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How tall is a 35 foot ext. ladder when up all the way at the propar climbing angle..Is there a formula for figuring this out?

2. Yes, there is a formula. Its called the Pythagorean Theorem.

C = square root of (A squared plus B squared)

This works perfectly for a ladder placed for rescue, not so perfectly for a ladder placed for roof access. A 35' ladder fully extended placed for rescue would give you a 34' working height.

For roof access you must subtract the length of the ladder from its resting point on the roof from its fully extended length thus changing your hyptenuse, the ladder length, to around 31'
Knowing a ladder placed for roof access should have 3-5 rungs above the roof line will reduce your working height to about 30'.

Its really quite simple

3. ## Easy rough rule for ladder

Easier one to remember.

Take the working distance of the ladder that is extended and reduce it by 1/4. for proper climbing angle. So if you are using a 24 foot ladder you should have 6 feet from the building and this reduces the height to 18 feet. A 35 foot ladder in reality should give you a working length of 26 feet. Rough rule 35 foot ladder round off to 36 feet 1/4 of 36 feet is 9 feet and that gives you roughly 26 to 27 feet.

Plus or minus if your leaving tip over the top of the roof or window entry etc.

Dave Williams
City of Orlando Fire Department
Engine 101 station 1 " The Big House"

4. Originally Posted by doughboy758
Easier one to remember.

Take the working distance of the ladder that is extended and reduce it by 1/4. for proper climbing angle. So if you are using a 24 foot ladder you should have 6 feet from the building and this reduces the height to 18 feet. A 35 foot ladder in reality should give you a working length of 26 feet. Rough rule 35 foot ladder round off to 36 feet 1/4 of 36 feet is 9 feet and that gives you roughly 26 to 27 feet.
This is off quite a bit. If this was true a 100 foot aerial with a 50 ft. setback could only reach 50 ft up, when in fact it can reach 85 ft! This is a huge difference.

Using the Pythagorean Theorem, a 35 rounded to 36 ft. gives you 34 ft. of height. Basically using (B sq.)9 ft (1/4 the overall length as you distance from the wall) and 36 ft. as the ladder length (C sq.) so the formula looks like this:

A squared X 81 (9 squared) = 1225 (35 squared)
A squared = 1225-81 (1144)
A = 33.8

Basically the distance from the wall can not be completely subtracted from the height. By your formula the difference is nearly 10 ft.

5. Originally Posted by RFDACM
This is off quite a bit. If this was true a 100 foot aerial with a 50 ft. setback could only reach 50 ft up, when in fact it can reach 85 ft! This is a huge difference.
An aerial device is rated differently than a ground ladder. A 35' ground ladder is 35' in length when fully extended. A 100' aerial ladder is 100' from tip to the ground when fully extended at 70 degrees.

7. It would still be 35'. I dont think they shrink when you raise them.

Ill take what is the REACH of a 35' extension ladder for a \$100 Alex.

8. Rule of thumb...Ladders 35' and less reach 1' less than the designated length.
Ladders over 35' reach 2' less than the designated length.

9. Take the working distance of the ladder that is extended and reduce it by 1/4. for proper climbing angle. So if you are using a 24 foot ladder you should have 6 feet from the building and this reduces the height to 18 feet. A 35 foot ladder in reality should give you a working length of 26 feet. Rough rule 35 foot ladder round off to 36 feet 1/4 of 36 feet is 9 feet and that gives you roughly 26 to 27 feet.

This is not accurate at all.
The tip of the ladder, when against the building is a pivot point and will only come down inches. An example would be if you raise a ladder straight up against the wall to a window sill and then pull the base out the tip only drops an inch or two.
Your best formula would be to do it and measure it and remember it. When you need the ladder is not the time to do the math.

10. Originally Posted by masterFF
An aerial device is rated differently than a ground ladder. A 35' ground ladder is 35' in length when fully extended. A 100' aerial ladder is 100' from tip to the ground when fully extended at 70 degrees.
While the manner of rating may not be the same it does not change the Pythagoreum Theorum that dictates the "working length".

AxA (hgt of ladder @ wall) + BxB(dist. from Bldg) = CxC (ladder length)

rewritten as:
AxA= (CxC) - (BxB)
AxA= (35x35) - (1/4 of 35: 8.75x8.75 )
AxA= 1225 - 76.5
AxA=1148.5
Height up wall = square root of 1148.5 or 33.8 ft.

Same number as rounding within one tenth of a foot.

11. I'm usually big on numbers and preplanning what goes where but in this case get out and throw the ladder. I'm finding out, fast, that guys aren't very good at judging distances by eye.
The only way you will know for sure is to throw the ladder, a lot. Use different buildings, houses under construction, vacant buildings etc. After a while you will get a feel for what goes where. These kind of drills are a must for the progressive ladder company, know what your stuff can do, know your district and know your guys.

Stay safe

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