Posts: 207
Joined: 9/4/2002 From: Stockholm, SWEDEN Status: offline
Hi there For the AMA428 i guess 5 1/4 oz would be fine, but because the length of the tank is probably more than the space between the firewall and the wall under the LE. So my question is where do you people put the tank? in front or under the wing. One more thing, here in Sweden we don't have to use throttle so we have ordered our Nelsons with a FAI venturi, So we have to do a shut off like the F3D use, by squeezing the fuel tube. I think all this stuff would not fit behind the firewall. I would like your ideas and how you solving this problem over there.
Posts: 303
Joined: 12/29/2001 From: Chatsworth,
CA, Status: offline
Per_N
All the 428 guys I know use one of the following tanks.
Tettra 5.25 oz, Tettra 6oz, Jett flat 6oz or standard Jett 6oz. All these tanks are bubble less in design. Our Q500 airframes are designed with these tanks in mind. I would question using a 4oz tank. My stuff is reasonably competitive and I am very close to being out of fuel after 11 laps with the 5.25 tettra. Most guys put the tank pretty far back which puts it at least 2 or 3 inches under or over (high or low wing) the front part of the wing and a couple of inches behind the firewall. You have to cut an opening in the bulkhead in front of the wing for the tank to slip through. Most of us do not use hatches to access the tank. It is simply pulled out from the wing compartment. I have room in mine to put the battery in front of the tank if I need additional nose weight. There is plenty of room even in a NEM-Q, Bird of Prey or V-Max which has the servos in the wing compartment also. (most wood Q500's put the servos in the fuse behind the wing. As far as the fuel shut off goes it should not be a problem. I find the "tube" type the best which you could imbed in the firewall just like a Q40. Maybe someone could post a picture of one. It works off a normal throttle servo.
Posts: 207
Joined: 9/4/2002 From: Stockholm, SWEDEN Status: offline
Thanks everybody! It will be under the wing. But my bubbles tank (don't now the brand of it) is 1,88" x 1,61" x 4,33" so i have to put the servo for the servo pretty long back, otherwise it will crash with the tank. I post a picture so everybody understand. I have not put the things together yet as you can see.
Posts: 4000
Joined: 12/23/2001 From: Kingman, AZ, USA Status: online
That is a Tettra tank and looks to be a 51/4 ounce but can,t quite make it out. Position looks about right for a wood Quickee. If neccessary you can cheat it forward a bit. It does not have to be right on the C.G. but the ideal position is centered on the C.G. Usually the throttle servo works toward or all the way to the rear of the wing compartment sometimes just forward a bit. Can,t offer any thoughts on 'engine pinch offs' haven,t used those since my controlline combat days.
Barry is right a four ounce Tettra is not enough for .40 size engines. I do use use one for a 'Slow Quickee' class but that is with .25 engines. The 51/4 is ideal for our 424 class with Thunder Tiger .40's and I do not race 428 so will not address that.
Posts: 207
Joined: 9/4/2002 From: Stockholm, SWEDEN Status: offline
Thank's John Yes it is 5 1/4. I Think i can put the throttle servo (shut off servo) just behind the tank and against the fuselage side. Or as you say behind the wall of TB. Just have to wait and see what the weight will be.
Posts: 1570
Joined: 1/6/2002 From: Team Coldies,
CA, USA Status: online
Per_n, here's a pic of my current Neme Q lay out,,,
The 2 V tail servos are Jr 3141 DS and the throttle is a HS81. The Rx is an Airtronics 94777 and a NMiH 720 maH battery. The tank is a tetra 6oz.
Something else you may want to consider when designing your fuselage,,, Locate the High point of your wing and transfer that point to the fuselage. Make this point on the fuselage the "Fat point" of the fuselage to match the wing. The Goal here is to use the thickest part of the fuselage to the thickest part of the wing to acheive the minimum combined thickness of 3.5 inches. Also remember your gonna need 2.875 inches between the fuselage sides at some point between the Leading edge and the Trailing edge of the wing saddle, The current trend is to have it back there by the #2 bulkhead
BV
< Message edited by Bill Vargas -- Jan 5 2003 6:26AM >
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Posts: 207
Joined: 9/4/2002 From: Stockholm, SWEDEN Status: offline
I see you have mounted the servo in front of the wings TB wall bracket. Usually on our AMA424 Quickie we put them about 4" back of the wall, inside the fuselage. That means you never reach them without making a hole in the fuselage. We do this only because we need weight in the back to get the CG right. My plans was to do the same with this one. Maybe i should consider this now. About the 3.5" , I have made a straight line in the bottom of the fuselage so there should be no problem. I post some picture so you understand. (A picture tells more then a 1000 word)
By the way, where have you put the battery Bill to get the CG right?
On our club 20 models we don't use a servo to kill the engine. I have a homemade tank made out of tin (fuel can) with the fueltube soldered to the bottom. Some negative G's are enough to kill the engine
Posts: 207
Joined: 9/4/2002 From: Stockholm, SWEDEN Status: offline
Hi Bill I post a picture of how we mount the servos on the AMA424 This is only to get the CG right. This plains is a little bigger also. I don't think we have the same rules here as you have.
Thank's again Bill for you post, it really give me some good ideas.
Posts: 2853
Joined: 12/29/2001 From: Brantford, ON, CANADA Status: offline
I use the 5.25 oz Tettra for both Quicky and 424. I install the tank backwards. The back of the tank is against the firewall cushioned with some foam. With this installation the tank will not move. The fuel lines cannot be pinched and are easily checked. The lines loop from the tank and then have a straight run to the fuselage exit and the engine. This only works with bubbless tanks. It will not work with clunk tanks.
The shutoff on the Q40s does not go to the firewall with all of the tangled lines that needs. The fuel line comes out of the tank and immediately loops through the shutoff on the inside of the fuselage. My shutoff wire is only about three inches long from the servo. Again all of this stuff is visible and accessible every time the wing is removed.
When I first suggested this I was greeted with sarcasm and laughter. It is up to the reader to decide whether or not you believe a guy actually puts his tanks in back-wards!!...................
Posts: 1570
Joined: 1/6/2002 From: Team Coldies,
CA, USA Status: online
Per_n, The battery location for that particular model (Neme Q) is located just behind the Tank, the Rx is next to that and then the servos. The reason for this configuration is that this is how the plans illustrated the internal components location.
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