04/13/2017 at 9:20 pm #79860
I’m thinking of building a Big Dog for slow gas at the Lost Hills contest next week. The kit has been sitting around the garage for awhile and needs to be built before I lose any parts. Already the instructions have done a walkabout, but it doesn’t look too complicated, the plans are there.
I’m going to use a Veco 19 on a Taibi tank mount, salvaged from the late Tom Hammond’s Perris Special. The distance from the back of the tank mount to the prop hub (rear of the propeller) is 4 and three eighths inches. The plans show the firewall to be 4 inches in front of the base of the pylon. I think the nose will be too long. What would be a logical distance from the prop to the pylon?
BTW, any idea what the starting CG should be?
John in Kalifornia04/15/2017 at 2:00 pm #79866Robert Dunham IIParticipant
Just looked at Top Notch’s website to get an idea of the “Top Dog” size and appearance- very nice, should make a decent conversion to glo engines. At 544 sq. in, it is a little large for a Veco 19 but we’ll have to accept that and try to get the plane built in a week. Best guess as to distance between wing leading edge and back of prop is range of 4.375″ to 5″. Your Veco 19 with tank mount measures 4.375″ from back of prop to back of mount, so…the firewall will range from being flush/even with the wing LE to approx 5/8″ ahead of wing LE. Good starting CG to be 72 to 75%. Also might be good idea to have 2 to 3 degree of left thrust and 2 degree of downthrust.
Robert Dunham II04/16/2017 at 3:24 pm #79869
John, the Big Dawg (B.D.) is a great flyer either as on electric or gas, I fly it in both classes!! C.G. should start out at 80%. Robert is right in stating that the Firewall should be approx. 1/2″ from the leading edge of the wing using a suction tank behind the motor. The Veco .19 will be a little bit light on pwr. for the 544 sq. in. wing but once you get it in the air the glide is outstanding!!!! My gas version is pwr’d by an ST .23 swinging an APC 9×3 prop and it really hauls it!! Attached is a pic. of the gas B.D.
Scott04/16/2017 at 3:26 pm #79870
john, I guess the pic. didn’t take I’ll try it again.
Scott04/21/2017 at 7:04 pm #79885
Here’s dem Dawg Bones. 9 ounces bare with no fittings. All doped and sanded ready to cover. The wing is very stiff; I built in the warps and think they will stay.
I opted to shorten the nose by three inches. You can see where I faired in the round firewall to the square fuselage. Yes, the timer is on the RIGHT side; I am left handed.
John in Kalifornia
Attachments:You must be logged in to view attached files.04/22/2017 at 9:12 am #79889
John, looks really good! Can’t wait to see the final build. Trimming should be very simple!! Let me know if you have any questions.
Scott06/20/2017 at 4:47 pm #80159
John, just wondering how you’re Big Dawg for Slow Open Pwr. came out.
Scott06/22/2017 at 10:22 pm #80166
I crashed it at Lost Hills. I’m better at building than trimming. Nothing wrong with the plane, all my fault. Our local, if you can call 90 miles away “local”, field at Perris is overgrown with weeds so I have no incentive to repair the plane for more test flying.
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