Gravel Bags for Packstock United States

Department of

Agriculture

Forest Service

Technology &

Development

Program

2300-Recreation

June 1995

9523-2840-MTDC

The contents of the publication are not to be used for advertising, publication, or promotional

purposes. The Forest Service, United States Department of Agriculture, has developed this

information for the guidance of its employees, its contractors, and its cooperating Federal and State

agencies, and is not responsible for the interpretation or use of this information by anyone except its

own employees. The use of trade, firm, or corporation names in this publication is for the information

and convenience of the reader, and does not constitute an endorsement by the Department of any

product or service to the exclusion of others that may be suitable.

The Forest Service is a diverse organization committed to equal opportunity in employment and

program delivery. USDA prohibits discrimination on the basis of race, color, national origin, sex,

religion, age, disability, political affiliation, and familial status. Persons believing they have been

discriminated against should contact the Secretary, U.S. Department of Agriculture, Washington,

D.C. 20250; or call (202) 720-7327 (voice); or (202) 720-1127 (TDD).

Gravel Bags for Packstock

Brian Vachowski

Project Leader

Technology & Development Program

Missoula, Montana 59801

5E52A59

Gravel Bags for Packstock

June 1995
Introduction _____________________________________ 1

Gravel Bag Designs ______________________________ 2

Fruit Picking Bags _______________________________ 3

Testing _________________________________________ 4

Gravel Bag Test Results___________________________ 5

Recommended Design ____________________________ 6

Gravel Hauling Panniers __________________________ 6

Sources ________________________________________ 6

Fabrication Plans ________________________________ 7

Contents

Technical Assistance:

Maggie Brinks, Missoula, Montana

Ivan Carper, Wallowa, Oregon

Mike Dolfay, Wenatchee, Washington

Brenda Holland, MTDC

George Jackson, MTDC

Patti Johnston, Lewis and Clark National Forest

Jim Kautz, MTDC

Ray Mills, Lewis and Clark National Forest

Taylor Orr, Gallatin National Forest

Tony Petrilli, Northern Region Smokejumper

Professional Wilderness Outfitters Association

Sara Lustgraaf, MTDC

Acknowledgment

ii
A fabric bag for hauling gravel or

fill material with packstock is

available for Forest Service use.

Replacement fill material is often

needed for trail work, especially for

turnpike construction and tread

maintenance. Using packstock to haul

gravel or other fill material is practical

when motorized equipment is

impractical or not allowed.

The Missoula Technology and

Development Center (MTDC) was

asked to develop plans, and fabricate

and test fabric bags that could be

mounted on packsaddles. MTDC

worked from a design developed in the

1970’s by retired Wallowa-Whitman

National Forest (R-6) employee Ivan

Carper. Missoula smokejumper Tony

Petrilli fabricated the bags for MTDC in

1994 and they were tested on a

partnership turnpike construction

project on the Rocky Mountain Ranger

District of the Lewis and Clark National

Forest (R-1) that same year. MTDC

also tested and evaluated some bags

that closely followed the original Carper

design built by the Professional

Wilderness Outfitters Association

(PWOA), and some off-the-shelf fruit

picking bags.

Included in this report are test results,

recommendations, a design pattern,

and some alternatives.

Introduction

1
Heavy canvas and liberal use of leather and rivets for

reinforcement around a steel hoop make up the basic design

developed by Ivan Carper. MTDC modified the design in

several ways (Figure 1). Overall dimensions were kept the

same as the original, but 16-ounce (455-gram) coated nylon

CorduraTM was used instead of canvas. MTDC did not use

leather or rivets, but relied instead on sewn seams, which

are stronger. MTDC also used tubular nylon instead of

manila rope for the release cord. The bags were rigged with

short chains and a snap clip to fit a decker saddle. With

minor modifications, the bags could be rigged for a sawbuck

packsaddle.

Partners in the testing and work project, the Professional

Wilderness Outfitters Association, also fabricated some

gravel bags using the basic Carper design. Theirs featured

“truck tarp” fabric instead of canvas, manila release ropes,

and rivets instead of sewn seams (Figure 2).

Figure 1.–Gravel bag design features sewn seams around a steel

 hoop. Release strap was changed slightly in final design.

Figure 2.–This design is similar to the first, but has riveted seams

 and truck tarp fabric. Bags were filled one bucket at a time.

 Gloves should have been worn.

Gravel Bag Designs

2
Based on a report from Mike Dolfay on the Wenatchee

National Forest (R-6) that trail contractor Pete Harvill had

been successfully using inexpensive, off-the-shelf fruit

picking bags to haul gravel with his string, we included two

different sets of these bags in the test. These were Wells &

Wade #80 Super picking bag, and Citrus Bag with Rope

Hook. These bags (Figure 3), while admittedly not designed

to haul gravel on the side of a mule, readily fit a decker

saddle with no modification. Instead of being released by

jerking a knot, the load

had to be released by

getting close to the

animal and lifting the

loaded bag of gravel

enough to lift the hook

off the side of the bag.

The hoop at the top of

the bag was smaller

and not as strong as

the steel hoops on the

other designs.

Figure 3.–Fruit picking bags require lifting the load to release the

 rope clips.

Fruit Picking Bags

3
For 8 days in June, 1994, up to 24

head of mules packed gravel for a 3/4-

mile (1.2-kilometer) stretch of new

turnpike construction on the South Fork

Sun Trail No. 202. The packstock

belonged to members of PWOA. They

also provided workers at the gravel

source to work alongside the Forest

Service crew.

Each bag was tested by carrying about

eight loads per day for 8 days (64 trips).

The gravel was hauled from a river

bottom gravel bar, up a hill

approximately 1/2 mile (.3 kilometer) to

the turnpike construction site.

Both Carper design bags were loaded

with about 160 pounds (72 kilograms)

per bag, for a total load of 320 pounds

(144 kilograms) per mule. The

outfitters believed the mules could

handle that load for short distances, but

about 120 pounds (54 kilograms) per

bag would be better for longer hauls. It

was easy to overload the animals. In

fact, the initial loads weighed 200

pounds (90 kilograms) per bag until

they were better calibrated.

Because of their smaller dimensions

and lighter construction, the fruit picking

bags could hold only about 80 pounds

(36 kilograms) of gravel per bag.

Each mule string was led through the

gravel pit area, with workers on each

side filling bags a bucket at a time. The

bags were quiet, although the metal

buckets were not. When all the mules

in the string were loaded, they were led

to the turnpike. Two workers were

stationed there, one to hold the mule

and the other to unload it one side at a

time. The packstring was separated

during unloading. This proved to be the

most difficult procedure, since the

mules varied in temperament and some

were quite contentious.

Because of the difficulty of positioning

some of the mules exactly where the

gravel was needed, the ability to direct

the flow of gravel from the bag by

pulling the rope on the bottom was very

useful (Figure 4). Also, by lifting up on

the rope, the flow of gravel could be

halted and redirected to a slightly

different spot.

In all cases, the empty bags were left

mounted on the packsaddles, tied and

adjusted, ready for the next load.

Figure 4.–Bags allow directing the flow of material under or away from the pack animal.

Testing

4
Table 1 compares test results of the two versions of Ivan Carper’s design and the fruit picking bags. The MTDC bag proved to

be most efficient. Fruit picking bags would be adequate for lightweight jobs.

Table 1.—Packstock Gravel Bag Test Results

• Wells & Wade #80 Super

picking bag;

• Citrus bag with rope hoop;

• Treated canvas;

• Lightweight metal hoop;

• Sewn seams

• $22-$27 per bag, plus freight

• Approximately 80 pounds

(36 kilograms) per bag

• Economical;

• Able to direct flow somewhat;

• Lightweight 2-3 pounds

 (.9-1.4 kilograms) each;

• Quiet;

• Easy to roll up and pack

away

• Metal rim not heavy enough,

tendency to collapse;

• Small opening made loading

harder;

• Limited capacity;

• Had to get close to animal

and lift load to release hooks

• Top side of one bag ripped

out, but repairable

• Bags not designed for gravel

but serviceable for light duty

use, especially when cost

and quick availability are

most important

• 18-ounce (510 gram)

polyester with PVC resin

truck tarp;

• Riveted seams;

• Manila release rope;

• 3/16-inch (4.76 millimeter)

steel hoop

• No current manufacturer—

small lot fabrication costs

about $80 per bag

• Average 160 pounds (72

kilograms) per bag;

• Easy to overload

• Direct flow up to 4 feet (1.2

meters);

• Lightweight 5.5 pounds (2.5

kilograms);

• Quiet;

• Easy to roll up and pack

• Chain rattled when bag was

empty

• Two tops came undone at

rivets, but repairable

• 1/4-inch manila ropes wore

out...replaced with 3/8-inch

(9.5 millimeter) manila;

• Fabric tore on one bag, but

repairable

• Fabric held up well and costs

less than nylon CorduraTM,

so it is recommended for

final design;

• Riveted seams not as strong

as sewn seams

• 16-ounce (455 gram) nylon

CorduraTM sewn seams;

• Tubular nylon release strap;

• 3/16-inch (4.76 millimeter)

steel hoop

• No current manufacturer—

small lot fabrication costs

about $80 per bag

• Average 160 pounds (72

kilograms) per bag;

• Easy to overload

• Direct flow up to 4 feet (1.2

meters);

• Lightweight 5.5 pounds (2.5

kilograms);

• Quiet;

• Easy to roll up and pack;

• Tubular nylon worked well

• Chain rattled when bag was

empty;

• Tubular nylon sometimes

caught in chain (fixed in final

design)

• Stitching in bottom of one

bag wore out, but repairable

• Final strapping design

modified so it will not catch

on chain;

• Nylon CorduraTM held up

well but more expensive than

polyester with PVC resin

truck tarp;

• Sewn construction stronger

than riveting

DESIGN THAT WAS TESTED

POINTS

CONSIDERED

 "Carper" Design - MTDC Fabricated "Carper" Design - PWOA Fabricated Fruit Picking Bags

Construction

Approximate Cost

Load Carried

Best Features

Limitations

Observed Wear

Comments

Gravel Bag Test Results

5
Ivan Carper’s design as modified by

MTDC is the recommended bag.

Fabrication plans are included in this

report. The design is sized to the

original specifications, but is modified to

require sewn seams and a slightly

different load release rigging. Although

the bags originally fabricated by MTDC

used 16-ounce (455-gram) nylon

CorduraTM, the recommended plans

call for 18-ounce (510-gram) polyester

with PVC resin truck tarp material, a

less costly yet durable fabric that held

up well in the bags made by the

outfitters. CorduraTM could also be

substituted if desired.

The fruit picking bags could be

considered serviceable for light duty

use, especially when initial cost outlay

and quick availability of an off-the-shelf

product are the most important

considerations. The bags do not quite

utilize the full load capability of pack

mules, and are unlikely to stand up to

sustained heavy-duty use. They may

be a good alternative to hauling gravel

in buckets or wheelbarrows in many

instances.

Fruit Picking Bags: The Wells & Wade

bags are manufactured by:

Superior Fruit Company

PO Box 3444

Wenatchee, WA 98807-3444

Phone: (509) 662-5881

or (509) 662-6065

Aluminum Gravel Panniers:

Wyoming Outdoor Industries, Inc.

1231 13th St.

Cody, WY 82414

Phone: (307) 527-6449

Dave Fish Saddlery

1706 Brooks St.

Missoula, MT 59801

Phone: (406) 543-8566

For additional copies of this report or

further information on bag fabricators,

contact:

Brian Vachowski

USDA Forest Service, MTDC

5785 Hwy. 10 West

Missoula, MT 59808-9361

Phone: (406) 329-3935

Hard-sided panniers were not evaluated

in the tests. Often fitted with hinged

drop doors, these have been around for

many years. Often gravel would bind

or break the hinges, the boxes are

bulky, and most designs provided no

way to direct the gravel on its way out

of the box.

Improved aluminum gravel panniers,

featuring a sliding, rather than a hinged

door, are available from Wyoming

Outdoor Industries, Inc. Similar panniers

have been fabricated by other saddle

shops. We did not evaluate hard-sided

aluminum panniers, but based on

reports from some who have used

them, the panniers work well and are

very sturdy. They are bulkier, noisy

(should be lined with some type of

fabric to cut down on noise), and are

more expensive than fabric gravel

bags. The aluminum panniers

available from Wyoming Outdoor

Industries, Inc., currently cost $395 per

set of two, not including rigging.

Discounts are available when more

than one set is ordered.

Sources

Recommended

Design

Gravel Hauling

Panniers

6
Fabrication Plans

The schematic MTDC gravel bag pattern on page 9 shows the general layout. Plan dimensions could vary slightly based on fabric

used. Fabricate a prototype before mass producing. The steel hoop should be fabricated first.

33-1/2"

❤

Placement

of weld.

❤

❤

❤

12"

❤

1. Steel bar is 1-1/4" x 45-1/2" x 3/16".

2. From the center point of the bar,

measure 6" out on each side and make

90° bends on both. Now round the free

ends together and weld.

3. Weld the chain links to the hoop.

A carabiner or metal double snap clip

can be used to connect the chains to

each other. Decker saddles require 9"

of chain on each side, while sawbuck

saddles require 20" per side.

STEEL HOOP DETAIL

SEWING INSTRUCTIONS

1. Fold material with wrong sides

together, and match 1" side dots with the

back side 2" dots and stitch (Figure A).

2. Check to make sure the material will

fit snugly around the metal hoop, then

remove hoop.

A

R

W

B

❤

Stitch line

from Step 1.

R

3. False Fell Seam: Fold the 2" side

around the 1" side (Figure B). Tuck by

folding it again and stitching as shown.

The second stitch line must be started

from one end to the halfway point. Clip

thread and finish stitch line from the

other end.

R = right side of material, and W = wrong side

7
SEWING INSTRUCTIONS, continued

❤

❤

❤

Cut here.

4-1/2"

C

R

4. The hoop end will

be double-folded. To

reduce bulk, cut

4-1/2" of false fell

seam from the hoop

end (Figure C).

F

R

Cut-away detail ❤

Stitch line in Step 6.❤

W

Stitch line in

Step 10.

❤

❤

❤

❤

Fabric fold

❤

Steel

bar

9. Fold fabric around

the hoop. Hoop edge

should be on the

8-1/2" fold line dots.

10. To attach the

hoop inside the bag,

stitch close to the

fold edge on the

inside of the hoop

(Figure F).

❤

R

4-1/2"

❤

❤

❤

5-1/2"

W

❤

Cut-away detail

D 5. At the hoop end,

fold at the 5-1/2" fold

line.

6. Stitch completely

around on the 4-1/2"

stitch line (Figure D).

G

R

W

❤

Stitch made

in Step 10. ❤

❤

Lock stitch made

❤

in Step 11.

Stitch made

in Step 6.

❤

Steel

bar

Cut-away detail❤

11. To secure the

hoop, stitch over the

stitch line created in

Step 6, reinforcing it

since the machine

will not sew

completely into the

corners. Lock

stitches (Figure G).

E

❤ ❤ 1-1/4"

❤

❤ 1/2"

R

R

7. Cut rectangular

holes for hoop chain

links. Use a hot-knife

if material is

CorduraTM, and burn

through both layers

(Figure E).

8. Insert the hoop

and pull the chain

links up through the

holes.

H

R R

❤

Match

diamonds

D-ring❤

12. Bottom D-ring:

Webbing 1-1/2" x

10". Use 3-point,

running 'W' stitch

(Figure H).

13. Bottom support:

Material 17-1/2" x

2-1/2" with 1" seam

tape on all four

sides.

14. Attach taped

piece on three sides

(two long sides and

one short side).

15. Insert 1" x 16"

steel or aluminum

strip. Sew open end

shut.

8
Stitch Line

Fold Line

Fold Line

( Right side of material)

 Stitch Line

Selvage Edge

Hoop Edge

➛ ➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛

➛ ➛

➛

➛ ➛

➛

➛

➛

➛

➛

➛

19-1/2"

Holes to be made 

in Step 7.

Placement points for 

bottom D-ring in Figure H.

28-1/4"

29-1/2"

49"

2"

These vertical rows of dots match. 

(The left row should be marked on 

the wrong side of the fabric).

1"

24-3/4"

32-1/2"

23-1/4"

15"

8-1/4"

2" 12" 22" 32" 42"

2-1/2"

4-1/2"

4-1/2"

5-1/2"

8-1/2"

49"

8-3/4"

18-1/4"

MATERIAL LAYOUT

M A T E R I A L S L I S T

49" x 49", 18-ounce polyester with PVC resin, (PVC "truck tarp")* 17-1/2" x 2-1/2" 18-ounce polyester with PVC resin, (PVC "truck tarp")* 1" x 40" seam tape

1-1/2" x 10" nylon webbing

3/4" x 3' tubular nylon

3/4" x 9' tubular nylon

*Alternative material: 16-ounce coated nylon CorduraTM

1-1/2" D-ring

1-1/4" x 16" x 3/16" steel, or 1/4" aluminum flat stock

1-1/4" x 45-1/2" x 3/16" steel bar

1 medium-size carabiner or metal snap clip

2 each 9" chains for decker; or

2 each 20" chains for sawbuck

9
Notes

10