Can anyone tell me what type of expanding foam is best for 3D archery targets? I'm guessing the flexible type, but what density? What holds up the best from arrow punctures? I'd really appreciate any advice. Thanks!
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A flexible foam is what you want yes. "Flex Foam It" from Smooth-On may do the job. Go with the highest density they have to obtain more stopping power. The density of the foam acts on the arrow in two ways.. at it's tip as it pushes through, and along it's length. Softer foams don't resist compression as well as dense foams... so as the arrow pushes the foam out of its way, a low density foam won't push back much. A high density foam will. It's that extra pushing back that slows the arrow.
With that in mind; FlexFoam-It X is the most dense one I know from Smooth-On and has a density of 10 lbs with an expansion rate of 6 times.
If you use a very secure, rigid mold like that of thick fiberglass, and seal your flanges well, you can overload the mold with extra foam and force it to a greater density. Use caution as this can build up a LOT of pressure!
You'll have to do some research from the archery target suppliers and find out what density they use. They may list it in thier info about the item, or you may have to email them. No guarantee they will want to tell you though...
I sure appreciate the info. You told me exactly what I needed, thank you!
R J it is called self heeling foam same method as taxidermy foam except you use 2 parts of "A" and 1 part " B" Flex foam will work but not as good as the self heeling foam McKenzie use it since they owm McKenzies TARGETS
Suggesting something else on a completely different track here... I'm sure you know of "The Block" I believe it's called? A big white archery target with red targets on the front? You can make something like that to insert into your body cavity. It is basically layers of a material that I *think* is ether foam. Ether foam is a thin white foam used to wrap objects before shipping them. Pile up a thousand layers of this stuff and bind it tightly together and you would theoretically get something that looks like "The Block" and works the same way. The arrow enters between the layers - and the friction acting on the shaft of the arrows' length slows it to a stop. I saw a review of the product once and after 1000 arrow shots - it still looked almost new! So if you find a place that sells packaging material like bubble wrap etc - check for this ether foam and maybe it will do the job for you. Like I said -a thousand layers or so (whatever it takes really - I dont know exactly how many layers....), 2 ft square, weigh it down with a few cinder blocks on a plywood sheet so it's REALLY compressed tightly.... Might work. Bind it up with a bunch of duct tape and theres a target. Make a smaller version to put in a deer cavity perhaps?
Based on the same physics of friction slowing that arrow to a stop... how about a stack of newspapers? Weigh them down on top with all the spines (the folded edge of the papers) at the back. The arrow would (theoretically) enter between the layers and friction along the sides cause it to stop.
The benefit to that option? Old Newspapers are a hell of a lot cheaper than buying foams or ether wrap!
The benefit of BOTH of these methods? You aren't actually piercing the product - so theres no where near as much wear n tear on it. Ever seen those ninja movie where someone swings a sword at him and the guy cathces the blade between the flats of his two palms? Same principle.
I just thought of those ideas today and thought Id throw them out there for ya in case ya wanted to experiment =)
As for mix ratios of foam? Be careful there - urethane is picky stuff and a soft urethane foam can be disasterous for this application. Improper ratios can result in foams that are not fully cured etc. You can end up with more problems than aid when you alter ratios that drastically. This was discussed some time ago in the habitat category when someone was doing mix ratios with foams. It's a foam that hasnt fully cured because you used half the required amount of curative. The Flex Foams for example are a 2:1 ratio ONLY in their very low densities. Once you get to higher strength stuff - it's a 1:1. Im not sure if a fully cured 10 or 15 lb foam would have the density to stop an in flight arrow.. but an uncured foam or half cured foam? WOW - I'd be REALLY sure I had a good backstop - because I could see the arrow flying through that as easily as a seat cushion... Just a lil safety heads up on that one. Urethanes are VERY picky in their chemistry about these sorts of things. This is why water around urethanes is such a huge problem. The water reacts with the part A base stronger and faster than it gets to act with the Part B.. and you get an improper cure resulting in spongy soft foam.
I do really appreciate the help I've received here, you guys are super! Thank you so much! RJ
Raven: you have the right idea,but a little more to it.I hunt with a bow,as well as many others,and tried many targets.I shoot an 80 lbs bow at 325 F.P.S. and use a round target as Raven said thounsands of layers and use a banding machine to compress the daylights out of it.
The target is 2 feet thick and my arrow will go 3/4 the way in it.
The main reason for the self wealing foam is, it will last a lot longer then ever the target I use and the holes close up.This foam is 2to1 ratio and if eg. if you poor a life-size bear and you use 2 lbs foam (taxidermy foam) and you use eg.3lbs A and 3lbs B for the self healing foam use 6lbs A and 3 lbs B and your target will last longer.
The problem is foam cost more Mckenkie used self healing for the vital replacement area and now use only a sqare block in the vital area,to save them money.Their older targets much better then the newer ones.I've tried many targets over the years,I was a product tester,and as Raven said their are many ways, BUT to stop the arrow you need a lot of compression to stop it,this is why I said use a banding machine to compress it as much as possible.
A Banding machine was my first thought - those things are brilliant! BUT... keep in mind the fact that the average reader of the forum PROBBALY isn't goign to have a bnading machine in thier garage to use. Nor will they want to spend the money for it and strapping etc. A sheet of plywood and some cinder blocks puts it in the realm of possibility. But yup - I agree whole heartedly -a banding machine would be PERFECT for an applicaiton like this.
Now a question about the foam for ya Laurier.... Using that soft foam.. I get that it will last longer etc, BUT.. will it have stopping power? That was my big concern about using those foams. That's why I made the comment about it being like a seat cushion. It wasn't a chemistry issue so much as a safety one. So with a low density flexible foam, you are saying it has enough stopping power to be safe and the arrow won't go right through? I wasn't even sure that 15 lb density would be enough in a soft foam... I guess experimentation on RJs part would figure it out in no time eh? LOL!
Raven: this was the reason I said use a banding machine, you would need about 20 8" blocks to put enough compression on the foam shetting
Now the self healing foam will stop the arrow with no proplem.
Importatant: same as taxidermy foam,if you don't use enough your foam will be soft.More foam the more density to the foam.
For taxidermy foam,I use 2 lbs foam and I will get the same as if you use 4 or 6 or 8 lbs foam you just need more foam to do the same job.
The self healing foam when using it call the manufactuer and talk to the Tech and explain to him your plans and they will walk you though it.
where can you get flex foam it?
I know this is a little off topic but as I was reading I started thinking I was making a big mistake. I am building a 3d elk target out of spray foam, just that great stuff you get at a hardware store. I figured the width of an elk of that should stop my arrow but not too sure now. Do you think it will hold up to stopping my arrow, I only shoot 65 pounds and aluminum arrows? Oh and I put a rubber coating on it.
Mad - "Flex Foam-It!" is available from smooth-on.com
Becky? (BP)... It likely wont stop it. Flesh and bone have more stopping power than spray foam and it's common for arrows to pass through critters completely.
Another option for stopping power is to create yourown bullet-proof style set up. Stack up a lot of corrugated carboard... but put it vertically so you hit it broadside - not slide between layers. Where the layers horizontally use friction to squuze the shaft and stop it that way... by stacking layers and making the arrow shoot through each of these - a little inertia is lost with each penetration. This is the basic concept of how bullte proof vests work. Each layer of Kevalr (a name brand for particular type of carbon fiber reinforced plastic) absorbs a little bit of the bullets energy. If it were one solid piece of material the bullet would penetrate. Basically... it's harder for a bullet to pass through 10 layers at 1/10th inch each than 1 layer at one inch.