I would attempt it myself. The other option is a muffler shop with the patience to bend the tube parts for the ring. Any ideas would be appreciated.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

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  5. #565
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    Try to find someone with a mandrel tube bender if you want to bend the tubes without collapsing one side. I found a custom truck shop that had one they used to bend tubes for grilles and roll bars.

  6. #566
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    Last edited by Cub junkie; 03-02-2014 at 06:04 AM.

  7. #567
    skywagon8a's Avatar
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    You might try these folks: http://www.wentworthaircraft.com/ They may have a bent Cessna 172 engine mount from which you can salvage the ring.
    N1PA

  8. #568
    Lowrider
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    Thanks Jimbo and Sky!!

    Sent Wentworth an email...we'll see what they have. I'm glad you mentioned them.

    I suddenly realized I don't know what size and thickness of tube is used in the ring. Anyone know?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  9. #569
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    Sky,

    You are the answer man for sure. Wentworth has a like new ring for the H2AD for $150 which I snatched up and it is on the way in the AM. Thanks for the idea!!
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    There are no new ways to crash an airplane no matter how hard you may try!

  10. #570

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    I was home to see mom a few years back and stopped in to see the guys at Wentworth. They treated me like a long lost brother, gave me a tour and let me dig through boxes of stuff looking for small parts. The have a box after box of small parts in the store rooms. The guys where great about helping me find stuff for my friends 170. The knew just where to look for whatever part I wanted. Great guys and gals to work with.
    DENNY

  11. #571
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    Quote Originally Posted by DENNY View Post
    I was home to see mom a few years back and stopped in to see the guys at Wentworth. They treated me like a long lost brother, gave me a tour and let me dig through boxes of stuff looking for small parts. The have a box after box of small parts in the store rooms. The guys where great about helping me find stuff for my friends 170. The knew just where to look for whatever part I wanted. Great guys and gals to work with.
    DENNY
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    Strangers are friends I have not met yet

  12. #572
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    Couldn't agree more! Dave in the engine shop did a fine job, friendly and knowledgeable unlike some you run into in other states which will remain nameless.
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  13. #573
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    New subject....I put the 2 rails on each side in for the sun roof this morning and it looks like if I use the 1/16" Lexan as suggested there will be a lot of flutter and flapping of the skylight with in flight and probably from prop wash also. It is 30" between rails and I wonder if this has been addressed in wide body Cubs and how it was dealt with? I'm thinking a center rail to reduce the flapping of the Lexan would solve the problem.

    Also, I'm planning a channel on the underside of the rails to allow a Kydex sun screen to slide fore and aft as needed to keep over head sun from shining directly down into the plane. It will also block the sun from fading the interior when the plane is parked. Anyone else do this and if so how did it work out?
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  14. #574

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    I used .080 Lexanne for my side windows and skylights and have no issues other than Leksand little soft and scratches easier.

  15. #575

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    Here's how RAN's does it with the S-7S, 3 pre bowed 1/2" anodized aluminum tubes that match the airfoil, and secure front and back into welded tabs. Also supported in the middle. Aluminum strips to pop rivet through, to spread the point loading on the lexan, SOFT rivets used here on purpose. It is 30" between wing roots, to give you an idea of the spacing. It doesn't seem to leak, and doesn't move, plenty strong. I used tinted lexan. Don't recall the thickness but pretty thin, 1/16" sounds about right.
    Last edited by courierguy; 03-08-2014 at 10:38 PM.

  16. #576
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    Thanks guys!

    The supports on the Rans are in addition to the rails (what I'm calling the outside supports) and the Lexan is actually riveted to the alum tube. That makes sense to me but I think I might try using the 3M two sided tape to attach it. No drilling and no pressure from the pop rivet. I'm planning to use it on the edges to seal the sides and I guess RTV front and rear or maybe 3M 5200 but I'm not too sure how well that bonds to slick Lexan or plexiglass.

    Don,

    I may end up using plexiglass instead of Lexan for the reasons you mention as well as the potential problems with mogas or 100LL. It's also easier to break out if need be and I sorta look at the skylight as an "emergency exit" anyway.

    Courier,

    How's the snow down there? We're having break-up early and some flooding...lake is filling fast.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  17. #577
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    I used 1/8" plexi on my wide Cub. 6 screws across at the windshield and aft joint. 3 screws on each side. There is an inverted "U" channel which crosses at about mid point and another down the center. Two screws with a wood washer centered on the cross channel. None on the center channel. The plexi lifts at the highest point of the curve just behind the windshield in flight. It is enough to stick my little finger between the plexi and the channel. Doesn't seem to do any harm nor any fluttering in flight. It sure demonstrates the amount of lift on top of the fuselage. I am not sure whether it would be a good idea to add a screw here or not? It might place a stress concentration point causing a crack. Plexi is strong when the loads are properly applied.

    If you use plexi, I would not use pop rivets, as courier guy has done, since they will apply a concentrated load at the hole and thus generate cracking in the plexi. Screws should not be tight in the plexi. Snug them down then back off a little. Large washers or trim strips to distribute the load. And make the holes over sized. Plexi has a high coefficient of expansion, so when fastened tightly can and will crack. Done properly it lasts a long time without any troubles.

    Use a unibit to drill the holes since it makes a nice clean smooth hole with no jagged edges which could start cracking.
    N1PA

  18. #578
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    Thanks Ski!!

    That's good info.

    What do you think of using the 3M two sided tape? The main reason I am considering it is the reduction of vibration on the plexiglass and the fact no or few screws are needed. I'm in the process of figuring out how to use it on the door and windows without screws since it seals and holds very well. When I was playing with the different adhesives, it showed the best adhesion and was dead simple to use...unroll and stick one side, pull the paper off and stick the part to it...done and it does not apply any localized pressure like a screw or rivet might. It also remains flexible to dampen vibration which I'm told is a reason it has been used successfully on long-haul truck and trailer bodies for many years. The plexiglass would fail way before the tape from what I could see.

    Also, I was thinking of 3M 5200 since I have had very good results using it in a variety of of ways but I'm not sure how well it would adhere to plexiglass.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  19. #579
    skywagon8a's Avatar
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    Low,
    I have minimal personal experiences with adhesives, so will say, from my perspective you are on your own here. I can see that adhesives, in addition to hardware, will help dampen the vibration. Using adhesive on the center "U" channel will place it in a tear off situation. I would think that, over time, it will peel off.

    The lifting loads on the top of the fuselage are high. Let me relate a story of long ago, when I was still wet behind the ears (a teenager). I bought and rebuilt my first airplane. It was a wrecked BC-12D for which I paid $400. I had to make some other deals to raise the $400. I had it mostly assembled when I decided to do some high speed taxi tests. Below flying speed, but with the tail in the air, there was a very loud sharp noise over my head. The top 4" of the windshield had broken completely off. I had not yet put in those screws to hold the trailing edge down. Hey, that is part of the learning process. I suspect that the trailing edge was sucked/bent up to the point of snapping the plexi. It was a straight break completely across from one side to the other.
    N1PA

  20. #580
    jimboflying's Avatar
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    When you want to limit the compression forces of a pop rivet use could try a CherryMax rivet since the compressed length is determined by the rivet not the thickness of the parts.

  21. #581
    skywagon8a's Avatar
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    Since there still is a large difference in coefficient of expansion between the plexi and the CherryMax the potential for cracking of the plexi is still there.
    N1PA

  22. #582
    Lowrider
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    How about a piece of 0.032 2024 that is machine screwed with nut plates into tabs from the frame with no holes or mechanical attachment thru the plexiglass and 3M tape under it? That would sandwich the skylight but not put localized pressure on it and allow for it to be removed and replaced fairly easily.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  23. #583
    skywagon8a's Avatar
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    Sounds good to me. Tape optional.
    N1PA

  24. #584
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    Thinking ahead, I've been doing some research on composite fuel tanks and have found a potential problem with carbon fiber based tank...namely, static electricity and no sure way of getting rid of it during fueling. I'm pretty sure there is a solution since I think there are lots in service and you don't hear of flash fires with them. Anyone know what the best route to take here might be...use fiberglass instead of CF?
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    There are no new ways to crash an airplane no matter how hard you may try!

  25. #585
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    Hmmm...no thoughts on the CF fuel tanks?

    Next question. Sky used 1/8" plexiglass for his skylight. A friend of mine with a standard Cub used 0.080" Lexan for skylight and side windows and has some "flutter" in flight but has had no problems so far with using thinner Lexan and he believe it to be more stable and certainly lighter than 1/8" plexiglass. Any thoughts on which might be better for a wide body or any disadvantages of the thinner material?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  26. #586
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    I used .080 plexi for side windows and one piece for the full size swingup door (Crosswinds cargo door). No problems with flutter and no problems in full slips.
    Gordon

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  27. #587
    SpainCub's Avatar
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    Quote Originally Posted by Lowrider View Post
    Thinking ahead, I've been doing some research on composite fuel tanks and have found a potential problem with carbon fiber based tank...namely, static electricity and no sure way of getting rid of it during fueling. I'm pretty sure there is a solution since I think there are lots in service and you don't hear of flash fires with them. Anyone know what the best route to take here might be...use fiberglass instead of CF?

    In my tests, the biggest problems with CF thank has been leaks. If you what to go this route, consider an SPX sandwich with resistant resin to the fuel. This should be done with a vacuum, and even there great care hast to be taken to get full saturation and avoid leakage. My first attempt was a had layup, I have decided that Aluminium what the safest and least eight solution for this problem in my case, unless you are considering an in-bay tank layout.
    Last edited by SpainCub; 03-15-2014 at 12:44 AM.

  28. #588
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    Thanks Gordon! I think there is a weight savings to be had using 0.080". I thought about the full swing up door/window but my wife nixed it over a concern of falling out. I tried to tell her I probably wouldn't roll this plane much but that logic went nowhere.

    Spain,

    Interesting that you are having leaks. I think the old tried and proven aluminum tank is the way to go but my #2 son wants to try a CF fuel tank so we're going to try building one for a 4 wheeler to add some range to the stock tank and see how that come out. We'll see if it is holding up and if it does, we may try something else. I still have a concern over the static charge issue so we're thinking maybe some aluminum insect screen in the mold tied to a grounding strap and see how it drains off static.
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  29. #589

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    Lowrider,


    I believe the VariEze folks use composite tanks, may be a place to get some info. I looked at CF tanks for weight savings also, I believe it's the type resin that's the limiting factor not the matting. Ethanol fuel with react with the resin and you have a mess. If you know you'll only ever use 110 LL or no ethanol fuel you could probably get away with it. I'm going aluminum so I don't paint myself in a corner on fuel. There may be better resins out now, it was a few years ago I looked into it.

  30. #590
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    Thanks Steve!

    I was on their site awhile back and from what I saw they use glass and not CF. You are correct regarding resin. Vinyl ester is the proper resin to use for fuel tanks but I have read that it is sometimes difficult to get it to saturate CF while fiber glass will work much easier. Spaincub mentioned above that vacuum bagging is probably necessary to use CF in most application.

    I'm certainly not an expert here...just reading about things on the web and it looks like wing tanks should be made from fiber glass/vinyl ester and when the parts are vacuum bagged properly there probably isn't a significant difference between CF and glass...weight wise.

    I'm not using a header tank and one of the reason I'm thinking about using composite instead of aluminum is the extra fuel an in-bay tank holds. By completely filling the bay there is apparently 2 gallons to be gained per tank so that's a half hour extra flying time or more with less weight. Can anyone confirm this?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  31. #591
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    Guys, Hi.

    1. Carbon Fiber is conductive. Where was it said that "static issues" would be inherent to carbon fiber tanks? They are completely conductive.......just like aluminum! (some might argue that the resin finish could act as an insulator) edit: why would regular fiberglass be better? regular fiberglass IS NON_conductive.

    2. weight of regular fiberglass vs. carbon: Carbon fiber cloth is often used in a layup EXACTLY like regular fiberglass cloth. If one uses the same weight carbon cloth substituted in place of regular glass.......you will get the same weight layup........but the carbon one will be much, much stiffer! (conversely, if you substitute a properly designed carbon structure for a regular fiberglass structure of the same strength.........the carbon structure will weigh less!!) (Also, it has been said that a properly-designed carbon structure will save roughly HALF the weight of an aluminum structure. But this does not translate or transfer to all kinds of structures)

    3. The issue with LEAKS: leaks and pinholes in composite structures often show up in open, hand lay-ups. As SpainCub said, vacuum bagging the laminate will help, as the vacuum compresses the laminate and evacuates air bubbles............but one must not have a 'resin-starved' or 'dry' layup before the vaccuum process, or leaks could occur........which brings us to #4.

    4. resin-starved layups: carbon fiber is black and opaque when dry and also when wetted-out with resin. Regular glass cloth changes from white when dry to transluscent or even perfectly clear(!) when wet-out with resin. It is easy to tell a perfectly wet-out regular glass cloth laminate. It is not so easy to know when carbon cloth is properly wet-out.

    5. resin: Definitely use the right resin for fuel tanks.

    6. Science: This is not rocket science! or is it???

    I think it is cool that your kids are involved in this project and are pushing the envelope.
    Last edited by Dave Calkins; 03-15-2014 at 02:26 PM.

  32. #592
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    edit: double post

  33. #593
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    Lowrider,
    I'm at the same point; need to build fuel tank and have been going back and forth between composite vs aluminum. For me, the aluminum would be a big learning curve as I don't have a Tig so I would be gas welding the aluminum. Composite gives me the flexibility to more easily match the size and shape to my wing. Both my aileron cables run in front of my fuel tank for ease of installation and I eliminated the cross brace through the tank by using a shear plate. My understanding is that by using the vinyl ester resin along with polyurethane foam the tank will be impervious to fuels including alcohol. Proper bonding for static discharge is necessary. Here's a good link to how that can be accomplished http://www.contactmagazine.com/Hanga...k-Bonding.html The Polyurethane foam can't be hot wire cut but it cuts and sands to shape very easily. The 1/2" thickness takes up some space but would make for a strong tank with minimal glass required. I need to make a decision and pull the trigger and get to it soon.

    Marty57
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  34. #594
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    Dave,

    Good to hear from you as always.

    Agree, CF is conductive but apparently there is a problem with getting it bonded so it can bleed off to the airframe and the to earth ground while fueling. I frequently don't hook up a ground when fueling, certainly not with 5 gal jugs. I read it somewhere on this site, maybe under modifications...don't remember and as I said above there must not be much of a problem or we wouldn't have folks building them from CF. I'm not the expert but maybe the slosh causes static like it can in poly gas cans and why you're supposed to remove them from your vehicle when filling. Not saying it's a big problem but I would like to address the issue if I do try a CF tank.

    Proper bagging should make a resin rich part properly by sucking out the excess resin. The little bit of hand lay-up with CF I've tried seems to be MUCH more difficult to get the resin into the CF compared to glass. I need a vacuum bag system big enough to make a 18 gal tank(s) from CF or use glass and hand lay it. Question for you Sir...can you really pick up extra fuel by filling the entire bay with fuel tank? On my wing I can do that using torque tubes in the wing leading edge or in front of the rear spar.

    #2 son is eager to spend my money and not afraid to bite off more than he can chew. #1 and #3 have no interest in building but both like to fly inverted if I'm driving.

    Marty,

    I have the same problem as you since I need to make a decision on how to build my wing. I can TIG but I need a lot of practice to get it right with 0.040 alum 100% of the time...that's pretty thin stuff when using aluminum...at least for me. Please let me know what you choose...I'm leaning to composite tanks.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  35. #595
    skywagon8a's Avatar
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    Long ago, in 1976, I installed a set of Flint aux tanks in my 185. They were made of hand layup fiberglass. One of them was great, the other one had pin hole leaks which took me many years to find and fix. You need to remove rivets from the trailing edge of the wing to get them in and out. I lost track of how many times that tank was removed. Since it is an aux tank, sometimes a long time would pass between uses and the leak would not be apparent. It's OK now, finally. My point? If I were to do it, I would make them out of aluminum, particularly in Marty's case where his wing has a rigid tank compartment. I would hate to have a fuel leak into that beautiful wood. If you do not have TIG equipment, hire a good welder for the job. It will be worth it.
    N1PA

  36. #596
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    Marty's wings do look great!!

    Here's my plan...build the wing tank bay like my C-170 with 20 or so machine screws into nut plate to remove then lift off the panel, undo the 2 straps, pull the hose and you have the tank out. This is the plan for aluminum or composite tanks. Further, since I'm not in a big hurry to get them into the plane, I will put 5 psi of air and a gauge and monitor it for awhile until I feel comfortable there are no leaks. Might even fill it with colored water and monitor for a bit. Leaks should show up if they exist.

    I'm excited that your one tank is fine after almost 40 years...I'm pretty sure I won't be even though I've given up my thought of being shot by a jealous husband!!

    #2 son and I were TIGing some 0.063 6061 today and it was OK so we may try 0.050 and see how that goes. I think 0.040 will be a challenge though and I could hire it out. Boy, you gotta keep that aluminum stuff clean to get a good weld.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

  37. #597
    Dave Calkins's Avatar
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    Quote Originally Posted by Lowrider View Post
    Marty's wings do look great!!

    Here's my plan...build the wing tank bay like my C-170 with 20 or so machine screws into nut plate to remove then lift off the panel, undo the 2 straps, pull the hose and you have the tank out.

    You could save some weight by not having a "...lift off panel...".

    ...in other words....just cover the tank bay with fabric and if you have a leak....cut off the fabric to get the tank out...no big deal

    EDIT: SORRY ....I was not thinking about this being a metal-skinned wing.
    Last edited by Dave Calkins; 03-16-2014 at 11:10 PM.

  38. #598
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    Lowrider,
    Your tank bay sounds same as mine; no brace through the tank? Do y0u have a sheer plate on the bottom of the wing? As for saving weight by covering the top with fabric it's not a good option as I was told by an engineer who helped me re-design the bay. The bottom sheer plate only translates the sheer strength half way up the spar; the top cover held in place with nut plates and machine screws doubles as a top sheer plate; translating the sheer strength down half the height of the spar. The two sheer plates work together. The covered bay would work well if a brace were through the center of the tank but I didn't like that ides at all. My bay will allow quick removal of the tank. I an also sealing the entire bay in epoxy so the fuel spills won't be a problem unless it were an alcohol based fuel and it sat for a long time. That's not likely as I have good venting to the bay to keep water and fuel spills from pooling. I will likely build the aluminum tank. At an EAA seminar on gas welding aluminum we gas welded 5052 and it was pretty easy. I just need to get the proper glass filter for my hood and it runs $250 from an outfit called "The Tin Man". Any one have one of these laying around?

    Marty57
    N367PS
    Psalm 36:7 "High and low among men find refuge in the shadow of His wing"
    www.marty2plus2.com

  39. #599
    marcusofcotton's Avatar
    Join Date
    May 2009
    Location
    Cotton, MN
    Posts
    342
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    Lowrider,
    I know you are planning many things different than Bob Barrows had in mind, but I'm curious, is the .040 6061 tank on the plans. Are there others using it for fuel tanks? Curious to know how it works out if it is. On the 4 place Bearhawk he specs .050 5052.

    I recall when someone discussed not dimpling the fuel tank cover on the 4 place, it was said it needed to be dimpled as part of the structural strength of the wing.

    Mark J
    Practicing open cockpit extremism

  40. #600
    Dave Calkins's Avatar
    Join Date
    Jul 2002
    Location
    Anchorage, Alaska
    Posts
    5,358
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    Quote Originally Posted by Dave Calkins View Post
    You could save some weight by not having a "...lift off panel...".

    ...in other words....just cover the tank bay with fabric and if you have a leak....cut off the fabric to get the tank out...no big deal
    SORRY. I was not thinking about this being a metal-skinned wing.

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