High precision nail darts?

[BoyntonStu]

Heres another try at fins. I was surprised how flat it flew out of the blowgun. I'll have to make a few more to check the grouping.




It was really easy to make and it both centers and stabilizes the dart. If anyone wants to try it out, I can post some pics.

That looks like a military rocket.

Please show us hot to make it.

I eagerly await a 4 shot group.

[FighterAce]

Alright... first thing you need to do is mark the outlines. Your barrel ID might be different from mine so you'll need to play with the dimensions a bit. If the fin tips dont fit inside the barrel, reduce the length of the fins and if the nail doesnt fit inside the hole, increase the space between the fins.


Next cut it out. The darkened pieces will be your fins.


Crease the paper at all 9 lines in one direction.

And then in the other


That is just to make the paper more flexible for the next steps.

Then fold the creases so it looks something like this...


Glue the 2 part fins together by applying glue to the underside. Leave the fin on the far end. It will be glued using another method.


This is how to glue the 3rd fin (view from above)







Then give it some angles


Attach it to your dart and thats it.


btw. sry for the fuzzy images, I have no idea why they turned out so bad. My camera used to have an image stabilizer.. dunno what happened to it.

[Forum Admin]

That is a good way to combine ideas.   Those fins are better than a sabot any day for centering the dart in the barrel. I've been playing with foam sabots for a week now with lots of frustration. I havent posted anything on it since I try to keep foul language to a minimum.   Been fishing a lot lately as well, it has been a pretty good season so far.

[FighterAce]

Attach a line to your dart and shoot away 

[FighterAce]

I took a test shot this morning. It flies pretty straight and doesnt wobble. Heres a pic


I was gonna shoot a group this morning too but the glue is still wet. It will have to wait till tomorrow cause I got school in the afternoon.

Took me awhile for a crappy picture but its still worth it. It clearly shows how the fins hold the dart in place inside the barrel 

[FighterAce]

I must say I'm pretty surprised by the results. I was expecting the darts with fins to have much tighter grouping but it was the other way around 

Heres a control - short tailed darts, no fins. I was aiming for the black dot since the center has too many holes 


And with fins...


I'll try to move the fins up n down the shaft, see if that makes a big difference. Also I might try a longer tail...
What do you guys think?

[BoyntonStu]

Here's my take:

Shotshell hulls are uniform lightweight cylinders.

You are a great paper fabricator,

Try rolling a thin paper cylinder almost as long as the nail.

Place a nose cone with the point of the nail sticking out the front and another cone inside the cylinder at the rear to keep the nail centered.

If the paper is light enough it should crush easily on impact.

Can you picture it?

[FighterAce]

I think that would be too unstable and it would present a large face to the wind so theres more area the wind can work on and blow the projectile off its course.
Isnt the point to keep most of the weight at the front and not the back? a piece of 200 gram/m² paper wrapped around the 2 cones would be pretty heavy and mess up the stability. heck.. just by adding another cone, you already shift the center of gravity closer to the tail end.

I did actually thought of this before but never actually made a prototype because I know it would be just too heavy.
I'd rather look into some shapes other then the cone. The reason for it is this: http://en.wikipedia.org/wiki/Drag_coefficient

Look at the cone and then the streamlined body. I would of done something like that weeks ago but I'm still not sure how to manufacture such a tail for a nail dart.

[Forum Admin]

If only we can find a way to mold plastic into a nice hollow aerodynamic tail... possibly using plastic from shopping bags.

[FighterAce]

You could use those milk jugs. Make a 2 part mold of the tail. Heat the milk jug, push the positive through the melted part just like with the plumb bob and then put the positive into the negative mold to finish it off.

The problem is, we dont have milk jugs, we use paper ones 

btw. what about transparent rubber/synthetic tubing? can anyone try and heat them up to see if they can change shape if pushed into a 2 part mold? I've found a supplier that has 12mm ones but I'm not sure how the material behaves when heated. and..totally forgot bout this one... hot glue 

[Forum Admin]

The problem I had with the milk jugs was they couldnt handle the pressure unless I used a ball valve. Even then, once I started getting past 150 psi, they would blow out. Now I can vouch for hot glue, it will take whatever shape you mold it into. How well it will perform hollow, I'm not sure about. The hot glue I have is pretty flexible, perhaps they have one that cools more like a harder plastic?

[FighterAce]

I'm not sure about the harder hot glue but I'll look around for it. The one I have is pretty hard, I think it will do fine
I will try to make some kind of mold and make a tail out of it. For start I'll mold the cone and from there go to some other designs.

[FighterAce]

Dang... my hot glue gun broke yesterday  

I've been going back to the original design with the longer paper tails with 5cm nails. They outperform the 7cm nail ones because their center of gravity is more forward. Any ideas how to move the center of gravity forward on the 7cm nail dart without making the tail longer because if I go longer, the tail will become heavier then the nail.

I bet that small 5cm nail will struggle to drop a larger rabbit... not to mention anything bigger... right?

[FighterAce]

I finally got my shock pump and now I can test those darts with consistent pressure. Until now it was pretty much a wild guess with a bad gauge on my larger pump.
I tried pumping the M4 with it and it takes about 160 strokes with the shock pump alone. If I use 2 pumps, it takes 6 strokes with the larger pump to 13.5 bar and then 85 strokes with the shock pump. I'm very pleased with this cause it almost cuts the number of strokes in half 

[Forum Admin]

On the positive side, you will get a healthy work out for every shot you take.  Having consistent pressure is important to getting consistent shots, this will likely improve your grouping.