Wright Stuff C

Locked
bjt4888
Member
Member
Posts: 649
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by bjt4888 » October 26th, 2018, 7:49 pm

Noah,

Good job posting some data with your question. One pretty significant bit of WS history to pay attention to is that every other set of rules included a limit on the propeller diameter and top results were achieved by using the largest propeller allowed.

This year, without a limit on propeller diameter, the likely area for experimenting is larger diameter. The largest commercially available is probably the Ikara 24 cm prop. Larger will require custom construction.

With your current propeller, the data you noted in your question does not include: Max turns, Max torque, back off turns, turns remaining, propeller style (flaring or not), ceiling height or any of the airplane specs (nose moment, tail moment arm length, wing incidence, wing offset, left wing washin, thrust offset, motor stick length, tailboom offset, rudder offset, stabilizer tilt, stabilizer incidence, etc.).

If you supply all of this info, and the characteristics of the flight (initial climb rate; e.g. number of feet of climb per circle; number of circles to the ceiling; ceiling hits or not; length of the cruise in seconds and length of the let-down phase of the flight in seconds) it will be possible to give you very specific, useful feedback.

If some of this terminology is new to you, it would be very helpful for you to read last year’s division B thread and also the 2015 division C thread on Wright Stuff. Doing this reading will take you to a very advanced level of understanding very quickly.

A number of us that have experience with this event have posted very detailed information in these previous year threads.

Brian T.
AMA Since 1968

noah.blome21
Member
Member
Posts: 10
Joined: March 15th, 2018, 7:20 am
Division: C
State: IL
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by noah.blome21 » October 27th, 2018, 10:51 pm

Right Now we are not flaring the propeller and we believe the max turns to be around 135 on a 15:1 or about .45 inch ounces. There is awash in on the left side of the wing and stab. The motor stick is about 25 cm. The tailboom is about 10cm. Depending on how we adjust the stab it can either climb quickly reaching the top of the gym which is about 25-30ft with 3-4 circles up and 2-3 down or I can have it cruise at 10-15 ft getting about 1:00min time with about 3 circles on the way up and 2 on the way down the rotor is adjusted to a 15 degree deviation to the left of the tail boom causing a medium flight circle. While in flight the nose is at about a 20 to 30 degree angle up from parrel to the ground. The stab is adjusted for the back wing post to be about 1/16 or 3/32 of an inch above the leading wing post of the stab for a quick climb and slow climb respectively. What do you recommend?

retired1
Member
Member
Posts: 675
Joined: July 25th, 2012, 5:04 pm
Division: Grad
State: FL
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by retired1 » October 28th, 2018, 6:22 am

Set it for cruise and add a few winds / torque to get a higher rate of climb. Should solve the problems that you mention.

bjt4888
Member
Member
Posts: 649
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by bjt4888 » October 29th, 2018, 6:26 am

Noah,

Good job supplying additional information. It is best to measure and refer to rubber by density instead of thickness as it is actually not possible to measure rubber thickness accurately (it's "squishy"; right?). Vendors that sell rubber by inch thickness need to do this for convenience, and I agree that this is what they need to do.

Rubber strip varies in density along it's length due to the slight variations in the manufacturing process. The rubber my four teams used last year (September 2017 vintage), varied from .0798 g/in to .0828 g/in), 3.75% variance. Your 2.06 g 23" motor, if it has two black rubber o-rings on it (each weighs .04g) is actually .0426 g/in (remember that about 0.5" of rubber is contained in the knot). For the purpose of entering rubber into the maximum turns calculation equation that I use, I back into the approximate thickness of this density rubber using a standard/typical density for 1/8" rubber strip of .083 g/in. Using this "back in" method, your motor is the equivalent of .064" thick if it was standard density. This thickness of rubber in a 23" loop will take approximately 3,651 turns before breaking if properly lubricated and stretched to 7x length for the first 50% or 60% of the winding process. A safe winding of this rubber would be about 219x15 turns of the 15:1 winder, which would be to about 0.8 in oz. It sounds like you need to launch at 0.3 in oz to stay under your sit ceiling (launch torque is how you regulate climb height using the winding process; there are other ways to trim for or design for less or more climb also).

So, after winding to about 219x15 (or maybe on the first winding you will only get to about 200x15; stop at the target maximum torque of 0.8 in oz), you will backoff wind to 0.3 in oz and launch. This approach will most likely give you an additional 30 to 40 seconds of duration and this is the standard approach to wind rubber for maximum duration.

The other trimming methods you mention (changing decalage angle to change climb rate) are not the recommended approach. You will see my writings and other experienced coaches and student's writings on topics like this (extensive writings) in last years division B Wright Stuff thread and the 2015 division C Wright Stuff thread. In some cases, I also included pictures in the 2015 thread. I advise you to look through these threads. It doesn't take that long to read all the substantive comments in a year's thread.

Brian T.
AMA since 1968
Mid-Michigan SO Coach for four HS teams and two middle school teams

User avatar
klastyioer
Member
Member
Posts: 425
Joined: April 22nd, 2018, 4:46 pm
Division: C
State: PA
Location: somewhere on planet earth
Has thanked: 1 time
Been thanked: 1 time

Re: Wright Stuff C

Post by klastyioer » November 1st, 2018, 5:53 pm

hello,
so recently, our team has been considering homemade props and we have been having issues with making sure that the curves are the same on both blades, any advice on how to make this an easier process?

bjt4888
Member
Member
Posts: 649
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by bjt4888 » November 1st, 2018, 8:43 pm

Klast,

See Jeff Anderson’s post of helpful links on the previous page. Especially the propeller info for the My Way penny plane on page 87 of the middle link.

For a more efficient propeller forming method see the INAV120 F1L propeller article or the Hobby Shopper EZB article, also both linked in Jeff’s post.

Always good to read the entire wiki to see if your question has already been answered.

Brian T.
AMA since 1968

SluffAndRuff
Member
Member
Posts: 69
Joined: November 27th, 2015, 8:26 am
Division: B
State: VA
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by SluffAndRuff » November 6th, 2018, 8:28 am

Has anyone done some flying with the FF kit yet? Wondering what kind of times we can expect from it
()_]_[___]_[_/_]..... .. .. ... . . .
()'''''''''''''''''''''

bjt4888
Member
Member
Posts: 649
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by bjt4888 » November 6th, 2018, 11:13 am

Sluffandruff,

The FF kit supplier was getting over 1 minute with 1/3 motors of his supplied .094" rubber.

This would translate to approximately 3+ minute flights.

Of course, with good testing of better prop and rubber combinations, more duration should be possible.

Brian T

noah.blome21
Member
Member
Posts: 10
Joined: March 15th, 2018, 7:20 am
Division: C
State: IL
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by noah.blome21 » November 6th, 2018, 11:22 am

Do you know the specs of his flight? and of the motor length and propeller?

bjt4888
Member
Member
Posts: 649
Joined: June 16th, 2013, 12:35 pm
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Wright Stuff C

Post by bjt4888 » November 6th, 2018, 11:51 am

.75 g of the kit .094" rubber with a 1.5 g spacer to approximate a 2.25 g motor are all the details know.

Locked

Return to “Wright Stuff C”

Who is online

Users browsing this forum: No registered users and 1 guest