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Old 08-18-2017, 11:49 AM   #51
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Originally Posted by DavePittsS2E View Post
If you are speaking of N4MG it was # 16 and built in 1974. Don't know what the empty weight was. I do believe it was Ceconite but not sure. Maybe N95R was cotton.

Yea Dave my memory isn't perfect. Cotton/Ceconite? Could be? I stopped by the liquor store a couple times when Meyer was covering N4MG and was surprised that he was using cotton so it makes sense that he might have also used cotton when he rebuilt 95R?

#23 is still firm in my mind, don't know why? 1974 is what I recall anyway....

Did you ever see that "Blue Angel" S1C?

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Old 08-18-2017, 12:41 PM   #52
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Thank you Jay,I back up all you have said.
A lite weight ultimate is by far the top of performance range in any 4 cly biplane
Danny Bond


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Old 08-18-2017, 01:15 PM   #53
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Some places where Curtis saved weight are less than obvious. The cabanes need to be 1" x 035" SL tube but the landing gear has 1" x .049" SL tube. The factory plans show the same wall thickness for both. How do I know this? I talked to Curtis about it after I discovered .035" wall tube was used for the cabanes on one of my projects. He told me it was fine as-is and they only changed to .049" so they could stock one size of tubing instead of two. The old (1967) long fuselage S-1C plans I have show the two different sizes for the cabanes and the main gear legs. How much weight are we talking about here? 1.6# according to my quick calculation. That's 1.6# a factory airplane will always carry that a Homestead airplane didn't.

There are other examples like the wing tips -- changed from 1/16" plywood to FG parts by the factory at some point. Are they a little heavier? I'm betting they are. Nosebowls, wheel pants, turtledeck, etc. It all adds up. And the finishes the factory used could add a few more pounds. Curtis used zinc chromate on the steel, the factory used epoxy. The factory put a nice finish on the fabric, better than the typical Homestead airplane. If it has a canopy that's an adder as is a top wing tank and the plumbing that goes with it. I'll guess the Christen oil and fuel components added some weight too over what was being done in Homestead.....

There's no way an airplane built from factory parts will be as light as a Curtis-built airplane. They're different in too many ways.
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Old 08-18-2017, 03:48 PM   #54
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The factory nose bowls were thick glass and then had an aluminum tube glassed around the perimeter. Plenty of wt. there to cut. I'm wondering how many stock afton built S1's exist, probably not many.
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Old 08-19-2017, 10:55 PM   #55
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I agree with everything Bill said. The landing gear tube that the bungees wrap around was changed at some point. Relatively short tubes but the increase in wall thickness was very significant. I used the lighter tubing in my S1 and never had a problem.
Also the earlier airplanes including most S1C's had fabric on the sides and belly in the cockpit area. The Homestead airplanes had fabric covering on the gear V's. The list goes on and on.
As far as an Afton fuselage, when Herb Anderson was manager he built a fuselage for me that had a long list of items left off. All secondary structure, the most significant was the battery support structure. I used the S1T method of sheet metal supports, aluminum angles and partial bulkheads, held in place by nylon clamps.
The added weight of the Afton doped fabric finish can be very significant.
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Old 08-19-2017, 11:00 PM   #56
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Afton at some point added reinforcing straps to cabanes at six locations. Totally unnecessary. The lower rear wing fitting mod is not necessary if the fitting is properly built and installed. Most if not all of the cracked wing fittings were caused by over tightening the wing attach bolts as Kevin has mentioned.
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Old 08-19-2017, 11:37 PM   #57
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Afton at some point added reinforcing straps to cabanes at six locations. Totally unnecessary. The lower rear wing fitting mod is not necessary if the fitting is properly built and installed. Most if not all of the cracked wing fittings were caused by over tightening the wing attach bolts as Kevin has mentioned.
Can you tell me more about why the cabane straps/gussets are not necessary? I've got them templated out right now, and have been told that they help with cabanes walking apart over time. The plans don't call for them, but just about every bare fuselage I've seen has them.
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Old 08-20-2017, 12:30 AM   #58
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....have been told that they help with cabanes walking apart over time......
That's a new one on me, I'd love to hear some details. And I thought I had heard all the stuff people think is wrong with the Pitts design.

Update: As of 1988 the factory didn't seem to include finger straps on the S-1 airplanes.
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Old 08-20-2017, 01:50 AM   #59
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That's a new one on me, I'd love to hear some details. And I thought I had heard all the stuff people think is wrong with the Pitts design.

Update: As of 1988 the factory didn't seem to include finger straps on the S-1 airplanes.
I apologize for the thread drift, and I look forward to an education:
The plans call for no straps, and no horizontal cross member between the two upright cabanes. Here's what the 1972 1-210 drawing looks like, as drawn by VR3:
http://vr3.ca/Kit%20PDF/39212.PittsS...m.pdf#view=Fit

Yet factory fuselages, and most flying Pitts, seem to have a forward / aft horizontal spreader near the cabane pins (for example, http://www.biplaneforum.com/showthread.php?t=15190), and some of them also have the bottom cabane clusters finger gusseted. Finger gussets are suggested in 43.13-1b as a way to repair damaged clusters, but don't seem to appear in the plans for these clusters. There was an AD for S-2s cracking longerons at this cluster (http://acro.aerobaticsweb.org/ac_inf...ad_30mar98.txt), which is probably what led to all of the finger gusseting of S-1 cabane clusters. The finger gussets often look like http://www.merlinengineers.co.uk/images/A10.JPG at the top, and http://i.imgur.com/qZQ2nuZ.png (an example from 43.13) at the bottom.

The S-1S drawings were no longer updated by the 1990s (or even the 1980s), which makes it hard to be certain about what the factory was thinking then. The horizontal brace made sense to me as an attempt to keep the cabane pin to cabane pin distance from changing, the top straps would match the landing gear pin retention straps (230-11 and company), and the bottom cabane gussets would make sense as an attempt to reenforce the longeron/cabane/diagonal cluster. I think I'm probably doing more then my share of trying to justify someone else's engineering here, so I'd really like to hear your opinion.
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Old 08-20-2017, 02:43 AM   #60
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here is a short vid...a half loop with 10 consecutive nose high harrier type rolls started at 60mph and ending at 80 mph..It's alot of fun.

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Old 08-20-2017, 01:55 PM   #61
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..........Yet factory fuselages, and most flying Pitts, seem to have a forward / aft horizontal spreader near the cabane pins
Yes, that's one structural change but it was not done at the factory until the T model (and I'm not sure when -- were the early production T's so equipped?). All the S and C models sporting those braces were done by the builders or owners. The factory solution for the problem the braces address was the flanged front upper wing fittings.

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and some of them also have the bottom cabane clusters finger gusseted.
That may be true but the factory didn't add these AFAIK.

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Finger gussets are suggested in 43.13-1b as a way to repair damaged clusters, but don't seem to appear in the plans for these clusters.
43.13 does not trump the factory's type certificate. The airplane was engineered and the cabanes did not benefit from finger straps so they were not used. Adding them would not be anything more than adding weight IMHO. There's no structural weakness they address that I'm aware of.

The S-2 AD is specific to that airplane.

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The S-1S drawings were no longer updated by the 1990s (or even the 1980s), which makes it hard to be certain about what the factory was thinking then.
I have seen factory fuselage drawings updated in 1988 and those show no finger straps anywhere and the cabane brace only on the T fuselage. As I mentioned above, the solution for the S was the fitting change to the upper wing. If someone knows of a factory ECO for finger straps on the S-1 series I'd love to hear about it.

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The horizontal brace made sense to me as an attempt to keep the cabane pin to cabane pin distance from changing, the top straps would match the landing gear pin retention straps (230-11 and company), and the bottom cabane gussets would make sense as an attempt to reenforce the longeron/cabane/diagonal cluster. I think I'm probably doing more then my share of trying to justify someone else's engineering here, so I'd really like to hear your opinion.
You have to keep the cabane loads and their design separate from the landing gear loads that set of solutions. Apples and hand grenades, Same with the S-2 upper longeron AD, that's a different airplane than the S-1 -- the unbraced bays in the cockpit are much longer and I'm sure have different deflections than an S-1.

I'll be using a cabane brace and not the flangged fittings on my airplane. No finger straps are planned.
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Old 08-20-2017, 11:36 PM   #62
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The flanged upper front fittings did not work out very well. Mine bent despite the flanges. The connector tube between the top of the cabanes allows the loads to be shared between both front and rear spars and should eliminate fitting bending.
The connector tube is one of a very few examples where something added to a homebuilt S1 was actually worthwhile.
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Old 08-21-2017, 01:41 AM   #63
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Here's one!
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Old 08-21-2017, 02:18 AM   #64
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Here's a picture of N22XP taken in the mid 70's. It clearly shows the upper cabane tie in brace. It was welded into the ''v'' of the cabanes. The airplane didn't have an upper wing tank.

Bottom picture shows the tie in brace and the center section cut out. The cut out was not replicated in the Afton T models 10 years later but the cabane tie in brace was smaller diameter, thicker wall tubing welded to the left outside cabane area to allow for fuel tank/smoke oil plumbing if the upper tank was installed.
BillThomasandN22XP#2.jpg   CurtisPittsandN22XPPittsS-1T.jpg  
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Old 08-21-2017, 01:04 PM   #65
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"S-2 upper longeron AD"

My understanding is that the longerons were breaking because some S-2 drivers thought that the S-2's were as unbreakable as the S-1's. They found out the hard way that snaps at stupid speeds overstressed that location on the airframe. If I recall correctly one S-2B landed with both upper longhorns broken and something like a 3" air gap behind each of the rear cabane welds.

Best of luck,

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Old 09-18-2017, 04:49 PM   #66
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I remember flying an S1 with Ultimate wings and cowl and what I noticed over stock S1 is unbelievable roll rate!!! Beyond that it seemed very draggy even tough the cowl looked much more streamlined it didn't seem to help. Later I helped Delmar Benjamin with the "smile" cowl that is now the Wolf cowl, installed RV3 gear legs and had a 150 mph cruise with fixed pitch and later went to CS (had to move wings forward) and had a nice cross country cruise of 175 mph. You could take off, pull to vertical 4 point, hammerhead and come back across the bottom at 240. That was clean.


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