Saturn V Fin
I have heard modelers wonder why the Saturn V would have fins at all. Should it not be a relatively easy task to "stabilize" a vehicle like the Saturn V in much the same way that finless missiles and space launchers are? Just how much stability can the almost insignificant fins add to the Saturn V?
The truth is, a lot of time was spent on studying finned and finless versions of the Saturn V particularly with respect to anticipated configurations of the vehicle to be used after the initial lunar landing missions. These configurations included massive third stages of 33-foot diameter, various nuclear-powered upper stages, and stretched versions of the basic vehicle. There was even some consideration after the Saturn V began flying to eliminate the fins to achieve higher performance, particularly in the Saturn's ability to lift ever-heavier payloads. But, when budgets were cut and it was evident the Saturn would have little use after the one proposed Skylab loft and the idea of a finless Saturn V became pointless.
The fact is, all Saturn V vehicles had fins and so, as modelers, our choice is simple. The real issue is just how accurate do you want to be?
Like the engine fairings, the dimensions of the fins as they actually flew varies considerably from the many various sources of dimensional information both from sources in the Saturn V era and newer commercially available or online sources.
Fin Construction and Details
In particular, the fin had a considerable taper in thickness from its root (over 15") to a fin tip thickness of 4". Many data sources typically list the root as too thin and the tip too thick. Also, by clicking the photo above of the "B" fin (click photo for enlarged view) of the Saturn V on display at Johnson Space Center, you will note the interesting construction of the trailing edge of the fin. The two projections along and aft of the spar line are steel fin handling lift points which, in the photo, have rusted considerably after years of exposure in the Texas elements (the vehicle is now indoors) and are removed for flight.
The factory photo (above right...click photo for enlarged view) is of one of the S-IC-3 fins while it is being fabricated. It is included to give a reference for the arrangement and location of its interior structure and the positioning of rivets on the exterior of the fin.
Though not mentioned in most documentation, even the fins were instrumented with various temperature and strain gauges with the electrical connections passing from the fin and into the fairing to which it was attached at the fin spar. A single trapezoidal cover for access to these connections is provided on one side of each fin just aft of the fin spar.
The primary structural attachment for the fin was via eight bolts through the fin spar which attached it to a semi-circular forging under the fin fairing which itself was attached to the aft end of the thrust structure. Furthermore, the fin was attached to the fairing along the entire length of the fin root via bolts and rivets spaced approximately 1-inch apart through 1.5-inch tall external stringers (themselves riveted to the fairing) on either side of the fin.
The internal structure of the fin is primarily of stamped and forged aluminum components while the fin skin is of titanium. Four sheets of titanium compose the covering for each side of the fin with three sheets covering the fin forward of the spar and a single sheet aft of the spar.
The leading edge is machined from solid titanium and has a leading edge radius of .25" across the entire span of the fin.
Dimensioned Fin Drawing
The downloadable drawing (below) is based on NASA/Manufacturer data which is verified by actual measurement of the dimensions of the fins on the Saturn V located at Johnson Space Center in Houston, TX. The dimensions measured were the fin tip thickness and length, trailing edge length, trailing edge root thickness, and length along the root edge of the fin. Any dimensions derived from geometric construction within the CAD program used to generate the drawing are indicated by "(Calculated)" next to the derived dimension on the drawing. All other dimensions are from NASA/Manufacturer data and copies of engineering drawings from microfiche.
The location and number of rivets on the drawing are the result of careful examination of many photographs where the individual rivets are clearly visible.
Saturn V Fin dimensions and rivet details (GIF File)
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