Site hosted by Angelfire.com: Build your free website today!
Index
Main Page
Welcome
Manual
Construction
Pictures
Wind Chart
Guest page
Safety
Hazards
Books
Links



blueprint of Plain Frog


INDEX

Choice of wood
Steps in carving
Finishing
Experiment: Weight of Finish on Plywood Boomerang
Weighting your boomerang


I make these boomerangs as a hobby and put far more time into each one than if it were a business. Why? Think about it! Each week I have several brand new boomerangs to fly. That makes me very happy!


Choice of wood.

  1. 6 mm, 5 ply baltic birch plywood. See my Do-it-yourself page
    Good for beginner boomerangs and the occasional thrower.
    Not quite as dense as Finnish Birch.
  2. 5 mm, 10 ply finnish birch plywood See my Do-it-yourself page A superior plywood manufactured in Finland with strict quality control.
    If you throw a lot or are competitive, you will certainly want your boomerang made of this wood.


Steps in carving

( a nice term for cutting and sanding)
  1. A pattern is drawn on the appropriate sheet of plywood. My patterns are both personally designed or modified patterns from other sources. I first make a pattern on paper and cut it out. I place it on the plywood and trace it with a pencil.
  2. Each boomerang is individually cut out with a scrolling saw (A hand held reciprocating saw with a scroll blade. I have recently purchased a "Grizzley" saw. It is inexpensive and works like a fine sewing machine. I use Bosch or
    Sears 20 teeth per inch scrolling saw blades. They make a sandpaper smooth cut.)
    When I get a boomerang from this pattern that flies perfectly, I finish it with clear finish and mark it "pattern". I use it from then on as the definitive pattern for that model. It shows me all of the bevels, airfoils, undercuts, etc. to get a consistant product. I then use it to trace subsequent outlines on the plywood to be cutout.

    Cutting out booms

    Here is a reference about sandpaper. It is must reading if you plan to make boomerangs  Sandpaper 101

  3. Each blank is shaped with a Singley 3" diameter x 6" long drum sander using 60 grit J weight cloth-backed, resin bonded sanding cloth. I obtained both the drum and the cloth from Woodworker's Supply of North Carolina.
    The drum is directly attached to an electric motor turning at 3450 rpm. I have tried using 60 grit paper but it wouldn't hold up at those rpms. I now use 60 grit cloth backed medium.
  4. Smoothed with an orbital sander using 120 grit paper.
  5. Sealed with Val Spar sanding sealer. I do this so that the raw wood will not get grass or dirt stained. It also seems to be stronger after sealing.
  6. Test flight.
  7. Field adjustments if needed or shop adjustments if needed and retested.
  8. Sanded with an orbital sander with 180 grit paper.

Click here for a pictorial account of the above steps as I designed and built a triblader fastcatch boomerang



Unfinished Baltic Birch Boomerangs

Finishing

  1. Already sprayed with sanding sealer before the first test flight.
  2. Cleaned up with 180 grit paper if necessary
  3. The front is primed with a latex primer if necessary ( if a super smooth gloss is required or if there are some irregularities in the wood surface that sanding could not remove). Normally, I do not use a primer. It adds too much weight to the boom.
  4. The front is then smoothed again with #0000 steel wool and painted using a variety of techniques with Krylon or Val Spar acrylic paint and allowed to dry.
    Painting booms
  5. A coat of water soluble polyurethane Or Krylon or Val Spar crystal clear acrylic is then applied.
  6. I have recently started using Minwax polycrylic which seems to do a good job as a clear finish.
After completely drying which takes about 1 day for polyurethane to harden, I test fly again. Hopefully, It will fly properly. If not, there are several tuning measures that can be done to correct the flight. If I can't make the boomerang fly properly, I do not sell it.


The boomerang is then packaged in a poly bag with an informative 4-page manual. I have in the past included a piece of colored plastic surveyor's tape for a wind indicator. I have discontinued that since I found a piece of the plastic stuck to a boom that had been packaged and damaged the finish. .

I usually ship Priority mail. Please allow 2 to 3 weeks for delivery of these boomerangs, however I usually manage 10 days or less.



Want to know how to make a lap joint boomerang?
Dave Hendrix has a great page!

Lap Joint Instruction


Experiment: Weight of Finish on Plywood Boomerang

This experiment consists of making a plywood boomerang and weighing the boomerang before and after each application of finish including sanding sealer, primer, acrylic latex colors, and water soluble polyurethane. Please remember this is only one data point, just to get an idea of how much weight is added to a boomerang both in grams and in percentage.



The model I chose to experiment on is a Gray Frog of Baltic Birch with a 1" hole in the elbow. I am redesigning the Gray Frog and decided this would be a good subject. Started on 8/10/98


gray frog

Finish applied Weight Total Finish weight layer wt. Total finish %
Raw Wood
8/10/98
72.30 g 0 g 0 g 0 %
Sanding Sealer, both sides, 8/11/98 74.14 g 1.84 g 1.84 g (1.84/74.14)X100=2.5% of total
Latex primer to front side, 8/11/98 75.43 g 3.13 g 1.29 g (3.13/75.43)X100=4.15% of total
Acrylic latex base color and accents, 8/12/98 77.63 g 5.33 g 2.20 g (5.33/77.63)X100=6.87% of total
Water soluble polyurethane, both sides, completed on 8/14/98 79.44 g 7.14 g 1.51 g (7.14/79.44)X100=8.99% of total

Data Analysis

There is more than one way to assess this data.



#1 How much weight will this finish add to the raw boomerang:

Weight of boomerang = 72.30 g

Total weight of finish = 7.14 g



(7.14g/72.30g) X 100 = 9.88% of the raw boomerang weight.



#2 What is the percentage of finish on the totally finished boomerang:



Weight of finished boomerang = 79.44 g

Total weight of finish = 7.14 g



(7.14g/79.44g) X 100 = 8.99% of the finished boomerang weight.



BUT WAIT


We didn't even consider surface area, which is probably more significant.

The approximate surface area of this boomerang was found by the tried and true method of finding the area under a curve. This consists of tracing the boomerang outline on a piece of paper, cutting it out and weighing it accurately. A standard size piece of the same paper is weighed and by ratio and proportion the area of the paper to its weight is calculated. From that the surface area of the boomerang can be approximated

Standard paper 11x17 inches = 27.94 cm x 43.18 cm Area= Length x Width

Area = 1206 cm 2 , Weight = 13.04 g

area /weight =1206 cm 2 /13.04g = 92.48 cm 2 / g

Paper tracing of boomerang cutout Weight = 2.48 g x2 for two sides = 4.96 g

Area = 92.48 cm 2 / g x 4.96 g = 458 cm 2

So the total surface area of the boomerang = 458 cm 2 neglecting the sides because I traced the boomerang liberally hoping to approximate that.

Total finish weight / total area = finish per unit area

7.14 g / 458 cm 2 = 0.0156 g / cm 2



From this conversion factor, I can calculate the approximate weight of finish that I am going to put on any size boomerang(using my finishing procedure) if I can measure the surface area.


Here is the painted gray frog

painted gray frog



Weighting your boomerang

Speaking of weights, here are some weights that might help you experiment with using weights on your boomerangs. These are nominal values

US penny 2.5-3 g
US nickel 5 g
US dime 2.2 g
US quarter 5.7 g
#4 split lead shot 3.2 g
#3 split lead shot 4.5 g


Some "class notes" from "Weighting 101":
These are some epistles from the rang-list on how to weight your boomerang

Bill Wachspress <wow@grapevine.net>: was so kind as to repost them to the list and gave me permission to publish them here

From: Bill Wachspress<wow@grapevine.net>

"Drill holes and hammer lead into them." was the concensus last time

around, "...and laugh off the very real dangers of handling the lead,

mostly." This thread left me really wanting to try brass, whenever I

graduate out of the tape and coins phase. Brass isn't so poisonous

and doesn't stain the wood so easily. Because it is less dense than

lead, it might not hammer itself loose so easily after repeated

landings. I also like the way it looks. Most of the more specific

advice that I saved follows.



From: "Chris Cotter" <slx@earthlink.net>

On wood rangs I like to use brass weights rather than lead. The

brass looks nicer and doesn't leave smear marks on the wood like lead

does.

I have a 1/2" diameter brass rod which I cut slices from to produce

the weights. Use 5 minute epoxy to glue the weights into the boom.





From: "William K Sotak" <katos@pathway.net>

I know this was a subject a while back but I think I have a good

method of installing weights. It may have been done before but here

it is from me. First, I drill a hole using a Forstner (optional) bit.

Then I take my Dremel tool and attach the tip that is a little

abrasive metal ball. It looks like a little dental tool. I have the

router attachment so I set the depth to have the ball 1/2 the

thickness of the boomerang cord. (You do not need the router

attachment but it makes it safer and faster.) Then I carve out a

groove around the hole. When you pound the weight it assumes the

shape of the groove and can not move. I tried it a few times on scrap

before trying it on boomerangs. I broke them apart to see how well

they were seated. With just a slight pressure the lead does assume

the grove shape very well. I have tried it on several boomerangs and

have yet to see even a slight stress crack in the finish even after a

severe crash. I use .445 lead ammunition balls as weights. I rotate

the a few times while pounding them into a cylinder then cut them

with a dremel cut disk. This make a more accurate cut for me. I

hate having to sand a weight much on bare wood if I am planing on not

painting the boomerang (clear finish). This may all sound complicated

but it is only a couple minute process. I also want to add I find the

alloys added to the lead only effect the weight a neglectable amount

for boomerang purposes (IMHO).





From: "William K Sotak" <katos@pathway.net>

Hint:

Ask your local tire shop what they do with the lead weights when they

pull them off of tire rims. A lot of them throw them away. Recycle

them for something good and save money.



Also:

I like to pound out lead into a flat disk or block, like heavy lead

tape. I then tape it on with lacquer masking tape. This allows more

room for weight adjustment (especially when testing) and does not

weaken the structure. Again some of you may notice a difference

between weighting the top or bottom of a rang. (again, the ultimate

boomerang book explains this) I often adjust some of my boomerangs

with different winds and even different moods. You can even play

games with spin rate in this manner.



Let me beat the politically correct rang list police.



More drag more drag....I know I know. ADJUST!



If I do install a weight I use a flexible glue. I hate to always be

the odd one out but I think most epoxy glues are like putting the

lead in a glass setting.





From: Fredric Malmberg <fmalmb@pol.net>

Dear William,

This is interesting, and I suspect it would work well. I use a

slightly less complicated system, which, on a much smaller scale,

does what you are accomplishing here. I make a hole just slightly

smaller than the lead plug I am going to use, take two small strips

of posterboard (which I also use to make templates out of), and use

these strips as "sawhorses". I place them on a cement surface about

an inch apart, and place the hole in the boom between the

"sawhorses". I then pound the plug into the hole. It flattens out on

both sides slightly bigger than the hole, and I have never lost a

plug so set.





From: Pollocknel@aol.com



Lead weighting...At CB, as most of you know, we use a 1/4" drilled

hole and hammer in a OO lead pellet. We have never had a problem

with fit. Actually, the led shots are obtaind by bag from Bullet

Weights and it is a coated lead shot.

Yes, you need to use a very firm, flat surface.

RP-N





From: Bill Rusky <mazerang@megsinet.net>

You can buy heavy metal (~90% tungsten) rod from Mi-Tech Metals

Inc., P.O. Box 5519, Indianapolis, IN 46255-5519, 1-800-624-1895.

They have several versions with specific gravities from 17 to 18.5.

It's not cheap, but it is denser than lead. Hacksaw it to size and

glue it into place.





From: Bart Derks <bderks@zeelandnet.nl>

I drilled a load of holes through a brick, each a little wider as the

one before. I placed the brick on another brick and filled each hole

with melted lead. After cooling down the pieces of lead can be

removed with a hammer and a metal bar.

When weighing a boomerang i take a piece of lead with a diameter

that's just a bit smaller as the holes in the boomerang. The lenght

of the piece of lead has to be a bit longer as the thickness of the

boomerang.

Lead is a very soft metal, so by hitting it gently with a small

hammer on something that can function as anvil the lead will expand

and secure itself inside the boomerang. Before hitting, insert the

lead in the hole of the boomerang and let it stick out on both sides

of the hole.

A warning...

When the piece of lead is too long, stop hammering, the expansion of

the lead might ruin the boomerang. Carve the lead untill it almost

fits the boomerang and only neads a few soft hammerings to get it in

shape perfectly. Another warning, lead is soft, but not as soft as

the boomerang itself, so be sure to hit(/carve) the lead, not the wood !!!

Back to Index of this page

© 1998-2000 Thomas G. Conally

LE FastCounter