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Rudy Lee

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Apr 26, 2020
Messages
31
One reason for not gluing to ribs is that you want the fabric to be able to shift and equalize the tension across the entire surface when you begin heat shrinking it. If you glue it to the ribs, then bay tensions may differ and it will start pulling your ribs out of straight alignment. Once the fabric is taught from shrinking, then your paint application will soak into the weave and provide light adhesion to the ribs and skins.
That makes a ton of sense! Thanks for the explanation.
 

Rudy Lee

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Apr 26, 2020
Messages
31
Why not use the same material as the trailing edge?
We tried a bunch of different methods to get it to adhere along the curve of the leading edge, but it just wouldn't go on well. For the trailing edge we were just able to use a brake and bend the metal at an angle. For the leading edge we would need a giant roller to get it to shape
 

Rudy Lee

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Apr 26, 2020
Messages
31
Ok in a previous drawing there is a thin leading edge; is that gone now? If you removed that, I think you will have an airplane that does not fly well. It takes the impact of the air. I’m not saying it will not fly, but the airfoil will be changing constantly with the air hitting it. It will take a lot of skill to fly it. A leading edge is also first line of defense to hitting a bird. You don’t want all the ribs to be broken and loose shape. It will not fly enough to make an emergency landing. Glueing at the the spar is fine as long as it is a secure spot. Plenty of real covering jobs do this to hide a leading edge seam for looks, but they still glue to the leading edge.
Yes, there is no leading edge anymore. After some research, we determined that scalloping wouldn't be an issue.
 

TFF

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Apr 28, 2010
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Location
Memphis, TN
If you can change the shape with out a lot of pressure, it’s going to not be the best flyer. You will have an infinite number of airfoils on the wing at once. I’m not saying it won’t fly, but the flight character can change moment or moment. I would not like flying something like that. It might be easier to build, but I would not leave normal convention on your first design. Just for safety sake.
 

bmcj

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Apr 10, 2007
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Fresno, California
Yes, there is no leading edge anymore. After some research, we determined that scalloping wouldn't be an issue.
Not even something like a 1”x1/4” strip inserted int a leading edge slot (Kind of like balsa models do) to give the ribs more stability?
 

M Clarke

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Joined
Nov 8, 2020
Messages
20
Location
California
Hi, just found this thread, good stuff! in regards to leading edge skins and fabric covering, I highly recommend looking at the skypup ultralight. It is almost entirely foam construction. uses a 0.8mm plywood leading edge epoxied to foam ribs. very easy to bend and gives your fabric a good surface to bond to. The construction manual shows a very simple process for covering the foam wings as well. You guys are not the first to run into these problems and the skypup plans and construction manual have a lot more useful info relating to this project. If you would like to borrow my copies, let me know and we can make it happen, Im located in socal and can mail or fly them there... I saw you tried aluminum leading edge skins with no success. I'm guessing you didn't use dead soft aluminum? dead soft aluminum should not take a lot of force to wrap around and wont want to spring back. 3m panel bonding adhesive has worked extremely well for me on sheet metal repairs. Id have to see how compatible it is with foam though.
 

Attachments

Protech Racing

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Jul 10, 2020
Messages
422
Nose ribs at 6 in will be fine . Over 100mph you may need a sheet covering .
I glued to each rib as I pulled the covering on.
 

BJC

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Oct 7, 2013
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97FL, Florida, USA
Would binding issues still be an issue if we're creating hinges that look like this? View attachment 108887
If so, then better not risk it and go with your suggestion with sticking to 1" aluminum. Sounds like a detachable tail is our best option then?
Not a recommendation, but an example from a new Aerolite 103:
D3BB59B3-05E2-4AAC-965B-2FBB44B4F1B0.jpeg
Two hinges per elevator, used on rudder and ailerons too. Light and simple plus easy to make and install. Note, also, the gap seal.


BJC
 

radfordc

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Joined
Feb 5, 2008
Messages
1,444
Do you have any recommendations about leading-edge material?
Why not use what has been proven? A round aluminum tube for the LE and TE with compression ribs forming a strong ladder structure. Look at how almost every ultralight ever made was designed.
 

Agastya Raghavan

New Member
Joined
Jun 2, 2021
Messages
1
We are currently researching wing fabric attachment, and with our current strut-spar attachment design (below), it would be impossible to bolt the gusset to the spar after fabric covering. We’re not sure how to proceed if we attach the strut to the spar first and cover the wing second. We are considering bolting the gusset to the spar first, then covering the wing and cutting a hole in the fabric to attach the strut; would this be feasible? Is there a better way?

1622668186863.png
 

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proppastie

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cutting a hole in the fabric to attach the strut;
look at a certified fabric covered aircraft Champ or Cub there will be a cuff or inspection hole and plate for access to these types of fittings......
 

Gregory Perkins

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May 25, 2019
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Atlanta
Not necessarily related but from the drawing it appears your connector bolts from the strut to the spar are attached at the extreme top and bottom of the spar. These are the most highly
stressed areas of the spar and you would instead be better off attaching to the very middle of
the spar to avoid unwanted weakening of the spar.
 

maya.ayoub.32

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Apr 6, 2020
Messages
78
Not necessarily related but from the drawing it appears your connector bolts from the strut to the spar are attached at the extreme top and bottom of the spar. These are the most highly
stressed areas of the spar and you would instead be better off attaching to the very middle of
the spar to avoid unwanted weakening of the spar.
Yes! Our CAD just broke before taking that photo but they are in the middle of the spar - thanks for pointing that out.
 

maya.ayoub.32

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look at a certified fabric covered aircraft Champ or Cub there will be a cuff or inspection hole and plate for access to these types of fittings......
Oooo these are perfect! We’ll do some research into them and I think this should be great for the gussets/ spars. So you would recomend against having an unsupported hole in the fabric?
 

proppastie

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unsupported hole in the fabric
the rings are glued to the fabric and support the hole.....again look at some certified fabric covered aircraft and their inspection covers..... AC 43.13-1B google and you will have more than you want to know.

2-14. INSPECTION RINGS AND DRAIN
GROMMETS.
a. Inspection Rings. Inspection access is
provided adjacent to or over every control
bellcrank, drag-wire junction, cable guide, pulley,
wing fitting, or any other component
throughout the aircraft which will be inspected
or serviced annually. They are installed onl

9/8/98
AC 43.13-1B



on the bottom side of the wings except where installed on the top surface by the original
manufacturer.

(1) Cutting the holes may be delayed until needed; however, all covers should be finished
in matching colors with any trim lines and stored until needed. Spraying matching colors a year
later is expensive and time con- suming.

(2) The 3-9/16 inch inside diameter cel- lulose acetate butyrate (CAB) plastic inspec- tion
access rings have become popular and bond satisfactorily with Nitrate Dope or Fabric Cement. Any
metal inspection hole rein- forcements of a particular shape or special de- sign or size, installed
by the original manufac- turer, should be reinstalled after cleaning.

(3) Tapes or patches over aluminum re- inforcements are optional, but recommended in the
prop-wash areas on the wings and for- ward fuselage bottom.

(4) Fabric patches over plastic rings are strongly recommended because plastic is not a stable
material, becomes brittle at low tem- peratures, and fatigues and cracks from prop blast vibration.
Plastic rings are often cracked during removal and installation of spring, clip- held covers.
Patches with a minimum 1-inch overlap, should be installed with dope.

b. Drain Grommets. Atmospheric tem- perature changes cause the humidity in the air to condense
on the inside of aircraft surfaces and pool in all low areas. Rainwater enters



through openings in the sides and top, and when flying, everywhere throughout the struc-
ture. Taxiing on wet runways also splashes water up through any bottom holes. There- fore,
provisions must be made to drain water from the lowest point in each fabric panel or plywood
component throughout the airframe while in a stored attitude. Drain holes also provide needed
ventilation.

(1) Install drain grommets on the under side of all components, and the lowest point in each
fabric panel when the aircraft is in stored attitude. Seaplane grommets, which feature a
protruding lip to prevent water splashes through the drain hole, are recommended over
drain holes subject to water splashing on land planes as well as seaplanes. The appropriate- size
holes must be cut through the fabric be- fore installing seaplane grommets. Plastic drain
grommets may be doped directly to the fabric surface or mounted on fabric patches then doped to the
covering. Installing a small fabric patch over flat grommets to ensure secu- rity is optional.
Alternate brass grommets are mounted on fabric patches, then doped to the fabric.

(2) After all coating applications and sanding are completed, open all holes through flat drain
grommets by cutting through the fab- ric with a small-blade knife. Do not attempt to open drain
holes by punching with a sharp ob- ject because the drain hole will not remain open.

2-15.¾2-19. [RESERVED.]







































































Par 2-14
Page 2-23 (and 2-24)
 
Last edited:

Dana

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CT, USA
Most often the gusset plates are bolted to the spar before covering. There should be a reinforcement patch around the cutout in the fabric. The bolt holding the strut to the gusset plates should be on the outside, so you don't have to go inside the wing to attach it, though the inspection plates allow you to access the gusset attachment bolts.

Often the reinforcing rings are doped onto the fabric but not cut out... they can be easily cut out later if access is needed for some reason and a cover plate installed at that point.
 

maya.ayoub.32

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HBA Supporter
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Apr 6, 2020
Messages
78
Fabric patches over plastic rings are strongly recommended because plastic is not a stable
material, becomes brittle at low tem- peratures
Okay gotcha I understand the use of these rings then. To provide more support for the fabric and secondary as a makeshift "inspection hole." Thank you for the tip to research other planes with certified fabric covering - we'll get on that asap!
 

maya.ayoub.32

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Apr 6, 2020
Messages
78
Often the reinforcing rings are doped onto the fabric but not cut out... they can be easily cut out later if access is needed for some reason and a cover plate installed at that point.
Sweet! We'll attach the gussets as soon as the bolts come in, reinforce it with a patch, add a ring, and bolt the gusset to the spar attachment. Thank you for the process and help!
 

maya.ayoub.32

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HBA Supporter
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Apr 6, 2020
Messages
78
On a completely separate note:

We plan to use 3/32” stainless steel cables for the control system for our ultralight, and we’re not sure whether to use tin-plated copper or stainless steel nicopress sleeves to secure our cables.

On the one hand, tin-plated copper sleeves would be weaker, taking around 80% less force than the rated strength of the cable. We don’t expect this to be much of an issue since our cables can take around 920 lbs of force and we’re only expecting around 100 lbs of force on them.

Stainless steel sleeves would be able to take the full rated strength of our cables, but we’ve heard that they might require hydraulic tools to crimp, and hydraulic tools cost several thousand dollars (too expensive for our purposes). Would we need hydraulic tools for the stainless steel sleeves, or would it be possible to secure the sleeves properly with hand tools? Should we stick with tin-plated copper sleeves?

Thank you for your help!
 
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