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Old 05-20-2018, 06:27 PM
SuperCub WQA is offline
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91” EF Extra 300

Hi all,

Have a new 91” EF Extra 300 and I am wanting to hear how you have set up your throws and C of G. I am wanting to use this for IMAC, so no 3D throws. Currently the C of G is slightly aft and the throws as per the manual but looks a little much for IMAC.
Any feedback, recommendations appreciated!
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Last edited by SuperCub WQA; 05-20-2018 at 08:10 PM.
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Old 05-20-2018, 07:52 PM
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wrongwayfeldman
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This model builds tail heavy. If you want neutral or forward cg...you will need to move bats or whatever you can forward.
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Old 05-20-2018, 10:17 PM
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What engine? I have a friend with one that started with a DLE 61 and then went to an EVO 62. Batteries are by the wing tube and plane flies fine. Can't really talk about CG without knowing the effect of the weight of the engine.
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Old 05-21-2018, 09:41 AM
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I have a DA70 in mine, and even with the batteries way forward it's still tail heavy. I need to add some weight.
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Old 05-21-2018, 09:44 AM
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curious how you are determining it is tail heavy. Unless you have some weight in the rear I suspect it is fine. you might want to talk to the guys at EF before chasing a non existent CG issue.
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Old 05-21-2018, 11:48 AM
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wrongwayfeldman
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I like how you assume no one but you knows how to check the cg...
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Old 05-22-2018, 02:29 AM
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What ever the plane is, setting up for IMAC is an about 20 flights job.
You already chose a good plane so start setting it up as vendors reccomendation: It's always a good start point.
Use servo throw as follows: Since you're not doing 3D, set up maximum servo throw to the maximum surface throw reccomended from manufacturer. Example: PAU says for its Sukhoi that 25 degrees for ailerons with 0 to 20% expo are good for IMAC; so measure that throw with maximum servo throw you can get. You will have then a "aileron long arm - servo short arm" configuration. Set a reasonable expo too... PAU reccomends 20%; But I'm currently at 38%.
Once you take off, take your time to get some confidence with the plane before start moving things. Don't change anything unless it's mandatory. You NEED to be sure of what you're reading on the plane while flying (10 to 15 flights are a reasonable number...). Once you're there, you can start all the trimming process. There are several recipes... the one I use is the "Triangulation method" which is a F3A recipe developed by Bryan Hebert (i think), yet there are several others simpler. Attached here there is one very popular here in Italy; good enough, very graphic and easy to understand even if it's in italian (use google translate!!).

https://docs.wixstatic.com/ugd/01378...4185345553.pdf

https://docs.wixstatic.com/ugd/01378...a20c20f147.pdf

Hope it helps....
Cheers
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Old 05-22-2018, 10:08 AM
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Quote:
Originally Posted by FGNewbie View Post
curious how you are determining it is tail heavy. <snip>.
Quote:
Originally Posted by ponyboy082662 View Post
I like how you assume no one but you knows how to check the cg...
Pretty sure he started his response with a question asking just that..................
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Old 05-22-2018, 01:48 PM
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I’m determining tail heavy by hanging from the wing tube to start. After that, I’m rolling inverted on a 45 upline. My plane climbs instead of gently falling. I’m using pull-pull for rudder so no extra servo in the tail.

I’ve been slowly going through the triangulation trimming method to get ready for my first IMAC with this bird. I spent the first 10 or so flights just getting used to it. Now I’m trying to get through the process. It’s slow though when there isn’t anyone available to write the results for me. I end up forgetting by the time I land.

Poke around the 91 Extra forum here on FG, and lots of people end up tail heavy. Some were adding nearly a pound of weight in the nose.
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Old 05-22-2018, 05:13 PM
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The 91" Extra is well known to be tail heavy - hence some in my area put 85cc engines on them.
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Old 10-05-2018, 06:14 PM
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Update, long overdue but this is what I had to do.

I ended up pulling the engine forward 1/4” (DLE 61), putting a aluminum spinner on vs carbon fibre, heavier batteries (2x LiFe 2500 A123) and added some lead weight, I can’t remember but I think 3.45oz.

Again this is for IMAC, other types of flying may differ.
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Old 10-10-2018, 05:09 AM
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Quote:
Originally Posted by Guille2017 View Post
What ever the plane is, setting up for IMAC is an about 20 flights job.
You already chose a good plane so start setting it up as vendors reccomendation: It's always a good start point.
Use servo throw as follows: Since you're not doing 3D, set up maximum servo throw to the maximum surface throw reccomended from manufacturer. Example: PAU says for its Sukhoi that 25 degrees for ailerons with 0 to 20% expo are good for IMAC; so measure that throw with maximum servo throw you can get. You will have then a "aileron long arm - servo short arm" configuration. Set a reasonable expo too... PAU reccomends 20%; But I'm currently at 38%.
Once you take off, take your time to get some confidence with the plane before start moving things. Don't change anything unless it's mandatory. You NEED to be sure of what you're reading on the plane while flying (10 to 15 flights are a reasonable number...). Once you're there, you can start all the trimming process. There are several recipes... the one I use is the "Triangulation method" which is a F3A recipe developed by Bryan Hebert (i think), yet there are several others simpler. Attached here there is one very popular here in Italy; good enough, very graphic and easy to understand even if it's in italian (use google translate!!).

https://docs.wixstatic.com/ugd/01378...4185345553.pdf

https://docs.wixstatic.com/ugd/01378...a20c20f147.pdf

Hope it helps....
Cheers
Any chance there is an English version of these documents?
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