The Bird-of-Prey Size Paradox
The Klingon Bird-of-Prey ship type was designed by Nilo Rodis of ILM and was first featured in "Star Trek III: The Search for Spock" as the ship of the Klingon villain Kruge. In an early draft of the script Kruge was intended to steal the ship from the Romulans, which explains its name and appearance (inspired by the Romulan Bird-of-Prey from TOS: "Balance of Terror") as well as the fact that the ship is equipped with a cloaking device. The Romulan reference was dropped in the final version, probably to simplify the story. The plausible explanation for the Romulan-Klingon technology transfer (Klingon D7 battlecruisers for the Romulans and in exchange Romulan cloaking devices for the Klingons) is that they formed an alliance in the 2260's, although it was never mentioned in any episode or movie. In spite of the "worn out" look of the Bird-of-Prey studio model it is advantageous to assume the ship type was new as of the 2280's to explain the fact it is still not obsolete 90 years later during TNG and DS9. Since ENT: "The Expanse" we know for sure that the familiar BoP is actually neither a Romulan design nor a design inspired by Romulans, but a 23rd century version of a similar, yet much older genuine Klingon ship of the 22nd century.
Nilo Rodis originally devised the studio model with a length of 360ft (roughly 110m) as illustrated on the ILM size comparison chart for "Star Trek III". However, there are few to no details on the miniature that would allow to verify this figure. A possible approach to determine the ship's dimensions based on its structure is to take the rectangular lights in the BoP nose section and the forward engineering hull as windows. This gives us two decks above the cloaking device bulge and two below. If these decks have a height of 3m each, the intended length of 110m can be confirmed.
The Klingon Bird-of-Prey is the most obvious example in Star Trek for excessive scaling of a starship, sometimes accidental, sometimes intentional. Various designations have been used throughout the years, creating the impression that "Bird-of-Prey" is merely a generic term for the ship's appearance, whereas the actual types or classes are called B'rel, K'Vort or D-12. Many fans take this as a sign that the different types should differ in their sizes too. The following paragraphs summarize the appearances of Birds-of-Prey, their VFX dimensions, names, crew sizes and other details pointing to the ship's length(s). The list is extensive, yet far from being complete. It will be supplemented as new evidence becomes available.
Star Trek III
The Klingon ship is called "Bird-of-Prey class" by Sulu and has a crew complement of twelve. The VFX comparison with the Merchantman is a moot case, because the freighter was rendered much too small apparently just for the dramatic impact of the mighty Bird-of-Prey destroying it. It would require a huge BoP for the Merchantman to be reasonably large, but this would be in strong contradiction to most of the later appearances of the very same BoP (which will become the "HMS Bounty" in "Star Trek IV"). The comparison of the BoP and the Enterprise in "Star Trek III" corroborates the intended 110m for the most part, although it would basically permit a small 60m BoP just as well.
After the ship has landed on Vulcan at the end of the movie, there is a very brief scene with a person leaving the aft exit hatch, pointing to an overall length of roughly 100m.
Star Trek IV
A very similar scene as at the end of the previous movie shows a number of people standing on the hatch of the "HMS Bounty", but this time they appear to be much taller, making the ship only 50m long. On the other hand, the same "HMS Bounty" is said to have a 60ft (~20m) cargo bay, big enough to hold two 45-50ft (>15m) humpback whales. Fitting this cargo bay into a 50m ship is virtually impossible, since the rearward section is just not long enough - especially considering that the aft end is indented and the impulse engines need some room too, at least five meters, rather more. So 60m is the absolute minimum length for the ship, but then the whole engineering section would be nothing but a cargo bay. In this case the question would be what the Klingons need with such a single spacious room on a warship, with all other sections being incredibly crammed?
Another good size reference in the movie is the scene in which the BoP sinks in San Francisco Bay and only the bridge is sticking out. The comparison with the people standing on the cloaking device bulge leaves us with a BoP of well below 50m! It should be annotated that in the case of the aft hatch as well as of the bridge full-scale mock-ups were involved that had to be built large enough to be recognizable but small enough for technical and financial considerations. Still, it is noteworthy that the movie generally attempts to render the BoP as small as possible.
But one scene of "Star Trek IV" paradoxically does the exact contrary of keeping the BoP small. The Klingon ship is huge beyond reason when we see it hover straight above the whaling ship, arguably for the "dramatic impact". If the BoP were only 60m wide (at 50m length), the boat would measure hardly 7m! The boat must be at least 40m owing to its structure (the actual boat, a former mine sweeper named Golden Gate, measures 42.6m), so the BoP is exceedingly scaled up here. Just for fun, we would obtain a width of no less than 330m.
Side note On a side note, not only was the size of the very same ship subject to change considerably from "Star Trek III" to "Star Trek IV". Also the bridge (image of previous configuration) was completely rebuilt. Kruge's "throne" was removed, all stations re-arranged, and even the floor and the walls were moved. This alone would be no problem, if we consider that Klingons, like the Federation, could use bridge modules. But the ship was serviced on Vulcan. Even if we believe that the refit was necessary because of battle damage, we can't assume that the Vulcan engineers or Scotty would have the expertise to do that or would even have another Klingon bridge readily available. As Scotty himself said, "Reading Klingon is hard", suggesting that there are already problems to decipher the manuals for the ship in its current configuration. If we nonetheless insist on them rebuilding the bridge, why are all controls in "Star Trek IV" still in Klingon? The only way for it to make any sense is that the bridge in "Star Trek IV" is actually an auxiliary control room. We wouldn't expect something like that on a 50m or 60m ship, which takes us back to the size paradox.
Star Trek V
There is only one scene together with the Enterprise that allows to establish a size for the Klingon ship. It appears to be about as wide as the distance between the Enterprise's warp nacelles, about 100m. There are also a couple of nice close takes of the ship. One of them shows us the lid on the torpedo launcher as it was arguably present on all incarnations of the vessel, so this is not a distinguishing mark that could help in making up plausible different dimensions.
Star Trek VI
It is obvious that Chang's prototype is supposed to be essentially the same small ship type again. When the Enterprise crew speculate about a cloaked ship that could have fired at the Kronos One, a Bird-of-Prey is the foremost candidate for a ship capable of cloaking, which suggests that this is the only known cloakable ship type at this time. No size can be determined in the battle sequences, as we always see Chang's BoP well behind or in front of the Enterprise or Excelsior.
Subsequently the BoP miniature had several appearances in STTNG, and although the K't'inga-class battlecruiser was available too, mostly the BoP was chosen to represent a generic 24th century Klingon warship. This is the time when the systematic upscaling of the vessel type begins, supposedly to make it look good and threatening enough next to the Enterprise-D.
TNG: A Matter of Honor
This episode shows us an encounter of the Enterprise-D and the Klingon cruiser Pagh. The Pagh's width in attack mode with the wings down is roughly half of the Enterprise-D's width, and from another perspective its length is at about half of the Federation ship's saucer length. Both comparisons result in a length of 230m. The ship's crew is implied to be more than just twelve, although only few Klingons are shown at a time.
TNG: The Defector
The episode appears to show us extremely oversized BoPs, not much smaller than the Romulan Warbirds (some 1200m in length), but at least the size of the Enterprise-D (642m). Yet, the perspective of the scene is deceptive. Actually, if the two BoPs is the background are about as close to the Warbirds as the one in the foreground is to the Enterprise, they would all be about 350m wide, exactly as in most other TNG episodes. Read more about the 3D reconstruction in Suricata's Blog (archived).
TNG: Yesterday's Enterprise
When three Klingon cruisers attack the two Federation ships, one of them can be seen passing by above the Enterprise-D. The Klingon ship (in flight mode, wings horizontal) is almost 400m wide, giving us a length of more than 350m. It is obvious the VFX team intentionally scaled them up so as to pose a visually considerable threat to the Galaxy and Ambassador classes. They might have been aware that a large ship is not likely to have moveable wings (see scaling paradox), so their wings remain in the flight position all the time, like already in the brief take in TNG: "The Defector". Moreover, the new name "K'Vort" for the Klingon vessel may suggest this is a different ship type than the familiar small scout from the movies that was simply called "Bird-of-Prey". It has been speculated for some time that K'Vorts exist just in the parallel reality of "Yesterday's Enterprise". But a K'Vort-class vessel was identified in "our" timeline as well, the IKS Koraga, the lost ship with Worf on board that Ezri went searching in DS9: "Penumbra".
The Vor'cha-class cruiser and the two BoPs in flight mode on either side (namely Vorn and Buruk) all seem to have the same width of 350m. This results in a length of 320m for the BoPs.
TNG: Redemption I
The Vor'cha-class cruiser BortaS is attacked by two Birds-of-Prey. One of them is shown directly above the BortaS and seems to have about the same width as in TNG: "Reunion" (350m) in flight mode, which yields 320m length yet again.
We can see a BoP facing the Enterprise-D. With the BoP being behind the Federation ship, no upper limit can be given for the Klingon vessel. But it seems like this ship is supposed to be the same size as in the other recent uses of the model in TNG.
The BoP is called "B'rel" for the first and only time. It seems obvious that the Ferengi could rather have got hold of small and obsolete Klingon ships than of the supposedly larger and more powerful ships that are shown elsewhere in TNG, namely the supposed K'Vort class. So far the B'rel concept sounds like a good idea. But actually TNG: "Rascals" features two scenes with 350m long BoPs attacking with their wings up, which are stock footage of the BoPs from "Defector" and of the K'Vort-class cruisers from TNG: "Yesterday's Enterprise", respectively. This renders the whole official theory (in the Star Trek Encyclopedia) of the B'rel being smaller than the K'Vort incredible. They are evidently the same size! There is just one other scene with the Enterprise-D and one of the Birds in orbit where the latter is at most 300m wide or 260m long. This too is stock footage (from "Redemption I") but was recomposited and resized.
Summarizing, TNG shows BoP types which are noticeably larger than the movie version (more than twice the length) and which don't have foldable wings on five occasions where we would have expected to see them in attack mode with the wings down. They might be all the same size if an uncertainty range of the visual evidence of some 50% is conceded. Unlike we previously assumed, the BoPs in "The Defector" don't have to be any bigger than that.
DS9: Past Prologue
Lursa's and B'Etor's Bird-of-Prey can be seen next to a Danube-class runabout, and it appears to be about five times as long. This would correspond perfectly with the BoP design size of 110m.
Star Trek Generations
Although seemingly unnecessary, the movie introduces "D-12" as another designation for the Bird-of-Prey type, and Worf says the ships have been taken out of service because of technical deficiencies. This detail shows it is supposed to be a different, most likely smaller and less powerful design than the now familiar large TNG types, which would make sense considering that even the B'rel from TNG: "Rascals" is actually quite large. Still, the D-12 is not as vulnerable as one would expect, after all even a weakened Galaxy-class ship should have been capable of penetrating a small BoP's shields, if not completely destroy it, with two or three phaser blasts and one photon torpedo volley. On the other hand, we are tempted to believe that the ship of the two Klingon women is the very same that we saw in DS9: "Past Prologue" and which unquestionably measured around 110m.
DS9: Way of the Warrior
When the Klingon fleet approaches DS9, there is a number of very small BoPs that are only half the length of a Vor'cha front module. Thus, unlike any other DS9 episodes, it gives us a length of only 50m for the ship. The same can be observed in relation to the Galor class. The BoP that flies by in front of the Cardassian vessel seems to be well below 60m long.
The station Deep Space 9 is anything but a reliable size reference. Yet, we can see that the BoPs passing by measure somewhat less than a tenth of the station's diameter. This would give us about 100m for the BoP with a broad uncertainty range, but definitely substantially longer than 50m. In still the same episode we see a BoP which is almost the same length as the Xhosa, a ship that must measure some 200m.
DS9: Return to Grace
A crew complement of 36 of the BoP is mentioned. This is not necessarily an argument that this particular starship must be bigger than the one from "Star Trek III" with a crew of just 12, but can be taken as a sign that in wartime the Klingon vessels are manned with troops that are not needed on a scout ship on a less honorable and more or less peaceful mission. A helpful size comparison with the Cardassian freighter Groumall is not possible in the episode.
DS9: Shattered Mirror
This is a Mirror Universe episode, and it is rather the Negh'Var that is unreasonably scaled up than the BoP is scaled down. The comparison with a Galor-class ship makes the parallel Negh'Var at least 2,5km(!) long, while the Galor-BoP comparison yields something reasonable between 100m and 200m for the BoP. The Mirror version of the Bird-of-Prey can also be compared to the Defiant, where the latter is somewhat bigger and just as wide as the BoP.
DS9: Soldiers of the Empire
In this and some other episodes Martok's ship Rotarran can be seen docked to the station and is as wide as one outer docking port plus the two neighboring pallets in the rim. Basically, Deep Space 9 is a very bad reference, since the station is routinely scaled up. However, a diameter of 1100m or less would be consistent with the deck structure. This would give the BoP a width of 135m (attack configuration) and a length of 115m, i.e. very close to the BoP's original design dimensions. There is also a close fly-by in DS9: "Soldiers of the Empire" that clearly reveals the above mentioned apparent windows in the nose piece, resulting in two decks above the cloaking device.
DS9: A Call to Arms
Here the Rotarran is roughly the size of the Defiant, maybe a bit shorter. The latter being in dispute as well, this is not exactly a good reference, but at least it demonstrates that the Klingon ship must be noticeably less than 200m long.
DS9: Sons and Daughters
The Rotarran (in flight mode) is around 2/3 the width of a Vor'cha class, giving it a length of a little less than 200m. Martok says he requisitioned 15 new crew members, which implies that the complete crew consists of 30 or more warriors. Furthermore, a deck 5 is mentioned. This is possible with 2.5m tall decks on a 60m or any longer BoP if the decks are counted from the top of the rearward hull. A 110m BoP could have 7 decks of 3m each.
In the same episode we see Klingon BoPs protect a convoy of cargo ships. These Klingon cargo ships are modifications of the model of the Cardassian freighter Groumall, and in relation to the BoP they are considerably larger. A much better relative size estimation is possible with the Jem'Hadar fighters, however. The dimensions of these Dominion ships are anything but clear. Anyway, the camera shows the latter in front of as well as behind the Klingon Bird-of-Prey. The two ships appear to have almost the same width, with the BoP being perhaps a few meters wider. In this case both ships would have about the same length.
DS9: Sacrifice of Angels
BoPs appear at the scene of the battle for Deep Space 9 and join the Federation forces. The Klingon ship appears to be somewhat smaller than the Defiant, but with a wider wingspan. And both ships are dwarfed by the Jem'Hadar battlecruisers which are irrationally huge on this occasion.
DS9: Tears of the Prophets
At the beginning of the battle for Chin'toka Jem'Hadar fighters begin to ram the Klingon fleet in suicide attacks. Here they look considerably smaller than the BoPs, unlike it still was in DS9: "Sons and Daughters". The Dominion vessels would be considerably less than 100m long assuming a length of 110m for the BoP. Well, they could be 150m long, as sometimes stated, if these BoPs were the big ones from TNG.
DS9: Once More Unto the Breach
The Rotarran can be seen docked to DS9 again, this time from another perspective. The ship may be a bit wider than in "Soldiers of the Empire".
It is remarkable that no big BoP appears in any DS9 episode, except for one appearance of a 200m Rotarran in DS9: "Sons and Daughters", whose length is otherwise consistently 100-150m. David Stipes, Visual Effects Supervisor, gives the VFX length of the Rotarran as 450' = 137m in a newsgroup post (see Starship Size Table), while there is also a small BoP of allegedly 360' = 110m which corresponds with the original design length. It seems entirely unnecessary to create another, slightly different scale for the Rotarran just for the reason that this one ship should look good next to the Defiant.
According to the Star Trek Encyclopedia I there are two sizes of Birds-of-Prey: the smaller B'rel class ("Star Trek III", TNG: "Rascals") and the larger K'Vort class (TNG: "Yesterday's Enterprise"). The B'rel is depicted in a size comparison chart together with other Klingon ships, the length is 110m. The size of the K'Vort-class is not specified, nor are other appearances except for "Yesterday's Enterprise" mentioned.
The Star Trek Encyclopedia II depicts an alleged K'Vort-class BoP somewhere between 130m and 160m in the "Ships of the Galaxy" chart. See the Starship Size Table for further comments on the chart's reliability. The class name is an obvious mistake taking into account that it is postulated everywhere else in the book that the B'rel class should be the smaller type and the K'Vort class much bigger. The chart remains untouched in the updated Encyclopedia III.
The Star Trek Fact Files have various entries about the BoP, but they largely conceal the size paradox. The official two sizes (B'rel and K'Vort again) always share the same description, and the impression is created that all BoPs have moveable wings and are capable of atmospheric flight and landing. File 34/1 mainly portrays the small BoP, where "B'rel" and "D-12" are used synonymously. The length is said to be only 51.2m. The size comparison in the same file, on the other hand, shows a K'Vort type along with the Enterprise-D, resulting in a length of 320m for the Klingon ship, which would be consistent with TNG: "Yesterday's Enterprise", "Reunion" and "Redemption". The crew of the small ship is given as 12 (standard) to 24 (maximum). File 34/1C depicts a size comparison between a D7 battlecruiser and a nonspecific BoP, where the latter is 110m long. File 34/1D states that a "larger BoP" may have a crew complement of up to 35.
Finally, the DS9 Technical Manual tops all size figures with a length of 685m for the K'Vort-class BoP (consistent only with the exceptionally large ships in TNG: "The Defector", if we still believe in them), whereas for the B'rel a new figure of 158m is introduced. Most likely this medium-sized BoP was originally intended to be of the aforementioned VFX length of 137m, but was accidentally increased. The error probably occurred because the depiction of the Vor'cha in the Star Trek Encyclopedia II size chart is too small relative to the other ships, but Rick Sternbach took exactly this one to determine the other ship sizes in the DS9TM, which therefore appear too large. Further implications of this error are discussed along with the Starship Size Table. The DS9TM also provides a different armament for the K'Vort-class BoP (4 instead of 2 disruptors, 2 instead of 1 photon torpedo tube), which is not viable if the ship looks the same as the B'rel.
The screen evidence reveals several different sizes of Klingon Birds-of-Prey, and the official publications promote the idea of at least two distinct types. All names for the ships are problematic, since they are used only occasionally and, moreover, the B'rel was never shown as being smaller than the K'Vort. Yet, fandom solutions create up to seven(!) types and sizes of BoPs, namely the tiny ship seen only in DS9: "Way of the Warrior" (35m), the small scout from "Star Trek III" (50-60m), the D-12/B'rel (110m), the Rotarran (137m according to Stipes), the IKS Pagh (230m), the K'Vort (some 300m) and finally the huge "Defector" and DS9TM BoP (>600m). Some sources even feel the necessity to establish a difference between the 110m BoP and an 88m variant. This reasoning does not take into account that VFX inaccuracies don't allow a distinction of a 110m and a 135m BoP anyway. Moreover, occasionally even one and the same ship (like the Rotarran and most obviously the HMS Bounty) was shown with different dimensions that were further apart than the figures in the above list. Seven or eight sizes is definitely far too much variance. We also need to consider that larger and smaller constructions inevitably require at least slightly distinct shapes in order to avoid the scaling paradox. The number of different sizes has to be minimized, if not reduced to only one size.
The design size of the BoP as evidenced by the scale chart and window rows is consistent at 110m, and the screen evidence from "Star Trek III" largely favors this size. "Star Trek IV" shows the very same "HMS Bounty", but this time it is sometimes at most 60m. On the other hand, the BoP is capable of carrying two humpback whales, and the 60m warship could hardly have the shown huge cargo bay. This is a reason to favor a 110m size for the Bounty. Another point is that the Rotarran also works at 110m if the Defiant is 120m long and DS9's diameter is 1100m, which corresponds to their supposed design sizes. With these dimensions it would be no trouble to accommodate 36 instead of 12 crew members, even if the cargo bay remains that large. The Rotarran is somewhat larger than 110m in comparison to the Vor'cha in DS9: "Sons and Daughters", but this has to be ignored for the sake of overall consistency. Another problem is the very small BoP in DS9: "Way of the Warrior". Although it can't be a factor in the reflections on the "real" BoP sizes, it can be exposed as careless VFX, because there has never been any other 50m BoP since the definitely wrong one in "Star Trek IV". Moreover, the small BoP on Vulcan and in the water in the latter movie have to be regarded as errors anyway, so this should be possible once again.
These ships appear in a number of TNG episodes and are increased to dimensions of 230m ("A Matter of Honor"), 320m ("Reunion", "Redemption") and 350m ("Yesterday's Enterprise", "Rascals", "The Defector"). The 230m Pagh could be interpreted as a small BoP of 110m, since the screen evidence is not that clear-cut and this one ship has moveable wings. There are two practicable explanations for the other five ships:
1. The five large BoPs are substantially different and much larger types, with K'Vort class and B'rel class being evidently the same size. Due to the lacking resolution of the TV screen they nevertheless appear to have the same hull profile as the much smaller movie type (D-12 class). The large BoPs, namely the practically identical K'Vort and B'rel, have fixed wings and they are obviously serious threats to a Vor'cha, Galaxy or D'deridex class. There is naturally only one size of large BoPs. The length is most likely around 350m. The large BoPs don't appear any more after the time of TNG, which could mean all of them, like the B'rel, are obsolete by then, while the smaller type is still in service.
2. The three large BoPs are actually the same size as the small ones, they only appear enlarged by a weird "lens aberration". Sometimes the BoPs seem to be reduced in size likewise. There might be different types or classes of BoPs, but the hull is always essentially the same size. It is possible that some BoP types don't need to change to a special attack configuration of the wings and are better equipped so as to be a match for much larger ships. The only BoP length is 110m.
The "Titius-Bode" Law of Klingon Ship Sizes found by Mark Dezaire
I was contacted by Mark Dezaire who explained to me his stunning finding that the length ratios of different Klingon ship types are following a similar rule than the planet distances in our solar system - the Titius-Bode Law which is still unexplained although it doesn't look like a coincidence. Well, the "official" Klingon ship sizes are most likely coincidental because too many different people messed around with them, but it's interesting nonetheless.
This is what Mark told me:
"When I was reading the chapters concerning (wrong) ship sizes and the Klingon Bird-of-Prey size paradox, one of my first thoughts was that the larger BoP could be exactly three times the size of the smaller BoP. Then I thought: maybe there is a simple formula for calculating the length of (all?) Klingon ships. After a little time I came to the following 'solution': take the number of the size of the smallest ship, and multiply that, again and again, by the cubic root (I don't know if this is the correct English term for it, I don't even now what it is called in my own native language Dutch) of 3 (= 1.4422496).
Now, if you take for granted that the small BoP measures 360 feet (109.728 meters), then you get the following numbers (in meters):
109.7 - 158.3 - 228.2 - 329.2 - 474.8 - 684.7
Most of these numbers resemble very much certain actual Klingon ship sizes that are either canon or that are 'educated guesses'. I'm not saying the Star Trek people (writers, designers etc.) have a hidden agenda concerning what Klingon ships sizes should be, but my numbers don't seem very unlikely, don't you think so? Of course, there might be Klingon ships with different sizes that have been or have not been (yet) on television; and I think you and others are right when you are saying that, for dramatical purposes, some ship sizes are clearly wrong; but on the whole I think my solution is rather simple and effective."
So we have the following sizes, all separated by the cubic root of 3:
109.7m - exact original design size of Klingon BoP
158.3m - roughly the size Martok's BoP is supposed to (although it should be actually the same size as all small BoPs!)
228.3m - exact length of D7 cruiser
329.2m - length that the BoPs seemed to have in TNG
474.8m - almost exactly the length of the Vor'cha class
684.7m - length of the Negh'Var (and of the DS9TM BoP)
Klingon Ship Classes - from all eras
Starship Gallery - Klingon Bird-of-Prey - Scout, D-12, B'rel, K'Vort or whatever name you prefer
Some screen caps by Jörg Hillebrand. I am grateful to Boris S. for invaluable discussion. Special thanks to Jack Bohn for allowing me to use his screen caps. See Jack's analysis of the BoP sizes. Special thanks to Mark Dezaire. Finally, a big thank you to Suricata for reconstructing the scene in "The Defector" in 3D and Jan Kockrow for his anylysis of the fly-by in "Star Trek V" and other annotations.