DMM Tendon DIY Knee Ascender Guide (Arborist Hack For Easy Climbing)

As an arborist, I’ve learned a thing or two about getting up trees efficiently. One of the best tricks I’ve picked up is using a DMM Tendon and a DIY knee ascender. It’s a game-changer for single rope technique (SRT) climbing. But here’s the expert tip: Don’t just slap it together. Take the time to fine-tune the friction hitch and the length of your tether. A poorly adjusted system can be exhausting and even dangerous. Now, let’s dive into the DIY knee ascender guide, arborist style!

Step-by-step instructions: On assembling a knee ascender using a DMM Tendon rope (or similar) and readily available components.
Arborist-specific advice: Tailored techniques and considerations relevant to tree climbing, such as safety, efficiency, and equipment compatibility.
Troubleshooting tips: Solutions to common problems encountered when building and using a DIY knee ascender.
Performance optimization: Methods to enhance the speed and comfort of climbing with a knee ascender.
Alternative solutions: Considerations for other climbing methods or commercial knee ascender options.
Safety information: Crucial warnings and best practices for safe climbing with a DIY system.

Article Outline:

Introduction: The expert tip on fine-tuning the friction hitch and tether length.
Understanding the Basics of SRT Climbing:
- What is SRT?
- Why use a knee ascender?
- Advantages of a DIY system.
Components of a DMM Tendon DIY Knee Ascender System:
- DMM Tendon Rope (or equivalent): Specs and considerations.
- Ascender: Choosing the right one.
- Foot Loop: Material and adjustment.
- Tether: Length and connection.
- Friction Hitch Cord: Material and diameter.
- Carabiners: Locking and non-locking options.
Step-by-Step Guide to Building Your Knee Ascender:
- Measuring and cutting the rope.
- Tying the friction hitch.
- Attaching the ascender.
- Creating the foot loop.
- Connecting the tether.
Adjusting and Fine-Tuning Your System:
- Adjusting the friction hitch.
- Adjusting the tether length.
- Adjusting the foot loop.
Using Your Knee Ascender: A Practical Guide:
- Attaching to the climbing rope.
- The climbing motion.
- Descending techniques.
Safety Considerations:
- Pre-climb inspection.
- Proper technique.
- Weight limits.
- Environmental factors.
Troubleshooting Common Problems:
- Slipping ascender.
- Binding friction hitch.
- Foot loop discomfort.
- Tether length issues.
Advanced Techniques and Customization:
- Adding a chest harness.
- Using a mechanical prusik minder.
- Customizing foot loop design.
Alternative Climbing Methods and Gear:
- Comparison to other SRT systems.
- Commercial knee ascender options.
- Double Rope Technique (DRT).
Maintaining Your System:
- Cleaning and inspection.
- Storage.
- Replacement schedule.
Conclusion: Emphasizing safety and continuous learning.

DMM Tendon DIY Knee Ascender Guide (Arborist Hack for Easy Climbing)

Understanding the Basics of SRT Climbing

What is SRT?

Single Rope Technique (SRT) is a climbing method where you ascend and descend a single rope, rather than the two ropes used in Double Rope Technique (DRT). SRT is popular among arborists for several reasons, mainly because it allows access to specific branches without needing to wrap the rope around a crotch. It’s also generally more efficient for longer climbs.

Why Use a Knee Ascender?

A knee ascender is a device that helps you ascend a rope by using the power of your leg. It essentially turns your leg into a powerful pulling mechanism. With each push of your knee, the ascender moves up the rope, bringing you closer to your destination. This reduces the strain on your arms and upper body, making longer climbs much more manageable.

Advantages of a DIY System

While commercial knee ascenders are available, building your own offers several advantages. First, it’s often more cost-effective. Second, you can customize the system to perfectly fit your body and climbing style. Finally, building your own system gives you a deeper understanding of how it works, making troubleshooting and repairs easier.

Components of a DMM Tendon DIY Knee Ascender System

DMM Tendon Rope (or equivalent): Specs and Considerations

The rope is the heart of your climbing system. I prefer using a DMM Tendon rope (11mm) because of its durability, low stretch, and excellent handling. However, any high-quality, low-stretch rope designed for SRT climbing will work.

Diameter: 11mm or 11.5mm is ideal for most ascenders and provides a good grip.
Material: Low-stretch nylon or polyester is crucial for efficient climbing.
Length: Determine the length based on the trees you typically climb. Always err on the side of caution and get a longer rope than you think you need. I recommend at least 150 feet for general arboricultural work.
Consideration: Always check the rope’s Minimum Breaking Strength (MBS) and Working Load Limit (WLL). Stay well within these limits for safe climbing.

Ascender: Choosing the Right One

The ascender is the device that grips the rope and allows you to move upward. There are many ascenders on the market, but I recommend a handled ascender for ease of use and comfort.

Handled vs. Handle-less: Handled ascenders are more comfortable for prolonged use.
Cam Design: Look for an ascender with a cam that grips the rope securely without damaging it.
Compatibility: Ensure the ascender is compatible with the diameter of your rope.
Example: Petzl Ascension is a popular choice.

Foot Loop: Material and Adjustment

The foot loop is what your foot rests in and provides the leverage for pushing the ascender up the rope.

Material: Use strong, durable webbing (e.g., nylon or polyester).
Width: 1-inch webbing is comfortable and strong.
Adjustability: The foot loop should be easily adjustable to accommodate different boot sizes and climbing styles. A simple buckle or knot system works well.
Comfort: Consider adding padding to the foot loop for increased comfort during long climbs.

Tether: Length and Connection

The tether connects the foot loop to the ascender. The length of the tether is crucial for efficient climbing.

Material: Use dynamic rope or webbing with some stretch to absorb shock.
Length: The ideal length depends on your height and climbing style. Experiment to find what works best for you. Generally, a tether length that allows your knee to be bent at a comfortable angle when the ascender is fully extended is a good starting point.
Connection: Use strong, reliable knots (e.g., bowline) or sewn loops to connect the tether to the foot loop and ascender.

Friction Hitch Cord: Material and Diameter

The friction hitch is what allows you to move the system up the rope while providing a secure hold.

Material: Use a high-quality arborist-grade cord (e.g., Tenex Tec or Ocean Polyester).
Diameter: The diameter of the friction hitch cord should be smaller than the climbing rope but not too thin. A 8mm cord works well with an 11mm rope.
Length: The length depends on the type of friction hitch you use.
Example: Distel hitch, VT hitch, or Prusik hitch.

Carabiners: Locking and Non-locking Options

Carabiners are used to connect various components of the system.

Locking Carabiners: Use locking carabiners for critical connections, such as connecting the ascender to the harness or connecting the friction hitch to the system.
Non-locking Carabiners: Use non-locking carabiners for less critical connections, such as connecting the foot loop to the tether.
Strength: Ensure all carabiners are rated for climbing and have a high Minimum Breaking Strength (MBS).

Step-by-Step Guide to Building Your Knee Ascender

Measuring and Cutting the Rope

Determine the Length: As mentioned earlier, determine the length of rope you need based on the trees you typically climb.
Cut the Rope: Use a sharp knife or rope cutter to cut the rope to the desired length.
Seal the Ends: Melt the ends of the rope with a lighter or heat gun to prevent fraying.

Tying the Friction Hitch

Choose a Hitch: Select a friction hitch that you are comfortable with. The Distel hitch and VT hitch are popular choices.
Tie the Hitch: Follow the instructions for tying your chosen friction hitch. Ensure the hitch is tied correctly and securely.
Practice: Practice tying the hitch until you can do it quickly and easily.

Attaching the Ascender

Open the Ascender: Open the cam of the ascender.
Insert the Rope: Insert the climbing rope into the ascender, ensuring it is oriented correctly.
Close the Ascender: Close the cam of the ascender, ensuring it is locked securely.

Creating the Foot Loop

Cut the Webbing: Cut a length of webbing to the desired length for your foot loop.
Sew or Tie: Sew or tie the ends of the webbing together to create a loop. If tying, use a strong knot such as a water knot.
Adjustability: Add a buckle or knot system to allow for adjustment of the foot loop.

Connecting the Tether

Cut the Tether Material: Cut a length of dynamic rope or webbing for the tether.
Connect to Ascender: Connect one end of the tether to the ascender using a carabiner or a sewn loop.
Connect to Foot Loop: Connect the other end of the tether to the foot loop using a carabiner or a sewn loop.

Adjusting and Fine-Tuning Your System

Adjusting the Friction Hitch

Too Much Friction: If the friction hitch is too tight, it will be difficult to move up the rope. Try loosening the hitch by reducing the number of wraps or using a different cord.
Not Enough Friction: If the friction hitch is not tight enough, it will slip. Try tightening the hitch by increasing the number of wraps or using a more aggressive cord.
Experiment: Experiment with different hitch configurations to find what works best for you.

Adjusting the Tether Length

Too Long: If the tether is too long, you will have to bend your knee excessively to push the ascender up the rope. This can be tiring. Shorten the tether until your knee is bent at a comfortable angle.
Too Short: If the tether is too short, you will not be able to extend your leg fully. This can limit your climbing efficiency. Lengthen the tether until you can extend your leg fully.
Fine-tuning: Make small adjustments to the tether length until you find the sweet spot.

Adjusting the Foot Loop

Too Tight: If the foot loop is too tight, it will restrict circulation to your foot. Loosen the foot loop until it is comfortable.
Too Loose: If the foot loop is too loose, your foot will slip out. Tighten the foot loop until it is snug but not too tight.
Padding: Add padding to the foot loop for increased comfort during long climbs.

Using Your Knee Ascender: A Practical Guide

Attaching to the Climbing Rope

Throw Your Line: Throw your climbing line over a suitable branch.
Attach the Ascender: Attach the ascender to the climbing rope.
Attach the Foot Loop: Place your foot in the foot loop.
Connect to Harness: Connect the friction hitch to your climbing harness with a locking carabiner.

The Climbing Motion

Push with Your Leg: Push down with your leg, extending your knee and moving the ascender up the rope.
Slide the Friction Hitch: Slide the friction hitch up the rope with your hand.
Repeat: Repeat the process, alternating between pushing with your leg and sliding the friction hitch.

Descending Techniques

Lowering: Lower yourself by slowly releasing the friction hitch, allowing the rope to slide through the ascender.
Controlled Descent: Practice controlled descents to get a feel for the system.
Backup: Always have a backup system in place, such as a second friction hitch or a mechanical descent device.

Safety Considerations

Pre-Climb Inspection

Rope: Inspect the rope for any signs of damage, such as cuts, abrasions, or discoloration.
Ascender: Inspect the ascender for any signs of wear or damage. Ensure the cam is functioning properly.
Foot Loop: Inspect the foot loop for any signs of wear or damage.
Tether: Inspect the tether for any signs of wear or damage.
Friction Hitch: Inspect the friction hitch cord for any signs of wear or damage.
Carabiners: Inspect the carabiners for any signs of damage. Ensure the gates are locking properly.

Proper Technique

Stay Balanced: Maintain your balance while climbing.
Use Your Legs: Use your legs to do most of the work.
Avoid Shock Loading: Avoid sudden, jerky movements that can shock load the system.
Communication: If climbing with a partner, communicate clearly.

Weight Limits

Rope: Do not exceed the rope’s Working Load Limit (WLL).
Ascender: Do not exceed the ascender’s weight limit.
Carabiners: Do not exceed the carabiners’ weight limits.
Overall System: Ensure the entire system is rated to support your weight.

Environmental Factors

Weather: Avoid climbing in wet or icy conditions.
Tree Condition: Avoid climbing in trees that are dead, diseased, or unstable.
Obstacles: Be aware of any obstacles in the tree, such as branches or power lines.

Troubleshooting Common Problems

Slipping Ascender

Cause: Dirty rope, worn cam, incorrect rope diameter.
Solution: Clean the rope, replace the ascender, or use an ascender that is compatible with the rope diameter.

Binding Friction Hitch

Cause: Too much friction, incorrect hitch configuration, dirty rope.
Solution: Loosen the hitch, try a different hitch configuration, or clean the rope.

Foot Loop Discomfort

Cause: Foot loop too tight, lack of padding.
Solution: Loosen the foot loop, add padding, or use a different foot loop design.

Tether Length Issues

Cause: Incorrect tether length, changes in climbing style.
Solution: Adjust the tether length until it is comfortable and efficient.

Advanced Techniques and Customization

Adding a Chest Harness

Purpose: A chest harness can help keep you upright and prevent you from tipping backward.
Attachment: Attach the chest harness to the ascender or friction hitch.

Using a Mechanical Prusik Minder

Purpose: A mechanical prusik minder can help you advance the friction hitch more easily.
Attachment: Attach the prusik minder to the friction hitch.

Customizing Foot Loop Design

Padding: Add extra padding to the foot loop for increased comfort.
Shape: Experiment with different foot loop shapes to find what works best for you.
Materials: Use different materials for the foot loop to improve durability or comfort.

Alternative Climbing Methods and Gear

Comparison to Other SRT Systems

Knee Ascender vs. Foot Ascender: Foot ascenders attach directly to your boot and can be more efficient for some climbers.
Knee Ascender vs. Hand Ascender: Hand ascenders use your hands to pull yourself up the rope. They can be less tiring than knee ascenders for short climbs.

Commercial Knee Ascender Options

Advantages: Commercial knee ascenders are often more durable and feature-rich than DIY systems.
Disadvantages: Commercial knee ascenders can be more expensive than DIY systems.

Double Rope Technique (DRT)

Description: DRT involves using two ropes to climb.
Advantages: DRT can be more versatile than SRT in some situations.
Disadvantages: DRT can be more complex than SRT.

Maintaining Your System

Cleaning and Inspection

Rope: Clean the rope with mild soap and water. Inspect the rope regularly for any signs of damage.
Ascender: Clean the ascender with a brush and mild soap and water. Inspect the ascender regularly for any signs of wear or damage.
Foot Loop: Clean the foot loop with mild soap and water. Inspect the foot loop regularly for any signs of wear or damage.
Tether: Clean the tether with mild soap and water. Inspect the tether regularly for any signs of wear or damage.
Friction Hitch: Inspect the friction hitch cord regularly for any signs of wear or damage.
Carabiners: Clean the carabiners with a brush and mild soap and water. Inspect the carabiners regularly for any signs of damage.

Storage

Dry: Store the system in a dry, cool place away from direct sunlight.
Away from Chemicals: Store the system away from chemicals or solvents.
Organized: Store the system in an organized manner to prevent tangling.

Replacement Schedule

Rope: Replace the rope every 3-5 years, or sooner if it shows signs of damage.
Ascender: Replace the ascender when it shows signs of wear or damage.
Foot Loop: Replace the foot loop when it shows signs of wear or damage.
Tether: Replace the tether when it shows signs of wear or damage.
Friction Hitch: Replace the friction hitch cord when it shows signs of wear or damage.
Carabiners: Replace the carabiners when they show signs of damage or when the gates no longer lock properly.

Conclusion

Building and using a DMM Tendon DIY knee ascender system can significantly improve your climbing efficiency and reduce strain on your body. However, safety should always be your top priority. Regularly inspect your equipment, practice proper technique, and be aware of environmental factors. Continuously learn and refine your skills to become a safer and more efficient arborist. Remember, the information provided in this guide is for informational purposes only. Always consult with a qualified arborist or climbing instructor before attempting any new climbing techniques. Climbing is inherently dangerous, and you are responsible for your own safety.