Spray Swath Uniformity – New String

System and Field Measurements

Clint Hoffmann, Dan Martin, Phil

Jank, and Ab LatheefUSDA ARS

Aerial Application Technology Research Group

College Station, Texas

Operation S.A.F.E.

This research effort is designed to support Operation

S.A.F.E. and help applicators and S.A.F.E. Analyst in

properly setting up aircraft.

We strongly recommend that you regularly attend a

fly-in in your area.

Why routinely test swath width uniformity?

• Goal: Most uniform pattern

– Account for a number of issues

• Prop wash

• Wing-tip vortices

• Interferences under the belly of the plane

• Etc…

– Determine the effective swath width to

optimize swath deposition and overall

application efficiency.

Boom Layout and Swath Uniformity

• Initial boom setup might follow the following guidelines:– Nozzles evenly spaced along effective boom length;

– No nozzles past 70% boom width for fixed wing and 100% for helicopters;

– All nozzles on drop tubes or drop booms to get into “clean” air;

– Possibly extra nozzles to the right of the prop and fewer to the left to account for prop wash;

– Etc…

• There are likely others you may follow based on your experience in the field.

Swath Pattern Problems

• Streaking

– Over or under loading of spray deposition

– “Holes” in pattern

– Too broad or narrow of swath width

• Generation and movement of fine droplets

– Pushing boom width limits

– Wing-tip vortices

– Incorrect nozzle setup

– Bad nozzles

Field Streaking

String Analyses System

• String Analyses System for measuring

spray uniformity;

• Basic setup is very similar to the WRK

Systems that everyone is familiar with

through S.A.F.E. clinics;

Current Fluorometer

• The Turner 112 has not

been made for years;

• Only one place to get

them repaired and it is

expensive;

• Requires adjustments

each time and very often

requires multiple runs of

the string to get a good

reading.

Fluorometer: The heart of the System

• There have been many issues with the

older Turner fluorometer used by Analysts.

• Ocean Optics USB2000+ was selected;

• Retails for ~$2600

• Ebay for ~$1500

Measurement Cell

• Cell is 3D printed;

– ~$300 for high quality prints

• Drawings will be made available;

• Optical filter allows for use Rhodamine or

PTSA dyes.

• Different optical glass filters ($150) are

used for each dye.

LED Cell

Glass filterLED

Inside the Cell

String is

illuminated by

the LED and

dye fluoresces.

Mirrors insure all sides of the string are

illuminated and mirrors focus light onto light

collector for the fluorometer.

Looking Into the Cell

Printed Components

Shaft for Spools

Pulleys

LED Cell

Drive System and Electronics

Cordless Drill

Powers spool take-up, LED, and encoder

Motor Controller and LED Power

Slip Clutch

Encoder

DAQ Board

Trigger is replaced with wires and

connected to the motor controller

Assembled System

Field Spool

Direction of

Line travel

LED Cell

And

Fluorometer

Pickup Spool

String is read at 1.25 ft/sec = ~2 mins per pass

Opening Screen in LabVIEW

Pilot/plane information is captured here.

Swath Pattern Output Screen

Average Swath Width and CV

New System

• SAFE Analysts field testing;

– Further software/hardware refinements.

• A parts list will be made available;

• Drawing files and software will also be

available with manuals;

• Total cost of the system will be ~$5,000 for

all the components;

• Hope to have everything ready by late

Spring.

Thank You

• Please come by our booth (#1202) to see

a hands-on demonstration and ask any

questions.

• Other questions

Clint.hoffmann@ars.usda.gov

2 n’s on Hoffmann

mailto:Clint.hoffmann@ars.usda.gov