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  • March 29, 2024, 07:12:47 AM

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Author Topic: Comparing weight of Sterling S2 P51 to the Brodak version of the same kit  (Read 2021 times)

Offline Dennis Holler

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We all know the old die crushed kits could be heavy, even real heavy..  I had a partial original Sterling kit  and originally was thinking of buying the rib kit from Brodak since I was missing the wing parts.  But I had a moment of weakness and bought both a rib set and a Brodak P51 kit  LL~

So the nicely packaged Brodak box of stuff showed up  while I was traveling for work.  I also got one of the Dihedral kits because I want to try that out as well.  I may go order another of those for the second plane lol.

So the fun part, I weighed the Sterling brick and the Brodak Balsa....  The Sterling was 3 times the weight.  Sterling fuse 158g and the Brodak 56g. I also checked the stab and it was also 3 times the weight, 24g to 8g  LL~ LL~

At least they more or less match in shape profile  y1
I've started plenty...would be nice to finish something!!!

Offline kenneth cook

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                 I just built my Sterling P-51 which I've owned for years. I covered the fuse and tail feathers with silkspan. The airframe with paint minus engine and wing covering is now at 12.5 oz's. I don't think that's too shabby for a Sterling kit. The only change I made was to replace the crap plywood with my Sig ply and delete the center spar.

Offline Dennis Holler

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That is great. Maybe it is safe to say there was a range of quality with the Sterling kits?   I don't doubt your build for a second.  I'm well aware there can be some variation in these old kits.  Just thought what I measured was pretty extreme!  Here are the pictures after a resize to fit the forum limits.

Will be curious how the weight compares between my Brodak kit and the Old Sterling wood with a Brodak wing rib kit in it.
I've started plenty...would be nice to finish something!!!

Offline BillP

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That weight difference is interesting. I wonder if the rib thickness on the Brodak kit is the same as originally on the Sterling kit?
Bill P.

Offline Brett Buck

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That weight difference is interesting. I wonder if the rib thickness on the Brodak kit is the same as originally on the Sterling kit?

   I wouldn't doubt it - I have had very recent experience comparing old kit wood to decent balsa, and at least some of the kits had wood that was in the range of 2-3x what we would normally use as the "medium" wood. These were Top Flite, not Sterling (or worse, Jetco or Dumas), but more-or-less all the manufacturers had similar issues.

   The other thing that struck me was how much it varied from kit to kit and sheet to sheet. Say, two kits that had two sheets of ribs per kit. 3 of the 4 looked like mahogany, other like perfectly usable medium-light wood.  It's absolutely no surprise that no two of them ever flew the same.

       Brett

Offline Dennis Holler

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Well, like we say about vintage trains when people ponder on variations or quality.... They were making toys for the most part and volume and cost were probably the only keys that mattered.
I've started plenty...would be nice to finish something!!!

Offline Paul Smith

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Back in the day, the issue was the kid getting something into the air, not saving a ounce or two to gain advantage in a stunt contest.

Did you ever consider that the guys working in the kit factory skimmed-off the light wood for themselves?

Circa 1960 we didn't own personal postal scales.  Those who cared about weight might take the model the nearest friendly grocery store and try to get it weighed on the meat scale.
Paul Smith

Online Ken Culbertson

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Back in the day, the issue was the kid getting something into the air, not saving a ounce or two to gain advantage in a stunt contest.

Did you ever consider that the guys working in the kit factory skimmed-off the light wood for themselves?

Circa 1960 we didn't own personal postal scales.  Those who cared about weight might take the model the nearest friendly grocery store and try to get it weighed on the meat scale.
I am agreeing with Paul.  Nobody really cared about weight back then unless you were well into pattern flying.  The first time I picked wood and built light was my 1964 Nats plane and even then it was never weighed until I was at the Nats.  I was 17 and I had already built most of the Sterling and Goldberg profiles.  Now I weigh everything!

ken
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Offline Dennis Holler

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At my current skill level, it probably doesn't matter much lmao  LL~
I've started plenty...would be nice to finish something!!!

Offline Brett Buck

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At my current skill level, it probably doesn't matter much lmao  LL~

  It is pretty rare for it to make all that much difference at any level, and I have only rarely seen airplanes that did not fly acceptably well *just* because they were too heavy. Not unheard of, but not common. That's because of other, resolvable, problems with trim and power are far, far mode common. It's particularly bad because when someone weighs the airplane and they declare it "too heavy", they tend to give up on it, rather than make the changes necessary to get it working as well as possible.

   Weight does make a difference at some point, but I have seen a lot of stunt contests, even the very biggest, won using airplanes that the typical Advanced flier would have long since discarded due to weight. This is particularly true since power has become unlimited.

   There are still people who think they can determine how good the craftsmanship is by weighing it, so, there are certainly differing views. In my very recent experience, however, even I have to draw the line on some of the old kit wood - you can't have a 35-sized fuselage side that weighs an ounce and a half and has the consistency of red oak!

       Brett

Offline Dennis Holler

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You make a very good point as when I was getting back in a few years ago ( short dip unfortunately) I was making things harder than need be, over analyzing I think.   Just a simple Ringmaster but I was messing with it and finally got it so tail heavy I could barely keep it in the air.  Fortunately, I listened to the fellows I was flying with ( The Sheeks Indy crowd) and removed the anchor I had thought I needed on the tail and frankly that was pretty much it.  I got it balenced correctly finally with their help and the darned thing flew nice and flat with none of the hunting and darting I had been seeing before.  I just used old wood when I built it and I am pretty sure it is heavy compared to many of the well built Ringmasters I have seen on here.  But like you said, it still flew well and served it's purpose.  So now after another 6-7 year break, It will serve again and then hopefully these two P51's allow me to have some fun with flaps...

Maybe the question I should ask for reference only is what do finished examples of that P51 weigh?
I've started plenty...would be nice to finish something!!!

Online Dennis Adamisin

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Dennis H

Your weight comparison is...BRUTAL!  I do not think there is any other part of the Brodak that does not use less wood than the Sterling either so each sub-assembly should repeat what you discovered on the fuse.

BTW, I finally completed my Brodak F-51 which was the build prototype for the wing mods (Dihedral & wing gear) and the electric conversion package.  Here's a few pix to help keep you going - wing mods sure help it look like a Mustang!

Of course you can also do just the dihedral and keep the kit's fuse gear for durability and possibly a weight save.
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Dennis Holler

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Love it Dennis!  I plan to add both the wide gear and the dihedral to my planes.
Hey what source did you use for the checkerboard on the rudder?  One of the schemes I am looking at has the same pattern but also wrapped around the nose as well.
I've started plenty...would be nice to finish something!!!

Online Ken Culbertson

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Here's a few pix to help keep you going - wing mods sure help it look like a Mustang!

I love that rendition!  Can you answer a couple of questions on the Brodak?  Is the Airfoil the Sterling one?  If it is, do you think it would be any better if I sheeted the LE and added capstrips to give me an extra 1/8" thickness?  I have had two or three of the Sterling Mustangs and an equal number of the Yaks but never with wheels or dihedral.  It really looks better, a lot better.  Also can you elaborate on the motor mount. It looks in the pictures like a rear mount with standoff posts, RC style.  That makes it easily adjustable and I like adjustable!

Ken   
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If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Online Dennis Adamisin

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Hey what source did you use for the checkerboard on the rudder?  One of the schemes I am looking at has the same pattern but also wrapped around the nose as well.

Deep research.  I had a piece of Monokote checkerboard Trim Sheet in my scraps bag and I thought it would be an easy way to trick out the rudder in a sorta realistic way...
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Dennis Holler

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Deep research.  I had a piece of Monokote checkerboard Trim Sheet in my scraps bag and I thought it would be an easy way to trick out the rudder in a sorta realistic way...

 LL~ LL~

Ahh that works you know!

I've started plenty...would be nice to finish something!!!

Offline Brett Buck

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I just used old wood when I built it and I am pretty sure it is heavy compared to many of the well built Ringmasters I have seen on here.  But like you said, it still flew well and served it's purpose.  So now after another 6-7 year break, It will serve again and then hopefully these two P51's allow me to have some fun with flaps...

  Or at least find out why you need larger tail volume when you have flaps...

   BTW, while it is very common to overestimate the value of reduced weight - a Sterling P-51 is not a good case to test this theory!  It's tiny and dense even at the best of times.  Unfortunately, much like the Ringmaster, there is very poor structural design and if you attempt to lighten it too much, with "contest" wood and carving away on things, it is very likely to come apart in any sort of cornering.

   The airplane would benefit from the speed stability of a small modern engine with a low-pitch prop, just to keep it flying in the corners. This might make it nose-heavy because they weigh more than an unmuffled Fox or similar.

    So, again, don't get too clever, build the airplane as you want and adjust from there. Enjoy them for what they are - fun-flying sport planes from the dawn of time.

     Brett

Offline Gary Dowler

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We all know the old die crushed kits could be heavy, even real heavy..  I had a partial original Sterling kit  and originally was thinking of buying the rib kit from Brodak since I was missing the wing parts.  But I had a moment of weakness and bought both a rib set and a Brodak P51 kit  LL~

So the nicely packaged Brodak box of stuff showed up  while I was traveling for work.  I also got one of the Dihedral kits because I want to try that out as well.  I may go order another of those for the second plane lol.

So the fun part, I weighed the Sterling brick and the Brodak Balsa....  The Sterling was 3 times the weight.  Sterling fuse 158g and the Brodak 56g. I also checked the stab and it was also 3 times the weight, 24g to 8g  LL~ LL~

At least they more or less match in shape profile  y1

A few years ago I had a Sterling Flying Fool kit.  I used it as a template, but then scaled it up 25%.  The H Stab/ elevator from the original were 1/4" "balsa", while the pieces for the enlarged version were 3/8".   Despite scaling it all up 25%, and going up 50% in thickness, the new stab/elevator weighed exactly half of the original kit wood.  Scaled up, top wing stretched a rib on each side (45"), added flaps,  Thunder Tiger 46 Pro for power and three line throttle and it weighed 54 oz.   Built from the kit wood the original size version would probably have been just as heavy.

Gary
Profanity is the crutch of the illiterate mind


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