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Author Topic: Roll-Out 16" wingspan 4" cord CLG  (Read 605 times)
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« on: April 24, 2021, 04:13:54 PM »

Roll-Out   16" wingspan  4" cord    CLG

   I've had this glider on my to build list for quite some time, and when spotting a 48" X 4" X 1/4 sheet of balsa wood at the local hobby shop that turned out to weigh 5.98 lb/ft³. The thought occurred to me that I could get six wing blank's from one sheet of balsa wood if I cut it diagonally through the cord. All didn't go as planned as 4 of the wing blanks had wavy trailing edges.
   I shaped one of the wing blanks with the wavy trailing edge to see if when I cut the center dihedral break it would relieve the stress in the wood, and it did the resulting wing had a straight trailing edge. So now I have some confidence that the glider wings will make good gliders.

   Being that the bandsaw was still set up I decided to cut a second sheet of balsa wood to get a comparison. The selected balsa sheet was  36 x 4 x 1/4     6.1 lb/ft³   the grain didn't run straight with the long edges of the sheet but it turned out that the trailing edges were very straight and when measured there was only a 0.02 variation in the thickness from end to end.  Thumbnail #4
     After holding the blanks up to a strong light I could see that the sheet with the wavy trailing edge had a greater variation in the density of the growth rings . Thumbnail #5
The second sheet  looked more even in density across the sheet cord wise.Thumbnail #6

   2 wing blanks had straight trailing edges one in the hard area and the other in the softer area.

                                 Bob
Attached files Thumbnail(s):
Roll-Out 16" wingspan 4" cord CLG
Roll-Out 16" wingspan 4" cord CLG
Roll-Out 16" wingspan 4" cord CLG
Roll-Out 16" wingspan 4" cord CLG
Roll-Out 16" wingspan 4" cord CLG
Roll-Out 16" wingspan 4" cord CLG
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« Reply #1 on: April 25, 2021, 03:10:46 PM »

   I spent way too much time trying to find out what possibly could be the reason for the wavy trailing edges of the cut balsa sheet for wing blanks.
   It's my opinion that the difference in the 2 cut sheets of balsa wood, was because the new sheet of balsa wood that I purchased with the Midwest brand came from a plantation grown tree and I'm guessing it came from Papua New Guinea. The trees are growing so close together that in the dryer times of the year, the trees are competing for water and that slows the growth rate down, hence the denser bands of balsa which creates stress in the balsa sheet.
   Late May or early June through to October are the best months to visit Papua New Guinea as there is less chance of rain.

   The balsa wood sheet with the straight trailing edges came from SIG and  from the difference in price that it was purchased somewhere between 2000 and 2005 probably from Ecuador before corporations started widescale plantation growing.
https://www.airplanesandrockets.com/resources/balsa-wood-facts-sig-catalog.htm

   "Ecuador supplies 95 percent or more of commercial balsa. In recent years, about 60 percent of the balsa has been plantation grown in densely packed patches of around 1000 trees per hectare (compared to about two to three per hectare in nature)."  China is the largest importer of balsa from Ecuador because of its premium quality.
  Ecuador is in the inter-tropical convergence zone, where they have a more even rainfall and the so-called dry season is only 3 to 4 weeks long. Reducing the denser bands of balsa.
https://www.cargohandbook.com/Balsa_Wood

"Balsa trees grow naturally in the humid rain forests of Central and South America and New Guinea. However, the small country of Ecuador, on the western coast of South America, is the primary source of model aircraft grade balsa in the world. Balsa needs a warm climate with plenty of rainfall and good drainage. For that reason, the best stands of balsa usually appear on the high ground between tropical rivers."
https://www.rcscalebuilder.com/tutorials/Balsa/balsa_1.htm

     So in conclusion, the best source of balsa wood, would be from estate sales.
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Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #2 on: April 26, 2021, 04:08:08 AM »

Sunday and I have the whole day without any other obligations, And the wind still howling, so I thought I would get on with it.
  I really like this little SOLINGEN block plane, at about 140 g it has the right weight to make cruelly cuts without having to press it down .

    Sanding blocks for the leading edge profile makes for quick rough shaping. I decided to use bass leading edge for protection on the Roll-Out gliders.  .024 x 1/16 x 24" at 3/10 of a gram. Glued on with  cyanoacrylate, 1 inch at a time, pressing on with my thumbnail. 24 inches was enough to wrap the whole wingtip, so I went with it because I've never done it before.

   After sanding the Basswood flush to the bottom edge, the thought occurred to me that I could put the wing blank on top of the cardboard cutout that I made to find out how many in²  the wing was.    ( 54 3/4 in² ). If you're curious.

   After moving the wing blank directly over the cardboard I used the same sanding block to make a tapered airfoil profile on the wing tips. The cardboard let the sanding block drop-down while sanding to get the taper. It works so well I think I'll keep doing it this way.
                                             Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #3 on: April 26, 2021, 05:44:35 AM »

   Another sanding block for the Phillips entry, 24°. Sweeping the block back and forth along the bottom of the leading edge creates a flat that is visible and helps in seeing that it is evenly tapered across the wing.

   Finished airfoil and Phillips entry. I recoated the leading edge with cyanoacrylate to make sure the Basswood leading edge was secure and for extra hardness before sanding sealer and clearcoat.

    Cut and glued together the poly dihedral on wing blank B with the wavy trailing edge. The trailing edge turned out very straight. Tomorrow I'll do the other five wing blanks to see if it works with all of them.

   For a record I drew a diagram with some of the information all on one page for future reference. I think it will make it easier than flipping through 6 pages of notes to make a comparison.
                                                                  Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #4 on: April 27, 2021, 03:32:33 AM »

   I made some progress today after work, I didn't like the shape of the stabilizer and fin so I reduced the plan to 65% and used the wingtip outline for the stabilizer and fin shape.

   Had some 5.3 lb/ft³ C grain already cut into wedges so making six of each went fairly quick. The stabilizer weighs 1 g , Coated the leading edge with cyanoacrylate & one coat of sanding sealer and the weight gain was 0.06 grams each stabilizer.

   The fuselage is Pampas grass with 2 1/2 inches of bamboo in the nose. The fuselage weighs 5 g.  Stabilizer and fin weighs 1.2 g.   The wing 8.6 g.      Total weight without nose weight or color      14.8 g.

   I've built in a little decalage and I'm using a  2-56 nylon screw for decalage adjustment. I'll only be able to take out decalage with the adjustment screw by forcing the tail boom down. It should be a little easier than using sandwich picks like my other 12 inch Stinger 2 gliders.

    Dihedral 2 3/16 inches each wingtip. With some stabilizer tilt for turn. It shouldn't take much nose weight to get the center of gravity right on this one.
                                                         Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #5 on: April 27, 2021, 10:42:53 AM »

That is some gorgeous wood you have for your stabs. I just love the look of good C-grain. Model looks great. looking forward to the colors. Great work.  Bruce
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« Reply #6 on: April 27, 2021, 11:46:33 AM »

Bob:
Looks great! Hope you're able to get some flight shots!

Best-
Dave
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« Reply #7 on: April 27, 2021, 04:00:50 PM »

That's an unusual idea in the plans showing the optional tissue covered lightening holes.  Anyone seen that in use?
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« Reply #8 on: April 27, 2021, 07:42:30 PM »

Yo Bruce, Thanks for the Compliment. I keep staring at it myself, I think it's the Ralph -Ray fuselage look, it reminds me of a pelican. I was out to C.A. last week, flew into Limburg field with my daughter and her beau . spent the day along the coast admiring those Graceful pelicans,  We were Visiting my mom of 96 years. My folks retired to Ramona in 1985. While  their, I saw my first Bobcat out the kitchen Bow window. It seems everywhere I go, everything reminds me of free flight gliders. Anyway it's good to be back,  everyone in Southern California is changing from growing avocados into growing grapes. After the fires most people took the insurance money to change over to grapes and and most are doing wine tasting to make ends meet. Sarah and Kevin are really into sampling all the wineries, and I'm just not accustom to that much wine.
   
    I keep thinking I should change my color scheme, but you can probably guess as to what you're going to see.  It doesn't make sense to spend a lot of time coloring a glider so that the person that finds it will be impressed.

Dave, I hope to be able to take some videos of my gliders In-flight this year. I bought a used Sony camera with a stabilized 20 X zoom lens. The same one that Tom Hallman uses in his videos. I still need to get a patch cord for the computer and video chip so that I can try to upload to BitChute . I'm going to skip YouTube, I think they're done. It's a pretty steep learning curve for me so it might take a while.

    Strat-o,   I haven't seen anyone do lightening holes or a model of it. But you might see it this year as it's on a build list of mine. Not on the Roll-Out, because the glider turned out very light using the Pampas grass tail boom. The tail boom had a diameter of  .202" and its total weight behind the center of gravity was just 1 g. Originally an all wood fuselage weighed quite a bit and to lessen the wing loading it might've been a benefit to punch holes in the wing.
     This summer Don De is getting together a one model design  event for society of antique modelers competition. Don gifted me one piece of 3/8 thick balsa wood still looking for another piece. It's called The Monster. Plan and article on outerzone. I've been thinking on just how to go about building it, it's absolutely huge . The stabilizer is 4" by 14" by 1/16",  as big as a lot of catapult launched glider wings. The thumbnail is of Ray Acora with The Monster. He must be a big man that model is a 30 inch wingspan and would probably take someone that size to throw it. From the photo it looks like he used Aniline Dye to color it. I've heard of this type of dye, but it's the first time I've seen A photo of a model with it. I still need to finish 5 more gliders before I can get on to Another build, but if I really end up doing it I will post it. I don't think I'm going to be winning any competition.  but I might have some fun bungee launching it off a ramp when the Contest is over.
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #9 on: April 29, 2021, 06:44:46 AM »

Roll-Out wing blank  C has a wavy trailing edge and is the thinnest one.  0.26".

     I'm using a center finding ruler to lay out the dihedral joints, just marking the leading and trailing edge perpendicular to the trailing edge. Then marking the trailing edge 1/16 inch to the inside of the trailing edge mark for washout .

    I cut the wing apart at the center dihedral join and laid them back to back to make sure that the wing blanks were equal. Then tape them together at the trailing edge, and using a Zona Saw cut through the Basswood leading edge on the marks. I did the same to the trailing edge on the washout marks, just a small notch. This way all the dihedral joints will be the same on each wing.

    I decided to do winglets on this one. Set the front of wing on the cut mat Using straight pins in the cut notches, just pushed into the cut mat & using a straight edge up against the pins. Holding the straight edge down tight remove the pins and make the cut. Zona Sawing through the Basswood leading edge first makes it a lot easier to cut the joint. I've never seen anybody make their dihedral cuts this way but it works for me, so I thought I'd show it.

   I measured the washout skew, the poly dihedral joint is 1° in the winglet joint is 2° for a total of 3° tow out. When I cut the balsa wood sheet diagonally to get the six wing blanks, the bandsaw angle was set at 2 3/4°. So I believe the tow out at the winglet shouldn't create any excess drag as the bottom of the wing tip is parallel to the line of flight.

    The glue up jigs that I use worked out well with this warped wing blank, holding the wing  into the jig keeps the back of the wing flat while the glue sets up. The right-center wing panel still had a cup in the trailing edge. I glued 0.003 thick carbon fiber 1/16 of an inch wide along the trailing edges top and bottom. It eliminated most of the problem but I still see a slight low maybe 1/ 64th of an inch. If it creates a problem on the launch I might try rubbing it out between my fingers to see if that'll work.
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #10 on: April 29, 2021, 06:59:45 AM »


Total dihedral 2 9/16" under each wing tip.
Center dihedral 12°   poly dihedral 24°    wing tiplet 24°

The fuselage balsa wood was made with 10.5 lb/ft³, so this Fuselage weighs 4.5 g.
Roll-Out wing blank C weight 8.65 g         stabilizer and fin 1.35 g
 this glider weighs 14.5 g without nose weight.
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #11 on: April 29, 2021, 03:44:57 PM »

Roll-Out   16" wingspan  4" cord    CLG
 I cut it diagonally through the cord.

Bob it never occurred to me to try this, is it possible to be inviting a warp making cuts like that? I am gonna give it a go. I am a born straight grainer!
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« Reply #12 on: April 29, 2021, 08:06:01 PM »

Crabby,
The balsa sheet that I cut diagonally for this project was the newest piece of balsa wood I've purchased. I believe the problem is that the balsa wood came from a balsa wood plantation where the trees are grown too close together. And the lack of water during the dry season causes stress in the balsa wood.
   If you're going to cut pre-2010 balsa wood, you have a very good chance of having success.

     The second wing blank that I ever cut diagonally turned out just fine thumbnail #1 and #2.

     I bandsaw tapered  sheets of 0.25 x 4 x 36 from the High Point to trailing edge many times, this is the first time I've cut a sheet of balsa wood for outdoor gliders and the trailing edge has turned out wavy.

   The third thumbnail photo is of the remnants from all the other sheets that I've cut for hand launch gliders wings, and you can see that none of the remnants are wavy.

   There's only been one other time the balsa sheet 0.25 x 4 x 36 turned out wavy was when I was cutting some thin sheets for indoor catapult launched glider flaps. It was 3.8 (lb/ft³) A grain very even in density. It was not usable for glider flaps or anything else after it was cut. I should've made indoor scale airplane wheels with it, if I was clairvoyant.
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Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #13 on: April 30, 2021, 08:23:23 AM »

Not doubting you at all just thrilled to have new information. I am a creature of old habits.
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« Reply #14 on: May 04, 2021, 02:38:26 AM »

    The next glider, wing blank D, I'm going to try an under camber wing. I'm doing airfoil BDE5615VN4 from the HIGH ENDURANCE AIRFOILS  NFFS Symposium 2010. In the plan Gallery .
https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=11564

    Being that the wing blanks are already finished flat bottomed, I'll need a under camberd  form to glue up the center dihedral & Polly dihedral  so that the joints will hold the under camber shape in the wing airfoil. Thumbnail #1 shows the airfoil. The red line is the wing blank airfoil now. The form will have the shape of the bottom of the airfoil BDE5615VN4 so that when the joints are glued up the wing from the High Point to the trailing edge will be arched. The under camber will fadeout from the Polly dihedral joint to the winglet joint which will be without under camber. The balsa wing blank was A grain so the wing should be able to arch up without a problem, has long as it's equal on both wings halves it will be okay.

    The BDE5615VN4 airfoil shown is  5% airfoil. What I have is a 3.8% airfoil. I have made under camber forms before but this  form is going to need more accuracy than just eyeballing the amount of under camber. From my calculations I need to remove 3/64" maximum depth of material from the form.

    The jig's and forms that I use are made from medium density fiber board, and with my Hitachi 8-1/2-Inch Sliding Compound Miter Saw. I modifying my old jig to make it more accurate by installing rollers to hold down the MDF to the base & mounting a circle protractor on the saw with the pointing indicator attached to the depth gauge. I'll be marking the sliding tubes with permanent markers for the distance edge to edge. I  make my leading edge sanding airfoil blocks using the same method, by pushing the MDF passed the rotating saw blade at 90°.
    3/64" on the depth stop is approximately 100° divided in 4 sections each side of the highest part of the under camber and will be 25° turn of the depth stop screw.
 
    I'm almost to the point of making the under camber jig, I need to space out the platform 1/2 inch from the fence to get the center of the blade over the trailing edge of the wing airfoil. 1/2 inch stock is in my garage somewhere, I just have to locate it.

    The last thumbnail is of an indoor flapper catapult launched glider wing form and dihedral glue up.The left is the leading edge. After shaping the wing airfoil I would spray it with( Magic spray sizing) which is a cellulose starch, it would stiffen up the wing considerably without any noticeable weight gain. Then put it on the form and wrap it with gauze bandage until dry. This little trick would get me first-place without carbon fiber on the wing.    Hopefully more progress tomorrow.
                                                  Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #15 on: May 04, 2021, 08:59:51 PM »

   Everything went as planned making the under camber glue up jig. I'm showing  the progression in photos, I had one slight problem in one area where the blade took out too much material. It's that white spot. I couldn't understand what might have caused it until I turned the board over and saw that I'd left the barcode label on. I don't think it'll be a problem.

   I spray painted a light coat of primer on to it so I could see the progression in sanding.
When cutting the dihedral angles on the jig, I cut all the same angles without changing the setting and then do the other angle .
                                       
                                      Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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« Reply #16 on: May 06, 2021, 09:06:34 PM »

My first attempt at making an under camber glue up jig failed. It turned out being okay for a 5% airfoil wing but the wings I've made are 3.6% airfoil, so the camber turned out exaggerated. I can't get the accuracy I need trying to shape the MDF because I need to final sand it.

  The  airfoil I'm trying to copy is a 5% airfoil and the under camber is 0.040 so my 3.6 airfoil needs a under camber  depth of 0.028.I thought of using blue tape building up in layers on top of the MDF and it turned out really well, I impressed myself.

   The image shows the airfoil reduced to 3.6%
   The first & second photo shows the tape layup on the MDF, I took pictures of the end and marked lines in Microsoft  Paint. You might have to enlarge the picture to see the red lines.
   I cut the MDF to make up the dihedral joints for the jig & the tape stayed in place.
   The next photo shows the Polly dihedral joint. The tiplet joint is flat,
                                        Bob
Attached files Thumbnail(s):
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
Re: Roll-Out 16" wingspan 4" cord CLG
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