Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
October 15, 2019, 11:58:58 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 is the reasoning behind the Tandem designed indoor models?  (Read 139 times)
0 Members and 1 Guest are viewing this topic.
jswain
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 152

Topic starter


Ignore
« on: July 11, 2019, 06:45:35 PM »

Hello.

I was wondering what the *reasoning* behind using a Tandem design indoor rubber endurance model like some of the Wright Stuff/Sicence Oly/ A6 models?

Also, in practice has it proved to be a worthwhile advantage over the standard type tractor indoor design and if so in what way (climb rate/ease of trimming/overall endurance, etc).

thanks in advance, john s.
Logged
calgoddard
Gold Member
*****

Kudos: 23
Offline Offline

United States United States

Posts: 943


AMA, NFFS & FAC Member



Ignore
« Reply #1 on: July 12, 2019, 09:40:19 AM »

The sole reason I am aware of for using a tandem design, where the rules permit, is to minimize the wing loading on a model where the class has a minimum weight.  I have only seen tandem designs on indoor duration stick models.

In theory this minimum wing loading should produce the maximum flight duration.  Of course you still have to optimize the prop configuration, the rubber motor size (and type) and the winding.  

In addition, the aspect ratio and the camber of the two wings need to be optimized.

It seems to pay off as the current AMA A-6 record is held by Bill Gowen who flies a tandem design.  I think the plans for his tandem A-6 are available on the HPA Plan Gallery.

My understanding is that a tandem stick model is more difficult to trim that a stick model with a conventional tractor configuration where the stab area is noticeably smaller than the wing area.  Optimizing the CG location and the static margin can apparently become tricky issues with a tandem.  
Logged
frash
Gold Member
*****

Kudos: 12
Offline Offline

United States United States

Posts: 462



Ignore
« Reply #2 on: July 12, 2019, 10:08:36 AM »


For tandems with wing TE to stab LE equal to three chords, I put the CG at 185% of chord and the planes were not hard to fly well. Most of this was for ilLegal Eagles several years ago.

Fred Rash
Logged
Olbill
Titanium Member
*******

Kudos: 67
Offline Offline

United States United States

Posts: 2,545



Ignore
« Reply #3 on: July 12, 2019, 10:19:23 AM »

The sole reason I am aware of for using a tandem design, where the rules permit, is to minimize the wing loading on a model where the class has a minimum weight.  I have only seen tandem designs on indoor duration stick models.

In theory this minimum wing loading should produce the maximum flight duration.  Of course you still have to optimize the prop configuration, the rubber motor size (and type) and the winding.  

In addition, the aspect ratio and the camber of the two wings need to be optimized.

It seems to pay off as the current AMA A-6 record is held by Bill Gowen who flies a tandem design.  I think the plans for his tandem A-6 are available on the HPA Plan Gallery.

My understanding is that a tandem stick model is more difficult to trim that a stick model with a conventional tractor configuration where the stab area is noticeably smaller than the wing area.  Optimizing the CG location and the static margin can apparently become tricky issues with a tandem.  

Don Slusarczyk currently has the Cat 2 AMA record - also with a tandem.

I've never found them hard to fly.
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!