HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 05, 2014, 05:34 AM
RFJ
Registered User
RFJ's Avatar
Northern Ireland
Joined Dec 2004
1,607 Posts
Build Log
Fred Dunn 75% Astro Hog for AMPLAN Build Off

Although I can't begin the actual build until next month I though I would start a thread anyway.

The Astro Hog was first flown in late 1957 and is essentially a low wing version of the Smog Hog. Apart from the ailerons and tips the wings are identical. The nose is slightly longer but the moment arm is the same. Tailplane has a slightly greater aspect ratio.

Bob Dunham's Astro Hog won the 1958 and 1959 US Nats.

Ray
RFJ is offline Find More Posts by RFJ
Last edited by RFJ; Oct 06, 2014 at 03:55 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 05, 2014, 05:46 AM
Registered User
Paul_BB's Avatar
France, IdF, Lagny-sur-Marne
Joined Feb 2007
449 Posts
Good luck Ray!

-Paul
Paul_BB is offline Find More Posts by Paul_BB
Reply With Quote
Old Oct 05, 2014, 05:55 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,783 Posts
Should be a cracker Ray.
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Oct 05, 2014, 06:24 AM
Registered User
Warren B's Avatar
Mt Evelyn, Melbourne, OZ
Joined Dec 2008
644 Posts
I'm still intending to do a 100% version starting in a month or two
..... But I think there is room in two hemisphere's enough for both of us!

Are you making any changes Ray?
I note the positive incidence on both wing and tail (I think, bye eyeball).
I guess this is roughly equivalent to a bit more down thrust.
I'm planning to use all the interesting hinge details too.
Not sure about all the rubber bands, they look nice and vintage, but bolts aremoreconvenient.
Warren B is offline Find More Posts by Warren B
Reply With Quote
Old Oct 05, 2014, 10:25 AM
RFJ
Registered User
RFJ's Avatar
Northern Ireland
Joined Dec 2004
1,607 Posts
Warren,

The more the merrier - good luck with your "real" version and I look forward to the build log.

As you say the plan shows positive wing and tailplane incidence and no downthrust. I have changed this to zero tailplane incidence, about 1 degree positive on the wing and a couple of degrees of downthrust. This can affect the "sit" of the model in the air slightly but is easier to build accurately and is well proven.

The "interesting" hinge details will also have to go - too much work I will hinge the rudder conventionally and fit my usual center hinged ailerons.

I also don't care much for rubber bands. They were necessary on the Smog Hog as the front cabin dowels are such a prominent feature. Less so on the Astro Hog so I will use a front tongue and a rear bolt on the wing. The tailplane will be permanently glued on and the hatch held by magnets - no rubber bands anywhere.

As you can tell I'm not a purist in these matters - if I don't like something I will change it provided it does not alter the character of the original model too much. Basically the outline is sacrosanct but everything else is open to offers

Ray
RFJ is offline Find More Posts by RFJ
Last edited by RFJ; Oct 06, 2014 at 03:14 PM.
Reply With Quote
Old Oct 06, 2014, 05:02 AM
Registered User
United Kingdom, England, Richmond
Joined Apr 2011
81 Posts
Are you going to keep the original dihedral Ray? Personally I hate to see Astro Hogs with reduced dihedral as it is such an important part of the plane's character.
ukengineman is offline Find More Posts by ukengineman
Reply With Quote
Old Oct 06, 2014, 07:33 AM
RFJ
Registered User
RFJ's Avatar
Northern Ireland
Joined Dec 2004
1,607 Posts
A very good question Alan

I had a bit of a dilemma with this. The original dihedral is 7 degrees per side which frankly looks ridiculous to me but, as you say, is a big factor in the design's character. Modern thinking would have this at about 1 degree per side just to avoid the droopy wing illusion but that would certainly destroy the distinctive Astro Hog look.

So for me a compromise is necessary. I settled on 5 degrees per side which still looks "too much" but is the maximum I can live with. Sorry to all you purists out there

Warren - perhaps, just to be different, you might fancy a Dunham Astro Hog as shown below. Note in particular his changes to the longitudinal dihedral.

Ray
RFJ is offline Find More Posts by RFJ
Last edited by RFJ; Oct 06, 2014 at 03:09 PM.
Reply With Quote
Old Oct 06, 2014, 08:01 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,783 Posts
I appreciate your dilemma on the dihedral Ray, and for what it's worth I think you have arrived at a most reasonable compromise which should preserve the Astro Hog look whilst not looking excessive.
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Oct 06, 2014, 04:57 PM
pd1
Registered User
United States, MA, Haverhill
Joined Jun 2006
2,153 Posts
Ray I love the idea of a 70% Astro Hog. I built a full sized Sig Hog last year and it's too big for my small workshop.
The Sig Hog has reduced dihedral, my plane looks fine but it doesn't look like an original Astro Hog without the dihedral.

If I build a 70% Hog, I will use the stock dihedral.
I did zero the wing and stab incidences, my plane flies fine set up that way.
This is my second Hog, the first was over 50 years ago, maybe next year a third.

I just got a kit of a contemporary of the Hog, the DeBolt Pursuit, it too has ridiculous dihedral.
Gotta love the old designs.

Paul
pd1 is offline Find More Posts by pd1
Reply With Quote
Old Oct 06, 2014, 05:58 PM
RFJ
Registered User
RFJ's Avatar
Northern Ireland
Joined Dec 2004
1,607 Posts
Quote:
The Sig Hog has reduced dihedral
Paul,

I started to build a Sig Astro Hog kit when they first came out but didn't have the heart to finish it - just too many changes. High set tailplane, strip ailerons, too little dihedral and even a tricycle undercarriage.

Being a Sig product the kit was superb and the guy I sold it to still has it today. I did keep the rather nice decal sheet and will probably use some of it on my small version.

Quote:
If I build a 70% Hog, I will use the stock dihedral
....and quite right too. We should all build our models the way we want them

Quote:
I just got a kit of a contemporary of the Hog, the DeBolt Pursuit,
A very similar concept. Note "with built in inherent stability". Not exactly what you want in an aerobatic model - probably too much dihedral

Ray
RFJ is offline Find More Posts by RFJ
Last edited by RFJ; Oct 06, 2014 at 06:16 PM.
Reply With Quote
Old Oct 07, 2014, 03:36 AM
Registered User
United Kingdom, England, Richmond
Joined Apr 2011
81 Posts
Quote:
Originally Posted by RFJ View Post
A very good question Alan
So for me a compromise is necessary. I settled on 5 degrees per side which still looks "too much" but is the maximum I can live with. Sorry to all you purists out there
Ray
I think I could live with 5 degrees per side

Alan
ukengineman is offline Find More Posts by ukengineman
Reply With Quote
Old Oct 08, 2014, 01:29 PM
pd1
Registered User
United States, MA, Haverhill
Joined Jun 2006
2,153 Posts
All the airplanes I've built seem to give the dihedral angle expressed in inches under the wing tip. So I've not gotten familiar with using degrees, I went and measured the dihedral angle of the Pursuit to see what it looked like.

The plans called for 5 1/2 inches under each wingtip and it measure to 10 degrees per panel.
Is that 10 degrees total or 20 degrees total?
I don't want to drag your thread off topic so I'll stop at that question.
Thanks,
Paul
pd1 is offline Find More Posts by pd1
Reply With Quote
Old Oct 08, 2014, 04:11 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,783 Posts
Quote:
Originally Posted by pd1 View Post
All the airplanes I've built seem to give the dihedral angle expressed in inches under the wing tip. So I've not gotten familiar with using degrees, I went and measured the dihedral angle of the Pursuit to see what it looked like.

The plans called for 5 1/2 inches under each wingtip and it measure to 10 degrees per panel.
Is that 10 degrees total or 20 degrees total?
I don't want to drag your thread off topic so I'll stop at that question.
Thanks,
Paul
It's normal when quoting dihedral in degrees to mean the amount on one panel, so in this case you would say "10 degrees". Which is a lot!
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Oct 08, 2014, 06:31 PM
RFJ
Registered User
RFJ's Avatar
Northern Ireland
Joined Dec 2004
1,607 Posts
Quote:
I don't want to drag your thread off topic
Drag away Paul. Got to be more interesting than reading my ramblings

Yes it can be confusing when people don't stick to the convention described by George. I tend to write "X degrees each side" when talking about dihedral.

Degrees are a better measure than inches as they stay the same when you enlarge or reduce the size of the model.

The Smog Hog used 5 degrees each side, still a normal high wing R/E type model figure but I imagine than when these radical aileron equipped aerobatic low wingers were first being tried the designers were playing it very safe with the dihedral hence the excessive angles of 7 degrees each side (Astro Hog) and 10 degrees each side (Pursuit)

Experience soon showed that a low wing aerobatic model with ailerons performed much better with considerably smaller (even zero) dihedral angles.

I also like to see control surface deflections given in degrees but that's another story

Ray
RFJ is offline Find More Posts by RFJ
Last edited by RFJ; Oct 11, 2014 at 08:14 AM.
Reply With Quote
Old Oct 09, 2014, 10:41 AM
pd1
Registered User
United States, MA, Haverhill
Joined Jun 2006
2,153 Posts
I measured the dihedral of my Sig Astro Hog, it measured 10 degrees total or 5 degrees per panel. I like the plane but for a vintage Astro hog the wing seems a bit flat.

Now I'm in a quandary with the Pursuit, 10 degrees really looks funny and 5 looks a bit flat.

I think I'll wait until you show some progress and see how your Hog looks, I'm not looking for performance but a bit more for nostalgia.

Raising the stabilizer, We have always gone with the higher stabs do to having to fly off grass. The cut stalks of grass cut the underside covering of the low stabs quite often.
The high stab is less prone to damage.

Here's a couple pictures of my full sized Hog and a small jpeg of the Pursuit, check out the spar joiner.

You are right, I couldn't go with the tri cycle gear set up either.
pd1 is offline Find More Posts by pd1
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Bill Winter's "Airknocker" for AMPLAN Build Off - finished and flown Sundancer Vintage & Old-Timer Designs 105 Oct 24, 2014 12:47 AM
Build Log Phil Kraft GIMLET, 1956 single-channel low-winger for AMPLAN Build Off JMP_blackfoot Vintage & Old-Timer Designs 33 Oct 23, 2014 03:32 PM
Build Log Walt Musciano's Classy Gassy for AMPLAN Build Off brokenspar Vintage & Old-Timer Designs 68 Oct 14, 2014 06:04 AM
Build Log Howard Bonner 75% Smog Hog for AMPLAN Build Off RFJ Vintage & Old-Timer Designs 67 Oct 12, 2014 05:57 AM
Discussion Ben Shereshaw 1937 "Champion" - AMPLAN Build Off September 2014 to March 2015 cpmcgraw Vintage & Old-Timer Designs 38 Oct 10, 2014 09:30 PM