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A GLH for 2012

Old 06-27-2012, 04:05 PM
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hllywdb
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Default A GLH for 2012

OK, it's time to build another GLH. The last one I built was over 25 years ago so it's time. I am going off of Dave Fritzke's plans, but want to go a bit cleaner than the original. This is the airfoil I am going to be using. Comes in right at 7% and leaves me just enough room for a 3/32 X 1/4 spruce spar top and bottom. I moved the spar back to 30%. My thinking is that with a wing this thin, I need the lifting surface to be right. Since I am going to sheet from the LE to the spar with 1/32 and cap the ribs, the critical part of the wing will be sheethed so any sinking of the covering between the ribs should't make a huge difference. Any thoughts?

My next thought is, the original flew good with a TD but was a lot more fun with an 09, sooooo since I am using an AME 061 RC, should I scale it to 85 or 90%. With today's RC gear, it's not too hard. Anyone tried that one yet?
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Old 06-27-2012, 05:43 PM
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Default RE: A GLH for 2012


ORIGINAL: hllywdb

........ since I am using an AME 061 RC, should I scale it to 85 or 90%. With today's RC gear, it's not too hard.
Bare -

To get the benefit of the AME, you'll probably be running something in the neighborhood of a 4.75 to 5.25 diameter prop, which means the plane will need to be pretty clean. I did some rough calculations on area. At 100%, it looks to be about 195 sq. in. If scaled to 90%, it drops to around 160 sq. in.. Consequently, at full tilt, it might be inclined to drop out or high speed snap in tight turns. It also drops the chord to 5.5" - with a 7% airfoil, thickness is just under .4" - which is pretty thin. The spruce should be sufficiently strong, but being so close together, you'll lose some of the strength advantage. I think I would add spar webs 2/3 of the way out from the center section. With LE sheeting and webs, it will give you a D-tube design for a portion of the wing. Bottom line, 90% scaling is about as small as I would go. If it turns OK, you could always cut a bay off each tip.

However, the fuselage is a real candidate for going on a diet. You could cut the width back to the width of the firewall and reduce the height so it is straight from the bottom of the firewall to the tail. Parasitic drag is going to be your enemy as the speed goes up, so reducing the exposed area will be beneficial.

Just some of my ramblings........
Old 06-27-2012, 06:40 PM
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Default RE: A GLH for 2012

Thanks Andrew, in terms of drag, any suggestions for fuselage shape? Other than just getting down small at the tail.
Old 06-27-2012, 07:28 PM
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Default RE: A GLH for 2012

ORIGINAL: hllywdb

OK, it's time to build another GLH. The last one I built was over 25 years ago so it's time. I am going off of Dave Fritzke's plans, but want to go a bit cleaner than the original. This is the airfoil I am going to be using. Comes in right at 7% and leaves me just enough room for a 3/32 X 1/4 spruce spar top and bottom. I moved the spar back to 30%. My thinking is that with a wing this thin, I need the lifting surface to be right. Since I am going to sheet from the LE to the spar with 1/32 and cap the ribs, the critical part of the wing will be sheethed so any sinking of the covering between the ribs should't make a huge difference. Any thoughts?

My next thought is, the original flew good with a TD but was a lot more fun with an 09, sooooo since I am using an AME 061 RC, should I scale it to 85 or 90%. With today's RC gear, it's not too hard. Anyone tried that one yet?
Have you considered building a foam wing with thinner CF spars ?

The ribs you show are full size ?

Old 06-27-2012, 08:03 PM
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Default RE: A GLH for 2012

hllywdb

First, my apologies for addressing the post to Bare - I had been reading one of his posts earlier.

Other than keeping your frontal area minimized and reducing both the height and width of the fuselage, you may want to round the fuselage and add fillets under the wing, on either side of the fin and under the stab. I think if you start with a minimal frontal area and follow that shape to the tail with a very smooth transition (make it only wide and tall enough to hold your components), it should keep your parasitic drag to a minimum.

There was a plane that came out in '77 called the Hornet that used a very thin wing and minimal fuselage, but it carried 220 sq. in. Reducing the overall size should help out.

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Old 06-27-2012, 11:03 PM
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Default RE: A GLH for 2012

To cut drag to a bare minimum, the fuselage shouldn't be any bigger than the engine up front.
This might mean that a DIY fuel tank made from tin is needed to fit within the confines and plan on stacking the battery right above the tank and allow space to pad the tank.
It's OK to let the fuselage flare out so that the widest part of the fuselage coincides with the TE of the wing.
If you set the wing area at 160 sq inches and keep the RTF weight to around 13 ozs or less, the plane will fly just fine.
I almost universally use 1/4" as my standard thickness for 1/2A speedster wings in this size range, but your wing looks pretty fast. I think ACE RC knew something when they specified a sharp LE....very small radius.
At this size and weight a AME will make good use of a 4.2x4 or 4.5x4 prop and run over 100 mph.
Plan ahead to run backplate pressure and how to deal with the plumbing details.
Old 06-28-2012, 04:41 AM
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Default RE: A GLH for 2012

Sheet Wing Racer. 
Old 06-28-2012, 05:48 AM
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Default RE: A GLH for 2012

You might want to check [link=http://www.mh-aerotools.de/airfoils/index.htm]Martin Hepperle's Site[/link] for some other options on pylon racing airfoils.
Old 06-28-2012, 05:51 AM
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Default RE: A GLH for 2012

Hi Andrew,
I have one flying right now that is 31" span low wing, 6 3/8 at the root and 4 1/2 at the tip. At the tip the airfoil is only 3/16" thick and the plane is rock solid with no tendancies to snap out of a tight turn. That one is flying with a stock Big Mig RC with muffler and turning an APC 5.7 X 3. I am thinking that between the high wing and swept wings it should have a lot of inherent anti-snap stability, or am I wrong? Right now the GLH would be a 6 3/8" cord, at 90% it would be 5 3/4"

CP, 160 sq in sounds better, thats why I was thinking going 90% (around 170) I am going to run one of my AME RC motors, no muffler and backplate pressure. For a tank I am going to use a Hayes 1oz header tank. I have used them on combat planes as they are only 1" X 1" and around 2 1/2 long. This AME I have opened up the carb, cleaned up the crank, and evened up the boost port passages in the case. I haven't done any work on the crank counter balance or the piston. Since I'm not going for any records I am thinking it should hold together fine and be fast enough with a cut down prop. I still have a NIB old style RC AME to fall back on. For plumbing, I have used your idea before with TDs of putting a connector in the pressure line, turn the plane on it's nose and fill the tank from the pressure line until fuel comes out the carb.

Rafa, I thought about foam but I am happier with wood. Also thought about a 3/16 CF spar, but it's harder to build the wing straight, at least for me, and I still need to epoxy it to the ribs, so not sure I save any weight.
Old 06-28-2012, 06:00 AM
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Default RE: A GLH for 2012

Sorry Andrew, missed your last post. I checked out the site, if you compare airfoils, the one I am using is almost identical to his MH22 F3D airfoil. His may have just a slightly more laminar design to it, but I have found moving the lift point much past 35 or 40% doesn't translate well at these renyolds numbers. I had good luck with about 40% down to a 32 size plane, wasn't getting much return at 1/2A as at that size the slightest wrinkle in the covering breaks the stream early and starts working against you.
Old 06-28-2012, 08:21 AM
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Default RE: A GLH for 2012

Look at control line speed planes for the fastest 1/2A airfoils. They are simply thin and smooth.
The air on both sides of the wing travels the shortest distance and makes contact with the least amount of surface area [that the pilot and his plane can tolerate].
The AMA record was held by Carl Dodge last time I checked at 152 mph.....with a G&Z .049.
He posted a list of things done to the engine that a guy with a hobby lathe and simple tools could do.
The AME mod to create an open passage up the forward boost port via scooping out the counterweight and raising the piston skirt makes a big difference. I don't think the skirt needs to be hogged out to the point of making the piston unstable to make a big gain. I would do this mod without removing the piston from the rod, if I was to ever do it again.
At any rate, the ULTIMATE GLH has yet to be created...[:-]!!!
The highly swept wing might also be a handicap past a certain MPH...you would need to have a "regular" winged version of the same plane to verify that notion.
Old 06-28-2012, 08:56 AM
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Default RE: A GLH for 2012

Hey CP, I haven't tried the counter weight yet, from the pics in Todd's page it looks like if the crankpin is at 12:00. the scoop is done at 9:00. Does this sound right?
Old 06-28-2012, 09:42 PM
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Default RE: A GLH for 2012

The exact timing and duration of the mod is something that I have no exact figures for.
Toad would be the one with those details, if anyone has them.
Whatever you do, do not hog the piston skirt past the point where it overlaps the exhaust port.
Old 07-09-2012, 05:10 PM
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Default RE: A GLH for 2012

Got the balsa cut and started on the wing. Was looking for an easy way to build the TE and aileron, so found a piece of 2" aileron stock and cut it back (from the thin edge) to be the size of the TE and aileron and PRESTO! the remaining rounded leading edge of the aileron stock was the perfect size for the LE. So I got LE. TE, and ailerons from one peice of pre-shaped wood. I'm a happy camper. Would love to say I planned it that way, but I ain't that good.
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Old 07-09-2012, 09:43 PM
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Default RE: A GLH for 2012

That's a pretty amazing feat to get those "headaches" solved with just 1 piece of preformed stock.
The old airfoil was pretty thick, but it was still a pretty fast one. I think the sharp LE was the key.
I wonder how the GLH ranks on the all time most popular 1/2A RC kit list...?
Old 07-10-2012, 07:05 AM
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Default RE: A GLH for 2012

I know back when ACE was still in full swing, (god I miss them) every hobby shop I went in to had a GLH and a Whizard in stock at all times, a lot of them stocked both the foam and built up versions too. I think the GLH and Sig Hummer were realy popular with those of us who entered RC by way of CL Combat and were adjusting to speed withdrawals. "What do you mean you put an .049 on a 36" wing, that needs a Fox 36! An .049 is for an 18" wing, and flys even better if you accidently break off the outboard wing." Of course I can tell if the plane is inverted, it will be going to my right, clockwise!

Here is a picture of the airfoil, you can see why I needed to have such a long TE/Aileron surface, otherwise the tail end of the rib would have been a pencil tip. It is about 1/8" now, that's why I added the 1/2" of sheeting where it meets the TE.

What do you think of the LE? I don't want to go too sharp and get it way too twitchy to pitch changes. Remember this is built at 90% too.
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Old 07-10-2012, 07:40 AM
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Default RE: A GLH for 2012

hllywdb,

Plus 1 from an old Nemisis driver!
Old 07-10-2012, 07:50 AM
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Default RE: A GLH for 2012

Oh no! I just took the dial caliper to the wing and even using 1/32 sheeting it came out at .310 thick. So I over shot my 1/4" by 60 thousandths. Do you think that will make it unbearably slow?
Old 07-10-2012, 08:29 AM
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Default RE: A GLH for 2012

ORIGINAL: hllywdb

I know back when ACE was still in full swing, (god I miss them) every hobby shop I went in to had a GLH and a Whizard in stock at all times, a lot of them stocked both the foam and built up versions too. I think the GLH and Sig Hummer were realy popular with those of us who entered RC by way of CL Combat and were adjusting to speed withdrawals. ''What do you mean you put an .049 on a 36'' wing, that needs a Fox 36! An .049 is for an 18'' wing, and flys even better if you accidently break off the outboard wing.'' Of course I can tell if the plane is inverted, it will be going to my right, clockwise!

Here is a picture of the airfoil, you can see why I needed to have such a long TE/Aileron surface, otherwise the tail end of the rib would have been a pencil tip. It is about 1/8'' now, that's why I added the 1/2'' of sheeting where it meets the TE.

What do you think of the LE? I don't want to go too sharp and get it way too twitchy to pitch changes. Remember this is built at 90% too.
I built the ACE foam GLH "by the book" many years ago with the pointed LE and it was a plane that I could fly low and fast...not twitchy. Give it the tallest control horn that you can for elevatorand use one of the inner horns at the servo arm.
I had the same "mental size adjustment issues" coming from C/L Combat over to RC. I could not believe that a .049 could fly any of the 1/12th scale warbirds that this old man had on display at his hobby shop.
Back to the sharp LEs.....I do the slightest rounding off of the SWR's just because of TLAR instinct.
I've got nothing scientific to say about this topic, really. There's so many things that come into play from all angles, Lord only knows what the best shape is unless you are competing for .0001th of a second and take really good notes.
BTW, that's a REALLY good looking airfoil. I'll bet a really good TD or Norvel will haul your plane over 100 mph, no problem.
Old 07-10-2012, 08:56 AM
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Default RE: A GLH for 2012

Do you think I need to make the LE even sharper?

For power, I have a TD .051, backplate pressure, KK needle, Galbreath head/Nelson plug and shortened piston, but I also have 2 AME .061's with bored out RC carbs, polished cranks, Galbreath heads, and backplate pressure. My thinking is that the cranks on the AME's will hold up a lot longer and I can live without taking my piston reset tool to the field with me LOL. Since the bored out RC carbs work more like the old speed controls with High speed, mid speed, and stop, I'm thinking it's always nice to be able to choose when and where to land and mid speed is nice when getting the throws balanced and trimmed out. My eyesight is not what it used to be back when either. Not looking to set any speed records but 100 mph small planes are fun to fly and an AME should be able to do many more flights at 25,000 vs 32,000 rpm. I also seem to get more consistant runs with the AME motors too, the TD's are either a great run or a crappy run until the tank runs out and a rich run on a speed plane is no fun watching it wallow around for 5 minutes trying to keep it from snap rolling into the ground.
Old 07-10-2012, 09:31 AM
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Default RE: A GLH for 2012

It would depend on what mood I was in as far as the LE sharpness is concerned. What you show there you know for sure will work very well.
I only run TDs for nostalgia any more. Just to see how fast I can get one going.
My track record with AMEs and their longevity isn't too great either.
The Fora and Cyclon are so much more dependable and cheaper in the long run instead of stocking cans full of spare parts and cannabalized Cox and Norvel engines.
I have never used a spare part of any sort for the Cyclon or Fora....ever.
These engines can be restricted at the intake to run a little bit slower and they will handle 5x3 props just fine.
APC has a 4.5x4 prop that might be perfect for your plane.
Old 07-10-2012, 10:14 AM
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Default RE: A GLH for 2012

Thanks CP,
I have a couple of Bernie's Cox Grey 4.5 X 4 props I was going to try. Are the APC better?
Old 07-10-2012, 12:53 PM
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Default RE: A GLH for 2012

That's a very slick foil you've got going there, hllywdb - it should prove to be a real screamer. Better remember to take a rag to the field with you if you get much of a gnat buildup in the wing, it could add one percent to the thickness.

Actually, the effective percentage of your wing will be lower than what we are seeing in the root rib picture. Due to the sweep, the rib length in the airstream will be longer and the thickness still remain the same.

Waiting for more pics.

andrew
Old 07-10-2012, 02:06 PM
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Default RE: A GLH for 2012


ORIGINAL: Andrew

hllywdb

First, my apologies for addressing the post to Bare - I had been reading one of his posts earlier.

Other than keeping your frontal area minimized and reducing both the height and width of the fuselage, you may want to round the fuselage and add fillets under the wing, on either side of the fin and under the stab. I think if you start with a minimal frontal area and follow that shape to the tail with a very smooth transition (make it only wide and tall enough to hold your components), it should keep your parasitic drag to a minimum.

There was a plane that came out in '77 called the Hornet that used a very thin wing and minimal fuselage, but it carried 220 sq. in. Reducing the overall size should help out.


I scratch built one of those Hornets way back when.. back when a 22oz 1/2A plane wasn't all that bad! Radios have sure gotten smaller since the late 70's..
It was a fun plane, for sure.
Old 07-10-2012, 02:34 PM
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Default RE: A GLH for 2012

ORIGINAL: hllywdb

Thanks CP,
I have a couple of Bernie's Cox Grey 4.5 X 4 props I was going to try. Are the APC better?
IDK..........all I know is that both companys make top notch props.
The local 1/2A pylon racing club's lowest lap time and heat time is held by a Cox rubber 5x3 / AME .061 if I'm not mistaken. I was surprised when I first heard that, especially on a 2 turn...300 foot long course.

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