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Author Topic: wing loading FF rubber  (Read 591 times)
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stovebolt
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« on: March 20, 2019, 01:20:02 AM »

I'm new, (10 going on 70), seems like if I want to get a walnut size rubber (GUILLOWS) to fly I need to find a reasonable wing area to total weight ratio.
It's a Guillows Hawker Hurricane (bought 30 yrs. ago)in the 3rd rebuild/weight loss/bigger wing, session.
(I know- trash it and spend $$ for something that flies) this is my first build to fly, I'll sand it down to paper thin if i have to, this is the first one, you folks know you  only get "one first one"Wink
 I see a fellow has an excel program that maybe what I'm looking for, but my computer knowledge is limited (also my computer patience). It appears I have to "learn execel" programing?
 But I see a couple posts of wing loading "comments" that stated....49 grams per sq. inch being a good flier and .59 grams per sq. inch "should fly good". But I don't know the size of their  planes. Any help here? new wing 65.3 sq. inches
Thanks Pat
 
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Jack Plane
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« Reply #1 on: March 20, 2019, 03:02:46 AM »

65 sq in wing area walnut size rubber FF...

If an indoor floater, at 0.40 g/sq in => 26g flying weight (assume rubber weighs 2-3g, then model 23g).

If for outdoors, at a more penetrating 0.65 g/sq in => 42g flying (rubber 4-5g, model about 37g).

These are the rough parameters (easy to work out with a pencil or calculator:  loading = weight / area, or weight = loading x area).  I suspect your Guillows Hurricane will come out around the 35-45g mark depending on its design, the density of the wood in the kit and your building skills.

Build light obviously, especially the tail, but don't don't sand all the strength out of key components!  Steam-shrink the tissue for the flying surfaces and pin down at least overnight (some folk pre-shrink the tissue for the tail parts on a frame first).  Don't apply more than one coat of non-shrinking dope thinned 50%.

Move the rear peg forward at least one or two bays.  A longer loop (say 1.5 to 2.0 times prop-hook to peg length) will give you more duration, but you don't need the physical length in the model itself - which would just mean a lot more nose-weight to balance all that rubber at the tail end.

 Smiley

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Yak 52
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« Reply #2 on: March 20, 2019, 05:51:27 AM »

Hi Pat, welcome to the forum.

I see a fellow has an excel program that maybe what I'm looking for, but my computer knowledge is limited (also my computer patience). It appears I have to "learn execel" programing?

You might find this online version easier to use:
http://www.ef-uk.net/data/wcl.htm
Just punch in the wing area and weight and click calculate.
Only trouble with this one is it's either Imperial or Metric so you can't use mixed units like gram/inch2. But converting 65.3in2 to decimetres gives you 4.2dm2

As you probably realise the ideal wing loading differs as models get larger or smaller so 0.5g/in2 would be quite acceptable on a 24" model but heavy for a 13" Peanut.
The 'cube loading' number is useful because it gives you an idea of floatiness irrespective of size.

Cube loadings for rubber models roughly translate as
2 seriously light: heading towards indoor duration
3 is pretty floaty: average 14g Bostonian, light for scale models (RC gliders)
4 is a healthy target for scale where you still have a chance of reasonable duration.
5 will fly well but duration starts to suffer - still fine for detailed indoor scale model
6 getting a bit heavy for rubber, will still fly ok but not for long (RC Trainers)
Above 7 you probably ought to be a bit worried.

Of course there are always exceptions to this but it's a useful rough guide for target weights when building.

For your model the cube loadings would be

2 = 17g ...probably unrealistic
3 = 26g ...great!
4 = 34g ...pretty good for a Guillows model  Cool
5 = 43g ...Perfectly acceptable Smiley
6 = 52g ...should still be fun
7 = 60g ...get out and enjoy the model and learn something before the next one  Grin

Don't obsess too much about the weight but do look at what breaks (should have been stronger) and what's overbuilt (could have been lighter) and enjoy the progression as you build your first few models.


Jon
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dputt7
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« Reply #3 on: March 20, 2019, 06:55:13 AM »

  Congratulations Jon and Jon, great info that's taken most of us a long time to come to grips with. Thanks for taking the time to respond. kudos
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Pete Fardell
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« Reply #4 on: March 20, 2019, 08:09:11 AM »

I agree- great info delivered promptly and clearly as usual.
Pat, in your original posting you seem to say you built a ‘bigger wing’ for your Guillow Hurricane. I’m intrigued by that as I’ve often heard of tail surfaces being enlarged on scale models, but not usually the wing itself. If you really did enlarge it, how? Increased span or chord or both?
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flydean1
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« Reply #5 on: March 20, 2019, 10:30:49 AM »

Where are you located stovebolt?  There may be someone nearby.
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stovebolt
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« Reply #6 on: March 20, 2019, 12:20:50 PM »

Thanks folks that was quick, this forum seems to be pretty active. I spent a lot of time searching for info like that.I'm not concerned with "scale", more with park fliers for fun.
There is a club here in Seattle (Auburn), I think.
 The first build was way to heavy, tore it apart and built a bigger wing, removed weight. It wanted to fly, but need to be trimmed, glide was OK.
I learned along the way, every repair adds weight. The last disaster was my guard goose attacked and broke a wing, while testing the glide in the front yard.
 After that it didn't want to fly, it was over 40gr. I'm on my third rebuild/diet, and realized wing load would probably predict the glide.
I'll take a crack at resizing my photos, haven't had much luck though.
I'll get back with the pics, thanks again.
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stovebolt
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« Reply #7 on: March 20, 2019, 12:49:27 PM »

lets see if these pics will upload
1st one is first build
3rd is where it is now
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faif2d
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« Reply #8 on: March 20, 2019, 02:21:41 PM »

Are you perhaps a Chevy lover? (based on your name)
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stovebolt
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« Reply #9 on: March 20, 2019, 03:57:07 PM »

Are you perhaps a Chevy lover? (based on your name)
we used stove bolts at work
but I do have a 49 chev...... put a 302 Ford in it;)
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lincoln
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« Reply #10 on: March 21, 2019, 07:04:15 PM »

That 3rd wing looks good, but you may need a bigger tail. And/or a lighter, longer fuselage. ;-p

I think the weight advice you've been given sounds about right. The heavier the model, the longer the grass you should fly it over.

I suppose you know that if you can bring yourself to do it, some other, better design will give you more of a reward for your work.  When you build one part lighter, it may be strong enough to survive if the other parts are all made lighter too, so there's less energy to dissipate when it hits something.

If you want a full fuselage, I suggest Bostonian or Embryo designs. Or maybe the 20 inch Golden Age Pacific Ace, which Peck Polymers now has. If it has to be Guillow, their Javelin flies well even when built with Guillows oak. (They claim it's balsa, but it's heavier. ;-)     ) Not very scale looking, though. I used a larger prop, not sure if it flies well with the one from the kit.

I suspect that I've made some of the above advice to you in some other forum, so I hope you'll forgive me for the repetition.
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p40qmilj
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« Reply #11 on: March 22, 2019, 09:04:17 AM »

 Grin fwiw  i upscale guillows models to 20 to 24 inches and use the same size wood.  it produced great fliers.

jim Grin
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BG
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« Reply #12 on: March 22, 2019, 11:11:43 AM »

Hi All,
Ok so I read through this thread and I am going to drop some advice. This is the advice commonly given to aspiring free flight geeks and often ignored, mostly because it is hard to get all inspired by something that in not a "cool scale model". 

Start simple and work your way towards more complex models. Success with free flight rubber powered models requires the development of many separate skills and it is easy to become overwhelmed. The fact that you are worrying about wing loading on your first build and the design is a guillows hurricane suggests to me that you have picked a very challenging way to learn this already challenging (bet VERY rewarding) hobby.

What I would tell you were I your "mentor":
1. Trash the hurricanes and other scale jobs (or hang them from the ceiling, or shelve them for now) and clear your building area.
2. Pick a simple design that has a good chance of flying well and which is fairly easy to build. A p30 is ideal but one of the simpler ~30" old time rubber jobs would work as well. Does not have to be from a kit. You can build from a plan it just requires a touch of patience (and patience is also a learned skill).
3.  Build this and get feedback on your build as you go. Ask for honest criticism and be ready to rebuild and/or recover a part a couple of times to get it right. This sounds harsh but it will give you the experience to do it right the first time on your next build.
4. With completed model in hand set it up for flight on the workbench (again ask for help on this, it will save you hours of flailing around at the field).
5. Prepare your flight kit (stooge, winder, tool box etc.)
6. Go to the field on a calm day and work your way through the trimming process.
7. Catch your first thermal and watch that P30 DT from 200 m up.
8. Now pick your next project ... a simple high wing scale job could be a good choice, proceed from 3 above.

Ok advice column done. Good luck and thermals to ya.

BG
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stovebolt
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« Reply #13 on: March 22, 2019, 01:54:06 PM »


Cube loadings for rubber models roughly translate as
2 seriously light: heading towards indoor duration
3 is pretty floaty: average 14g Bostonian, light for scale models (RC gliders)
4 is a healthy target for scale where you still have a chance of reasonable duration.
5 will fly well but duration starts to suffer - still fine for detailed indoor scale model
6 getting a bit heavy for rubber, will still fly ok but not for long (RC Trainers)
Above 7 you probably ought to be a bit worried.

Of course there are always exceptions to this but it's a useful rough guide for target weights when building.

For your model the cube loadings would be

2 = 17g ...probably unrealistic
3 = 26g ...great!
4 = 34g ...pretty good for a Guillows model  Cool
5 = 43g ...Perfectly acceptable Smiley
6 = 52g ...should still be fun
7 = 60g ...get out and enjoy the model and learn something before the next one  Grin

Don't obsess too much about the weight but do look at what breaks (should have been stronger) and what's overbuilt (could have been lighter) and enjoy the progression as you build your first few models.


Jon
Thanks Jon
This gives me some hope, if the tail boom isn't too short.
 Yes BG I've gone at this all backwards. I built this kit before I ever heard of free flight, didn't know people did this for a hobby. But there's still time, summer here usually doesn't hit till the 5th of July (Seattle).
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Re: wing loading FF rubber
Re: wing loading FF rubber
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stovebolt
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« Reply #14 on: March 24, 2019, 07:17:58 PM »

Hi Pat, welcome to the forum.


Don't obsess too much about the weight but do look at what breaks (should have been stronger) and what's overbuilt (could have been lighter) and enjoy the progression as you build your first few models.


Jon
Jon you're right about obsessing on weight. Found a soft spot on the new glide tests. The cracked ribs... told my self "self reinforce these at least with glue" , self was busy doing something else I guess. But the plane feels like two feathers, instead of a baseball, to launch.
 It got in at a 3.4....
https://www.youtube.com/watch?v=5Lq-OwoAC6Y
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stovebolt
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« Reply #15 on: April 16, 2019, 01:13:38 AM »



For your model the cube loadings would be

2 = 17g ...probably unrealistic
3 = 26g ...great!
4 = 34g ...pretty good for a Guillows model  Cool
5 = 43g ...Perfectly acceptable Smiley
6 = 52g ...should still be fun
7 = 60g ...get out and enjoy the model and learn something before the next one  Grin


Jon
Hi Pat, welcome to the forum.


For your model the cube loadings would be

2 = 17g ...probably unrealistic
3 = 26g ...great!
4 = 34g ...pretty good for a Guillows model  Cool
5 = 43g ...Perfectly acceptable Smiley
6 = 52g ...should still be fun
7 = 60g ...get out and enjoy the model and learn something before the next one  Grin



Jon
It came out 34.3 all in, but it's nose heavy. Tested it on the bed. I made a cedar nose block for it when it was heavier. I'll carve some weight out of it.
Thanks for that link.
Pat       ps this is the 4th set of wings;)
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Yak 52
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« Reply #16 on: April 16, 2019, 05:22:24 AM »

Nice work Smiley

Pat, in your original posting you seem to say you built a ‘bigger wing’ for your Guillow Hurricane. I’m intrigued by that as I’ve often heard of tail surfaces being enlarged on scale models, but not usually the wing itself. If you really did enlarge it, how? Increased span or chord or both?

As Pete suggests, bear in mind that increasing the area and span of the wing will reduce stability, just the same as decreasing the tail would. It may not be an issue if you had a large tail to start with but it's good to be aware of the effect. As compared to previous trim, you will likely need a to move the CG forward (more noseweight) and give it a little more decalage (increased negative tail incidence.)
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stovebolt
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« Reply #17 on: April 16, 2019, 01:56:29 PM »

If you really did enlarge it, how? Increased span or chord or both?
Pete this was my first build.
My back ground is commercial construction, if the crane won't lift it, get a bigger crane;)
So the second set of wings were constant cord, same length, and some weight off the fuse.
Not much improvement.
I had a Spirit of St. Luis in sticks and found out it won't fly, so I used that wing, for the third, and more weight loss. It flew in a fashion, still to heavy
So a crash diet and a lighter wing design built from the Dumas Beaver plans. But I cut lightening slots in the TE and that wing didn't survive "glide off a hill".
Built the same wing again left solid, because the Beaver test flight was fine. And raised the dihedral to top of canopy. Waiting on weather for tests. I guess these are wings #5.
 Yak52
When it did fly, it didn't want to climb. So I may have to work on the tail feathers. I did put 4 * down in the new nose.
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Re: wing loading FF rubber
Re: wing loading FF rubber
Re: wing loading FF rubber
Re: wing loading FF rubber
Re: wing loading FF rubber
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TimWescott
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« Reply #18 on: April 16, 2019, 02:24:02 PM »


Cube loadings for rubber models roughly translate as
2 seriously light: heading towards indoor duration
3 is pretty floaty: average 14g Bostonian, light for scale models (RC gliders)
4 is a healthy target for scale where you still have a chance of reasonable duration.
5 will fly well but duration starts to suffer - still fine for detailed indoor scale model
6 getting a bit heavy for rubber, will still fly ok but not for long (RC Trainers)
Above 7 you probably ought to be a bit worried.


How are cube loadings calculated?
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stovebolt
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« Reply #19 on: April 16, 2019, 02:32:20 PM »



How are cube loadings calculated?
[/quote]
 check post #2 above Tim
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stovebolt
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« Reply #20 on: April 16, 2019, 03:12:07 PM »

I just calculated the wing load of the two planes I've got ready to fly.
quite a difference, they're both basically walnut size.
also calculated the first version out of the box built
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Re: wing loading FF rubber
Re: wing loading FF rubber
« Last Edit: April 16, 2019, 05:06:37 PM by stovebolt » Logged
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