Bows:From the Ground Up

[Nymdok]

Optional Additional Rules:

Crosssection: The D shaped cross section is the WORST possible shape and, sadly, is how english Longbows were made.

If you have a bow with a rectanuglar cross section, increase the length in Range and Damage calculations by 1/5 of its braced height.

Composites:
Historically, these were made with glue from animals. This makes them VERY susceptible to humidity. The ancient Chinese dried their bows for 6 months, the Turks for a Year! Roll against the HT of the bow for every Day in a high humididty environment (Jungle, Beach etc). On a failure it delaminates on the next pull rendering it useless!

To keep these numbers consistent with basic set, assume the Composite bows in the basic set have a recurve and a rectangualr cross section. For the players that do not want their bows recurved and rectangular, refer to them as Laminate bows as a more general term.

The Archers Paradox and Arrow Spine:
For ST higher than 14 all arrows must be custom made to fly straight. Multiply arrow cost by 10. For using regular arrows in High strength Bows, it is minus one for every 2 ST. A ST 14 bow using normal arrows results in a skill penalty of -2. Crossbows are NOT subject to this as they are centerfire weapons.

The One Second Pull: If your BL x 4 is double the draw strength of the bow, you may treat that bow as Shots 1(1) Meaning that with Fast draw arrow, you may fire an Arrow every turn!
Example: A ST 10 bow requires a 80# pull. A ST 15 charachter pulls at 180# and may (if he either has an arrow ready or fast draws one) Fire this turn.

Recurve makes it shorter: A recurved bow, due to its curvature, packs more wood into a shorter braced length. Treat as 1/5 longer than its braced length when calculating weight, range, accuracy, and Damage.

Essential Wood: For a bow with essential Wood cast upon it (For self bows) use TRIPLE the Specific Gravity in the calculations for Draw strength, but NOT bow weight.

Length and Accruacy:

This is just a basic Curve fit to match the Numbers in the basic set, but it leads to some interesting results.

Accuracy = 2.7-12*(Bowlength/ArcherLength -1)^2 (round)

THESE DO NOT APPLY TO CROSSBOWS.

Length and Damage:
GURPS allows longer bows to do more damge with the same arrows, Independent of ST. For every 1' increase in length, increase Damage +1. For every 1' decrease below 4' decrease Damage -1.

Length and Range:
This one is also tough, but Gurps Does allow Longer Bows more Range so we continue with their convention. 1/2 d range Multiplier is 2.5 times the length (Rounded to nearest 5) and Full range Multiplier is Length * 3.5 (again rounded to the nearest 5)


Length and Bulk:
Bulk is also dependent on the Weilder and Must be mated to the his size. Length of bow = to height of weilder is bulk -8. For every 1/3 of your height this increases, increase this penalty by 2. Decrease it likewise for for shorter bows. A 15 Foot tall Ogre would only have a Bulk modifier of -4 to conceal a 5' regular bow. A 6' Human trying to conceal a 15' tall bow would be at -13!


Nymdok
And Im spent.......

[nerdvana]

Originally Posted by Nymdok

The ideal shape is rectangular as used by the Native North Americans.

I'm not familiar with this style bow, could you profide an informational link? Perhaps one with pictures also...

[Nymdok]

http://en.wikipedia.org/wiki/Flatbow

Remember that Flatbow/Rectangular refers to the cross sectional shape.

Nymdok

[Nymdok]

Finally, we have an Example.

First an Easy one, Red Maple with a specific gravity of .54.

We want a bow of light strength and short stature for a theif so we'll make it a ST 8 bow.

ST 8 =>Bow pull 51 Pounds.

We want a short bow.....really short....40 inches short.

So its 48/(.54/.67) = or 60 cubic inches of this material.

Divide the Cubic inches by the height to get the cross sectional area 60/40 = 1.5 square inches in the cross section. For smallish man sized hands 2 inches wide is plenty, so it has a thickness of .75 inches. Note that these dimensions are the average of the bow, its a little bulkier at the grip and thinner at the tips.

Since we used specific gravity up top, all we have to do to Find the carrying weight of the bow is multiply its volume, times the Density of water (.036 lbs/cubic inch) or in this case 60 * .036 which gives us a 2 pound bow.


There you have it! Steps to a bow accurately desribed in detail for your players, of the ST YOU chose and the material YOU choose and the length YOU choose!

So to sum up
ST: 8
Material:Red Maple
Length: 40"
Width: 2"
Thickness:.75"
ST Required for ROF 1(1) = 12 (pull = 115)

Ill do one of a more complex example later right now my boss is looking at me funny :)

Nymdok

[DouglasCole]

The only issue I have here is that having a 50lb bow be ST8 is a bit harsh. In a different thread, we'd come to the conclusion that a person could draw a bow of BLx2 lbs, with StrongBow adding +0.5BL at DX and another at DX+2; Special Exercises (Arm ST) could be applied in two levels for the same bonus. So a specialized archer with good skill and special exercises could draw the bow with 4xBL of pull.

Otherwise, I worry that the damage of these bows will be extremely unrealistic. Using the firearms scaling style, I figured a 180lb warbow would likely only do 1d+2 damage...

[Nymdok]

Originally Posted by DouglasCole

The only issue I have here is that having a 50lb bow be ST8 is a bit harsh. In a different thread, we'd come to the conclusion that a person could draw a bow of BLx2 lbs, with StrongBow adding +0.5BL at DX and another at DX+2; Special Exercises (Arm ST) could be applied in two levels for the same bonus. So a specialized archer with good skill and special exercises could draw the bow with 4xBL of pull.

Otherwise, I worry that the damage of these bows will be extremely unrealistic. Using the firearms scaling style, I figured a 180lb warbow would likely only do 1d+2 damage...

BLX2 Doesnt reflect the 2 second effort [Rof 1(2)] that is used to draw a bow with both arms. I designed these rules to mesh fairly homogenously with the existing rules.

The Unrealistic nature of the damage again, is a function of the rules as written. The rules use strength based damage, I maintain that convention here.

The strength scale fits fairly well with Current world records for bow draw strength.

Nymdok

[DouglasCole]

Originally Posted by Nymdok

BLX2 Doesnt reflect the 2 second effort [Rof 1(2)] that is used to draw a bow with both arms. I designed these rules to mesh fairly homogenously with the existing rules.

The only issue I have with this is that there are strategies that increase drastically the RoF of the bow in RAW GURPS.

The bow RoF is Ready Arrow, Ready Bow, Fire. This can be dropped to Ready Bow, Fire with Fast-Draw (Arrow), and Heroic Archer I believe can even Fast-Ready bows.

I would suggest that BLx2 is what you can do with a one second effort, and that if you take two seconds, you may certainly draw a stronger bow; you may also draw a stronger bow by expending fatigue.

I'd base the calculations on the one-second ready, because that has a good chance of being the heroic base-case from which we scale.

[Polydamas]

Hi Nymdock,

Originally Posted by Nymdok

BLX2 Doesnt reflect the 2 second effort [Rof 1(2)] that is used to draw a bow with both arms. I designed these rules to mesh fairly homogenously with the existing rules.

The Unrealistic nature of the damage again, is a function of the rules as written. The rules use strength based damage, I maintain that convention here.

The strength scale fits fairly well with Current world records for bow draw strength.

Nymdok

Basing bow draw on the rules for how much weight you can lift off the ground and stagger around with seems sort of odd, and it isn't part of the rules as written but an interpretation. I wouldn't make draw weight 4 x BL, because then a ST 10 man with one point in Bow skill could use an 80 lb bow effectively. I would make a 50 lb draw standard for ST 10, so draw is 2.5 x BL. A lot of hunting bows have a similar draw, and I have heard of semi-skilled archers who could use 50 lb self bows effectively. I haven't heard of novice archers using 80 lb bows. A 150 lb bow using these rules would be ST 13-14, and there are only a few archers worldwide who can use a self bow that strong.

Originally Posted by Nymdock

Optional Additional Rules:

Crosssection: The D shaped cross section is the WORST possible shape and, sadly, is how english Longbows were made. The ideal shape is rectangular as used by the Native North Americans. The difference in energy transfer is a factor of 2 (40% to 80%). If your a simulationist, treat english bows as having 1/2 the listed strength for Damage and Range or Treat the Rectangualr crss section as having Double. I dont know which the Tables in Gurps are based on, so I cant say which way is the right way.

That doesn't agree with most of what I've read. Long D-sectioned self bows wouldn't have been used across a warlike continent for 3,000 years if they weren't effective. Blyth's appendix to Hardy's Longbow suggests that D-sectioned bows can tolerate more strain than flatbows. Pratt's appendix gives 67% efficiency for a 70 lb English longbow firing long bodkin or broadhead arrows. It suggests a lower efficiency for target or flight arrows which are probably what Klopsteg used in 1963. A couple of German scholars got around 40-50% efficiency firing various arrows from several sinew-backed Scythian bows.

Efficiency also varies with arrow weight and type. Light, long-ranged arrows tend to have less energy (but higher velocity) than heavy, destructive arrows. I don't recall why.

[SuedodeuS]

I like it. You might want to consider editing your initial post to include units, however. Also, I'm curious as to why you used 48 instead of 51 in your calculation. Finally, what is your justification for using the .67 conversion factor? I seem to recall you justifying it, but can't find that anymore.

50# does seem rather high for ST 8. I personally struggle with a 50# compound bow, and my ST is probably around that level. I can do it, but (in GURPS terms) it costs FP for each shot. Were it not for the let-off of compounds, however, I probably wouldn't be able to manage at all.

[Nymdok]

Originally Posted by SuedodeuS

I like it. You might want to consider editing your initial post to include units, however. Also, I'm curious as to why you used 48 instead of 51 in your calculation. Finally, what is your justification for using the .67 conversion factor? I seem to recall you justifying it, but can't find that anymore.

50# does seem rather high for ST 8. I personally struggle with a 50# compound bow, and my ST is probably around that level. I can do it, but (in GURPS terms) it costs FP for each shot. Were it not for the let-off of compounds, however, I probably wouldn't be able to manage at all.

The .67 conversion factor means I normalize everything versus Yew, the most famous of bow woods and the one for which an abundance of data is available.

As for 50# at Str 8, the struggle is well represented by being a 2 second effort, but a repeatable one.

Nymdok