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 11 
 on: Yesterday at 10:06:45 PM 
Started by RC Storick - Last post by RC Storick
I am still working on things maybe tomorrow I will get it sorted out

 12 
 on: Yesterday at 10:03:12 PM 
Started by RC Storick - Last post by RC Storick
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 13 
 on: Yesterday at 09:58:18 PM 
Started by Avaiojet - Last post by Brett Buck
Bob Hunt's method is by far the best in my opinion.  It really isn't all that complex or time consuming, either.  Have your ducks in a row before you start and it goes rather quickly.  Sets overnight and is ready for the next steps.  as long as you do the scraping off, the weight is very low.
A nats winning RC guy rolls his epoxy with a toilet paper roll instead of scraping, but I prefer Bob's method.

      If you put a coat of clear nitrate (or Bobby's hair spray which is about the same thing) on the mating surface, it's really not even all that critical how well you squeegee it off, because if you do enough to remove puddles of glue, the net weight gain compared to everything else gets to be negligible, and it's not worth a lot of effort to save 5 grams on a 120 gram wing panel, and certainly not worth risking taking off to much can causing a delamination later.

    I use a Signature Inn room key card (of which I have *many*), with notches about 1/16" wide and deep made with a triangular file every 3/8" to ensure I leave enough on there for a good bond. Compared to contact cement like 3M77 (or the foam-safe equivalent), HomeSafe, or Corebond, the epoxy weight just isn't significant. As with Randy, I had good enough results with Southern Sorghum, but epoxy is easier, lighter, and overall, better.

   A different interesting argument is what type/brand of epoxy you should use. I like West Systems or EZ-Lam, and EZ-Lam has by far the best working time of anything I have tried. I *don't* recommend finishing epoxy, even though it's nice and thin -  it gets too brittle and all the different types I tried self-heated to the point it cut the working time drastically.

     Brett

 14 
 on: Yesterday at 09:45:58 PM 
Started by Skip Chernoff - Last post by Tim Wescott
    The 8 minutes starts when you first flip the prop or flip the switch on your timer. You signal the judge as a courtesy, and I'm pretty sure by the rule book they start their watch when you flip the prop or flip the switch.

In a world with Internet, there is absolutely no excuse for being "pretty sure" about the rules.  It's right there, in the book, and your PDF reader will let you search on key words like "hand" or "signal".  At any rate, it's 8 minutes from the hand signal, with various other fillets and decorations around how long you have to get airborne after the hand signal and how long you have to give the hand signal after you've been called to the circle, etc.

   I don't think so, it's at the hand signal.:

Unless the contest officials are feeling particularly generous.  I just checked the rulz.

    In fact, if you don't give a hand signal and fly the flight anyway, you will get charged with an attempt (because you never signalled the beginning of your attempt, so it isn't an official flight, but you used up the 5 minutes):

Or you might be chatting with a fellow competitor right after your flight and hear some former world champion loudly announce "I'm giving the hand signal now, TIM".

 15 
 on: Yesterday at 09:40:37 PM 
Started by RC Storick - Last post by Brett Buck
I know where the issue is and I am working on it

  Very good, thanks!  There is a workaround, use the "edit" function at the lower right, rather than the "modify" form in the upper right.

    Brett

 16 
 on: Yesterday at 09:39:18 PM 
Started by RC Storick - Last post by RC Storick
   Actually, I think you still have a problem somewhere, because using the "modify" form still triggers a warning about a "non-secure site".

    Brett

I know where the issue is and I am working on it

 17 
 on: Yesterday at 09:37:58 PM 
Started by RC Storick - Last post by Brett Buck
I changed the forum stack order to make it easier to access. SSL is now installed and site is secure

   Actually, I think you still have a problem somewhere, because using the "modify" form still triggers a warning about a "non-secure site".

    Brett

 18 
 on: Yesterday at 09:32:18 PM 
Started by Skip Chernoff - Last post by Brett Buck
    The 8 minutes starts when you first flip the prop or flip the switch on your timer. You signal the judge as a courtesy, and I'm pretty sure by the rule book they start their watch when you flip the prop or flip the switch.

   I don't think so, it's at the hand signal.:

Quote
8. Duration of Flights.
Eight (Cool minutes total elapsed time is allowed from the time the contestant gives a hand signal prior to starting his engine (this should be done with a prearranged plan, and upon signal to or from judges) to start, take off, complete the flight pattern and land. Timing ends at either 8 minutes, when the model stops moving after successful landing, or when the model crashes. No maneuver, including the landing, will be scored after the eight (Cool minutes allowed have elapsed.

    In fact, if you don't give a hand signal and fly the flight anyway, you will get charged with an attempt (because you never signalled the beginning of your attempt, so it isn't an official flight, but you used up the 5 minutes):

Quote
7. Flight Procedure.
Each contestant will be called to the circle when it is his or her turn to fly. From the time they are called to the circle, contestants will have a maximum of five (5) minutes to give the hand signal to begin starting their engine(s). Once the starting hand signal has been given, contestants will be allowed a maximum of three (3) minutes to become airborne. A contestant may make as many starts as necessary, or may take off, land and restart if necessary, as long as the three minute time period has not been exceeded. If a second takeoff is made during the three minute time period, the first takeoff score will be canceled and a new score given. Failure to give the starting hand signal within five minutes of being called to the circle, or failure to become airborne within three minutes of giving the starting signal, shall be charged as an attempt. Contestants shall be allowed three (3) attempts to make two (2) official flights.

     Brett

 19 
 on: Yesterday at 09:23:08 PM 
Started by Skip Chernoff - Last post by Brett Buck
I have just this week been trying to learn the full pattern. I got through it Monday but ran way over 8 minutes.  Today I started using the fill it up suck it out method. First try ran 8min 10 sec.  Second try it started cutting out on the 2nd downward loop of the clover. So I abandoned the stunt and it ran 1 minute after that.  Is that normal or a tank problem? 

   It's a tank problem. The maneuvering is causing the fuel to slosh away from the pickup. When you do a loop near the end of the tank, the fuel wants to sling to the front of the tank, and towards the bottom of the tank. It wants to go to the front for two reasons - the drag of maneuvering slows the airplane rapidly, which makes the fuel want to run to the front. If it is an inside loop (like the first loop of the clover), the airplane will usually yaw the nose away from you, with tilts the entire airplane in such a way to make the fuel want to run to the front. Of course, the load of maneuvering makes the fuel want to move to the bottom of the tank.

   The net effect is that you can get air at the pickup, temporarily. This causes the engine to go lean a short time later - about where you said it did. This is how the cutoff loop works, if you had a little less fuel, it would have sucked air long enough to quit. In fact, if you had bailed out as you did, flew around level for 3-4 laps, then tried again, it would certainly have quit - thousands of stunt flights have ended that way on purpose.

     Of course if you fly around level, the fuel goes back to the normal spot along the wedge of the tanks and it runs most of the fuel out, so you get 8 minutes. You probably also get a lot of back-and-forth surging for several laps before it quits. Same thing, the airplane slows down, that sloshes the fuel to the front, that leans it out, it speeds up, sloshes the fuel to the back, picks up fuel again, goes rich, slows down, repeat.

     Some people think this is great, because it gives you lots of warning it's getting low on fuel. For competition, it's terrible, for the reasons you found - it screws you up in  the 4-leaf AND causes you to risk an overrun. What you really want is a tank that will run without changing anything about how it runs in the maneuvers, gives you no warning but will cut off very abruptly.  

  There are a few improvements you can make compared to standard hobby-shop tanks that will prevent this. The standard tank is either a copy of or a newly produced version of the Veco T21 tanks from the early 50's. Looking from the top/plan view, it is rectangular, and from the end, it's like a 3-story doghouse. Usually, it is shown with the inboard edge (bottom of the doghouse) flat up against the profile fuselage.

    The easiest thing to do is to put a shim under the rear of the tank, between the tank and the fuselage, to tilt the tank to the rear is kicked out. That make the fuel want to run to the rear of the tank under normal circumstances. 1/4" on a 4" tank is a good starting place. A variant of that is to make your own tank where the tank is tapered to begin with, the front being 3/8" or so narrower than the rear.

      The other problem is that the angle at the wedge (the roof of the "doghouse") is too flat. It needs to be about twice as sharp as a Veco T21. To fix this, you more-or-less have to make your own tank. It's actually quite easy. A very poor second alternative is to take a standard tank, remove both end caps (probably a good idea anyway so you can make sure the tubes are in the right spot and to clean it out), bend the wedge sharper, and then make new end caps to fit the weird new shape.

     Do those things, and it will cut off cleanly in most cases. One additional factor is the trim of the airplane. If it is yawed out a lot under normal circumstances, its like shimming the front end of the tank and will make the fuel tend to the front more than the back, and exacerbate the cutoff issues. That's why inside cutoff loops work, and outside cutoff loops don't work as well - the airplane yaws nose-in on outside loops, which runs the fuel to the rear of the tank.

 
Quote
Next I tried sucking out a little less but the flight was screwed from the beginning, stooge line popped off. By the time my helper launched it the test flight was no good. Flew the pattern anyway and it actually did cut off on the 2nd downward loop of the clover. Needless to say I landed upside down. Broke off my muffler pressure port. Tried another flight without pressure and it just went lean the whole time. So never did get a good timely run, then it got dark.

     Can't help you too much there, I think you learned something, anyway (if you have a problem, stop and fix it). If you tried without muffler pressure and without tweaking the needle out, then going lean is predictable. If you tweaked it out to run the same, then it ran away in the air, your venturi is probably too big.


Quote
Anyway besides the tank question, when does the 8 minute countdown start? When you raise your hand that you are ready to go or when the engine starts?


      I presume you mean AMA since you are talking about 8 minutes (vs 7 minutes in FAI), which matters because it's one of the few differences. In AMA, the time starts when you signal for start, and ends when the wheels stop rolling on the landing (or you crash). If you don't get it stopped on the ground before the 8 minutes, you lose the landing points (since you didn't complete the landing) and pattern points (because you did not attempt and complete all the maneuvers). I did it 3 days ago, cost me about 60 points and put me last in expert after the first round. I did better the second time around...

   In FAI, the timing starts *when the engine starts*. This is a very important, recent, change that was, near as I could tell, an accidental side effect of removing the 10 starting points. DO NOT hand signal,  just start cranking when you are ready.  When it starts, the timing should start. This saves you the time it takes to start the engine. Normally this is a few seconds, but if you have a problem, you get a huge amount of additional time over normal. This more-or-less solves the problem of having to take many attempts in FAI because now you don't have to worry about starting issues and running over at the end.

    Brett

 20 
 on: Yesterday at 09:18:34 PM 
Started by Skip Chernoff - Last post by Brett Buck
duplicate- still have a security certificate issue, this site show non-secure

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