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  1. Gnat

    Wanted pictures!

    Well if they do I am searching the wrong way lol. Spent about two hours on and off yesterday searching and didn't find anything which is why I asked here. I did run across images of 12 un-skinny guys standing on wall panels and so on but those three from Rutan were much more demonstrative of...
  2. Gnat

    Wanted pictures!

    I'm looking for a series of images that I think were in the education portion of the Quicke, LongEz and VariEz not 100% sure but I believe that is where they were. The images show a series of a stressed skin panel. It first shows a layer of cured fiberglass skin then the skin being bent into...
  3. Gnat

    Just when you thought it was safe....Gnat GK-7

    40,000 ( ~23,000 ) Cessna 150's were built that way because they were strut braced normal category air frames designed in the late 50's.That is what the original designers came up with. This is apples and oranges. The Gnat is not a high wing strut braced normal category air frame, it is a low...
  4. Gnat

    Just when you thought it was safe....Gnat GK-7

    What they said lol. There is theory and there is what actually works in practice. We have all grumbled over parts that fall apart if you look at them and other things you cant put together. Both caused by the sob eng who didnt figure out what works in practice. I have spec'd 16 or 20 for...
  5. Gnat

    Just when you thought it was safe....Gnat GK-7

    I am curious if you are calling the ribs "stringers". They are there in the Cessna and the Humlebird. Without knowing the design flight loads how can you guess?
  6. Gnat

    Just when you thought it was safe....Gnat GK-7

    Yup there is a process to remove and then stabilize the oxide layer. The CriCri used powdered dish soap and brill pads followed up by alodyne. It was a fairly manual process but it worked. As far as I know there haven't been any debonding on them. The Gnat and a lot others use a bit more...
  7. Gnat

    Just when you thought it was safe....Gnat GK-7

    The manual I had for my 172M showed approved materials for "field expedient" repairs. I am sure Cessna would love to sell someone a sheet of alum for a few times its value from any where else. Anyway even a 152 wing has nose ribs. Those are what will take the airloads from the skins and feed...
  8. Gnat

    Just when you thought it was safe....Gnat GK-7

    The wing skin on the Gnat is 0.025 6061-T6. It is 0.025 because it needs to be. You might want to check a Cessna repair manual and I think you will find the leading edge skins are 025 or 032 2024 which of course is even stronger than 6061. Your 0.010 5052 1/2h is a weaker material with only...
  9. Gnat

    Just when you thought it was safe....Gnat GK-7

    Yah I know what you mean, there is all that glamour and money with newspapers but then you have to deal with all those groupies...airplanes seem so much safer A lot of the foam stuff has been learned the hard way by someone. It really goes against what you might think logical as it is so weak...
  10. Gnat

    Just when you thought it was safe....Gnat GK-7

    BBerson It is unfortunate that what should have been easy to find materials is ending up hard to find in some areas. I don't know where you have looked but Port Townsend should have a few places offering the flotation billets. It actually should have several as it is the type of town I would...
  11. Gnat

    Just when you thought it was safe....Gnat GK-7

    Any span wise glue joints greatly reduce the strength of the core. From what I was able to find out you would be looking at having a core with only about 35% of the strength of a monolithic core. After the first few posts I actually went and ran FEA on a split core and the designed solid core...
  12. Gnat

    Just when you thought it was safe....Gnat GK-7

    Yah yah things are going great!! (should have forgot all about this #$%#$#@% airplane BS and got a paper route grumble grumble grumble LOL) The new workstation is allowing me to load much more complex assemblies into solidworks so I can spot gotchas that snuck by me before (nothing major) or...
  13. Gnat

    Just when you thought it was safe....Gnat GK-7

    Three(3) 10" x 20" x 96" bouyancy billets is enough to carve out ALL wing, tail, and control cores for the Gnat and have some leftovers.
  14. Gnat

    Just when you thought it was safe....Gnat GK-7

    The Scotch weld version I was referring to covers 320 sqr ft per gallon compared to about 80 sqr ft per gallon for T88 and most other epoxies. It does have superior characteristics compared to everything else and you have to use the right hardener to get it runny enough to be useful. I think the...
  15. Gnat

    Just when you thought it was safe....Gnat GK-7

    Epoxy Just as a quick update. Still working on drawings (groan er uhm YEA!!!! SO MUCH FUN!!) One of the guys her is plowing ahead an has ordered all the materials for building a Gnat. So we have been working on making sure he had the right materials and the right epoxy. Originally I used...
  16. Gnat

    Computational Fluid Dynamics

    If you create a bow bulge or nose if you get it to deflect the air to the sides instead of up. That makes the ass end easier to deal with as the air will tend to spill off to the sides. The other part to deal is usually forgotten but it makes almost as much or more drag than the rest will. That...
  17. Gnat

    Just when you thought it was safe....Gnat GK-7

    Gnat EPS Foam Just thought I would post some more information about sourcing the foam. This hopefully will let you look at alternate suppliers if you don't/can't buy Dow Flotation billets. Ok first thing is due to the process extruded polystyrene foams are actually fairly consistent when...
  18. Gnat

    Just when you thought it was safe....Gnat GK-7

    I had a quick look and am surprised it is foam safe it still has toluene and alcohol in it. The problem is that it is a very weak adhesive ~100psi compared to about 3600 for carpenters glue and about 10K for a structural epoxy. And just noticed something we definitely are not using XPS! lol Not...
  19. Gnat

    Just when you thought it was safe....Gnat GK-7

    I am assuming by top and bottom airfoil half's you are talking about bonding up a core? The problem is not the strength of the adhesive. The problem is how the stress is fed into the structures. The wing skin is just as critical as the adhesive as is the monolithic foam core as is the built up...
  20. Gnat

    Just when you thought it was safe....Gnat GK-7

    Have been busy for a few days but found some time to read the forum. The Gnat was designed around using epoxy to bond everything together. The total amount of epoxy used in about 2.5 liters. If you order Aeropoxy from Assco you might spend $120? for a gallon but at least you would know it...
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