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I have a creature who harvests resin from trees as a building material. These trees are similar to those on Earth, but not identical (I.e. there is biological wiggle room).

I would like the creature to be able to cast this resin into shafts for spears and bows. It appears that epoxy resin can be used for this purpose, though it’s likely resin from Earth’s trees would be a poor building material, and I would prefer if this resin remained biodegradable, which most synthetic resins are not.

The resin likely contains cellulose, which could be processed with the resin to strengthen it.

For the sake of the question, the creatures are human-sized and the weapons are used in the same way we use them.

As far as use in combat/hunting, could this resin work as the primary component in primitive weaponry? Could it be superior to wood?

While the process of manufacturing the shafts is also an interesting subject, I’d like to save that for another potential question and have this one purely about effectiveness.

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  • $\begingroup$ Sounds interesting. Just confirming - you are talking about making bows from the resin rather than making arrows (which are kind of like small spears)? $\endgroup$ Sep 14 at 22:07
  • $\begingroup$ @KerrAvon2055 Arrows would ideally be built in a similar way to the spears, but I’d prefer if the resin could do both since I don’t know what else to build the bow out of. $\endgroup$ Sep 14 at 22:16
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    $\begingroup$ IMO natural resins would be useless for weapons. They'd be either too soft or too brittle. Natural resins are used like graphite to lubricate things or as the base for lacquer. Synthetic resins are like natural resins only in that they share the same word in their names. They're chemically completely different. But the real question is, how "realistic" do you really want to be? I think resin with a bit of technobabble (mixing resin with finely ground fibers from the jumara plant create great arrow shafts!) is a great idea. $\endgroup$
    – JBH
    Sep 14 at 22:45
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    $\begingroup$ @JBH normally I’d probably do that, and I might here, but I like the idea of really developing how the creatures craft and use the weapons in detail, and I’d love to have a more “realistic” approach. However, you have a point that resin may not be the way to go. I’m considering some kind of cellulose fiber as well, but might ask about that separately. $\endgroup$ Sep 14 at 23:06
  • $\begingroup$ So does the weapon need to be entirely made of resin or just a majority resin? Because the latter is very practical while the former is much more difficult. For example a composite bow made of wood with resin as a powerful glue to keep it together would make sense $\endgroup$ Sep 14 at 23:33

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The Plywood Jungle:

Biology is capable of amazing things. But it doesn't always behave like you want it to in real life.

Thank goodness for the power of the pen.

There is nothing physically or biochemically impossible in what you want to do. But the resins by themselves are unlikely to be strong, per se. Your best bet is to make the resins as the glue of various composite materials. People have made thin veneers of wood for thousands of years and glued them to surfaces. But people didn't really start figuring out that you could recombine pieces of wood into fixed shapes until they started making plywood.

Your species is simply avant-garde.

Maybe the wood available to make tools is not very strong, or not very hard, or not very straight. People were very picky about what kinds of woods they would pick to make tools from. But people started to use glue derived from trees 200,000 years ago. For your purposes, the difference between glue and resin is semantics.

Your species is what people say Stradivarius could do - literally gluing wood together to make "super-wood." While people dispute Stradivarius, there's no disputing the potential of composites. They can make thin veneers of wood (or maybe even leather), steam them, roll them up with your resin, and make new wood in whatever shapes they want, to the lengths they want, hard or soft depending on the desired consistency. A different resin seals the wood against moisture.

After that, you need to figure out what your species needs this process for. To make wood the right shape? The right hardness? To make more flexible wood? To make wood composites to make stronger (composite) bows?

A mix of materials (like horn, bone, stone, even grass) can get you tools of most any desired function. But in the end, your species just got lucky to find organisms that produced the substances that matched their needs.

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    $\begingroup$ Composite bows are likely the best use of the resin. Maybe something like a composite shield is also possible. $\endgroup$
    – vinzzz001
    Sep 15 at 8:57
  • $\begingroup$ bravo, composites are the go $\endgroup$
    – Fattie
    Sep 15 at 20:02
  • $\begingroup$ Yes the Romans used plywood shields $\endgroup$
    – Slarty
    Sep 16 at 17:35
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Resin from the Xylonean tree combined with the acidic fruit juice of Tsaylean bush causes resin to harden to become a strong chitin like substance.

Instead of using always hard material that is difficult to process, your folks will use the resin, shape it, then strengthen it with the additional component. It is also possible to dunk the material in activator just enough to keep the core soft, object made of it will be much more durable.

Since the biology of your world is different, there is no reason that this cannot happen.

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  • $\begingroup$ "Epoxy resins usually comprise four ingredients: the monomeric resin, a hardener, an accelerator and a plasticizer. Manufacturers generally provide a standard formulation, however the hardness and flexibility of the polymerized block can be manipulated by varying the amount of the individual components" sciencedirect.com/topics/medicine-and-dentistry/epoxy-resin - You have resin and hardener, but the same problem as with cast iron: ductility. But as for, How to make epoxy w/o a degree in chemistry? ... +1. $\endgroup$
    – Mazura
    Sep 16 at 12:55
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I think @DWKraus is on the right track with composites.

Looking at actual composite bows, they are made from a combination of a thermoplastic or thermoset resin with a fiber or filament like glass.

I think you need to mix the natural resin with a strong natural filament like spider silk or a natural fiber taken from a vine or similar plant.

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  • $\begingroup$ Mixing with spider silk makes me really curious. If a sufficient amount could be gathered, how intensive of a process would it be to mix resin and filament? Would you need a large amount of heat? $\endgroup$ Sep 15 at 14:29
  • $\begingroup$ I think the amount of heat would depend on the properties of the resin. $\endgroup$
    – Theodore
    Sep 15 at 16:37
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The Rift War Saga utilises resin or, rather, lacquered wood as an alternative weapon and armour.

As with resin in real life, you could incorporate a process for the conversion of the tree sap to a final product, such as the creature has a much higher than normal acidity to its saliva, so either regurgitating or spitting on the sap forces a reaction when it is exposed to air.

As an alternative, small quantities of the sap could be combined with pouches at the back of the creatures throat that build up gas or air and can be used to fire this as a weapon, too! This does, of course, depend on how reliant the species is on the specific tree. (Therein lies a weakness).

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Resin weapons... Since you mentioned some biological wiggle room and an alien planet with environment conditions close to earth, it kidna depends on the resin types and qualities. Lets categorize some the important aspects to determine the effectiveness of a weapon.

One: Base material. You can literally grow more trees to get more resin. Carrying seeds and setting up a new village, with resource you literally grow from earth, would help a lot when it comes down to harvest base materials.

Two: Skill or tools. Depends on real or hypothetical resins, skill sets may require weaponsmithing, gardening, and maybe a bit herbalism to concoct the correct substance. Hardening the resin is an easy process, and sharpening the weapon, adding the handle and other properties can be handled while the resin hardens. Molds or hanging the resin is also an easy method. This part, depends on your resin and processing methods.

Three: Properties of the material. Maybe resin could be hard, flexible, and light. Which is good for making weapons and armors. Maybe it is too heavy, so only small weapons could be made. Maybe it is brittle, so only arrows and small daggers could be made. If the resin is strong, maybe making a shield from it and hiding behind could save lives.

Four: Long-term uses, or durability. If your cheap sword breaks after two days, no matter how easy it is to make, it will cause problems. Handling the weapon may requrie special training, which could require skillful warriors. And reducing the effectiveness. If your weapon keeps its best qualities a long time with less effort, it will be quite an effective weapon. Because, just getting one could help you a long time. Metal weapons require care. Sometimes special materials. Or certain regular actions. If your resin weapon can keep itself a long time with less requirement than an iron weapon, then it can even surpass the metal counterparts.

All these properties will be important to determine the cost, time it takes to "forge" a weapon, and how widespread it will be. Or in other terms, how effective it would be.

From my understanding, it could be superior to the wood if the resin at least as good as wood. Because, for wood, you either need good parts on big trees, or you need to chop a big tree, cut it to pieces, and use the chopped off wood.

For resin, you don't even need to cut the wood. Depends on the resin and obtaining method, you may need a small forest, cycle through trees to give them time to heal and make more resin, collect enough resin and work on that.

Obtaining base materials is easy, so even small tribes with small men power can get some.

If resin can be used as, even a one-use weapon, can be more effective than wood. Due to how easy it could be to access it and make weapons from it. Carrying a few resin javelins or arrows made from resins could be superior to wood.

But it all depends on how good resin is as a weapon. Since, there are several types and mixtures can offer even more options, it is hard for me to come up with a clear answer.

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There are good answers here already, and yes, proper composites would work best, but may need better tools to be build, so here's my spin on it. Thus let's look into Types, Performance and Curing of resins.

Types of resin

There are natural resins that get hard and there are natural resins that get rubbery. Commonly they loose water and terpentines in the process, but they may also polymerize. Hardened resine doesn't rot quite as easily, and may become amber under certain circumstances.

Performance and Usage

If you have mainly soft wood, it may outperform that. HOWEVER: Keep in mind that in the comparison "laminated wood" (plywood) vs fiber-composite vs pure resin, the pure stuff will lose as compounds are usually superior. Plywood is far more difficult than fiber composite, as you must get it very even. If your resin doesn't really harden, but only gets semi-hard and sticky, it may be better than fiber composite. For hard resin, fiber composite is probably the best to build, as it is easier to form and probably stronger as well.

Also: While if used like glue, plywood is an option, the question arises, why not to use the wood itself. A possible reason might be your plants: They might have good wood, but bad growth patterns. Making a composite may enable you to form it appropriately.

If (partially) transparent, the resin might be used for decorative reasons. Especially on spears and bows, if you use fibers for the composite, you might form it to build some holes in a decorative pattern, which may be filled with the resin and thus still provide (some) compressive strength.

It might also be used as shards-section in a weapon. If you have a spear, and the cured resin is a bit brittle, one might use it to attach break-away tips or to outright build a shard-tip to maximize damage to prey or opponents.

Sharpness of your weapons might also be a reason:

If we argue that you have only chalky stones, you might have a hard time getting a proper point to your spear. Especially when you have no access to hard woods. A bone will crack, yes, but it will not give a sharp edge. As the stones are soft, they won't give proper blades either. Also they are to soft to grind bones or wood to a point on them. You may break of strong-ish branches, but again the end will feather out and be difficult to be ripped in a way that produces a point. The result would be a spear with a rather meek tip. Hard resin or rosin to the rescue: you create a spear the old way, then dip the tip into hot rosin and let it harden. If you left it hanging tip-down for hardening, you already got a better tip than before. However, one may improve on it, if the resin is also at least a bit brittle. The tear-drop tip may be broken of and (at least for many types of rosin on earth) will form a semi-sharp to sharp edge. (Rosin is usually quite amorph and thus may crack building sharp edges. Think of rosin as a bit like a mix between the strength of most plastics and the shard production of glas.)

Curing your resin

At some point you'll want to cure your resin. There are a few options, each with their pros and cons.

Chemically

Cem Kalyoncu argued you might mix two or more saps and resins for them to react and harden. On its own, this would probably result in inferior plastics, caused by impurities naturally occurring in the saps / resins. HOWEVER you might wash it during reaction, getting rid of impurities and thus better quality. Alternatively you might cure with white ash or charcoal, but again washing might bring improvements, as might folding.

Two possible settings:

  1. Mixing results in granulate matter, which after washing may be used (probably by melting it)
  2. Mixing results in something that feels like a mix of bubblegum and honey. While washing you fold it and stretch it, rinse and repeat. The result may be formed like clay and will slowly harden.
Air

It might well be, that a certain plant has sap that will harden when exposed to air to clot a wound. The reaction would stop close below the surface as new air has a hard time reaching in. Thus your craftsmen might pull it apart and fold it, or if it's thin and runny, whisk it to bring it in contact with a lot of air. It would probably build a gooey foam that will start getting warm. You could then form it. Again, working it in water would keep it cold (probably slowing down the reaction), clean out impurities and might help removing the bubbles.

Light

Similarly, a plant might have sap that hardens when exposed to sunlight. Thus your workers might harvest it at night time. If transparent, this might be casted and left in the sun for a few hours or days to cure. For a compound, one might wet fibrous material with it and hang it in the sun to cure; subsequent layers could be added by painting them on.

NOTE: Neither the light nor the air version will work terribly well with cross-laminated wood. Air would probably work better, as it might get saturated before hardening, but both would need fast working.

So far, the results will most likely NOT compost. Let's address that.

Thermal curing

You may boil resins to make rosin / colophonium. Rosin is hard and plastic like. Basically it is the remainder of resin, after water and terpentines boiled away. Furthermore there are rubbery resins (usually not from the plant sap, but from the fruit sap) that work to make it flexible (latex, kauchuk, plum-resin). By mixing these resins and varying the boiling times the rosin may be customized.

The resulting rosin will compost, but not super-easily. Of course adding fibers would make it far stronger, but (if not overdone) it could be formed to build transparent sections.

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