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Author Topic: Brodak and Sig Profile Kits Pull Test Question  (Read 1629 times)

Offline Darryl W

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Brodak and Sig Profile Kits Pull Test Question
« on: March 16, 2022, 11:46:55 AM »
Sig Banshee, Sig Skyray 35, and Brodak Cardinal...I have built and have been flying these kits but have never subjected them to a pull test. They are all built per the included plans with no modifications to bellcrank or bellcrank platform. They have .027 braided leadouts with the ends copper wire wrapped. They each use the kit-supplied nylon bellcranks on kit supplied plywood mounts. I use Sig or Brodak .016 or .018 lines.

Since I am planning on maybe attending some cl events this summer that would require it, I am wondering how likely these airplanes would be to pass (or fail) the AMA or MAAC pull test for precision aerobatics when built from these kits without any mods ???

It would be great to hear from any of you who have had experience, good, bad or ugly, with this.

Thanks!

Darryl Wurtz

Offline Dan Berry

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #1 on: March 16, 2022, 12:37:31 PM »
Assuming that you glued things well enough you should not encounter any problems. I didn't.

Offline Darryl W

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #2 on: March 16, 2022, 12:53:16 PM »
Yes, very good point Dan!  Glue joints could be the deciding factor of course. I used slow set epoxy to glue the platforms to the spars and ribs.

dw

Online Dan McEntee

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #3 on: March 16, 2022, 02:23:18 PM »
  If you built the models as per plans and instructions, with some degree of care and precision, they will pass the pull test for their weight, which is how it is determined these days. They had to pass pull tests when they were designed and first introduced by engine displacement which was pretty close to what we have today. The pull test for them will probably be some where between 35 and 45 pounds depending on weight and I think you would have to screw things up pretty good for them to not pass.
  Type at you later,
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Offline Motorman

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #4 on: March 16, 2022, 05:26:47 PM »
Most contests don't weigh the plane they just give everybody some low number pull test like 25Lbs. The main thing is to hold the fuselage close to the wing joint with both hands and turn your head. When the guy at the other end starts pulling just let up. He'll think he did something and quit. If you think he's pulling too hard let up and go show him which side of the scale is metric and he's pulling 25 kilos (50lbs) on a Skyray.

Motorman :(

Online Dan McEntee

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #5 on: March 16, 2022, 08:31:26 PM »
Most contests don't weigh the plane they just give everybody some low number pull test like 25Lbs. The main thing is to hold the fuselage close to the wing joint with both hands and turn your head. When the guy at the other end starts pulling just let up. He'll think he did something and quit. If you think he's pulling too hard let up and go show him which side of the scale is metric and he's pulling 25 kilos (50lbs) on a Skyray.

Motorman :(

   This is one of the biggest blobs of utter bull @#$% I have ever seen posted on the forms! Every contest I have entered since the change over has weighed the airplane. Every pull test I have done on my models have been on the up and up, and every pull test I have done on some one else's airplane has been honest and by the book. To suggest that this is what happens at AMA sanctioned contests does the management of those contests a great dis-service and is an insult to them. Top suggest that a newcomer to the event do something the negates all the safety measures put in place is stupid and irresponsible. I really can't believe what I just read!!
   Type at you later,
  Dan McEntee
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Offline Brett Buck

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #6 on: March 16, 2022, 08:31:56 PM »
Sig Banshee, Sig Skyray 35, and Brodak Cardinal...I have built and have been flying these kits but have never subjected them to a pull test. They are all built per the included plans with no modifications to bellcrank or bellcrank platform. They have .027 braided leadouts with the ends copper wire wrapped. They each use the kit-supplied nylon bellcranks on kit supplied plywood mounts. I use Sig or Brodak .016 or .018 lines.

Since I am planning on maybe attending some cl events this summer that would require it, I am wondering how likely these airplanes would be to pass (or fail) the AMA or MAAC pull test for precision aerobatics when built from these kits without any mods ???

It would be great to hear from any of you who have had experience, good, bad or ugly, with this.

   Any of those should be fine as long as they were assembled correctly.

     Brett

Offline Brett Buck

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #7 on: March 16, 2022, 08:45:59 PM »
Most contests don't weigh the plane they just give everybody some low number pull test like 25Lbs. The main thing is to hold the fuselage close to the wing joint with both hands and turn your head. When the guy at the other end starts pulling just let up. He'll think he did something and quit. If you think he's pulling too hard let up and go show him which side of the scale is metric and he's pulling 25 kilos (50lbs) on a Skyray.

   I have not been to a contest where they used generic numbers. I have seen user-supplied weights (i.e. not measured for some regulars ), but as far as I can tell everyone is telling the truth about it. Additionally, I have yet to see anyone not be able to operate  a spring scale, so the error are about the tolerance of the scale (maybe 10%).

    Failures in test are very rare and almost always, it's because the leadouts have somehow been compromised through wear or fatigue. The airplanes from the OP are designed correctly for the loads, as long as they are put together correctly.

   I strongly urge you to spread the load beyond just the fuselage joint. The wing/fuselage joint only sees about 60-70% of the pull load, the wing takes the rest of it.

      I am not sure what you are on about with the rest of it, or if it is intended to be funny (if so, it's not). Attempting to game or cheat on the pull test is about the only way there is to cheat in stunt (since it about the only objective rule) , when you get caught playing games you will at least get a bad reputation, and may be asked to leave, and perhaps, not come back.

     Going to contests is a generally pleasant experience with a good bunch of guys. If you are not having good experiences, or think there is all sorts of incompetence and skullduggery going on, you are quite wrong. I base that on several hundred stunt contests from everywhere across the country.

    You are leaving a very negative impression - if that's not your intent, the please think about how you phrase things, because you are not coming across very well.   If you do mean it - then I suggest that the problem does not lie with the other people at the contest.

     Brett

Online Paul Smith

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #8 on: March 16, 2022, 09:13:27 PM »
The major failure point is the weak scheme that many old time kits used to mount the bellcrank - one side only.

If you use BOTH sides of the bellcrank axle you will have no problem.

Any pull test is better than nothing.  A failed pull test is a saved airplane.

Note also that my center rib is the same size as the fuselage body stock, thereby making a firm attachment between wing & fuselage.
Paul Smith

Offline Dave Hull

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #9 on: March 17, 2022, 01:21:59 AM »
It will all come down to workmanship and the quality of the wood. If these are even just average, the design should pass unless it is terribly heavy. The requirement for the pull is 10G's. I don't recall any examples of these planes failing the pull test.

If the Cardinal is an ARF, that adds a good bit more uncertainty. (But the description suggests that all three were built from the plans making this irrelevant.)

Of the three pull test failures I can recall as a contest worker, one was from a damaged line (not near a crimp), one was a wire break in the crimp, and one was a leadout which used plastic coated wire, with a crimp over that. The wire pulled thru. It should have never had a crimp over a plastic coated wire.

As far as MM's comments, we can assume he is speaking only of his personal feelings about whatever field he frequents. He can have that argument with them. Having done weigh-in and pull test for dozens of contests here on the west coast I can say his broad-brush remarks have no basis and hope in the future he can manage to avoid disparaging people that support his hobby.

Dave

Offline Dennis Toth

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #10 on: March 17, 2022, 08:52:54 AM »
Darryl, those ships should do fine. Just remember when doing the pull test to have the lines hooked up ready to fly (so the handle is being pulled at the neutral position). When you hold the ship grasp the inboard wing tip with the leadouts either between your fingers or if they are spread more than an inch have a few fingers on each side of a leadout. Steady the ship with the other hand. Pull smoothly, not a quick jerk motion, then release smoothly.

Best,   DennisT

Offline Brett Buck

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #11 on: March 17, 2022, 09:40:45 AM »
The major failure point is the weak scheme that many old time kits used to mount the bellcrank - one side only.


     Agreed, but as long as they use regular aircraft plywood, it's good enough. Unfortunately, both Sterling and Jetco, among others, used the cheapest of the cheap luan plywood like they use to skin hollow-core doors. Airplanes built stock with this as the mount material (like the Ringmaster, Shark 15, etc.) are notorious for failing at half the old pull test. Replace the luan with 1/8 5-ply birch aircraft ply, even gluing it to the spar with Ambroid, done properly, is just fine.

     I also note that for these types of airplanes, the 10G pull test is *far less* than the old engine size test. A Ringmaster with a McCoy 35 used to pull 40 lbs, now, that is typically around 25 lb since it weighs around 30 ounces.

     Brett

Offline Ken Culbertson

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #12 on: March 17, 2022, 11:27:30 AM »
The major failure point is the weak scheme that many old time kits used to mount the bellcrank - one side only.

If you use BOTH sides of the bellcrank axle you will have no problem.

Any pull test is better than nothing.  A failed pull test is a saved airplane.

Note also that my center rib is the same size as the fuselage body stock, thereby making a firm attachment between wing & fuselage.
IMHO this or the many variations of this is the ONLY way to mount a bellcrank.  I was introduced to the floating bellcrank in the 60's building I-Beam wings.  Never looked back and I have never had a bellcrank or mount fail.
The single floor may work fine for the planes we are talking about on this thread, but why not do it the modern way?

Ken
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Online Dan McEntee

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #13 on: March 17, 2022, 12:50:06 PM »
   All these other replies are all well and good, (except for one,) but keep in mind the OP was asking specifically about Brodak and SIG profile kits. All kits are produced with cost and profit margin in mind, along with safety, so the buyer will come back and buy more. I'll bet a dollar against a dozen donuts that no one has seen a bell crank pull out of a SIG or Brodak kit that was built according to plans and with proper glue used?? Of all of them that I ever crashed, that was the part that was still intact, and some times I didn't use epoxy on it because I couldn't afford it, and just used extra glue of whatever I was using to build it with. The SIG kits were engineered by guys that flew them at contests, and you know the designers of the Brodak kits have a good reputation along with decent quality materials in both brands. That only leaves the effort and attention to detail put in by the builder during construction, and the installation of the lead outs..
  Now, if you get into the ARF area, that's a horse of a different color!!
   HAPPY ST. PATRICK"S DAY!
   Dan McEntee
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Offline Ken Culbertson

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #14 on: March 17, 2022, 02:34:58 PM »
I'll bet a dollar against a dozen donuts.
Have you price donuts lately?  How about a dollar to A donut?

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Offline Brett Buck

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #15 on: March 17, 2022, 04:09:52 PM »
IMHO this or the many variations of this is the ONLY way to mount a bellcrank.  I was introduced to the floating bellcrank in the 60's building I-Beam wings.  Never looked back and I have never had a bellcrank or mount fail.
The single floor may work fine for the planes we are talking about on this thread, but why not do it the modern way?

Ken


I note that he already has built airplanes, so it will turn out however it turns out. Best thing to do at this point is to pull them to about 11 gs and see what happens.

Brett

Offline Steve Helmick

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #16 on: March 17, 2022, 05:01:40 PM »
If you are asked to be the pull test officer for any event, always remember that IF there is an accident, EVERYBODY involved will have to sign depositions at best, or go to court at worst. Be absolutely certain that you do it by the rule book! You need to be able to swear to that in a court of law, if it comes down to it.  y1 Steve

PS: Say "Howdy" to Monty for me, and any of the ACFC guys you run amok with...
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In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Darryl W

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #17 on: March 18, 2022, 09:23:49 PM »
Many thanks Gents, for your comments and sharing your expertise! Yeah, I had built these airplanes with out any thought that they would ever need would be pull tested, but from your answers I'm now much more confident that they will survive. If not I guess I will just chalk it up as another lesson learned the hard way.

BTW My Cardinal is built from the Brodak kit and not the ARF.

And yes Steve, I will pass along your greeting to Monty, he has been my good friend and mentor for many years...

Darryl

Offline Tim Wescott

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #18 on: March 19, 2022, 12:07:21 AM »
If you have any lingering worries, pull test them at home, well before any contests, slowly, somewhere quiet, while listening for cracking sounds.  Most probably, you'll go to your content satisfied that you'll pull without problems.  At worst, the planes will be damaged and you'll have time to fix them, and then you'll go to your contest satisfied that you'll pull without problems.

Note that you can get super-fancy mail order pull testers, or you can schlep down to your feed store (or your barn, if you have big animals) and grab a spring scale that's designed for weighing hay bales.  Or your local sporting goods store for a fish scale.

Note also that the next time you build you may want to pull test the pieces.  I did that when I was establishing how I build my control systems, and I still do it when I remember.  I like to have bellcranks and handles that'll pull to twice the rated load, especially if they look spindly.
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Offline Brett Buck

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #19 on: March 19, 2022, 12:33:10 AM »
Many thanks Gents, for your comments and sharing your expertise! Yeah, I had built these airplanes with out any thought that they would ever need would be pull tested, but from your answers I'm now much more confident that they will survive. If not I guess I will just chalk it up as another lesson learned the hard way.

   I presume this is obvious, but for others - pull test it yourself well before the contest, like tomorrow, so, if it does break, you have time to fix it. You don't want to find out it's not strong enough 10 minutes before an official flight!

    Brett

Offline Ken Culbertson

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Re: Brodak and Sig Profile Kits Pull Test Question
« Reply #20 on: March 19, 2022, 09:23:11 AM »
Note also that the next time you build you may want to pull test the pieces.  I did that when I was establishing how I build my control systems, and I still do it when I remember.  I like to have bellcranks and handles that'll pull to twice the rated load, especially if they look spindly.
That first pull test is also very important.  I also pull to well over what will be experienced at a contest.  You are not just testing overall strength; you are tightening your connections.  Another thing I do with a new plane is have a helper work the controls while being pulled.  If you have forgotten to clear out all of the wood around the leadouts or if one is rubbing on a LG mount, etc - you will hear it.

Ken
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If it is not broke you are not trying hard enough.
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