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We started day 7 by assembling the fuel tank. This is one area that traditionally causes better than half of engine problems over the life of a model. Relying on past experience with Saito twin cylinder engines, we installed larger than normal diameter fuel pickup tubing and heavier clunk to eliminate fuel starvation. While the 180 twin doesn't need the 2.4 ounces per minute the 300 twin does, this is an easy modification to make now. The tank will be sealed with silicone gasket type sealant. |
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3/16 OD (1/8-inch ID) brass tubing was used for the fuel pickup line with larger fuel tubing and a heavier clunk. The stopper holes were enlarged to allow the tubing to pass through it.
The standard brass tubing was used for the vent. We will use the exhaust tube pressure tap and fuel hose to provide positive pressure to the tank.
The tank is a Sullivan No. 444 24-ounce tank, not the kit's 18 ounce one.
You can see in the photo the sizes of the fuel tubing. The vent line does not have to be the same size as the pickup line. The clunk and flex tubing were checked to make sure it flexes to the bottom of the tank no matter what the orientation of the tank. The clunk is about 1/2 inch away from the back of the tank to prevent it from bottoming out on the tank during high G maneuvers.
Silicone gasket "goo" was used to seal the tank's stopper. This should last years and keep the tank sealed, preventing the problem alluded to earlier. |
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Not specifically mentioned in the instructions was the need to keep everything about the aileron and flap linkages symmetrical and straight. The addendum in the kit showed the orientation of the servo horns and push rods.
We used a square to make sure that the linkage was at 90 degrees to the servo horn. The parts from the kit are high quality. The locking nuts on the 4-40 push rods must be locked with thread lock or CA glue or they will loosen up in flight!
It is best not to rely on programmable radios to make adjustments to these controls. Do as much as possible to mechanically balance the right and left control surfaces (adjust the center and end points, make absolutely certain that the control horn attachment holes are at the hinge line when the control is aligned with the main wing.
Make sure to put CA adhesive in the holes for the control horns. The balsa is not strong enough to last long without this reinforcement.
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We have enough of the kit assembled to do a rough balance. This will help in deciding if additional weigh will be needed and where to locate the remaining components.
As seen in the photo, components were place on top of the model where they would be located. It is best not to add dead weight to a model to balance it. Instead, relocating components to achieve balance and installing larger functional parts is the best way. The model came up tail heavy. We need to move the rest of the components as far forward as possible.
This was the purpose of weighing many of the components in the beginning. We used a 6v 1600 Mah receiver battery under the fuel tank area. Also, two 2.0 Mah cells were added for the on board glow system. The radio was placed as far forward as possible as well. The throttle servo will be installed as far forward as possible, too. We could have used the kit wheels to assist in moving the CG within the range.
With all of these changes, the CG is right in the middle of the suggested range at 4-5/8 inches.
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The completed model is almost ready to fly. It weights 5539 grams (12.20 lbs), which is at the lower end of the 12 - 14 lb advertised range. We still have to paint the prop tips (for safety), add our AMA identification (AMA Safety rule), run the engine, verify that all the hardware is tightened. We will fly this plane during Easter weekend if the weather cooperates.
Hangar 9 has provided a high quality kit and a very capable airplane. We bought ours from Horizon Hobby . The additional adhesives, carbon fiber push rods, spinner, propeller, etc. were purchased from the local hobby shops. The hardware components in the kit are top shelf and include everything necessary to complete the model other than the radio system and engine.
Our choice was to "kit bash" the model somewhat as outlined in the construction notes. The instruction manual is very good, no plans are needed. We have seen this model fly and it is a very capable aircraft. It can be a good intermediate trainer and an advanced aerobatic performance machine depending on the pilot's skill level and control settings. A programmable radio is a real plus in bringing the special features and flight capability out.
We wanted to build this kit to learn some of the advanced radio setup features. We were not disappointed. Several radio setups are given in the instruction manual for four JR radio systems and one Futaba system. We learned many new setup hints for the JR PCM10, X347, and 388 radios we have. It was worth the price of the kit just to gain this knowledge without the pain of the mistakes of trial and error (some of which we were in the midst of)! This information will be applied to other models, making them far more enjoyable to fly.
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