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Will my homemade foamie fly??

Old 08-29-2018, 05:38 AM
  #51  
aaindthu
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Originally Posted by trying2fly View Post
Did you spray with polyurethane for stiffness?
No. I will experiment with polyurethane later as it is not easily available in my locality.
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Old 08-29-2018, 11:10 AM
  #52  
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aaindthu
I do have some concerns about the weight of your wing after you added the papier mashe.
I have a couple of reinforced foam RC plane wings that are actually bigger than yours but weigh quite a bit less.
Did you cover the whole wing with the same thickness papier mashe? If so then getting on for half of what you put on has simply added weight yet provides little extra strength or stiffness.
The trick is to add the stronger, heavier material only where is will have the greatest effect. For any plane what you are after is the best strength to weight ratio rather than just the strongest possible structure.

At this stage it is probably not worth taking off what you have done but there is always the next wing.

Keep on going!
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Old 08-29-2018, 06:10 PM
  #53  
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"aaindthu"

May I suggest you try and find a Builders Shop in Chennai or near ... a better Foam for building is the thinner Floor Insulation sheet ... its stiffer than the packing case foam you have used. You can actually work with it similar to balsa sheet.
The floor foam is based on Depron or Extruded Foam ... giving tiny beads that do not crumble like packing foam.





Bought in packs of 10 sheets and about 1.2m long ... 60cms wide ... 5.5mm thick ... you may be able to find up to 9mm thickness which I would prefer !! The price for a pack which would build quite a few models is about the same as just for a couple sheets of real Depron ...

Nigel
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Old 08-29-2018, 07:16 PM
  #54  
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For comparison, here are three wings I built that have flown and remain in flyable condition. As emphasized, you have to watch the weights.

The Old Fogey wing is Dollar Tree foam board, measures 40x11 inches (1016x279 mm) and weights 5 7/8 oz (166 grams). Comes out to roughly 2 oz per square foot (US measurements). It is reinforced against folding.

The Cloud Kitten is 48x8 (1219x203 mm), weighs 4 3/4 oz (135 gr), and is 1 3/4 oz per square foot.

The Q-Tee wing came out heavier than intended but still flies OK. It is 36x7 inches (914x178 mm), 4 1/2 oz (127 gr), and 2 1/2 oz per square foot. The build strength is high per the plan, and much of the weight is in the grey primer.

Seems to me you have two admirable but contradictory goals here, to design and build a basic trainer but also an attractive and long-lasting plane. Why not build one of each, a light version for your training then the more attractive one for once you are past the basics. A basic trainer should be thought of as expendable, thus light and cheap.
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Old 08-29-2018, 08:03 PM
  #55  
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Originally Posted by Abuelo View Post
For comparison, here are three wings I built that have flown and remain in flyable condition. As emphasized, you have to watch the weights.

The Old Fogey wing is Dollar Tree foam board, measures 40x11 inches (1016x279 mm) and weights 5 7/8 oz (166 grams). Comes out to roughly 2 oz per square foot (US measurements). It is reinforced against folding.

The Cloud Kitten is 48x8 (1219x203 mm), weighs 4 3/4 oz (135 gr), and is 1 3/4 oz per square foot.

The Q-Tee wing came out heavier than intended but still flies OK. It is 36x7 inches (914x178 mm), 4 1/2 oz (127 gr), and 2 1/2 oz per square foot. The build strength is high per the plan, and much of the weight is in the grey primer.

Seems to me you have two admirable but contradictory goals here, to design and build a basic trainer but also an attractive and long-lasting plane. Why not build one of each, a light version for your training then the more attractive one for once you are past the basics. A basic trainer should be thought of as expendable, thus light and cheap.
Forgive me for stepping in here ... Guy is in Chennai India and what goes for USA is often just not affordable or available.

DTF is basically not available outside North America and therefore substitutes need to be found and is why I posted about floor insulation sheet.

But overall - I agree with your posts intention ..

Reminds me - I must get some more packs of floor insulation ... being stiffer than Depron - it is ideal to stiffen a structure....

My SE5 is built of it ....










Nigel
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Old 08-29-2018, 09:36 PM
  #56  
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No offense taken, and I realize that materials in one area aren't available everywhere. The foam sheets you are using, which appear excellent for their various purposes, are not commonly used here in Arizona and would have to be special ordered. Foam board and balsa are readily available, and build light.

My intent was to show alternatives and weight savings. Our poster in India is facing several challenges and I hoped seeing some alternatives would be of assistance.
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Old 08-30-2018, 05:53 AM
  #57  
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Originally Posted by solentlife View Post
"aaindthu"

May I suggest you try and find a Builders Shop in Chennai or near ... a better Foam for building is the thinner Floor Insulation sheet ... its stiffer than the packing case foam you have used. You can actually work with it similar to balsa sheet.
The floor foam is based on Depron or Extruded Foam ... giving tiny beads that do not crumble like packing foam.





Bought in packs of 10 sheets and about 1.2m long ... 60cms wide ... 5.5mm thick ... you may be able to find up to 9mm thickness which I would prefer !! The price for a pack which would build quite a few models is about the same as just for a couple sheets of real Depron ...

Nigel

We do have a eps foam factory that i can reach in an hour by bus. And I can get the eps foam blocks of whatever density and dimension that I want.

I actually got the foam that I am presently using from that factory. Next time I go to him I am going to get a high density foam block. I did have a high density foam block once and it was heavy. So I thought I will get a low density foam for a lighter build.

Here's is what I am going to do to the wings:-

I am going to rip off the paper mache from the wings except the leading edge and the centre portion and I will glue some spars, see if that works.

I will post pics.

Last edited by aaindthu; 08-30-2018 at 06:17 AM.
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Old 08-30-2018, 06:04 AM
  #58  
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Originally Posted by Abuelo View Post
For comparison, here are three wings I built that have flown and remain in flyable condition. As emphasized, you have to watch the weights.

The Old Fogey wing is Dollar Tree foam board, measures 40x11 inches (1016x279 mm) and weights 5 7/8 oz (166 grams). Comes out to roughly 2 oz per square foot (US measurements). It is reinforced against folding.

The Cloud Kitten is 48x8 (1219x203 mm), weighs 4 3/4 oz (135 gr), and is 1 3/4 oz per square foot.

The Q-Tee wing came out heavier than intended but still flies OK. It is 36x7 inches (914x178 mm), 4 1/2 oz (127 gr), and 2 1/2 oz per square foot. The build strength is high per the plan, and much of the weight is in the grey primer.

Seems to me you have two admirable but contradictory goals here, to design and build a basic trainer but also an attractive and long-lasting plane. Why not build one of each, a light version for your training then the more attractive one for once you are past the basics. A basic trainer should be thought of as expendable, thus light and cheap.
Your wings look great !

But I also notice that they do not have ailerons servos. My wings weighed 220 grams including two servos(9grams each)and paper mache , and without paper-mache, it weighed 148 grams(with 2 servos) and wingspan is 1270mm.

You are correct about paper-mache, about increasing the weight. So I am going to rip it off from the wings and going to glue spars to it and see if it works. will post pics. Thank you
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Old 08-30-2018, 01:25 PM
  #59  
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If you want to 'case' wing ... then forget paper - it carries too much weight in glues etc.

I have an Aerobatics foamie that originally I covered with film ... but I started to hate its look.



So I decided to peel of the film and cover in micro light nylon window net. The stuff that wives hang across windows to stop prying eye's in. I used 50-50 mix of PVA with water to fix. I did not fully fill the weave but enough to fix the net and provide a good paint base.







I used spray cans of lacquer paint to colour it as final. Overall weight was LESS than the film by a few grams. But the strength factor was large. The skin it formed has resisted all my bad flights and still looks as good ..

Nigel
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Old 08-30-2018, 05:57 PM
  #60  
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Originally Posted by aaindthu View Post
Your wings look great !

But I also notice that they do not have ailerons servos. My wings weighed 220 grams including two servos(9grams each)and paper mache , and without paper-mache, it weighed 148 grams(with 2 servos) and wingspan is 1270mm.

You are correct about paper-mache, about increasing the weight. So I am going to rip it off from the wings and going to glue spars to it and see if it works. will post pics. Thank you

The reason for no ailerons is a lot of basic trainers do not utilize ailerons. They are two control only airplanes. Adequate dihedral in the wings allows the rudder and elevator to fully control the airplane. This would simplify your design and still let you learn to fly. You will reduce weight and complexity.

Last edited by Rabbitcreekok; 08-31-2018 at 07:25 AM.
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Old 08-31-2018, 01:15 AM
  #61  
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I have ripped off all the paper mache and glued some sticks that I removed from broom (used for sweeping). My wings weigh 172 grams now. Probably it will weigh a bit lesser because the glue isn't completely dry yet. The wings are now very rigid and strong.

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I am going to compromise on the looks of my plane and am going to use Tape for the leading edge and to cover over the 'spars' that I have glued onto the wings.
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Old 08-31-2018, 11:56 PM
  #62  
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aaindthu
Good going!
That's 50 g saved. A bit more than the weight of your motor?

It would be better to bind (cotton) and glue the sticks together to make one continuous 'long' stick before you glue it on the wing. As the foam is relatively soft you could always "score" a shallow channel into the foam and glue the stick into that. Then you tape over it to give a smooth surface.

Are the 'sticks' on both the top and underside of the wing? It will be many times stiffer and stronger if there is.
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Old 09-01-2018, 05:05 AM
  #63  
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Originally Posted by quorneng View Post
aaindthu
Good going!
That's 50 g saved. A bit more than the weight of your motor?

It would be better to bind (cotton) and glue the sticks together to make one continuous 'long' stick before you glue it on the wing. As the foam is relatively soft you could always "score" a shallow channel into the foam and glue the stick into that. Then you tape over it to give a smooth surface.

Are the 'sticks' on both the top and underside of the wing? It will be many times stiffer and stronger if there is.
If I do the same with the sticks underside of the wing it would add 8 grams plus glue. Total weight of the wings may come to 180 grams. Is 180 grams okay for a 1270mm wing?
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Old 09-01-2018, 11:33 PM
  #64  
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aaindthu
Any wing, without external bracing, sees compression loads on the top surface and tension on the underside.
Your foam is rather poor a resisting both of these forces. Gram for gram your sticks will be likely 20 times better a handling these loads.

A thin strip of wood top and bottom glued in at the wings maximum thickness and solid foam in between will create a 'beam' that will approach the stiffness of a solid piece of solid wood of the same total thickness but will only be a tiny fraction of the weight.

Any chance you could get hold of some thinner longer sticks?
With sticks placed top and bottom they could be much smaller and lighter and the wing will still be a lot stiffer than with just a bigger stick only on one side.

This shows the sort of thing I mean.
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It is a foam wing, albeit built up using 2 mm sheet foam. It has thin (2 mm thick) long tapered balsa 'sticks' built into the top and bottom wing skin. There is only foam in between them.
Obviously this was complex to construct and needed the right materials but the principle still holds good for a solid foam wing with thin sticks top and bottom glued on at the thickest point.

Don't worry. If you are happy your current 170 g wing is strong enough then ok and save the more complex but lighter construction techniques for then next one!
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Old 09-02-2018, 03:07 AM
  #65  
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Originally Posted by quorneng View Post
aaindthu
Good going!
That's 50 g saved. A bit more than the weight of your motor?

It would be better to bind (cotton) and glue the sticks together to make one continuous 'long' stick before you glue it on the wing. As the foam is relatively soft you could always "score" a shallow channel into the foam and glue the stick into that. Then you tape over it to give a smooth surface.

Are the 'sticks' on both the top and underside of the wing? It will be many times stiffer and stronger if there is.
I say get out there and fly it and you will probably never have a problem with strength. If you had a more powerful motor and wanted to try some serious aerobatic moves maybe consider a change....for now...fly it and have fun!! chas
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Old 09-02-2018, 03:48 PM
  #66  
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I made a "cowling" for the motor. This could protect the motor from impacts from crashing.

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This is how my plane is going to look.
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Still not complete. Probably I'll take it out for test flight next week.
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Old 09-02-2018, 11:08 PM
  #67  
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Don't forget that your motor needs airflow over it to keep it cool. If it is 'buried' it could overheat fairly quickly.
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Old 09-03-2018, 12:09 AM
  #68  
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Originally Posted by aaindthu View Post
I made a "cowling" for the motor. This could protect the motor from impacts from crashing.

Attachment 186937


This is how my plane is going to look.
Attachment 186938

Still not complete. Probably I'll take it out for test flight next week.
You might want to take a 3/16 inch drill bit and spin it with your fingers into the foam all around the motor. Put about 8 holes and space them so that they completely surround the motor(through the cowling). That way the cowling will still look great and afford you some more cooling. chas
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Old 09-07-2018, 05:48 AM
  #69  
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For the landing gears, I took bicycle spoke wire and bent it and glued it to a large piece of cardboard with epoxy. After it got cured, I applied some wood glue to the other side of the cardboard and simply pasted it under the fuselage.

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I have cut out the lower portion of the motor "cowling" exposing the lower part of the motor to the airflow for cooling purposes as pointed out by Panther.

And I painted it. Now the flying weight/AUW of the plane is 750 grams (1.65 lbs), 80 grams (0.176 lbs) lesser than the previous design. Watt per pound of the plane comes to 90.

And cg is at tip of the leading edge. So, I did not have to add any balast to move the cg. All looks good to me. I am going to try to fly it tomorrow

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Last edited by aaindthu; 09-07-2018 at 07:52 AM.
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Old 09-07-2018, 09:20 AM
  #70  
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CoG is at "tip of Leading Edge"

Nigel
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Old 09-07-2018, 09:41 AM
  #71  
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Originally Posted by solentlife View Post
CoG is at "tip of Leading Edge"

Nigel
Sorry, I meant that the plane balances itself close to the leading edge and not exactly at the "tip of Leading Edge", otherwise it would be in a nose-diving position.

When I lifted the plane from under the wings to find its CoG, the plane balances itself close to the leading edge. (like o% chord length from leading edge)

It is nose heavy. I thought it's a good thing for airplanes to be a little nose heavy. Should I add some tail weight?? Please do suggest. Thanks

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Old 09-07-2018, 10:09 AM
  #72  
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Nose heavy is much better than tail heavy. Safe CoG is usually rated as 20 - 30% chord back from Leading Edge. For this model being a high wing Cessna style - I would plump for 20% and be prepared for her to want to put nose down ..

There's an old saying …

Nose Heavy - fly again
Tail Heavy - Fly once.

Nigel
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Old 09-07-2018, 11:02 AM
  #73  
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That looks really good. I hope you have a successful flight and many more. Good luck.
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Old 09-07-2018, 11:42 AM
  #74  
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I would agree with solentlife and add tail weight to bring the CofG to 20% chord from the leading edge but no more.
At 1.65 lbs it is no lightweight. If it is very nose heavy you might find a it simply cannot go fast enough running on the ground to reach its flying speed or that you simply do not have enough elevator power to keep the nose up. Such a condition is not good even for an experience pilot.
A CofG at 20% is still a bit nose heavy for a conventional plane but it should be stable and controllable requiring only modest input from the pilot to maintain level flight.
Do let us know how you get on.
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Old 09-07-2018, 06:09 PM
  #75  
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Originally Posted by aaindthu View Post
For the landing gears, I took bicycle spoke wire and bent it and glued it to a large piece of cardboard with epoxy. After it got cured, I applied some wood glue to the other side of the cardboard and simply pasted it under the fuselage.

Attachment 186939Attachment 186940

I have cut out the lower portion of the motor "cowling" exposing the lower part of the motor to the airflow for cooling purposes as pointed out by Panther.

And I painted it. Now the flying weight/AUW of the plane is 750 grams (1.65 lbs), 80 grams (0.176 lbs) lesser than the previous design. Watt per pound of the plane comes to 90.

And cg is at tip of the leading edge. So, I did not have to add any balast to move the cg. All looks good to me. I am going to try to fly it tomorrow

Attachment 186941
Your CG may wind up being closer to 1.75" from the tip of the leading edge. The "tip" of the leading edge might be a little too far forward. Take it out to some high grass and chunk it out there at about 45 degrees and see how it comes down. chas
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