RoughLandin

The big day is nearing quickly. I just finished installing all of the control arms, sealing hing gaps setting throws etc.

Now I need to balance the plane's CG. The plans show it balkanizing just behind the landing gear on the profile view, but the instructions say I should measure from the T7 rib. These are the ribs that the I-struts plug into, which are located 3/4 of the way to the tip. Does this sound correct? It balances very close to this location but is WAY off at the location behind the gear. The reason I question this location is I have never balanced a model so close to the wing tips, then again I've never built a biplane

P.S. the plane came out at 10lb dry weight with an OS 120 fs III w/pump. I figured I will fly it for a while then try a smoke system if it doesn't fly like a pig from too much weight. I will post pics soon, she looks better than I ever thought.

rc-sport

My Feedback: (12)

Balance it just as the manual says, it's spot on. I balanced mine that way and it's perfect. I just put a piece of tape on the mark and placed a finger on the outside of each strut and picked it up, it balanced from the start with a Saito 120.

MinnFlyer

My Feedback: (4)

Go with the 7th rib balancing point for the first flight, then adjust as you like it.

RoughLandin

Thanks for the reassurance.

I'm feeling pretty good that it weights 10lbs it seems like that is right in there with everyone elses. That's good news because it ballances perfectly at the T7 rib. P.S. I broke in the engine today, maiden later this week.


A little off subject:
MinnFlyer how did you get your plane to smoke so well? What exhaust are you using with your YS91? Are you using a preheater? I mounted the OS120 inverted and a bit of the engine hangs below the cowl. I like the looks of the J-Tec inverted pitts muffler but I think it would hang out too much. Besides J-Tec has terrible customer service and has been back logged for 6 months. Do you have any suggestions for smoking a stock OS120 muffler, Where to place the injector nipple, is just wrapping the exhaust exterior with brass tubing good enough or do I need to insert something into the pipe?

rc-sport

My Feedback: (12)

I would place the smoke nipple on the header portion of the muffler, thats where you'll have highest temp.

jucava

stay away of J-tec

MinnFlyer

My Feedback: (4)

I am using an after market muffler on my YS 91, but unfortunately, I can't tell you who makes it. It was given to me by my dad, and he got it from another club member who doesn't remember where it came from. But I can tell you that it's nothing special.

Like Robert said, tap the header pipe as close to the engine head as possible. Not only is the exhaust the hottest there, but it will give the oil longer "Time in heat". Another reason for this is that the thinner the pipe, the lower the muffler pressure (That's why the pressure tap for the tank is always at the fattest part of the muffler).

I don't preheat, but if you do, don't do it at the muffler. Wrap the copper tubing around the head instead. Taking heat away from the muffler to heat the oil sort of defeats the purpose.

I use a product called Ultrasmoke. I like it a LOT for many reasons. One of the biggest is the fact that it is not petroleum based, so it doesn't attack covering or foam, and it doesn't stink up your car/house/etc. It has no smell at all. It is only available by calling (316) 522-4905. It's about $10 a gallon but worth every penny.

This is the pump I use:

http://www.jcwhitney.com/autoparts/P...atalogId-10101

It is the same pump used in the TME system, but it only costs 10 bucks. I run it with a 4.8 or 6v battery pack and use a servo to turn it on and off by hitting a microswitch (3 bucks at Radio Shack)

All in all, it's a great system and cheap!

RoughLandin

Thanks MinnFlyer,

I was at an AHDA (All Harley Dragracing Association) race lately and many of the bikes wrap the exhaust pipes with fiberglass cloth. I believe the reason is to maintain heat as the exhaust and unburned fuel leaves the manifold. Otherwise the sharp drop in tempature from the air hitting the exhaust pipes causes the exhaust air and unburned fuel to condense and reingites causing a backfire. I could be wrong in the reasoning but none the less the pipes are wrapped in fiberglass cloth and retain more heat.

After owning a Harley and knowing that airflow is critical over an aircooled engine like our model engines, I am reluctant to wrap the tubing around the head. I was thinking that wrapping the copper tubing around the exhaust then covering the tubing with the fiberglass may work for our model engines as well, especially when it comes to preheating smoke fluid. This would also help to clean up the unsightly appearance of the copper wrap job and tapped header. Hey it may even prevent burns from handling a hot plane...

Before I potentially destroy a perfectly good header I would like to hear your thoughts.

Brian

MinnFlyer

My Feedback: (4)

Like I said, don't wrap the muffler (Or header) to preheat.

The muffler and header is where you NEED heat. By heating your oil at the header, you are cooling the header, so in effect, you are "Robbing Peter to pay Peter"

I do like the idea of wrapping the muffler with fiberglass. That is something that I do, but forgot to mention.

RoughLandin

MinnFlyer, one last question.

Do you use a special injector nipple into the header? I was thinking of tapping the header and installing a backpressure nipple but I'm not sure that will create a nice mist it may only create a strong stream and not all burn.

MinnFlyer

My Feedback: (4)

I use a standard "Muffler Pressure" nipple.

RoughLandin

I have posted a maiden flight report on the skybolt. This plane is great but it just isn't complete without a smoke system. That will be coming soon.

http://www.rcuniverse.com/forum/GP_S...1978881/tm.htm