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Author Topic: FAC JET CATAPULT SCALE cook up?  (Read 1040 times)
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stupid
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« Reply #25 on: January 11, 2021, 12:55:59 AM »

Tony, have you ever been involved in any competitive indoor flying? I believe you have  the skills to be some serious competition in an indoor meet.
We had a small gym at a Baptist Church where a group got together to do some fun flying, it wasn't sanctioned as an event. We had a lot of fun anyway until well you know. I had a (Feather Shooter) glider that I used in Colorado Springs auditorium but it was a much higher ceiling and the glider weight 2.2 g to reach the ceiling. So I made a new one trying to keep the weight down is much as I could. The wing at the root is 0.032, at mid-wingspan 0.027 and the wingtips 0.012 the trailing edges were  0.010  the stabilizer and fin Weren't any thicker than 1/64 of an inch and the trailing edges like the wings trailing edge. It's completely bare and weighed 1.7 g I had a lot of fun flying it  The flaps would flutter as it went to the ceiling making a low rumble noise, just on the verge of destroying itself on the launch.
I think you would  be very good at it and would enjoy indoor flying. We'll have to see what happens in the future with our venues.

Bob

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« Reply #26 on: January 11, 2021, 01:12:02 PM »

THE FUSELAGE

Where to start? The problem with Jet Cat fuselages is that they break and they weigh too much. My solution may look unconventional but I will try to describe the logic behind the madness. Fuselages only need to be strong enough to hold the flying surfaces in the correct positions but with jet cat we need to represent the profile of the jet and that adds a lot of weight,  use the lightest pound per cubic foot balsa wood that we have but that limits strength. My solution was to insert a piece of basswood from the nose to the tail and  the bass would limit the amount of bending so that the balsa wood would not break. I've been experimenting reducing the sizes of materials to limit weight & to the point of unacceptable breakage. My first jet P-59 fuselage weighed 5.8 g in this build the fuselage weighs 3.5 g.

Photo #1 shows an end view. The perimeter of the fuselages 1/16"thick as you don't need the weight at the outer edges. The tapered pieces are made and my bandsaw at a 4° setting.You don't need to have bandsaw , size your materials between plate glass.

If you cut the excess wood from your wedges from the inside you will create a taper towards the tail and the perimeter will be 1/16"thick.
Photo #4. Shows the glue up, glue up the fuselage on the left side so that when you are planing the basswood down and shape the fuselage you will have a left glide circle,  it isn't very much but it's better than the opposite direction, prop up the perimeter with wedges so that when it's glued up one side won't be flat.
The top of the basswood gives a place to mount the bottom of the wing, so don't glue the balsa wood to the top of the basswood in the wing location ,you will need to cut this area out later.

      Bob
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« Reply #27 on: January 11, 2021, 04:01:35 PM »

Nothing much out of the ordinary just some pictures of the progress.

I have all the outlines coated with cyanoacrylate adhesive & a coat of sanding sealer.

I will record the weight gain from the sanding sealer after it sanded.

All the best         Bob
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« Reply #28 on: January 12, 2021, 12:18:14 PM »

Good morning
After sanding the first coat of sanding sealer the weight gain was 0.06 gram's. In order to try to save weight I will forgo the red color scheme as it's hard to make it look good with a lite coat of paint. I like the Navy color scheme, I think I can make it look  reasonably good just misting on the color. Typically the Design Masters Spray paint will add 1.6 g of finish to the jet cat and I'm already guesstimating that I'm going to go over the 16 g that I was aiming for, for this build. I do like the checkerboard effect on the nose although I'm not sure this is an legitimate airplane color scheme.
      Bob
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« Reply #29 on: January 13, 2021, 04:34:12 PM »

I've been doing a test to see if I can make a decent checkered pattern on the nose of the P-59.
 The Design Masters Floral Spray isn't a opaque finish, more transparent and when I sprayed the blue over the yellow it looks green and with just one coat of sanding sealer on the balsa wood the paint is seeping under the frisket masking , I suppose because of the woodgrain.

Has anyone tried a checkered pattern on balsa wood and did you have any success?

         Bob

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« Reply #30 on: January 13, 2021, 05:31:55 PM »

Has anyone tried a checkered pattern on balsa wood and did you have any success?
Somewhere on the internet is information on printing by iron-on techniques onto balsa, as per the old Frog kits. Someone will know - I can't remember.
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« Reply #31 on: January 13, 2021, 06:13:40 PM »

Bill is thinking of Paul Bradley's site I think: http://www.parmodels.com/transferring-part-images-to-balsa-using-t-shirt-ir.html

For me just using printed tissue doped onto the balsa is easy and works.

B
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« Reply #32 on: January 13, 2021, 07:41:50 PM »

 Thanks for the replies,

Wow..... All sheet balsa wood scale airplanes. Very Cool

 I don't think it would work in my situation. My fuselages are already shaped and I would like color around the edges. 

Printed Tissue Paper sounds like a good idea, but I haven't acquired those skills as yet. There was a fellow in our club who was an absolute master at  tissue printing, Tom  Norell,     and I would've loved to learn this skill from him But   Sadly he is no longer involved in the hobby.

My Latest Attempt:   I masked off the blue area and sealed the tape edge with clear Matt then sprayed  the yellow then applied  the frisket pattern, clear spray again and sprayed the black. When it was dry I taped over the yellow and black and sprayed the blue.
When I peeled off the tape some of the black came with it. I think I can live with that, after all they are just wooden toy airplanes.

         Bob
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« Reply #33 on: January 13, 2021, 08:08:43 PM »

 Markings can also be done the old fashioned way-- drawn on a piece of tissue which is then attached to the balsa with repositionable spray adhesive. The tissue can be "permanently" sealed/fixed to the edges/overlap with gluestick.  Of course it would be prudent to check all compatibilities on test scrap(s).  Some pens/markers may "bleed."
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« Reply #34 on: January 13, 2021, 08:23:32 PM »

My Latest Attempt:   I masked off the blue area and sealed the tape edge with clear Matt then sprayed  the yellow then applied  the frisket pattern, clear spray again and sprayed the black. When it was dry I taped over the yellow and black and sprayed the blue.


That looks damned fine. I'd go with that. Plus, who's going to be scrutinizing that when you fling it off your catapult? It's just going to look cool as hell(!).

-Dave
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« Reply #35 on: January 13, 2021, 10:02:01 PM »

I tried your suggestion indoor flyer: you're correct some markers will bleed, and mine do, plus the corners are hard to Mark. 
 although I'm sure it would work if I had the right markers and not so many corners.

Dave:  thanks for your compliment

It's amazing when you show people your models,  the remark is usually:   "you have a dent in your leading-edge ".   I'm taking your advice and go with it. and ignore the naysayers.

I noticed while doing my test  samples that with the cold weather the spray cans don't atomize the paint very well and I'm still concerned about the weight gain of the paint. Not so much on the nose of the glider but the total weight gain. I'm thinking of another harebrained scheme to deal with the problem, and if it works I will included it in the next posts.

                Bob
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« Reply #36 on: January 14, 2021, 08:13:42 PM »

Well Darn, the weather in Denver has me on hold with this project, today's high was 36°. And not warm enough to spray paint as I do it outside.

All I was able to do was put some filler strips on the wings to sand in the dihedral for mounting in the fuselage on top of the basswood strip.

Here's hoping for better whether.

         Bob
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« Reply #37 on: January 16, 2021, 02:33:53 AM »

Denver's high today 46° sunny and lite winds.

Not the best temperatures for spray painting outdoors but here's an idea I've used before and it does work in cold weather to keep the spray paint in aerosol cans from spitting  on the models or from becoming excessively heavy with paint. Preheat the oven, my ovens lowest setting is 170°. Once the oven is at temperature I TURN IT OFF & put the pre-shaken spray paint in the oven for about 10 minutes. This is after I have everything ready to be painted .  Most manufacturers of spray paint suggest you keep it under 120°. I'm almost certain this is on the low side .   Hot water heaters will deliver 125° temperature from the faucet but soaking  spray cans in water ruins the labels.
I was impressed by the increased pressure and the finer misting of the spray paint, the result is a thinner  coating and less weight. My red P-59 Jet total coatings weighed 2.5 g the current build total coatings is 1.3 g. So you can see the difference in weight, it's just not an opaque coating. But my main objective was to see if it would thermal and to test the undercamber on the wing and its effect on the flight characteristics.

I had no paint pulling off my black checker when the tape was removed. I didn't use the Krylon clear Matt finish to seal the tape edge instead I used the sanding sealer. So I'm only mixing two products instead of three and I believe it made the difference, something wasn't compatible with the Krylon clear Matt . I did have some paint bleed under the tape where the wood grain is but the pattern does have nice sharp corners. Would I do it again? I surely would, I love checkerboard patterns.

2001 Flying Aces Club Rules       APPENDIX  F
"Dihedral: a maximum of 1” per tip per foot of wingspan or, in the case of low wingers, no higher than the
 bottom of the canopy-whichever is higher. See graphic below. Models built from kits may be built to plan
 even if the specified dihedral exceeds these standards. In such cases—bring your plans! "
So do I have this right: cut out the parts, make a plan drawing & I can use any dihedral I want?

http://www.flyingacesclub.com/RULES/CURRENTFACRULES.pdf

Next are the control surface lines. "

         Bob
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« Reply #38 on: January 16, 2021, 09:28:57 PM »

Control surface markings

I've learned that every airplane plan that you download from online is not straight or balanced. When I'm building scale airplanes, I download a mirror image of the airplane plan also and just use a Single side left From the original and right part From the mirror of the drawings. All wood gliders are a different matter, I make templates so I don't bother downloading a mirror image. It doesn't start to matter until you do the control surface markings. To get everything identical top and bottom only use one half of the airplane drawing of the wing, the top markings on one wing and the bottom markings on the other and transfer of the lines to the opposite side using plastic rulers with close pins clipped to each. Line up the rulers on the markings that you've made and transferred them to the opposite side. I started doing this with the fins and it was easy so I also did the wings this way also. The stabilizers are balanced left to right when I redline the plan, do the markings one side and just flip the stabilizer end for end and mark the outlines on the other side.

I hope this makes sense, give it a try


         Bob
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« Reply #39 on: January 17, 2021, 11:04:33 AM »

I like the stiffener in your fuselage ass'y, and the way you taper the cross section from the belt-line to the edges.  Curious what your thoughts are for an "optimum" wing to fuselage joint?    Here's a sketch...
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« Reply #40 on: January 17, 2021, 07:34:08 PM »

I like the stiffener in your fuselage ass'y, and the way you taper the cross section from the belt-line to the edges.  Curious what your thoughts are for an "optimum" wing to fuselage joint?    Here's a sketch...

Thanks
I like the sketch on the left. Have you done them both ways?
 I'm mounting the wing on this P-59 like you have in the first sketch, it worked out well because of the undercamber.
in previous P 59   builds I didn't bother to flatten the bottom of the wing to then mount onto basswood strip and as long as the slot for your wing is just a little tight (the lightweight balsa wood compressed fairly easy just wiggling the wing into the slot) so I just used thin cyanoacrylate  adhesive. So far I haven't had any failures at the joint.
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« Reply #41 on: January 17, 2021, 08:28:19 PM »

The photos are a real help in the build, you don't have to try and interpret what I'm saying.

While the wing is still apart I place it on the fuselage and Mark its outline on both sides.I use straight pins on the leading and trailing edge, punched all the way through the fuselage to locate the other side.

Sanding in the dihedral angle. It only took me a few models to switch to this method instead of propping up the wings.

Most hand launched glider plans will give you a figure on how high to prop up the wing for each joint and they're all different, mostly because of the different wing spans and Polly dihedral breaks. If you make a drawing of all the different plans dihedral's and measure the angles they are all fairly common. They only differ in indoor , outdoor & windy weather outdoor models. Most gliders have a center joint total 12° and the Polly dihedral break 24° so that I only need one jig for most all my gliders because it's not critical in performance.

Just dabs of thick cyanoacrylate glue on only one half of the wing evened out with a sandwich pick. If there is too much glue I collect it on the sandwich pick.

Put wing locating red dots on each side of the joint so in gluing to the fuselage I can get it glued on perfect.  I do this on the stabilizer also using blue dots.
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« Reply #42 on: January 17, 2021, 08:48:14 PM »

checking the decalage  between the wing and stabilizer with plastic rulers, one under the wing and the other on the stabilizer mounting area.

with this sanded in area for the stabilizer I have some decalage because of the Philips entry on the wing.

Fully assembled and I'm so delighted, only 13.5 g as it sits now.
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« Reply #43 on: January 17, 2021, 09:57:59 PM »

Ah ha!  The light bulb went off...  Thanks for your pics and description.  I really like your P-59!

I've only built a few of these gliders, kit and scratch built. I will try your method on my next scratch build--it makes a lot of sense doing it this way.   I have not tried the offset joint as shown in my sketch--it was something I heard about that sounded "interesting."

This is my Cessna XT-37 built from the Volaré kit.  It is a "sacrificial" test model, hence no efforts expended on "decoration"  (the nose has 3D printed doublers--one per side) . 

Onward and upward!

  
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« Reply #44 on: January 17, 2021, 10:45:21 PM »

Ah ha!  The light bulb went off...  Thanks for your pics and description.  I really like your P-59!

I've only built a few of these gliders, kit and scratch built. I will try your method on my next scratch build--it makes a lot of sense doing it this way.   I have not tried the offset joint as shown in my sketch--it was something I heard about that sounded "interesting."

This is my Cessna XT-37 built from the Volaré kit.  It is a "sacrificial" test model, hence no efforts expended on "decoration"  (the nose has 3D printed doublers--one per side) . 

Onward and upward!

  

Thanks for the compliment, means a lot.
 Through repetition comes improvement.I think Lee Hinds tried offset wings & there were others but it never caught on.

A scratch built 17 inch wingspan  Cessna XT-37 went OOS  at a contest two years ago.I can't Remember his name it was in the NFFS  Digest.  The nose hook -weight is new to me.you'll have to let us all know how it flies.

I know what you mean by not decorating until you see how it flies. I usually forgo insignias unless there's a contest this year I will do them, most of paint I use is for waterproofing. My first P-59 I renamed, I now call it  " Crash Test Dummy"
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« Reply #45 on: January 18, 2021, 12:24:32 AM »

An interesting article on launch hook placement from NFFS Digest July 2009. this will be the first time   I tried placing the hook this high on the nose.

The aluminum is carpet edging stock, it slotted so it's flexible. Just some scrap I had around. I cut it into a 5° wedge & hammered the tail portion thinner.before shaping in a saw kerf slot with piano wire hammered in to form the trough. A little more shaping and it was curved to fit the nose.

I've had success with this style of hook on Jet Cats  as it grips the wood in a larger area.

 Brass tubing to drill holes in the nose for the lead weight. I glued the lead in with stick glue in case I might have to change it.

The photo doesn't  show the undercamber very well.

 Finished and balanced at  37% from the leading edge. The total weight is 16.4 g.  with wing tip weight for the turn  estimated at 0.6 of a gram        Brings the Total to...... 17 grams

  So Delighted, So Delighted

I started the build on January 6 so approximately 10 days. There were days I spent pondering solutions. And now that I have all my jigs made, the next one won't take so long.  I plan on changing the Philips entry on the wing &  to make the wing from lighter balsa wood.

If you would like to see how I made the Jig's just ask. I took a lot of photos.
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« Reply #46 on: January 18, 2021, 01:42:43 AM »

I'm enjoying your continued input - thanks.

John
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« Reply #47 on: January 18, 2021, 02:15:48 AM »

I'm enjoying your continued input - thanks.

John

You Betcha, this is one of my more enjoyable builds recently. A few problems to keep me on my toes, but easy solutions. It came to me in my dream :-)
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