News:


Advertise Here
  • May 06, 2021, 04:55:11 PM

Login with username, password and session length

Author Topic: What's The Best Way?  (Read 807 times)

Offline Dennis Saydak

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 578
What's The Best Way?
« on: February 23, 2021, 09:18:34 AM »
To sheet the second side of a fully sheeted built up wing while it is still in the wing jig?
Just when you think you're getting ahead in the rat race.....you find the rats just get faster! MAAC 13120L

Online Steve Berry

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 208
Re: What's The Best Way?
« Reply #1 on: February 23, 2021, 09:33:19 AM »
Probably using standard wood glue. Just make sure you don't use too much. It gives you a long enough working time so that mistakes in positioning are correctable, something not really possible in this situation using CA.

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3318
Re: What's The Best Way?
« Reply #2 on: February 23, 2021, 12:01:58 PM »
Back when I was sheeting everything I used Tightbond and lots of weights  Whatever you use do it the same on both sides or you are asking for a warp.

However, I have done a lot of FF and one PA using CA on all but the bottom aft plank/sheet.  CA was new on the scene and so we used it far too much!  So, I would tack the sheeting on the top then flipped the wing over in the jig (arrow shafts on blocks) and did the joints. (4" sheets aligned with the LE.)  Flip and repeat for each sheet till the last one on the bottom which you do with slow cure epoxy or Tightbond. Wipe the seam on the outside.  I prefer the epoxy since it will harden and sand easier sooner than the aphetic's and match hardness with the Z-Poxy (alcohol thinned Epoxy it the day) that went on next. Thin CA will run down a seam for as much as you have including the finger holding the sheet.  If there is even a hint of a gap don't pull the sheeting in, hit the gap with some thick CA and "kick" it.  Use those really long thin tube applicators.  Do the seams with slightly thinned epoxy and a brush from the inside.  CA will run into the seam and leave you with a ridge.  Epoxy doesn't.

If you have plenty of light and a good applicator, reaching 4" into the structure is no big deal.  As a side, the wing I did this way was still in tact after about 1000 flights and 30 years in the attic.

Good luck and make sure you have fresh bottles of kicker and de-bonder at your fingertips!

I didn't do this part "back in the day" but I sure do it now.  Doing sheeting with CA lets off a huge amount of CA fumes.  You need a fan and a really good ventilator mask.

Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Offline Dennis Saydak

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 578
Re: What's The Best Way?
« Reply #3 on: February 23, 2021, 12:13:48 PM »
Has anyone used the ZPOXY method that Bob Hunt documented for sheeting a foam wing? All the contact points on the sheet could get a brushed coating of ZPOXY and the excess can be removed using the "toothed" scraper. Carefully positioning the complete panel, then pinning and weighting it when positioned should do the trick? No?
Just when you think you're getting ahead in the rat race.....you find the rats just get faster! MAAC 13120L

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3318
Re: What's The Best Way?
« Reply #4 on: February 23, 2021, 12:26:44 PM »
Has anyone used the ZPOXY method that Bob Hunt documented for sheeting a foam wing? All the contact points on the sheet could get a brushed coating of ZPOXY and the excess can be removed using the "toothed" scraper. Carefully positioning the complete panel, then pinning and weighting it when positioned should do the trick? No?
From what I understand Z-Poxy is a finishing resin and as such it is formulated for hardness and finishing (sanding, etc.) but not for adhesive strength.  I would question whether or not those joints could take the vibration and flexing when mated to balsa instead of foam and in such a narrow surface area.  However the same approach with slow cure (which is probably fast compared to Z-Poxy) epoxy or double application wood glue might work, maybe even better.

ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Online Dave_Trible

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5268
Re: What's The Best Way?
« Reply #5 on: February 23, 2021, 07:09:39 PM »
Though I haven't used it for this purpose, I'd use LAMINATING epoxy.  This is what you would use to lay up carbon fiber parts or props.  It is nearly water-thin with usually around 25-30  minutes gel time so you don't have to rush.  You can brush it on like dope then scrape off excess if desired.  It will need to set 8-10 hours for a full cure.  It ends up being quite light and give all the strength you'll need.  It can be a little pricey unless you can order in quarts.  Fiberglast is a good source or maybe a West Systems product from, say CST Sales.  You could use a very small paint roller to roll it on the ribs, or the full sheet if doing a foam wing.  If I understand the question you'd have to lift the wing and turn it over. Then re-mount it to the wing fixture. This is how I do mine-apply the sheeting (and cap strips) to one side, then turn it over to re-mount.  Then do the other side.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Offline wwwarbird

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7640
  • Welcome to the Stunt Hanger.
Re: What's The Best Way?
« Reply #6 on: February 23, 2021, 07:35:08 PM »

 Is there a reason you can't simply undo and flip it in the jig?
Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Offline BillP

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 434
Re: What's The Best Way?
« Reply #7 on: February 24, 2021, 05:32:44 AM »
What type jig? If it doesn't rotate you have to turn it over one way or another. Epoxy is overkill. You will get the same results with titebond or elmers carpenter glue without the expense or hassle of epoxy.
Bill P.

Offline fred cesquim

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 541
    • Fred Cesquim Aeromodelos
Re: What's The Best Way?
« Reply #8 on: February 24, 2021, 05:59:44 AM »
To sheet the second side of a fully sheeted built up wing while it is still in the wing jig?

still in the jig both sides is not practical, will surely lead to poor glue joints, probably warps and ugly butt joints.
my sheeting method is: build up the whole wing on the jig or with the bottom tabs still attached to the board and to the ribs.
sheet LE/TE add the capstrips and as much of the center sheeting as possible. usually i already have bellcrank already attached.
cut loose from the board, add a spanwise lenght of wood or aluminium bar to support the TE (not tapered). then add shims to the last ribs under the spars to raise them to the proper alignment with the centerline of rib 1. (means both ribs centers are paralell and same distance from the board.
then i do the sheeting and capstrips. what ultimately prevents the wings to twist are the capstrips.
as a method for glueing: capstrips i use CA. for The TE titebond and a long metal bar over it. for the LE: i fix the sheeting to the front spar with CA. then spray windex(that stuff for glass cleaning) on the outside of the sheeting. While it softens the sheeting, i run titebond on the ribs. when the sheeting is ready to be curved due to the windex action ( not dripping just a bit is enough) i run a bead of CA on the main spar and with a metal bar i slowly works the sheeting over the ribs to the spar direction, then gently press over there for the final bond. no need to do extra pressure, to avoid warps. this wau i donīt need any pins, clamps or packing tape to hold anything and the wings finishes pretty fast and true.

Offline Dennis Saydak

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 578
Re: What's The Best Way?
« Reply #9 on: February 24, 2021, 08:34:32 AM »
Is there a reason you can't simply undo and flip it in the jig?

That's the easy part. Think of the jig as a lost foam cradle. The wing would be fully sheeted from L.E. to T.E (eg; Freeman Spitfire) on one side. There are no open bays with cap strips. The sheet for the second side would also be full size as if sheeting a foam wing. The second side sheeting has to be glued down onto multiple rib and spar contact points that are difficult to reach for gluing. Hope this explains things a little better?
Just when you think you're getting ahead in the rat race.....you find the rats just get faster! MAAC 13120L

Offline wwwarbird

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7640
  • Welcome to the Stunt Hanger.
Re: What's The Best Way?
« Reply #10 on: February 24, 2021, 06:43:46 PM »
Think of the jig as a lost foam cradle.

 Unless I'm missing something, then that sounds even easier.

 Lay your fully prepared sheet in the cradle, apply Titebond to all of the wing structure contact points, position the wing down into the sheeting in the cradle, sandwich and weight all the rest as typical, go to the fridge, grab a beer and wait til morning.





Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Online Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4620
Re: What's The Best Way?
« Reply #11 on: February 24, 2021, 06:53:50 PM »
   Do it like Wayne suggested or perhaps do it in sections. Plan it out, match sand the edges and mark where they will join. Make the seams where the sheets will join line up on the spars. Start from the front and pre-curve or preform the sheeting as much as you can to help it lay down, and then work towards the trailing edge. Use white glue of something slow drying to help you line things up.
  Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline wwwarbird

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7640
  • Welcome to the Stunt Hanger.
Re: What's The Best Way?
« Reply #12 on: February 24, 2021, 07:04:20 PM »
   Do it like Wayne suggested or perhaps do it in sections. Plan it out, match sand the edges and mark where they will join. Make the seams where the sheets will join line up on the spars. Start from the front and pre-curve or preform the sheeting as much as you can to help it lay down, and then work towards the trailing edge. Use white glue of something slow drying to help you line things up.
  Type at you later,
   Dan McEntee

 Have your full-size sheet all butt sanded, glued, and seam sanded first. That's what I meant by "fully prepared sheet" in the above comment. In this case especially, you'll never get it evenly sanded and looking decent if you try to do it in sections.
Narrowly averting disaster since 1964! 

Wayne Willey
Albert Lea, MN U.S.A. IC C/L Aircraft Modeler, Ex AMA member

Online Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4620
Re: What's The Best Way?
« Reply #13 on: February 24, 2021, 07:19:38 PM »
Have your full-size sheet all butt sanded, glued, and seam sanded first. That's what I meant by "fully prepared sheet" in the above comment. In this case especially, you'll never get it looking decent if you try to do it in sections.

   The last competitive R/C sailplane I built years ago was a Dwight Holley "Gobbler" full house ship with ailerons and flaps. It had a fully sheeted wing and the procedure for building it was to edge join all the sheeting in advance for the bottom side of the wing, which was a semi-symmetrical airfoil,  lay out the "plan" for the wing frame on the sheeting and build the wing right on the sheeting! The top sheeting was done a similar way, with a guide to tell you how to draw in the frame work so you knew where to apply glue. It actually worked pretty well that way for that wing, and probably would work for a stunt model also if it was engineered that way from the start. For a system like a lost foam jig,  having the leading edge preformed on a buck and glued in place first would make the whole works easier I think . You could apply the leading edge and when dry, apply the rest of that side of sheeting in sections. Then turn it over and set it in the correct cradle and apply that side the same way. If the jig is secured to a flat surface, and the frame work is secured to the jig, you should get a straight wing as long as you don't build in any stresses by forcing any joints.
  Type at you later,
  Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Robert Whitley

  • 21 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 193
Re: What's The Best Way?
« Reply #14 on: February 24, 2021, 08:44:00 PM »
Hi Dennis.
If this is for your Freeman Spitfire being built on the tube jig I suggest you look at Al Rabe’s videos of his Critical Mass and how he trims down the centre support to be able to flip it in the jig blocks.
He also shows how to do the glueing of both skins in that jig.

Well worth the viewing.


Advertise Here
Tags:
 


Advertise Here