gschuld
Well-Known Member
I have been contemplating fuel tank layout for a new KR and this came to me as an idea. If the idea is not workable, no need to beat around the bush. I can handle the critical thoughts( I am married you know
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I am curious as to whether this could work well. The common fuel tank setup for taildragger KRs would be a pair of equal sized fuel tanks in the stub wing area(of between 8-12 gallons each). These tanks are located between the main and rear wing spars starting immediately outside the fuse. If a smaller(roughly 5 gallon), triangular cross sectioned fuel tank (filling the void under the seat bottom area) was built to fit between the wing spars nearly the width of the fuse, and connected to both the right and left stub wing tanks, it would essentially create a 3 section fuel tank that would function as a single tank with the center tank being the active sump area.
I heavily lean toward (reasonably light gauge) welded alumunim fuel tanks. (A very good friend of mine builds aluminum fuel tanks for a living with 25 yrs. experience. His skills are absolutely top of the line, and I like the idea of being able to leak test them before installing them in a composite wing structure) My thought is to have a pair of small aluminum tubes (perhaps 3/4") protrude toward the fuse from each of the two stub wing tanks. One up high and all the way forward and one down at the bottom of the tank in the middle fore and aft. Both tubes would be long enough to protrude through the fuselage sides by about an 1 1/2". The center tank would also have a pair of aluminum tubes protruding (matching the location of the stub wing tank tubes). This way, a short flexible fuel hose could connect the tanks together by clamping them over the transfer tubes facing each other.
I would presume that a measure of slosh control would be needed (baffling in the stub wing tanks would be a given). Such as one way flaps on the inboard side of the lower fuel transfer holes to prevent fuel from draining quickly from high to low in a long banking turn, etc. Perhaps filling, or partially filling, the center tank with anti slosh foam could be useful. The wing will have its dihedral starting from the fuse sides, so there would be some measure of gravity promoting fuel to end up in the center tank(the lowest point).
The potential benefits:
1- a single fuel pickup in the center tank (fed by both stub wing tanks)
A- No need to worry about the safety and functional concerns regarding the fuel delivery from multiple independent fuel tanks. A BIG plus, considering that the complications involved with multiple fuel systems have been directly or indirectly involved with a fairly significant percentage of aircraft accidents.
B- Would allow a single fuel pump line and system. Far less complicated that selector valves, multiple fuel pumps, transfer lines, etc)
C- A single fuel sender and gauge (in the center tank) would simplify the calculations of remaining fuel.
2- The center tank could have a gasketed removable inspection port(that the fuel sender/fuel pickup line passes through) large enough (5" perhaps) to be able to inspect/maintain all mechanical parts(flappers, fuel pickup/filter, gauge sender, slosh foam?) This would not be possible with stub wing tanks being enclosed by the wing on its upper surface.
3- All 3 tanks would be in a location where there would be very little wiring(concerning possible sparks in case a tank/transfer tube was punctured in a crash). As opposed to having a header tank inches away from tons of active wiring, not that this has proven to be inherently unsafe or anything.
4- The center tank would increase the overall fuel capacity by a roughly 20-25%.
)I am curious as to whether this could work well. The common fuel tank setup for taildragger KRs would be a pair of equal sized fuel tanks in the stub wing area(of between 8-12 gallons each). These tanks are located between the main and rear wing spars starting immediately outside the fuse. If a smaller(roughly 5 gallon), triangular cross sectioned fuel tank (filling the void under the seat bottom area) was built to fit between the wing spars nearly the width of the fuse, and connected to both the right and left stub wing tanks, it would essentially create a 3 section fuel tank that would function as a single tank with the center tank being the active sump area.
I heavily lean toward (reasonably light gauge) welded alumunim fuel tanks. (A very good friend of mine builds aluminum fuel tanks for a living with 25 yrs. experience. His skills are absolutely top of the line, and I like the idea of being able to leak test them before installing them in a composite wing structure) My thought is to have a pair of small aluminum tubes (perhaps 3/4") protrude toward the fuse from each of the two stub wing tanks. One up high and all the way forward and one down at the bottom of the tank in the middle fore and aft. Both tubes would be long enough to protrude through the fuselage sides by about an 1 1/2". The center tank would also have a pair of aluminum tubes protruding (matching the location of the stub wing tank tubes). This way, a short flexible fuel hose could connect the tanks together by clamping them over the transfer tubes facing each other.
I would presume that a measure of slosh control would be needed (baffling in the stub wing tanks would be a given). Such as one way flaps on the inboard side of the lower fuel transfer holes to prevent fuel from draining quickly from high to low in a long banking turn, etc. Perhaps filling, or partially filling, the center tank with anti slosh foam could be useful. The wing will have its dihedral starting from the fuse sides, so there would be some measure of gravity promoting fuel to end up in the center tank(the lowest point).
The potential benefits:
1- a single fuel pickup in the center tank (fed by both stub wing tanks)
A- No need to worry about the safety and functional concerns regarding the fuel delivery from multiple independent fuel tanks. A BIG plus, considering that the complications involved with multiple fuel systems have been directly or indirectly involved with a fairly significant percentage of aircraft accidents.
B- Would allow a single fuel pump line and system. Far less complicated that selector valves, multiple fuel pumps, transfer lines, etc)
C- A single fuel sender and gauge (in the center tank) would simplify the calculations of remaining fuel.
2- The center tank could have a gasketed removable inspection port(that the fuel sender/fuel pickup line passes through) large enough (5" perhaps) to be able to inspect/maintain all mechanical parts(flappers, fuel pickup/filter, gauge sender, slosh foam?) This would not be possible with stub wing tanks being enclosed by the wing on its upper surface.
3- All 3 tanks would be in a location where there would be very little wiring(concerning possible sparks in case a tank/transfer tube was punctured in a crash). As opposed to having a header tank inches away from tons of active wiring, not that this has proven to be inherently unsafe or anything.
4- The center tank would increase the overall fuel capacity by a roughly 20-25%.
