Dene Collett wrote: > Thanks Mark J, Larry F & Bill C for the info concerning header tanks. I took > a look at your websights and that cleared up a few things too. Bill sure > makes a good argument for keeping the header tank.
"Keeping the header tank"...yes, as long as you also have wing tanks or a fuselage fuel cell like Bill mentioned. Header tank ONLY, I'd vote no. With wing tanks only, the CG changes very little throughout the flight. Mine moves a little more than an inch, but if I had a only header tank it would be at least double or triple that (depending on the size of the tank). And with wing tanks the CG moves more forward as you fly, unlike the header tank which moves the CG aft as you fly. Forward CGs make it easier to fly, and easier to land. Landing is not the time when you want an aft CG. Bill addresses that by moving fuel to the header, but that means you either land with extra fuel, or if you make a long flight with very little reserve, you land with a CG that would be aft of where it would be with wing tanks only. As for gravity being reliable using a gravity feed carb, that's only partly true in my mind. Gravity feed carbs rely on head pressure alone, and when climbing with a header tank, head pressure is going to be reduced during climbout as compared to level flight, which is not the time to be running lean. Apparently the Aerocarb is set up to run at really low pressures, so Bill's runs fine, but I've heard stories of some carbs running leaner on climbout than in level flight. And with only gravity feed, clogged filters or other obstructions can make a huge difference. With pumps there is a lot more "headroom" for such things. That's not to say that there aren't a lot of KRs flying around with header tanks only though. I do think that if you've got a gravity feed carb feed (or even a regular float bowl or pressure carb), a small header tank (used in conjunction with wing tanks) which you keep full all the time is probably a good idea. But you'd need to rig an automatic pump system to keep it full, a warning to tell you when it's not, and an overflow back to the tank for when something goes wrong and the pump doesn't shut off when it's supposed to. I think Ron Eason made something similar, as well as Don Reid and others. This makes sense, if you don't mind fuel in the cockpit. Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net --------------------------------------------------------------
