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Author Topic: Curved leading efges  (Read 6057 times)

Offline Geoff Goodworth

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Curved leading efges
« on: October 16, 2021, 02:05:49 AM »
I'm currently drawing a model where the wing has a curved leading edge in plan view. The span is 52" and the distance from the leading edge at the centre to the leading edge at the tips is 1.6".

So the curve is 1.6" in 26".

I think that the Lincoln Log method would be ideal for this wing. For those of you who have used this assembly method, do you think I can curve such a leading edge assembly and how wide should I make the tongue?
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Offline pmackenzie

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Re: Curved leading efges
« Reply #1 on: October 16, 2021, 09:51:15 AM »
Do the tongue with two or three laminations, the way free flight guys do curved outlines.
 This will eliminate any stress from bending it from a single piece. Laminate, then sand it flat.

Having built more than a few Bostas, the leading edge sheeting will do some strange stuff near the tips where the shape is more of a compound curve.
The Bosta did have a similar horizontal spar, but it was straight on the back edge from tip to tip, so that it provided more strength in the fore/aft direction when the model crashed.
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Offline Avaiojet

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Re: Curved leading efges
« Reply #2 on: October 16, 2021, 10:11:11 AM »
Quote from: Geoff Goodworth on October 16, 2021, 02:05:49 AM
I'm currently drawing a model where the wing has a curved leading edge in plan view. The span is 52" and the distance from the leading edge at the centre to the leading edge at the tips is 1.6".

So the curve is 1.6" in 26".

I think that the Lincoln Log method would be ideal for this wing. For those of you who have used this assembly method, do you think I can curve such a leading edge assembly and how wide should I make the tongue?

Plenty of ways to get this done.

Can you put up a photo or diagram of the airfoil?

Balsa can be steamed and bent easily. Just one option. There are others.

I designed this wing a few years ago, I don't remember why, I think for use on my GBR-3? The LE is 1" x .5", drawn this way just for the convenience. 
.
This LE could work with a choice of light wood, steamed for the arch and after sanding, 50% of the stock is gone anyway.

You could also use .25" x .25". I can think of a few more.

The drawing and a few comments are over at CFC Graphics Vendor's Corner.

OH!, does your wing thickness taper at the tips?

Charles

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Offline Mike Alimov

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Re: Curved leading efges
« Reply #3 on: October 16, 2021, 11:39:45 AM »
Geoff,
last year my son Gabe wanted to try an elliptical wing.  Here's how we went about it.

1) Used a piece of construction lumber, we cut out a bending buck with a band saw.  This is the first picture.  Notice we made cuts on both sides of the piece, so that wood bending for both leading edges can be done at once, which saves building time.  Protect the wood from moisture by applying a couple of coats of some furniture lacquer, or simply apply a wide strip of packing tape.  The idea is to prevent the wood in the buck from soaking up water from the wet balsa and warping as a result.

2) (Not shown on picture).  Cut approximate strips of balsa for the leading edge about 1/4" wider than the finished size.  We used two strips of light 3/16" wood.  Soak them in hot water for about 30 minutes, then remove, let the water drip for a minute or so, and apply wood glue (Titebond, etc).  To keep the two strips together, wrap masking tape in 3-4 places.  Quickly, while the wood is still wet and pliable, place on the buck and wrap with flexible bandage.  Let dry for 2 days.

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Offline Mike Alimov

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Re: Curved leading efges
« Reply #4 on: October 16, 2021, 11:40:49 AM »
3) Once the leading edges are ready, assemble the frame (picture 2) and place it in a jig (not shown).  Picture 3 gives another detail of the wing - notice the 1/4" notches in the spar.  The notches will accept ribs, which are sliced in a fixture per the I-beam method.

I will continue in the next post due to image size limitations.
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Offline Mike Alimov

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Re: Curved leading efges
« Reply #5 on: October 16, 2021, 11:46:51 AM »
4) While in the jig, fit and glue all the ribs into place.  Fit and glue the sheeting.  Since we chose a fairly blunt airfoil, most of the curvature will be in the leading edge, which will be shaped using a razor plane, and the sheeting does not require too much bending.   We also designed the spar with a straight taper, in order to avoid dealing with compound curves in the leading edge sheeting.
Once the wing has been glued together, remove from fixture and shape the leading edge with a razor plane as shown.

5) Once the rough shaping is done, sand the wing using progressively finer sandpaper, starting from 220 and progressing to 600 grit.
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Offline Mike Alimov

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Re: Curved leading efges
« Reply #6 on: October 16, 2021, 11:49:58 AM »
Gabe chose to cover the wing in fluorescent Ultracote, but the finish is obviously up to you.
The elliptical wing performed very well, earning Gabe a Jr. National title for the 2nd year in a row.
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Offline Dan McEntee

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Re: Curved leading efges
« Reply #7 on: October 16, 2021, 05:29:01 PM »
Quote from: pmackenzie on October 16, 2021, 09:51:15 AM
Do the tongue with two or three laminations, the way free flight guys do curved outlines.
 This will eliminate any stress from bending it from a single piece. Laminate, then sand it flat.

Having built more than a few Bostas, the leading edge sheeting will do some strange stuff near the tips where the shape is more of a compound curve.
The Bosta did have a similar horizontal spar, but it was straight on the back edge from tip to tip, so that it provided more strength in the fore/aft direction when the model crashed.

    I'm with Pat on this one also. It's been a while since I have really looked at the Lincoln Log method, but if done the way I think I remember it, it is similar to an I-bean construction and that will save you a lit of time lofting ribs if that is the case. I think I have a set of jig blocks I got from Tom Morris years ago and his instruction sheets some where. You might want to also visit the article for the Novi-4 by Jim Kostecky and see how he did that leading edge, and I have a model called a Charmer that was built from Tom Dixon plans for a model called Charisma. I would have to pull those plans also to remember how the leading edge was done but both of these model are curved more than what you plan, I believe. I got my Charmer off the wall after a 15 year or so hibernation, retrimmed the model and fell in love with it again. Made me wonder why I quit flying it!!   Give us a peak of what you get drawn up when you get that far, please.
  Type at you later,
    Dan McEntee
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Offline Geoff Goodworth

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Re: Curved leading efges
« Reply #8 on: October 17, 2021, 12:10:51 AM »
Thanks Mike. That wing is so close to the one I'm working on that it is uncanny.

I may have used the wrong description for the construction. I was thinking more about the jig blocks holding the LE and TE with small tongues locating the ribs on the LE and TE.

Charles, the front of the airfoil will almost certainly be an ellipse with an overall thickness of 20%. Max thickness will be somewhere in the range 25–30%.

Thanks for all the comments.
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Offline Avaiojet

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Re: Curved leading efges
« Reply #9 on: October 17, 2021, 08:57:10 AM »
Quote from: Geoff Goodworth on October 17, 2021, 12:10:51 AM
Thanks Mike. That wing is so close to the one I'm working on that it is uncanny.

I may have used the wrong description for the construction. I was thinking more about the jig blocks holding the LE and TE with small tongues locating the ribs on the LE and TE.

Charles, the front of the airfoil will almost certainly be an ellipse with an overall thickness of 20%. Max thickness will be somewhere in the range 25–30%.

Thanks for all the comments.

Geoff,

When I built Scott Reese's Mystery Ship, a zillion years ago, the arched stab was built with laminations, I don't remember how many. Between the liminations and glue, this created a stiff structure. The down side was sanding, the glue was harder than the balsa, but I got it done.

Last thing. The "frame" is a great idea. To do that Mystery Ship stab and elevator, I set up a row of spaced nails into .75" plywood to arrive at the correct curve.I put the heated and wet laminations in this "nail" jig until they dried. You can mark the top edges with a pen line here and there so when glued they can be placed in the same position. Only a left or right is needed, make two then flip one.

I'd be interested in seeing the design.

Mike, aren't kids the greatest thing.  H^^

Charles
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Offline Bob Hunt

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Re: Curved leading efges
« Reply #10 on: October 18, 2021, 06:19:44 AM »
Quote from: Dan McEntee on October 16, 2021, 05:29:01 PM
    I'm with Pat on this one also. It's been a while since I have really looked at the Lincoln Log method, but if done the way I think I remember it, it is similar to an I-bean construction and that will save you a lit of time lofting ribs if that is the case. I think I have a set of jig blocks I got from Tom Morris years ago and his instruction sheets some where. You might want to also visit the article for the Novi-4 by Jim Kostecky and see how he did that leading edge, and I have a model called a Charmer that was built from Tom Dixon plans for a model called Charisma. I would have to pull those plans also to remember how the leading edge was done but both of these model are curved more than what you plan, I believe. I got my Charmer off the wall after a 15 year or so hibernation, retrimmed the model and fell in love with it again. Made me wonder why I quit flying it!!   Give us a peak of what you get drawn up when you get that far, please.
  Type at you later,
    Dan McEntee

Interesting topic... Just one correction to your post, Dan... The Novi Four was designed and built by Dave Gierke, not Jim Kostecky. See photo below. That's Dave with his gorgeous ship at the 1969 Nats in Willow Grove, PA. I was there!  :)

Later - Bob Hunt


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Offline Bob Hunt

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Re: Curved leading efges
« Reply #11 on: October 18, 2021, 06:29:14 AM »
Here's one more shot of Dave's amazing Novi Four. Dave was, and still is, an amazing craftsman. I stayed with Dave and his lovely wife, Caroline at their beautiful home in Lancaster, NY the weekend of the Jim Kostecky memorial services. I had been asked to speak at the memorial, and Dave was gracious to extend an invitation to stay with him. During that visit I was given an extended tour of his shop. There was (and still is) an uncovered airframe of a Novi One hanging on the wall, and it was just perfect in every respect. I chided Dave to finish it, but I guess he'll just leave it on the wall as a piece of art... Which it is! y1

His Novi Four remains as one of the most legendary designs from Stunt's past.

Later - Bob Hunt

 
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Offline Dan McEntee

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Re: Curved leading efges
« Reply #12 on: October 18, 2021, 07:03:13 AM »
Quote from: Bob Hunt on October 18, 2021, 06:19:44 AM
Interesting topic... Just one correction to your post, Dan... The Novi Four was designed and built by Dave Gierke, not Jim Kostecky. See photo below. That's Dave with his gorgeous ship at the 1969 Nats in Willow Grove, PA. I was there!  :)

Later - Bob Hunt

     OOPS!! My bad! I always did those two mixed up !! Then throw in advancing age and it gets difficult some times!! I was at Schaefer's Hobby Shop the day before and was looking at Kostecky's original Formula S that is still hanging in the new shop and I had his name on my brain.  The Novi-4 is on my list of planer projects! Thanks for the correction Bob! Dave Gierke also did a great article on finishing and doing ink lines that was in Flying Models years ago
     Type at you later,
  Dan McEntee
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Offline Trostle

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Re: Curved leading efges
« Reply #13 on: October 18, 2021, 08:57:01 AM »
Quote from: Dan McEntee on October 18, 2021, 07:03:13 AM

This has drifted a bit off topic, but Dave Gierke's work is worth mentioning.
     
Dave Gierke also did a great article on finishing and doing ink lines that was in Flying Models years ago
 
  Dan McEntee

Dave Gierke had several articles in the magazines about finishing details.  These are the ones that I found.  There may be more.

"India Ink is Magic", American Aircraft Modeler, Jun 1970.  "All about fine lines, rivet marks, and lettering".  Shows a picture of his Novi IV.

"Dry Transfer Rivets and lettering", Flying Models, date ?.  "Tiny detailing presses on.  No muss, No fuss, no decal edges"

"A place for Lace", Flying Models, Feb 1972. 

(I have a 3" binder filled with articles from the magazines on coverings, finishing and paint and trim broken down into 8 sub-categories.)

Keith


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Offline Dan McEntee

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Re: Curved leading efges
« Reply #14 on: October 18, 2021, 04:22:57 PM »
Quote from: Trostle on October 18, 2021, 08:57:01 AM
Dave Gierke had several articles in the magazines about finishing details.  These are the ones that I found.  There may be more.

"India Ink is Magic", American Aircraft Modeler, Jun 1970.  "All about fine lines, rivet marks, and lettering".  Shows a picture of his Novi IV.

"Dry Transfer Rivets and lettering", Flying Models, date ?.  "Tiny detailing presses on.  No muss, No fuss, no decal edges"

"A place for Lace", Flying Models, Feb 1972. 

(I have a 3" binder filled with articles from the magazines on coverings, finishing and paint and trim broken down into 8 sub-categories.)

Keith

    And if you were to ever put together a bibliography if that collection I would buy the first copy!! I probably have the books and magazines, just not much direction other than my memory of some one like you to guide me!

   Type at you later,
   Dan McEntee
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