Smoke Setup: How To
I just typed this up today for those of you who would like to see a good how-to on smoke setups! (Typed it up somewhat formally with intro, body, and conc. so that I might use it as a school paper with some editing) Feel free to let me know what you think.
Smoke Setup: How To
If you have seen someone at the local field flying an airplane setup with smoke, you probably already know that smoke definitely adds a "wow factor" to flying! Lately, I have been seeing lots of people interested in setting up smoke in their airplanes, but some do not yet know how to properly set one up to get the most out of their smoke system. Here I will be covering the smoke installation in a Somenzini Yak with a DA 100; I am using a Don Harris electronic smoke pump and SuperDri smoke oil.
I am using a 24 ounce DuBro tank with a gasoline stopper(Make sure it is a gasoline stopper; if not, the smoke oil could eat through the stopper and cause a leak), using all tygon tubing except for where the lines attach to the mufflers; there I am using some black rubber tubing. The tank is setup with three lines; one fill/drain line with a clunk inside the tank, one pickup line also with a clunk inside the tank to feed the smoke to the mufflers, and one vent line which consists of a piece of brass tubing bent all the way to the top of the tank. Remember that this vent line will have to be uncapped when you are going to use the smoke system; if it is not uncapped, there will be no return air into the tank to fill the void that the smoke oil leaves when it is used, thus causing the tank somewhat crush down on itself and at the same time, it will make the flow rate unstable. (Much like a water dispenser bottle without a vent)
On the Desert Aircraft standard mufflers for the DA 100, I found a bolt halfway down the can that was screwed into a tap on each muffler; these taps were a nearly perfect fit for standard pressure tap fittings like the ones you would find on the muffler of a glow engine, so I used spare ones that I got from a few friends. If your muffler/mufflers do not have a tap on them, you will have to tap them yourself. The best location is usually near the header of the muffler or slightly below it. I have seen that gas engines are not as critical to the placement of the smoke tap as glow engines are, so even having it halfway down the can of the standard muffler was not a problem.
Since the DA has two mufflers, you will need a T fitting to evenly distribute the flow to both mufflers. I have tested the flow from both sides of the T fitting and have come to the conclusion that as long as your lines from the T are the same length, you will get a fairly even flow. Make sure that none of the lines are kinked in your installation; that can, of course, cause problems.
Although the Don Harris pump is an electronic pump (power is run through the receiver from the main battery), the flow is not adjustable from the transmitter; In this case I needed to come up with a good solution for adjusting the rate of flow to the muflers. After trying wheel collars and adjustable line clamps, I tried using a spare needle valve in line with the output from the tank and the mufflers. This works flawlessly; it is possible to fine tune the smoke flow rate to where it is allowing just enough smoke into the mufflers to make a great plume, but not too much that it will make a mess on the airplane and cool down the mufflers.
Once all the lines are installed, it will be a good idea to use fuel line clamps or zipties to help keep the lines from slipping off at all points of attachment.
First, you will need to assess what kind of setup you will need to fit the airplane and engine setup that you will be installing your smoke system in. A good place to start is to find where your system will fit best in your airplane. For me, this was the cannister tunnel. The cannister tunnel, if your airplane has one(if it is not in use of course), is a great option for a smoke setup due to the fact that most tunnels allow you to place the smoke tank directly on the center of gravity, and that it will keep the smoke setup seperate from your radio equipment. If you do not have the tunnel as an option, it will be best to keep the smoke tank on or as close as possible to the CG.
For the purpose of keeping the setup as neat as possible, my Dad came up with an ingenious idea: mounting the entire working system to a removeable tray. Since he has access to composite materials, we chose honeycomb for it's light weight and strength. Once we knew the placement of the tank and pump, we routed out small recesses for the tank and pump to rest in. Some thin foam was then placed under the tank and pump, while another thin sheet of foam was placed on the top of the tank with spray on adhesive to keep the tank from directly hitting the top of the tunnel. Next, the tank and pump were secured in with tie string fed through small holes in the honeycomb around the tank and pump; the servo lead extension was also lightly tied down to keep it from chafing due to vibration.
After all the components were installed on the tray, the next step was to devise a method of securing the tray inside the airplane. Two holes were drilled in the end of the honeycomb tray, followed by gluing two dowels into these holes; these serve as support for the back end of the tray. The plywood former at the back of the tunnel was reinforced, and two holes matching up with the dowels were drilled in it. Once these holes matched up with the dowels, a smaller hole was then drilled into one of the dowels and into a horizontal former below it for a cotter pin or a car body clip that will hold the entire tray in place, keeping it from moving forward and aft. The front of the tray had a snug enough fit with some foam that it did not need to be secured.
Once the tray was installed, it was then time to organize the lines. The fill line was routed to an aluminum fuel dot on the outside of the airplane, while the vent line was routed underneath the airplane to where it is easy enough to reach into the cowling and uncap the vent. The pickup line was routed to the adjustable flow remote needle valve, to the T fitting, and from the T fitting, two lines were routed to the mufflers. Once you are at this step, all that is left to do is to fill it up, start it up, and tune it!
Tuning the Flow Rate
Depending on what pump you are using, you will either need to adjust the flow manually or, if you have a proportional control on the pump, you can then adjust it from your transmitter. In my case, I have to manually adjust the flow from the remote needle valve that was placed between the tank and the mufflers on the pickup line. With a few people holding the plane, start up the engine, get it warmed up, set the throttle at halfor slightly higher, and flip on the smoke. Notice if the mufflers are spewing unused oil, if they are, turn the flow down until it stops spewing, but not too far down to where you decrease the amount of smoke produced. There is a delicate balance between too much and too little; once you find it, the airplane will be cleaner than when it is being fed too much flow.
If your transmitter has the ability, you may want to activate and program a mix that turns off the pump when the throttle is at idle. This will keep the mufflers from fludding if you forget to turn off the pump. (I have nearly dumped a whole tank of smoke due to me forgetting to power it off) If your pump is proportional, you can also use a mix to make the amount of flow proportional to your throttle stick position, possibly making your pump more efficient.
Whether gas or glow, big or small, it is definitely possible to draw a lot of attention to your flights! Setting these systems up has definitely been a learning experience for me and my Dad; I hope you guys can get something out of it too.
BTW: The flying pic with smoke is of the second flight on the airplane, I absolutely love how it flys. Needs some fine tuning, but once it's dialed in, it will be awesome.
The only thing I would add is that you can buy an external ESC and make any pump proportional instead of using the needle valve. Hobby King sells several low priced/ High quality ESCs that could be easily adapted for this.
I've never been a fan of manual adjustments as its harder to fine tune the flow through out the throttle range and with oil costing so much I'd rather now waste it. Good write up on the install though. Now you need to make part #2.....how you found the right adjusments.
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