Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
November 18, 2018, 10:07:07 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: What rubber does my engine carry?  (Read 695 times)
0 Members and 1 Guest are viewing this topic.
jose12
Bronze Member
***

Kudos: 0
Offline Offline

Argentina Argentina

Posts: 18

Topic starter


Ignore
« on: March 27, 2018, 07:36:29 PM »

Friends I have built two models the Baby Jodel by Jerald Zeingenfuse from the Model Airplae News magazine and a SortaSenator by Mike Stuart and I would like to know how many rubber threads the motor and thickness carries. Waiting for your comments that would allow me to make them fly. Thanks Jose
Attached files Thumbnail(s):
What rubber does my engine carry?
What rubber does my engine carry?
Logged
jose12
Bronze Member
***

Kudos: 0
Offline Offline

Argentina Argentina

Posts: 18

Topic starter


Ignore
« Reply #1 on: March 30, 2018, 07:03:19 PM »

help friends when I ask about the rubber for the engine of my models is because here in Argentina can not buy and shipping from abroad is very difficult, almost impossible to do. I got 16 foot rubber from 3/32 16 1/8 and 16 1/16. I do not know when I'll get it again, that's why it's my question so as not to waste the little rubber I have.
Logged
SBlanchard
Silver Member
****

Kudos: 10
Offline Offline

United States United States

Posts: 154



Ignore
« Reply #2 on: March 30, 2018, 09:29:41 PM »

Hi Jose,

First let me say that those two models look great. I'm sure you'll be able to get them flying with the right trimming work. Then I have to say order more rubber so when you fly the life out of the motors you make, you can replace them and keep on flying. Can you give the wingspan and propeller size for each model? That would make it much easier to give a suggestion for rubber size.

Steve
Logged
jose12
Bronze Member
***

Kudos: 0
Offline Offline

Argentina Argentina

Posts: 18

Topic starter


Ignore
« Reply #3 on: March 31, 2018, 06:29:29 PM »

The propeller that I think I should put is 6 inches but I could increase it to 7 inches for the SortaSenator and I think that the Baby Jodel will be better than the 6 inches. I hope comment thank you
Logged
SBlanchard
Silver Member
****

Kudos: 10
Offline Offline

United States United States

Posts: 154



Ignore
« Reply #4 on: March 31, 2018, 08:55:02 PM »

What is the wingspan for each?
Logged
jose12
Bronze Member
***

Kudos: 0
Offline Offline

Argentina Argentina

Posts: 18

Topic starter


Ignore
« Reply #5 on: April 01, 2018, 06:20:08 PM »

Thanks Steve for answering my question and sorry because I forgot to write down the model's wings. The SortaSenator is 17 inches and the Bebe Jodel is 19. I hope that it works for your calculations. Regards José
Logged
lincoln
Platinum Member
******

Kudos: 29
Offline Offline

United States United States

Posts: 1,753



Ignore
« Reply #6 on: April 01, 2018, 10:57:30 PM »

Knowing the weight will also help.
Logged
SBlanchard
Silver Member
****

Kudos: 10
Offline Offline

United States United States

Posts: 154



Ignore
« Reply #7 on: April 02, 2018, 01:25:59 PM »

I would start with 2 loops of 3/32" for the Sorta Senator with the 6" prop. For the Jodel I would go with one loop of 1/8" and 1 loop of 3/32" to start with a 7" prop. See how that goes.

Steve
Logged
jose12
Bronze Member
***

Kudos: 0
Offline Offline

Argentina Argentina

Posts: 18

Topic starter


Ignore
« Reply #8 on: April 02, 2018, 07:47:08 PM »

Thanks friends for your answers. For Lincoln the weights are 21 gr. for the SortaSenator and 46 gr. for the baby Jodel apologizes for not heberne realized to pass the weights.
For Steve I will try the suggested thing but with the Baby Jodel I will have to do another blok of nose to put a 7 helix since the one I have prepared is 6. Thank you and I will do the tests and tell you how the results were. Hugs José
Attached files Thumbnail(s):
Re: What rubber does my engine carry?
Re: What rubber does my engine carry?
Logged
TimWescott
Gold Member
*****

Kudos: 12
Offline Offline

United States United States

Posts: 888



Ignore
« Reply #9 on: April 06, 2018, 11:46:01 AM »

Knowing the weight will also help.

Isn't there a rule of thumb for motor weight vs. all-up weight?  Some percentage, or maybe some percentage vs. general style?  I seem to remember, but not well.
Logged
rpendzick
Bronze Member
***

Kudos: 1
Offline Offline

United States United States

Posts: 45

WWW

Ignore
« Reply #10 on: April 10, 2018, 06:56:05 AM »

A year or so ago there was an article by Don Srull in the FAC Newsletter. He started all new planes with with this:
Total_Weight / 90 = rubber_cross_section
So for example: a 45g TW / 90 is 0.5 or 2 loops of 1/8 rubber.

This also got me thinking in weight of rubber not length. I start with the new planes empty weight EW and add a percent of rubber to get TW. That percent depends on if a contest or not and the field size, etc. So now I have two numbers that define the motor: the Percent of EW and the Srull Factor

The Srull Factor is your TW / Rubber_Cross_Section. If you get 90 you're right on. A number lower and you have a stronger motor, a number higher and you have a whimpy motor. I know these two numbers on all my planes. This does not consider your prop so it just a starting point.

I live in an urban area but have a tree-less ball field 200m sq. nearby. I fly a half-golly with a 60sec DT and a forward peg. The motor is 10% of Empty Weight and a Srull Factor of 84 - it's a rocket.

have fun - Rick 


Logged
Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!