Moni Motorglider

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Angusnofangus

Well-Known Member
Joined
Sep 29, 2015
Messages
490
Location
Victoria, Canada
Hello and Happy Valentine’s Day!


1) Doable as described above
2) Not doable due to stresses and would need a total re-engineering of the spar
3) Or, a joggle is no big deal to create and just stick to the original design.

Cheers!
A joggle is real easy, not to mention it is as per drawings. To put a doubler on the inboard section would mean lots of field rivets and who knows what the structural ramifications are of doing so. I say stick to the drawing.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,015
Location
NJ
inter-rivet buckling is an issue.....spacing gets smaller depending on the stress....AC 43-13-1b has specifications for sheet splices, which might be useful......you really need to know what you are doing here...... might want to stick to the plans.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,526
Location
Memphis, TN
It’s not something you can guess at, although one thickness with doubler or tripler is seems more normal. I don’t like the idea of a joggle as it seems it’s a stress riser for that type of application
 

Zeusons

New Member
Joined
May 1, 2019
Messages
1
Hello and Happy Valentine’s Day!

As I’ve been going through my Moni stuff in preparation to begin building, I came across the spar design for the Aerosviluppi AS-10 motor glider. The AS-10 was the Italian version of the Moni and since they couldn’t get Monnett’s I-beam extrusion, they designed a standard built-up aluminum spar with sheet aluminum web and .125” angle for the caps. All aluminum is 2024-T3. The dimensions are the same for the Moni spar for spar depth and length/span so it could be a drop-in replacement (all fuselage attachments are the same).

One thing they did for the web was to use two different thicknesses of material and joined them with a riveted joggle. The inboard section was .063 mating to a .040 outer web. This is where my question comes in: It would be easier (maybe??) to construct the web if the web were .040 from the inboard end of the spar to the tip and then put a doubler to reinforce the portion of the inboard section that was originally thicker. If one were to put a .040 or .032 (or thicker) doubler on top of the .040 web it would have a total thickness greater than the original .063 inboard web. Is this:

1) Doable as described above
2) Not doable due to stresses and would need a total re-engineering of the spar
3) Or, a joggle is no big deal to create and just stick to the original design.

FWIW, I haven’t been able to find the original designer to ask him this question. The spar as designed was rated at +6/-3 G’s at 255kgs.

The reason I rehash this question is because I’m having reservations (again!) about cutting the original Monnett spar that can’t be replaced if I mess something up.

Any thoughts would be greatly appreciated. Thanks for putting up with my questions!

Cheers!
Are there any plans available for the built up spars?
 

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
8,769
Location
KWHP, Los Angeles CA, USA
A vertical joggle could possibly create a localized stress riser at one spanwise location. This may or may not be a problem, if it is located at the position of an existing rib. That is a job for an engineer to determine.

HOWEVER, most all of the doublers and reinforcements on spar webs that I have ever seen spread the loads out over some distance spanwise, with a tapering shape, to create a gradual change in the structural cross section. Since this is more effort than a straight joggle, there has to be some reason they do it.

 
Last edited:

wwz7777

Well-Known Member
HBA Supporter
Joined
Aug 8, 2012
Messages
81
Location
Northfield, MN
Hello all,
Here are two PDF's that show the Aerosviluppi AS-10 spar design. They are in Italian, with some English translations. The first one, the spar in "pages" format, gives a good overview of the design. This file came from Don Black who was the Aerosviluppi rep in the US. Pages 1-5 show some of the details while pages 6-10 are the spar but made up of copies of the main print. The second PDF, the "complete drawing," are pages 6-10 taped together to give the complete spar design in a single page. The joggle in the web is at 1178mm from the centerline and is between two wing ribs. Let me know if this helps.
 

Attachments

Top