Converting Sail Cloth a/c to standard fabric covering?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

robbvious

Member
Joined
Jun 10, 2020
Messages
7
Location
38WI
Hello all, first post here, be gentle. I recently acquired a T-Bird II and am not keen on the replacement cost of a complete sail set at nearly $3K. I'm trying to determine if it is possible to change the entire aircraft to a "standard" aircraft covering. The way I understand it, I can rivet the wing ribs to the spars through the poly tip rib ends, then cover with Stewart or Stits processes, preferably with a 1.8oz cloth. Does the wing structure need any additional spar or reinforcement to maintain the airfoil?
Advice appreciated.
 

Victor Bravo

Well-Known Member
Joined
Jul 30, 2014
Messages
9,832
Location
KWHP, Los Angeles CA, USA
Not familiar with the T-bird wing, but.... Unless the "sails" have pockets sewn in for "batten" style wing ribs (like hang gliders and some UL's) , then there should not be any reason you couldn't use aircraft fabric.
 

robbvious

Member
Joined
Jun 10, 2020
Messages
7
Location
38WI
Yes, It has the ultralight style frame wing structure with the ribs slipped into the pockets. Maybe I'd have to make new ribs?
 

Victor Bravo

Well-Known Member
Joined
Jul 30, 2014
Messages
9,832
Location
KWHP, Los Angeles CA, USA
Again I have not seen the drawings or seen a T-Bird in person, so I'm guessing. And there are several people here on this forum with far more experience than me on this type of aircraft.

BUT... if having a bent tube batten slipped into a pocket in the sail is structurally good enough for this aircraft, then a tube rib that is properly attached to the spar tubes should be good enough as well. The important question is how to attach the tube to the spars without weakening the spars.

I would think that you could make simple aluminum gussets that rivet the parts together, however you should not drill those holes in the top or bottom of the spars unless you have a properly trained engineer verify that this is safe. The top and bottom of the spar tubes are where the tension and compression loads are, so drilling ahole for a rivet could potentially reduce the strength.

I would create sheet metal brackets that rivet the rib tubes onto the middle back of the forward spar, and the middle front of the rear spar. These rivets will be on the "neutral axis" of the tubes and have the lowest possibility of creating a weak point. Again, have a real live engineer look at this and verify it... I am not technically qualified. Several people on tis forum are qualified to give you an educated answer as to whether I am correct or incorrect.

T-Bird Rib Attach.jpg
 
Last edited:

cluttonfred

Well-Known Member
HBA Supporter
Joined
Feb 13, 2010
Messages
8,688
Location
World traveler
Question...with the cost of the modifications, the cost of the aircraft fabric and coatings, and the time and energy involved, are you really likely to save much over the price of new sails? Maybe you could shop around for a better price?
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,336
Location
NJ
no reason why you can not sew pockets in the Dacron fabric or sail cloth if you need lighter weight. I would not change the structure just copy the sails. does your wife sew.?
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
15,832
Location
Memphis, TN
I would learn to sew. You can buy sail cloth just like Dacron. Tweaking a covering system is way different than just changing to a whole other structural system. It would be a big jump. I would save up for the real deal. Also if decide to sell it, it will be worth more having it covered right.
 

Doran Jaffas

Well-Known Member
Joined
Jun 25, 2019
Messages
498
Just my .02 here.
If you purchased the aircraft reasonably enough then stick with the original type sail. It is proven and considering time and labor will ultimately be less expensive. Considering the anxiety issue when in flight, peace of mind is priceless knowing that you have the proven system holding you aloft. Especially when getting bounced around.
 

Attachments

Woofbite

Member
Joined
Sep 15, 2010
Messages
22
Location
Forest lake MN, washington
id be really leary of the aircraft fabric warping everything. when You pass that iron over an area, theres a fine line between to much heat and all the sudden you get yourself a lot more wing wash than you had anticipated.
 

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
8,475
Location
Saline Michigan
Besides all that, have we checked the cost yet. The OP was put off by the $3k cost of new sails, but will the bill for conventional covering materials and tools plus whatever mods actually any cheaper?
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
10,204
Location
CT, USA
I would seriously suggest you stick with the original style sails, for several reasons:
  • Drilling holes to rivet the ribs to the spars will weaken both the spars and the rib ends.
  • Shrinking the fabric is likely to warp a structure not designed for such tension.
  • Ultralights tend to get bent from time to time. It's a lot easier to remove the sails, make the appropriate repairs, and slip the sails back on, than it is to strip and recover with doped on fabric.
  • Sewn sails usually have zippers appropriately placed for inspection and service of internal components like aileron linkages, etc.
  • Sewn sails will be lighter than painted fabric.
Also your list doesn't include the required Poly-Spray (UV protection) and Poly-Tone (color).
 

Doran Jaffas

Well-Known Member
Joined
Jun 25, 2019
Messages
498
Eve
Besides all that, have we checked the cost yet. The OP was put off by the $3k cost of new sails, but will the bill for conventional covering materials and tools plus whatever mods actually any cheaper?
Even IF there is a $1,500.00 savings using a different method because of the savings instead of the tried and proven for a given design is not worth the risk.
If he does, he should used a BRS and that alone is more than the sail.
I tell would be aircraft owners if they can't afford all of the expenses that our aircraft require, then they can't afford any of them. Sounds harsh but a good dose of reality to direct them toward safety is better than the possible alternatives.
If using a different aircraft covering is successful I will gladly be rebuked as learning something new is what experimental aviation is all about but please, he needs to be very very sure of the actions he is taking.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
15,832
Location
Memphis, TN
If you could do it for under a thousand, maybe. The difference between 1500 and 3000 is saving twice as long. It might be a year away instead of six months. It will be a lot safer the way it’s designed.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,336
Location
NJ
Sail cloth is not finished, and less finish even the higher priced one would be less expensive.....
 

deskpilot

Well-Known Member
Joined
Jun 30, 2009
Messages
1,132
Location
Morphett Vale, South Australia. Just south of Adel
G'day Rob.I'm in the same position as you with my Truster type T84. Had it gifted to me because the Dacron sails were rotten. It's been stored for over 11 years but all is well except the sails. A full new set cost about the same in Aussie dollars so I'm experimenting with a cheaper way to re-cover the Flying surfaces. I'm using cheap dress making materials for my experiments. Initially I used Lycra as it can be stretched to fit any shape. My initial trial was just a piece stretched over a wooden frame, the 'painted' it with polyester resin, The result was a very tuff, pliable and fixed colour sheet, a 'little bit heavier' than the original size piece of Dacron. As Lycra is somewhat expensive I redid the experiment using Chinese silk which is very cheap and lighter than Lycra. This failed as the procuring heat of the resine destroyed the silk in that it lost all it's tension. My next test will be using a lightweight cotton but will have to wait until the weather here in South Australia warms up a bit. In the meantime, I'm working on making the wings foldable. BTW, my original wings had tubular ribs insert into pockets sewn into the wing skins.
Thruster_T84.jpg T84 Thruster (not mine)

DSCF4920 (Copy).JPG

DSCF4931.JPG

DSCF5200 (Copy).JPG Trial comparing Dacron(lower) with resin impregnated Lycra. This test failed as I got separation between first and second layer of resin. You can however see the potential. A little heavier maybe, but smoother and therefore less draggy and ready coloured.

Good luck with your project.
Doug
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,336
Location
NJ
Sail cloth is not finished, and less finish even the higher priced one would be less expensive.....
.I do not know how heavy your existing cloth is so the links may be for too lite material.
 

Doran Jaffas

Well-Known Member
Joined
Jun 25, 2019
Messages
498
If you could do it for under a thousand, maybe. The difference between 1500 and 3000 is saving twice as long. It might be a year away instead of six months. It will be a lot safer the way it’s designed.
I have been around Aviation all of my life. Or at least as far back as I can remember. I took my first airplane ride at 4 and have been a licensed pilot for 36 plus years.
Though nothing seems to change it still surprises me to see people that want to do it in a different way than the engineers have. Sort of reinventing the airplane and making the same, sometimes fatal
G'day Rob.I'm in the same position as you with my Truster type T84. Had it gifted to me because the Dacron sails were rotten. It's been stored for over 11 years but all is well except the sails. A full new set cost about the same in Aussie dollars so I'm experimenting with a cheaper way to re-cover the Flying surfaces. I'm using cheap dress making materials for my experiments. Initially I used Lycra as it can be stretched to fit any shape. My initial trial was just a piece stretched over a wooden frame, the 'painted' it with polyester resin, The result was a very tuff, pliable and fixed colour sheet, a 'little bit heavier' than the original size piece of Dacron. As Lycra is somewhat expensive I redid the experiment using Chinese silk which is very cheap and lighter than Lycra. This failed as the procuring heat of the resine destroyed the silk in that it lost all it's tension. My next test will be using a lightweight cotton but will have to wait until the weather here in South Australia warms up a bit. In the meantime, I'm working on making the wings foldable. BTW, my original wings had tubular ribs insert into pockets sewn into the wing skins.
View attachment 98466 T84 Thruster (not mine)

View attachment 98467

View attachment 98468

View attachment 98469 Trial comparing Dacron(lower) with resin impregnated Lycra. This test failed as I got separation between first and second layer of resin. You can however see the potential. A little heavier maybe, but smoother and therefore less draggy and ready coloured.

Good luck with your project.
Doug
there are many books written about different materials that would save you a lot of time. If you enjoy building and enjoy exploring without the knowledge of others then have at it. Me being a lazy type and very cautious I'd rather err on the side of caution and take other professionals advise.
 

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
8,475
Location
Saline Michigan
I am accustomed to $5k in materials to recover a Cub or other LSA, which is why I questioned the cost save theory. Is this gadget a third to a half of the covered area of a Cub? If so, then this will save some money over a new set of cover from the factory.

We seem to be missing Poly -Spray - a couple coats of silver will keep UV in sunlight from quickly destroying the polyester fabric. We can skip color top coats to save weight.

Billski
 
Top