1. BOOMILEVER 2019
Think of a boomilever as a horizontal crane arm attached to a wall. The “holdback” for the load is a single mounting hook high on the wall, and the crane arm bears against the wall at one or more lower points. The load is suspended near the end of the boom.

2. UNDERSTANDING THE BOOMILEVER EVENT
This is an Experimental Engineering event that places maximum emphasis on innovative design, efficient use of materials, and quality of construction
Coaches primary job is to help students understand the expectations of the event; ALL competitors should arrive at competitions with TIER 1 boomilevers that can meet construction and competition requirements.
Coaches primary job is to help students understand the experimental process; students should be encouraged to push the design envelope and learn what works through repeated structural failures, design revisions, and retests.
Student experimentation with different designs, material selection, and construction techniques will result in gains in efficiency, and thus improved results.
Experimental process. Student design, photographs, video and testing data records help document sequential boomilever designs, failure modes and improved results.
UNDERSTANDING THE BOOMILEVER EVENT

3. UNDERSTANDING THE BOOMILEVER EVENT
SIGNIFICANT 2019 RULES
Materials …
No manufactured composites, plies or laminates, bamboo or paper products
No size limit on materials cross section
Construction …
Must be a single structure with NO separate or detachable pieces
Must be long enough to suspend load between 40cm and 45cm from wall
Contact depth line is 20cm for Division B and 15cm for Division C
ONE Mounting Hook will be used for both Division B and C
Scoring …
A minimum load of 3,000 grams (3 KG) is required for TIER 1
A maximum load of 15,000 grams (15 KG) is used for score calculations
TIER 3 is for competition or construction violations
1st tiebreaker is the estimated load score <= the actual load score
2nd tiebreaker is the lowest boomilever mass
UNDERSTANDING THE BOOMILEVER EVENT

4. UNDERSTANDING THE BOOMILEVER EVENT
Scoring Tiers …
Tier 1 boomilevers have NO violations AND hold AT LEAST 3,000 g. … SIMPLE
Tier 2 boomilevers have NO violations AND hold LESS THAN 3,000 g.
Tier 3 boomilevers have ANY violations AND hold any load.
SCORE for Tiers 1,2&3 = Load held in grams / mass of boom in grams
Tier 4 boomilevers are UNABLE TO BE LOADED CAN’T BE TESTED.
SCORE for Tier 4 = lowest mass of boom
Tier 1 boomilevers are ranked by score, and beat ALL Tier 2, 3 & 4 booms.
Tier 2 boomilevers are ranked by score, and beat ALL Tier 3 & 4 booms.
Tier 3 boomilevers are ranked by score, and beat ALL Tier 4 booms.
BOOMILEVERS in Tiers 2, 3 & 4 only result in TEARS
UNDERSTANDING THE BOOMILEVER EVENT

5. UNDERSTANDING THE BOOMILEVER EVENT
Photos of mounting hook installed on wall
Photo of testing wall mounted on sand loading device (breaker)
2019 rules have only ONE mounting hook for both Div B & C
Top of tape lines identify the Contact Depths for C (upper) and B (lower)
UNDERSTANDING THE BOOMILEVER EVENT

6. UNDERSTANDING THE BOOMILEVER EVENT
Photo of testing wall mounted on sand loading device (breaker)
2019 rules have only ONE mounting hook for both Div B & C instead of the through-bolt shown in this image
Top lines lines identify the Contact Depths for C (upper) and B (lower)
UNDERSTANDING THE BOOMILEVER EVENT

7. UNDERSTANDING THE BOOMILEVER EVENT
Knowledge base …
General understanding of loads and forces on booms and structural girders; and the relative strength of materials (balsa wood) subjected to tension, compression, shear, bending & buckling loads
Girder and truss designs for efficient, LIGHTWEIGHT load bearing structures; and how girders and trusses members are loaded (compression, tension); TRIANGLES for stiff and strong structures
Construction & gluing techniques; the importance of precise dimensions and balanced designs to resist vertical (gravity) loads and compressive and tensile loads
How to conduct Experimental Test Program, analyze failures, improve “weak” members, and achieve “Predictable” results
UNDERSTANDING THE BOOMILEVER EVENT

8. “UNDERSTANDING THE 2019 RULES” MENTORING THE BOOMILEVER EVENT
The COACH shares the responsibility if a BOOMILEVER DOESN’T MEET SPECS, but the students always pay the price
Only those meeting the construction and competition specifications will compete for medals. Common mistakes include …
Boomilever LENGTH and structure won’t support the load block assembly so the centerline of chain hangs between 40cm and 45cm from the testing wall (paragraphs 3.c and 3.d)
Boomilever DEPTH exceeds the CONTACT DEPTH LINE where it touches the testing wall before and/or during testing (paragraph 3.e)
… or … USING A PREVIOUS YEAR’S SPECIFICATIONS …
EXPERIMENTING is the ONLY approach to high load scores
The 2019 Tier 1 scoring rules require holding a minimum load of 3KG, and do not credit any “load supported” greater than 15 KG.
A boomilever that will hold 20 KG has extra weight, and will lessen the load score (structural efficiency).
Learn from it and build another, LIGHTER one.
MENTORING THE BOOMILEVER EVENT

9. MENTORING THE BOOMILEVER EVENT

10. MENTORING THE BOOMILEVER EVENT
Girder Designs
MENTORING THE BOOMILEVER EVENT

11. SOUND DESIGN FUNDAMENTALS MENTORING THE Inclined BOOMILEVER EVENT
Gravity acts DOWN, VERTICALLY at the point of the load.
The load will transfer through the boomilever structure to try to pull the “Mounting Hook” from the wall. Think of pulling a rope. TENSION.
The load will transfer through the boomilever structure to push against the wall. Think a tower on its side. COMPRESSION & BENDING
“Triangles” are more rigid than rectangles
ALL Trusses should incorporate diagonal members. Yours should, too.
Diagonal members should be incorporated in all three planes (L, W, H)
“Truss Beams” or “Laminated Beams” are efficient for bending loads
Place most of the material in these beams along edges
where the TENSION loads and COMPRESSION loads occur
MAXIMIZE glue joint surface area
Arrange structural members face-to-face for strongest gluing
Liberally use gussets for reinforcement of “butt” joints
Never “hang” a load on a simple “butt” joint
MENTORING THE Inclined BOOMILEVER EVENT

12. STRENGTH OF MATERIALS AND JOINTS
TYPE OF WOOD …
Balsa is the lightest wood available. Medal winning boomilevers are made from BALSA.
Basswood has a high strength-to-weight ratio, but use it SPARINGLY, if at all.
Spruce may also be available, but is MUCH TOO DENSE.
GLUE JOINTS …
Strong “sticks” but weak joints equals a weak boomilever
Strong glue joints maximize the surface area to be glued
Gussets maximize the “shear bonding area” for glue joints
Glue adds WEIGHT. Excess glue is excess weight … Trim it off
Use “quick-set” glue to build and test designs.
Thin CCA glue runs like water. Use a special TIP to control it DROP by DROP.
DON’T USE GORILLA GLUE.
SIZE OF STRUCTURAL MEMBERS …
Make “Thicker” structural members by gluing thinner sticks together (laminating).
Custom laminating can place the weight (wood) where the greatest stress is.
Cut “sheet” stock to size. A “skin” provides a lot of “directional” strength
There are lots of good glues
Its not so much which type of glue you use, its’ how you use it
MENTORING THE BOOMILEVER EVENT

13. QUALITY CONSTRUCTION MENTORING THE BOOMILEVER EVENT
Always inspect glue joints !!!
Some students weigh and mark each
“stick” to ensure “balanced” Structure
Use a sanding block
Inspect each “stick” for flaws
QUALITY
CONSTRUCTION
NEATNESS REALLY DOES COUNT
GLUE WEIGHS MORE THAN BALSA
CUT, DON’T CRUSH BALSA
ONLY NEW EXACTO OR RAZOR BLADES ARE SHARP
A “THIN” GLUE JOINT IS STRONGER THAN A “FAT” ONE
THE WOOD REALLY IS STRONGER THAN THE GLUE (IN TENSION)
DON’T LET “WOOD SHRINKAGE or EXPANSION” CREATE AN “OUT OF SPECIFICATION” BRIDGE (build it a tad longer, narrower, lower)
THE BOOMILEVER WORKS IN 3-DIMENSIONS
Use triangles to resist loads in each direction
MENTORING THE BOOMILEVER EVENT

14. MENTORING THE BOOMILEVER EVENT
The concept of gusset-reinforced joints
MENTORING THE BOOMILEVER EVENT

15. MENTORING THE BOOMILEVER EVENT

16. EXPERIMENTAL TESTING PROGRAM MENTORING THE BOOMILEVER EVENT
WHY ???
Students will load their own boomilevers during competitions
Bottled Sand, Loose Sand, Combination of bottles and loose sand, Hopper-loading
Students need to be cautious, yet confident.
Need to have done it before.
Testing EARLY will identify your team’s best builder Encourage students to build boomilevers at home.
Testing to failure will identify design deficiencies
Video recording & slow-motion replay can show failure mode
Testing & analysis will identify the weak link in the design
Always improve the weak link in the next design
Always test to destruction !!!!
Otherwise you don’t know how overbuilt
(AND OVERWEIGHT) a boomilever design is.
MENTORING THE BOOMILEVER EVENT

17. BOOMILEVER 2019 EXPERIENTIAL LEARNING WORKS.
BREAK STICKS/JOINTS BEFORE BREAKING BOOMILEVERS
BREAK “MOUNTING HOOK” CONNECTIONS BEFORE BOOMS
BREAK WHOLE BOOMILEVERS BEFORE COMPETITIONS
STRIVE TO BUILD FOR REPEATABLE RESULTS
EVOLVE DESIGN TO ACHIEVE MORE THAN 3-Kg held
EVOLVE DESIGN TO ACHIEVE CLOSE TO 15-Kg held
DOCUMENT YOUR TESTING AND DESIGN EVOLUTION [data table, photos, videos]
BUILDING & BREAKING IS JUST
TOO MUCH FUN
MENTORING THE BOOMILEVER EVENT

18. MENTORING THE BOOMILEVER EVENT
Suggested Materials for your BOOMILEVER Team
TESTING SUPPORT
Simulated Test Wall (see next slide) paragraph 5.a.i
2- 5cmx5cmx2cm loading blocks
Eye bolt, chain & S-hook(s)
2- 5-gallon buckets
50 # of dry, white sand
Digital bathroom scale (reading to 0,1 kg)
Digital balance, 0 to 100g, (reading 0.01g)
Bubble level
CONSTRUCTION TOOLS
Metric ruler, meter stick & caliper
2ftx3ft sheets of masonite, plywood, etc. for cutting & gluing surfaces
Exacto knives (or balsa cutter) COACH CONTROL
Fine sandpaper, sanding block
Engineering triangles (for right-angles)
Thin tip extensions for CCA glue bottles
Saran wrap & wax paper for gluing surface
BOOMILEVER MATERIALS
Balsa sticks_ various dimensions_ square & rectangular x-section_ from 3/16 to 1/32in dimensions
Balsa sheets_ from 3/16 to 1/32 thick, 2-ft long
CCA glue (thin & gap-filling), Insta-cure, Un-cure
Wood glue (yellow type)
MENTORING THE BOOMILEVER EVENT

19. MENTORING THE BOOMILEVER EVENT
Photo of simulated testing wall (not using mounting hook)
MENTORING THE BOOMILEVER EVENT

20. PROTECT THE INVESTMENT
Do not “over-test” the same boomilever.
Boomilevers previously tested to loads nearing the breaking point may have been damaged.
If you are getting consistent results, the smartest approach may be to build two identical boomilevers; one for testing to failure, and a second for the competition.
Stress the “fragility” of the boomilever to the student(s), the lighter it is, the more easily it can be damaged through mishandling.
The student should do all handling, assembling, and loading,
as it is his/her responsibility.
Even event staff have been known cause damage by mistake.
Plastic & cardboard boxes are great for storage & transport of boomilevers.
Foam inserts will restrict movements and limit damage from loose tools and objects inside the box.
MENTORING THE BOOMILEVER EVENT

21. BOOMILEVER 2019 Tips for a COMPETITIVE Boomilever
The Mounting Hook connection is critical, but don’t overbuild it. Build and break this piece many times as a component, then attach it to your boom
Choose structural members of different x-sections for heavily-loaded and lightly-loaded uses and locations
Diagonal cross-bracing can be quite thin, but is important. It keeps long, compressed members from BUCKLING. Diagonals are needed in all 3 axes.
Square & rectangular x-sections of the same area have the same weight, but the rectangular x-section is much stronger if oriented properly
Your stronger structural members should be aligned with the wider edge resisting the direction it wants to bend
Larger strength members should always have rectangular, never square x-sections. You can laminate multiple square members to make a rectangular one
Precision, balanced assembly can allow a good design to EXCEL, whereas a more haphazard assembly of the same, good design may result in only half the failure load (and scoring efficiency)
WHAT DO COMPETITIVE BOOMILEVERS look like ?