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Collecting Equipment Projects, Ideas and Sources

Super Gigantic "Net-a-Saurus Rex", AKA "Sky Sweeper" Collecting Net

Everyone who collects Lepidoptera has swung a net at a Lep and missed. At one point, we've all thought "If I only had a bigger net..." Well, here it is. Originally conceived to make catching male Saturnia albofasciata remotely possible, it's also proven effective at increasing the odds of capturing other difficult to net bugs such as Hemileuca species. This particular specimen is the quick and dirty prototype of the only Netasaurus Rex in existance (at present). I had planned to make a "nicer" one and to show construction detail photos along the way but time has been short and demand high!

See the video on here...

Besides improving the collectors odds, this net is intended to be lightweight, rigid, cheap and easy to make. You can get just about everything from your closet, garage and/or local Wal-Mart type store.

Basic materials list:
1 34" diameter Hula-Hoop (Wal-Mart, $1.98)
1 wood or aluminum (preferably telescopic) handle ($3 - $24)
1 wire clothes hanger/stiff steel wire (closet, shed, etc)
4 yards of tulle netting, any color (Wal-Mart, <$4)
1 roll duct tape
1 tube "Alex" caulking
1 roll waxed paper

Of course you may improvise and change the specs as desired although the measurements will have to be adjusted accordingly if the net diameter is changed. While there's lots of room for modification, I highly recommend that one design feature NOT be changed - the net handle connection at two points (top and bottom) of the net ring. Most "standard" nets connect to the handle only at the bottom of the net ring. However, a traditional handle connection to a net ring this large won't be strong enough to withstand the load. You'll find that the weirdness of the handle crossing the net opening is well worth the gain in strength and rigitidy as soon as you sweep this monster through the sky. As of this writing I've never had a specimen damaged from contact with the cross handle and sometimes I even find my specimens conveniently knocked-out in the net because of it!

pliers/wire cutters
caulking gun
measuring tape/long straight-edge
drill with 3/16" (more or less) bit

Here are some shots of the whole assembly with handle extended and collapsed. Yes, it's ugly and made with the cheapest materials ever. While unattractive, it's quite functional and certainly proved the concept viable. A 4-foot straight-edge is included for scale. No doubt about it - this is a really BIG net!

This cheesy (what can I say) MS Paint diagram shows the basic assembly and dimensions, which I will make reference to as this text progresses. I recommend that you take your own measurements before cutting anything to size, just to be sure no materials go to waste.

Let's start with the net bag, since it's assembled using a glue that will need to dry. The bag is made from the most arial netting I could find - "tulle" netting from wal-Mart. It costs $0.75 to $1 per running yard and is usually about 60" wide. This netting is extremely lightweight and allows air to pass easily so it won't slow your swing much. The downside is that it's not very strong and will rip to shreds if you snag any sharp objects.

You will need two pieces of netting, cut to the dimensions shown in the diagram above. If you changed the size of your net ring then you'll need to re-size your net bag. To calculate the net ring side of the bag (side D), use the formula [pi x Dia /2]. Example: a 34" diameter ring has a circumference of 107" (3.14 x 34). (I like to round-up AND add a few inches). Since the net bag is made from two halves, you divide that circumference by 2 and get about 54" (I recommend 56" or better for the 34" dia. net ring shown). As far as the net bag measurements - WHEN IN DOUBT, MAKE IT BIGGER than you need. A larger-than-needed net bag will fit a bit loose and "baggy" while one which is too small simply won't work. Play it safe - make your D side halves 56" or better.

Note that side "D" is not cut straight across but is curved. Without going into too much geometry, this is because we're dealing with a 3 dimensional cone rather than a simple 2-D triangle. If you don't cut the top of the bag this way it will fit the net ring funny (but should still work). The length of the bag should be about twice the diameter of the ring so that enough net bag can be folded over the ring to prevent a captured specimen from escaping. Longer is better.

Once you have both halves of the net bag cut, fold about 2.5" of the top edge (side "D") of one net bag half over onto itself and glue it down using the caulking. Note that due to the weird curve of side D that there will be extra material which whon't want to fold over neatly. Just do the best you can with it - it's OK if it's a little baggy.

Glueing can be done an any flat surface covered with strips of waxed paper to prevent it from sticking to the work surface. The seam (glued area) should be about 1/2" wide and thick enough to make a rubbery, contiguous band which cannot be torn apart when dried. For details on glueing net material with caulking, see my other project - "making your own sleeves".

Fold-over and glue side D of the other net bag half, and let the glue dry. See the pictures below for reference. When the glue dries, you should have a 2" dia. tube of folded-over net which the net ring will slip through. When side D dries on both net bag halves, glue the two halves together on 3 sides (A, B and C), again on a flat surface covered with waxed paper, and let it dry.

The net ring (a Hula-Hoop from Wal-Mart) costs less than $2 and is basically a long tube, bent-around in a circle, the ends of which are joined together with a smaller tube and a couple of pins. It also contained some small plastic beads inside to make it rattle when moved. Since I had to open up the ring to slide it through the net bag anyway, I opted to remove the rattles too. I figured I would look gooney enough swinging such a large net without rattles attracting even MORE attention. :)

I found an unused telescopic aluminum mop/utility handle in my shed which measured 36" collapsed, and 70" extended. It's lightweight, very strong, and "twist-locks" in any position.

The handle end (outer tube) has a hole in the end (for hanging it for storage). This hole made the perfect place to slide the cross-brace connector though. The cross-brace is a critical design feature, used to bind the top end of the handle to the net ring AND provide tortional/longitudinal rigitidy. Without it, the net would be weak and virtually uncontrollable.

The cross-brace connector (figure E in the diagram) is basically a length of stiff wire (brown) which is threaded through a hole in the end of the net handle (black), and then secured to the net ring (blue) on both sides with duct tape (grey) or similar. I used a short length of stiff steel wire, folded over once (doubling its thickness). If your net handle doesn't have a suitable hole at the end, you will need to make one. Make the hole only as large as necessary to fit the cross-brace though (a larger hole makes a sloppy and weak connection)and be sure to leave enough material at the end to prevent splitting/cracking (especially if you use a wooden handle).

The photos below show my very messy but strong and functional cross-brace.

Now that your net bag is dried, and handle/net ring are prepared, you should be ready to slip the net bag onto the ring. You'll need to disconnect the ring joint (or cut the ring if it's one piece) in order to get the bag on. Once the bag is on, reconnect the joint. If you had to cut the ring, place something stiff inside the tube and tape it up really good. Rotate the ring so that the joint is at the 3 O'clock or 9 O'clock position - as far away as you can get it from the 12 O'clock and 6 O'clock positions where the net handle will connect. This will help take the stress off of the naturally weak joint. Attach the handle to the ring using duct tape or wire at the top (12 O'clock position) [Ref. fig. E in the diagram] and strong wire (I used a clothes hanger) at the bottom (6 O'clock) [Ref. fig. F in the diagram]. You'll need to cut away a little of the net bag at the attachment points in order to make the connections. Cut only as much as needed. See the photos below..

Hopefully, the photos will fill-in any gaps in the instructions. I hope to one day re-do this page with proper documentation but for now, this should get you going!

Have success or failure with this or a similar project? let me know!

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