Wing Loading Question

[TJay 1041]

I need some opinions here, It looks like when I install my wing tips I will have a total length of 13 foot now with a 42 inch wing 42*156=6552sq" /144=45.5sq'*2=91sq' total now with a gross weight of 1050 we divide that by 91=11.53lbs per sq foot. what I am trying to figure out here is if this ceconite 103 fabric which was 1.7oz will work or not. The 103 looks like it has a wing load of 9lbs per sq foot. So now do I figure in the flaperons as a lifting surface or not and or anything else as a lifting surface? Or is this not how you figure this out?

[EDMO 1078]

TJay,

I think you need to figure again:  You should have about 32 feet wingspan, and 51 inch chord, including flaperons, (4.25 feet).

That should give you about 136 square feet of wing.  (fuselage is included)  1050GW divided by 136 = 7.72 lbs /sq.ft.

UL600 is good for 10 lbs/sf, and has a burst strength of about 60 lbs/sf.  1.7 Ceconite is about the same.

Hope this helps.  EDMO

Edited 29 Nov 2015 by EDMO

[C5Engineer 1170]

Is the weight difference significant enough to even bother with the Math? 

[1avidflyer 1983]

My Kitfox 4 project came with the ultralight fabric.  That plane was 1200 lb gross weight.  I ended up using that fabric on my Avid MK IV the first time I recovered it.  That plane was 1150 gross weight and it flew at that weight lots of times.  Never had any issues with the fabric.  I believe you also do figure in the flaperons when you figure sq. footage of the wings.  Jim Chuk

[TJay 1041]

Ok so when figuring in the flaperons as part of the lifting surface I still only have 110.5 square foot of wing area with two 13 foot wings. Divide that by 1050 and I am still at 9.5lbs per sq foot which is still over the limit. Maybe I better extend my wings ha, Nah I have heard of several people that have removed that end bay of there wings and said they love it. ED how do you get 32 foot are you figuring in the skylight as lifting area?

[1avidflyer 1983]

When I mentioned that my Kitfox 4 project came with the ul fabric, I meant that the ul fabric was in the kit supplied from the factory.  They must have thought it was good enough.  I do have to admit, that the latest Avid recover is with the medium grade uncertified fabric though.  I bought 70 yds. so I have enough to do two planes.  Jim Chuk

[EDMO 1078]

Ok so when figuring in the flaperons as part of the lifting surface I still only have 110.5 square foot of wing area with two 13 foot wings. Divide that by 1050 and I am still at 9.5lbs per sq foot which is still over the limit. Maybe I better extend my wings ha, Nah I have heard of several people that have removed that end bay of there wings and said they love it. ED how do you get 32 foot are you figuring in the skylight as lifting area?

Yes,  all the aircraft books, including Kitfox, include the fuselage as a lifting surface,  part of the wingspan, which is measured tip-to-tip, including the tips - and Kitfox also includes the flaperons in the wing chord, as do all other aircraft with ailerons and flaps.  Kitfox has published the same figures I gave you.

EDMO

Edited 29 Nov 2015 by EDMO

[TJay 1041]

Ok thanks ED and Jim is this the stuff you used. It is alot cheaper than poly fiber, what is the difference?

http://www.aircraftspruce.com/pages/cs/dacron/peelply2.php

[EDMO 1078]

Ok thanks ED and Jim is this the stuff you used. It is alot cheaper than poly fiber, what is the difference?

http://www.aircraftspruce.com/pages/cs/dacron/peelply2.php

I don't mean to get between you guys - But, TJay, I would say to check and see if the weave is the same as the 1.7 Ceconite - If memory serves me right, it is supposed to be a finer weave than the 2.7 - I am thinking 84 x 84, or was it 90 x 90?  better check this out before buying, IMO.

EDMO

[TJay 1041]

ED it looks like the older 1.7 oz ceconite was 98 by 98/in I not sure what all that means.

[EDMO 1078]

ED it looks like the older 1.7 oz ceconite was 98 by 98/in I not sure what all that means.

That's the thread count per inch both in chord and span - I tried looking at Spruce for Ceconite and Polyfiber and could not find this older material - the numbers I got for several ones were different.   That was a great fabric - I would buy it if I could find it - The tighter the weave, the less paint it takes to cover it. I think the shrinkage is better controlled too.

EDMO

Edited 29 Nov 2015 by EDMO

[TJay 1041]

I dont think they make the 1.7 anymore,  Maybe they do its just not in the spruce. 

http://www.ceconite.com/articleselecting.htm

[EDMO 1078]

The Ceconite article you listed is what I had remembered seeing.   We talked to Dan Stewart when we were covering the J3, using 2.7 fabric, and he told us that the NEW 2.7 shrinks a lot more than the old 2.7 did, and not to heat it as much - AFTER we bent the root rib on one wing!  Ha!

He also said that he would not use  the NEW 2.7 on a Kitfox wing, and he has covered several of them.

I don't think you will go wrong if you listen to Jim - he has experience with these fabrics - I don't know much about the uncertified new ones, and nothing about the "peal-ply".

EDMO

Edited 29 Nov 2015 by EDMO

[EDMO 1078]

TJay,   Have you checked with Wicks on fabrics?  I found SF-104A 1.7 no thread count given for $6.49 yard, and also, P106 1.7 with a thread count of 94x94 for $8.40 yard on page 42.   Ceconite Light 17 is lower thread count in one direction, 90x76, and also $8.40 yard, page 47.

EDMO

Edited 30 Nov 2015 by EDMO

[akflyer 1427]

You can use the non certified light stuff from ACSpruce.  I used Medium and I wish I would have used light most of the time, but it does hold up a bit better to me beating the snow and ice off of it.  The weight difference really is not that much, you will just see a bit more weave in the finish unless you really load the paint on which is a nono unless you want the paint to start cracking in pretty short order.

 

[1avidflyer 1983]

Here is the link to Spruce's lightweight uncertified fabric.  http://www.aircraftspruce.com/pages/cs/dacron/peelply3.php  As far as using the medium weight fabric, I'm not that concerned with completely covering/filling the weave of the fabric.  I think if the UV barrier is sufficient to protect the fabric (I always keep the plane hangared) and the color coats are sufficient to cover the UV/silver layer, I'm happy with it.  I don't plan to take it to Oshkosh and win a trophy.  YMMV :-)  Jim Chuk

[tcj 150]

Tjay, did you clip your wings?  The spars should be 13.5 feet plus one foot wing tips for 14.5 foot wing length.

[TJay 1041]

Yes sir She is a clipped wing

[EDMO 1078]

Yes sir She is a clipped wing

Then the figures I gave you for a 32 foot wingspan are not valid for yours - You got to figure the new wingspan and area and loading.  If you have 29 foot wings, then the area would be 123.25 sq.ft. divided into 1050 would be 8.52 lbs.sq.ft.

EDMO

Edited 1 Dec 2015 by EDMO

[EDMO 1078]

Yes sir She is a clipped wing

Then the figures I gave you for a 32 foot wingspan are not valid for yours - You got to figure the new wingspan and area and loading.  If you have 29 foot wings, then the area would be 123.25 sq.ft. divided into 1050 would be 8.52 lbs.sq.ft.

EDMO

Also, you don't want flaperons going all the way out to the tips, so you now need to shorten them the same amount. 

The reasoning for that, is because if the flaperons get into the variable vortex at the tips, it can cause flutter...

EDMO

Edited 1 Dec 2015 by EDMO

[Av8r3400 1178]

Got a friend got a friend with a clipped Kitfox with full length flapperons.  (JimS on TeamKitfox)  1500 hours, 20 years of flying and no flutter.  That a IV-1050 with only one counterweight per flapperon, too.

 

Where did that little tidbit come from, Ed?  

[TJay 1041]

I have never heard that one ED. See alot of planes out there with full length flaperons.

[EDMO 1078]

I have never heard that one ED. See alot of planes out there with full length flaperons.

The "full-length flaperons" on the standard wing are about a foot short of the tips.

That remark came from the Aeronautical Engineer and Test Pilot who wrote my design book, Darrol Stinton - You can look it up.  Maybe he was talking about planes that can go faster than cars?

EDMO

Edited 1 Dec 2015 by EDMO

[1avidflyer 1983]

Is that just with drooped wingtips?  Avids flaperons go out to the end of the wing, not counting the wingtip.  Jim Chuk

[EDMO 1078]

The writer just said that they should not extend TO the tips - No specific tip design mentioned.  I imagine Dean was aware of that when he designed the flaperons, and Kitfox flaperons are about a foot shorter than the wing spar.   I would not make mine to the end of the spars, or past the spars, but everyone has to design their own if they are not using the factory parts.  It probably don't matter on these slow flyers.  AND, the writer was talking about ailerons as part of the wing - not flaperons which are below the wing.   I probably should not have even brought this up.

I wonder if TJay's wingspan is maybe 28 feet?  Would you know, Jim?  I could figure his wing loading again...

EDMO

Edited 1 Dec 2015 by EDMO