Nobody had poured anything yet and the wall was already out
Four panel bays of 3.6 m wall form, ganged and stood on a Thursday for a Monday pour, rakers hung off the strongbacks and footed on the slab with drilled-in anchors. On Friday morning the top of bay three sat about 40 mm off the string line, all in one direction, and the rakers on that bay were finger-slack. Nothing had failed. No anchor had pulled, no timber had split, no plate had cracked. The assembly had simply been pushed by a night of wind against a set of rakers that were never tightened past hand-tight, and it stayed where the wind put it.
That is the whole subject in one anecdote, because the load that moved it had nothing to do with concrete. The trade instinct is to size a brace against the thing everyone photographs — a form bellied out by a fast pour — and that instinct sends you to the wrong load in the ordinary case and to a badly undersized one in the case that actually matters. Getting the raker right starts with being precise about which push it is resisting, and the answer changes completely depending on whether there is a second face of form on the far side of the wall.
The ties swallow one load; the rakers are there for the other
On a conventional double-faced wall form the fluid concrete pushes outward on both faces at once. Those two pushes are equal, opposite, and connected — by the ties running through the wall. A tie is in tension precisely because it is holding two faces together against a pressure that is trying to separate them, and once it does that, the pair of forces closes on itself. It never reaches the slab. Nothing outside the panel sandwich has to react it. This is why a 3 m wall form can be poured full of concrete generating tens of kilopascals on every square metre of sheathing while the rakers behind it carry a load you could lift by hand.
So what does the raker do? It resists overturning, which is a different problem with a different set of causes: wind on an exposed panel face, workers and hose crews leaning and pulling on the top rail, a delivery line snatching as the pump strokes, a bucket swung slightly wrong, a concrete truck reversing into a kicker, and the plain fact that a stood panel is a tall object with a small footprint. None of those is calculable to any useful precision on a Tuesday afternoon, which is exactly why the governing documents put a floor under the number instead of asking you to derive it.
ACI 347R states that minimum as a lateral force per unit length of wall applied at the top of the form, and points at ASCE/SEI 37, Design Loads on Structures During Construction, for the construction-stage wind case that frequently governs above it. Take the figure from the edition your specification names. Both documents have been revised, the floor is written per linear foot or metre of wall rather than per unit of face area, and a remembered number from a previous job is the single most common way a bracing design starts wrong. In the UK the same duty runs through BS 5975 and the project's temporary works procedure; across much of Europe through EN 12812; in Australia through AS 3610; and in the United States, 29 CFR 1926 Subpart Q makes bracing formwork against the loads applied to it a legal obligation rather than a matter of judgement.
There is an arithmetic trap in moving from that code floor to a page that wants a pressure. A line load applied at the top of a form of height H makes a moment about the base of w x H per unit length. A uniform pressure p over the same height makes a resultant of p x H acting at mid-height, so its moment is p x H squared over two. Equate the two and p equals two w divided by H, not w divided by H. Dividing once looks right, produces a tidy number in the correct units, and halves the design moment. For a 3.6 m form, a code floor of w kilonewtons per metre of wall becomes a uniform pressure of 0.56 w kilopascals; divide once and you get 0.28 w, which is in the right units and the right order of magnitude and therefore survives every sanity check anyone applies to it.
Work the ordinary case through and the scale becomes obvious. Take 720 Pa as the design lateral load on the face, a 3.6 m panel, rakers at 1.8 m centres so each one is tributary to a 1.8 m strip, attachment at 3.0 m up the panel, raker at 55 degrees to the slab. The strip carries 4.67 kN. Resolved about a base assumed pinned, that is 8.40 kN.m of overturning, 2.80 kN of horizontal reaction at the attachment, 4.88 kN of axial load in the raker and 4.00 kN of vertical reaction into the slab. Those are numbers a 100 by 100 timber and a single drilled anchor will handle without discussion. Which is the point: on a double-faced form, bracing is genuinely a modest problem, and treating it as the same problem as the ties is what leaves crews unprepared for the case where it is not.
Take the far face away and the pour rate walks straight into the slab
Cast a wall against sheet piling, against a blinding and an existing basement wall, against rock, or against a previously poured lift on a shaft, and there is nothing on the other side to tie back to. Every tie you would have used has been deleted from the drawing, and the load they were carrying does not disappear — it goes down the bracing frame, into the anchorage, and into whatever the anchorage is fixed to. This is the case where the description at the top of this page is literally true: what the brace has to survive is set by how fast the concrete goes in, because nothing else is holding it.
The size of the jump is the thing to internalise. Same 3.6 m form, same 1.8 m raker spacing, same geometry, but now with the concrete's own lateral pressure to carry. Take ordinary concrete at roughly 23.5 kN per cubic metre and assume it is still behaving as a liquid the whole way down, which is what a fast pour in cold weather delivers: 84.6 kPa at the base and an average of 42.3 kPa over the height. The tributary strip now carries 274 kN rather than 4.67 kN, the horizontal reaction at the attachment is 164 kN, and the axial load in the raker is 287 kN. That is not a bigger timber. It is a different category of object — a proprietary single-sided support frame, designed by the formwork supplier, working through a designed bearing and anchorage arrangement, and signed off as temporary works rather than assembled by a gang from what is on the rack.
Two honest qualifications sit on those numbers. First, the statics behind the brace-force arithmetic assumes a uniform pressure over the form height, and a genuinely hydrostatic distribution is triangular, with its resultant at the lower third rather than at mid-height. Entering the average of a triangle therefore overstates the overturning moment by half — 493 kN.m against 329 kN.m, which is 287 kN of raker load against 191 kN. Second, a rate-limited pour under ACI 347R is not triangular either: pressure builds to a maximum and then holds roughly constant below it, so the true envelope sits between the two, and the uniform assumption is closer to right for that shape than it is for pure liquid head. Neither qualification is a reason to design on the lower figure without a temporary works designer putting their name to the distribution.
What both qualifications share is that they depend on a pressure you have to establish before any of this arithmetic means anything. Placement rate, concrete temperature at the wall rather than at the plant, unit weight and the admixture regime all move it, and a supplier quietly switching to a more flowable mix moves it without any drawing changing. Self-consolidating concrete removes the rate from the argument entirely and should be treated as full liquid head unless the supplier can substantiate otherwise — which on a single-sided form is the difference between a designed frame and an incident.
On a single-sided form this is the number that becomes the bracing load rather than a sheathing check, so run it at the coldest placement temperature and the fastest rise the pump can actually deliver, not at the ones the pour plan hopes for.
The fresh concrete's unit weight.
How fast the concrete surface rises at this form location, in feet per hour.
The temperature of the fresh concrete at placement, in °F.
ACI 347R Table 2.2 chemistry coefficient for the cement/admixture combination used.
The total vertical height of the wall being poured.
Maximum lateral formwork pressure
970 psf
Wall pressure is rate-limited rather than height-limited. Because a wall is filled over a long period, the concrete at the base normally stiffens before the top arrives, and the pressure envelope caps out well below full hydrostatic.
- Unit weight coefficient Cw
- 1 (dimensionless)
- Full hydrostatic ceiling
- 1,500 psf
They open the calculator with your figures already in it
ACI 347 Wall Formwork Rate-of-Placement Pressure Calculator: 970 psf — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 970 psf — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The rate-based reduction depends on the concrete stiffening as expected. Retarders, cold weather and high cement replacement all delay that and raise the pressure.
- Excludes wind load on the form face, which on a tall free-standing wall form can govern the bracing even though it does not affect the ties.
- Does not address the uplift and lateral load at a construction joint, or the loads from the placing equipment resting on or against the form.
Angle and attachment height are the only two dials you have
Once the lateral load is settled, everything else about a raker is trigonometry, and both variables push in directions the site does not want. The axial force in the raker is the horizontal reaction divided by the cosine of its angle to the slab, and the vertical force it drives into the anchorage is that same reaction times the tangent. Steep is cheap on floor space and expensive in every other way: at 60 degrees the raker carries twice the horizontal reaction, and the anchor takes 1.73 times that reaction vertically on top of the shear it already has. Flat is kind to the raker and to the anchor and eats deck the job wants for rebar, reo bundles, hose runs and access.
Attachment height is the more brutal of the two because it enters the moment directly. The overturning moment about the base is fixed by the load and the panel height; the horizontal reaction is that moment divided by the height at which the raker connects. Attach at mid-height instead of near the top and the reaction, the axial load and the vertical pull all double for no change whatsoever in what the wind or the concrete is doing. Crews attach low for real reasons — the walkway bracket is in the way, the panel's top rail is not a designed connection point, the raker on the rack is short — and every one of those reasons costs a factor that shows up at the anchor rather than at the panel.
The other thing attachment height sets is footprint. Reach along the slab is the attachment height divided by the tangent of the angle, so the same 3.0 m connection needs 5.2 m of clear deck at 30 degrees and 1.09 m at 70 degrees. That is the trade being made in the table below: read across a row and you are trading anchor load against square metres of working platform, and the decision is usually taken by whoever is standing there rather than by anyone who has seen these multipliers.
| Raker angle to slab | Axial force in raker (x horizontal reaction) | Vertical force at anchor (x horizontal reaction) | Deck taken up, attaching at 3.0 m |
|---|---|---|---|
| 30 degrees | 1.15 | 0.58 | 5.20 m |
| 40 degrees | 1.31 | 0.84 | 3.58 m |
| 45 degrees | 1.41 | 1.00 | 3.00 m |
| 50 degrees | 1.56 | 1.19 | 2.52 m |
| 55 degrees | 1.74 | 1.43 | 2.10 m |
| 60 degrees | 2.00 | 1.73 | 1.73 m |
| 65 degrees | 2.37 | 2.14 | 1.40 m |
| 70 degrees | 2.92 | 2.75 | 1.09 m |
What stops a stood panel from lying down
- Raker — the only member here sized by trigonometry rather than by pressure, and the one whose load doubles if it is connected at mid-height instead of near the top Formwork Brace & Kicker Force Calculator
- Strongback — spreads one raker's reaction across several panel ribs, because a point load taken on a single rib tears the rib out rather than moving the wall
- Form panel — sized by the concrete's pressure on its face and by the tie grid, which is a separate problem from the one the raker answers Concrete Formwork Calculator
- Kicker plate at the foot — restrains the panel base against sliding, which is the assumption the raker arithmetic makes when it treats the form as pinned there
- Slab and anchorage — takes the horizontal reaction in shear and the vertical component in tension or bearing, often in concrete only days old and close to a free edge Concrete Anchor Bolt Breakout Capacity Calculator (ACI 318)
Enter the lateral load you settled in the section above, not the concrete's pressure on the sheathing, and read the vertical reaction as carefully as the axial one — it is the line that usually decides whether the anchorage works.
Full height of the form panel that the lateral pressure acts against.
Centre-to-centre spacing of the kickers, which is also the width of form tributary to one of them.
Lateral load per unit of form face, taken from the governing construction-loads document.
Angle the kicker makes with the slab it bears on, measured at the anchorage.
Height above the base of the form at which the kicker connects to it.
Axial force in the brace
1.13 kips
This is one brace resolved by statics. Whether the slab can take it is a separate anchor check against the concrete's age and strength on the day, the embedment available, and the edge distance at the fixing — a young slab is the usual weak link, not the kicker.
- Total lateral force on the braced strip
- 0.9 kips
- Horizontal reaction at the anchorage
- 0.56 kips
- Vertical reaction at the anchorage
- 0.98 kips
- Lateral force per unit length of form
- 150.38 lbf/ft
They open the calculator with your figures already in it
Formwork Brace & Kicker Force Calculator: 1.13 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 1.13 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Single-sided bracing on a form pinned at its base; a form braced from both faces, or one restrained at the base by a kicker plate, distributes the load differently.
- Does not check the brace member itself for buckling, nor its end connections — a compression kicker at this angle is often governed by slenderness rather than by axial capacity.
The number that catches people out is the one pointing down
A raker in compression presses its foot into the slab, and a raker in tension pulls its foot out of the slab. Both are routine on the same wall: kickers on the pour side push while ties or turnbuckle braces on the other side pull, and a form being plumbed is doing both alternately in the ten minutes before the concrete arrives. The vertical component is what the anchorage has to take, and at 55 degrees it is 1.43 times the horizontal reaction, while at 65 degrees it is 2.14 times. It is not a secondary effect, and it is not the shear the anchor was probably selected for.
Concrete breakout in tension is the usual limit, and the geometry conspires against it. Brace anchors sit near the wall being formed, which is frequently near a slab edge, which is where the breakout cone runs out of concrete. They sit in slabs that may be four days old rather than at 28-day strength. They sit at whatever embedment the drill and the slab thickness allowed rather than at the embedment the anchor was rated on, and on a topping or a slab with a void former beneath it, the depth available is nothing like the depth on the datasheet.
ACI 318 Chapter 17 is the governing procedure in North America, and it is worth seeing how much of it a basic figure leaves out. A 100 mm post-installed anchor in 20 MPa concrete has a basic breakout capacity around 32 kN, which against the 4.00 kN of vertical reaction from the worked example looks like a comfortable margin — until the edge-distance factor, the anchor-spacing factor, the cracked-concrete modifier and the strength-reduction factor are all applied, at which point a good part of it is gone. Where a specific product is used, its ICC-ES evaluation report and its qualification testing under ACI 355.2 or ACI 355.4 govern over any generic figure, and ASTM E488 is the test method those qualifications run to.
The practical answer on site is to stop treating brace anchorage as a fixing and start treating it as a tested component. Set anchors to the manufacturer's hole depth, cleaning regime and torque; keep the specification's proof-load regime rather than pull-testing whatever looks doubtful; record which slab pour they went into and how old it was; and where the anchor lands within an edge distance the report does not cover, move it or design it, because there is no site adjustment that recovers a cone that is not there.
This gives the basic single-anchor figure before any of the reductions that will actually apply, which makes it useful for exactly one thing — seeing early whether the vertical reaction is in the same order of magnitude as the concrete's capacity, or nowhere near it.
The effective embedment depth of the anchor into the concrete.
The concrete's specified compressive strength.
Whether the anchor was cast into the wet concrete or drilled and fixed afterwards.
Basic breakout capacity
8.6 kips
This is the BASIC single-anchor breakout strength only (ANc/ANco = 1, no edge-distance, spacing or eccentricity reduction, and no Psi-c,N cracking modifier — ACI 318's basic equation is on a cracked-concrete basis, and an anchor verified to sit in uncracked concrete earns a further increase this figure does not take) — it assumes the anchor is far enough from any edge or other anchor to develop a full breakout cone. Real anchor design requires the complete ACI 318 Chapter 17 procedure, verified by a licensed engineer.
- Equivalent in lbs
- 8,601.4 lb
They open the calculator with your figures already in it
Concrete Anchor Bolt Breakout Capacity Calculator (ACI 318): 8.6 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 8.6 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- This is a nominal strength, not a design capacity. No strength-reduction factor is applied and no factored load is checked against it, so the figure cannot stand as a code compliance check on its own.
- Only concrete breakout in tension is modelled. Anchor steel fracture, pullout at the head, side-face blowout near a free edge, shear breakout and combined tension-plus-shear interaction are not calculated, and any one of them can govern the anchor instead.
- The full unrestricted breakout cone is assumed. Member thickness, group behaviour where several anchors share a cone, and anchor reinforcement designed to carry the load past a breakout failure are all outside this calculation, on top of the edge-distance, spacing and eccentricity factors the result note already flags.
- Normalweight concrete in ordinary service is assumed. There is no lightweight-concrete modification, no cracked-versus-uncracked modification, and no seismic provisions — an anchor in a seismic force-resisting system is subject to extra requirements this page does not touch.
- For post-installed anchors the generic coefficient of 17 stands in for the actual product. It carries nothing about adhesive bond strength, elevated-temperature or sustained-load performance, hole cleaning, drilling method or installation torque, all of which the manufacturer's qualified evaluation report governs.
A raker is a column, and usually a long one
The statics that resolves a lateral load into an axial force says nothing about whether the member can carry that force. A raker at 55 degrees connecting at 3.0 m is 3.66 m long, unrestrained along its whole length, pinned at both ends in any practical sense, and loaded in compression through both connections. That is a slender column by any definition, and slender columns fail by buckling at loads far below their crushing capacity. The Euler critical load falls with the square of length, so the raker you lengthened by half a metre to clear a rebar stack lost around a quarter of its critical load in the process.
For the worked example, a 100 by 100 timber raker at 3.66 m with a modulus of elasticity around 11,000 MPa has an elastic critical load near 67 kN against a demand of 4.88 kN, which is ample. That comparison is illustrative rather than a design check: the Euler load is the elastic instability point, and real timber design under the NDS or under EN 1995-1-1 applies a column stability factor that brings the usable capacity well below it, before any duration-of-load or moisture adjustment. It also assumes a straight, sound member with both ends genuinely pinned and no load applied along its length — none of which describes a raker somebody has hung a hose off.
Adjustable steel push-pull props change the question rather than removing it, because their rated capacity is a function of extension. A prop near its closed length can be worth several times the same prop wound out, and the manufacturer's load-versus-extension table is the only source for that curve; EN 1065 is the product standard adjustable telescopic steel props are made and assessed to in Europe. Reading the box end of the prop, or assuming a rating that was true of a shorter one, is how a bracing frame gets designed for a capacity nothing on site actually has.
The brace-force arithmetic deliberately stops at the axial load and does not check the member carrying it, so this is the second half of the same question — enter the raker's full sloped length, not the height it reaches.
The wood member's modulus of elasticity along the grain.
The column's cross-sectional moment of inertia about the axis it will buckle around.
Accounts for how the column's ends are restrained against rotation and translation.
The column's unsupported (unbraced) length between points of lateral restraint.
Critical buckling load
262.7 kips
They open the calculator with your figures already in it
Timber Column Euler Buckling Calculator: 263 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 262.7 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The calculation takes only the moment of inertia, never the cross-sectional area, so it cannot compare the Euler load with the load at which the wood simply crushes. At the default values the 1,206 kN (271,120 lbf) returned implies a section roughly 186 mm square, which at a compression-parallel-to-grain strength near 20 MPa crushes at about 690 kN (155,118 lbf). Stocky columns fail that way long before the Euler load is reached, and this page will not tell you when that is the case.
- The moment of inertia box has no unit selector: it stays in millions of mm⁴ even when the unit switch is set to imperial and the modulus is being read in psi. A 5½ × 5½ in post has I = 76.3 in⁴, which must be entered here as 31.7, because one in⁴ is 416,231 mm⁴. Entering the inch value directly overstates the buckling load by a factor of more than two.
- One run checks one buckling axis. A rectangular post has two moments of inertia and frequently two different unbraced lengths, because sheathing or noggins may restrain the weak axis at mid-height while the strong axis runs the full storey height, and the governing case is the largest (KL)²/I rather than automatically the smaller I. Run it once per axis and take the lower answer.
- Buckling is governed by stiffness, and design codes require a low-percentile modulus for stability checks — Emin in the NDS, E0,05 in Eurocode 5 — not the published mean value that the 11,000 MPa default represents. The size of that reduction is jurisdictional, but it is substantial, and sustained load reduces effective stiffness further through creep, which this page does not model at all.
- No factor of safety is applied. The figure is the load at which a perfectly straight, concentrically loaded elastic column collapses, and it carries no adjustment for load duration, moisture content or elevated temperature, so none of CD, CM and Ct in the NDS or kmod in Eurocode 5 appear in the arithmetic. A post with a beam framing to one face, or with the initial bow that graded timber is permitted to have, is also carrying bending, and that axial-plus-bending interaction is a separate check this page does not perform.
- The four effective length factors offered are Euler's textbook end conditions and assume ideal restraint. A base plate bolted to a slab is not the perfectly fixed end that K = 0.5 describes, design practice commonly recommends higher values than theory for exactly that reason, and a column free to sway at the top can exceed the K = 2.0 that the cantilever option allows.
The most exposed the form ever is, is the night before
A form full of concrete is a heavy, damped, laterally loaded object that is mostly restrained by its own ties. An empty form is a light sail on a small footprint with the whole of its face presented to the wind, and it typically stands like that for days. The condition attracts less attention than the pour precisely because nothing is happening, and the collapses that do happen to stood formwork happen overwhelmingly to forms with no concrete in them. Construction-stage wind is a design case in its own right rather than a caveat on the pour: ASCE/SEI 37 exists because permanent-works wind loads, with permanent-works return periods, are the wrong basis for something that stands for three weeks.
Treat the erected-and-waiting condition as its own check with its own duty holder. Rakers get tightened to snug and then verified, not left hand-tight for a plumbing session that never happens; both faces of a ganged run get braced if the wind can come from both directions, which on an open slab it can; a run left over a weekend gets walked on the Monday before anybody starts fixing to it. Where panels are ganged for craning, the lifting arrangement and the standing arrangement are different load cases and the supplier's data covers both separately — a gang designed to be lifted is not automatically a gang designed to stand unattended in a gale.
Setting them so they stay where you put them
The sequence matters more than the hardware, because almost every out-of-plumb wall was plumb at some point and drifted while people worked around it. Bracing is a system with slack in it, and slack comes out in one direction only.
- Mark raker positions off the panel layout before anything is stood, so a raker never ends up landing on a rib that is not there or on a floor box that is.
- Drill and set the slab anchors first where access allows it, and confirm the slab's age and the edge distance at each position rather than at one representative one.
- Stand the panel run and fit the kicker plate at the foot before any raker is loaded, because the arithmetic assumes the base cannot slide.
- Connect rakers at the highest designed attachment point on the strongback, hand-tight only, both ends fully seated in their brackets.
- Plumb the run with an instrument or a long level, working across the whole gang rather than bay by bay, and take up slack in opposing rakers alternately.
- Tighten to snug and check plumb a second time, because tightening moves the wall — this is the step most often skipped and the one that produced the 40 mm at the top of bay three.
- Record the check, and re-check after the first metre of concrete goes in, when any settlement of the anchorage or bedding-in of the connections will have already happened.
What a brace does before it lets go
Rakers announce trouble early and quietly. A brace that was snug and is now slack has either moved at its foot or the wall has moved away from it; either way something has already happened. Grey dust collecting in a ring around an anchor head is the anchor working in its hole. A base plate that has crept across the slab leaves a clean arc on a dusty deck that is visible from ten metres away. A shifting plumb reading during a pour is the most reliable signal of all, because unlike everything else on that list it accumulates in one direction and does not come back.
Give one person the walk and no other duty during the pour, with the plumb line as their instrument rather than their eye, and make sure the raker feet are reachable — a deck stacked with hose and rebar between the wall and the raker anchors turns an inspection into a guess. The far face of a single-sided form cannot be inspected at all, which is another reason those pours are designed rather than assembled.
If the reading is drifting, the intervention is to stop placing and let the concrete at the base stiffen, not to add rakers into a loaded frame. A raker fitted to a wall that is already leaning is being asked to push it back rather than to hold it still, and the force needed to do that has nothing to do with the number anyone calculated. Stop, wait, resume slower, and treat the resulting line as a joint you chose.
What the bracing design needs before panels go up
Six answers turn a raker from a piece of timber leaning on a wall into a designed load path — and all six are settled at a table, not at the slab edge with a gang waiting.
- Which lateral load case governs this form — Double-faced walls are braced against wind and the code minimum; single-sided ones are braced against the concrete itself, and the two differ by roughly two orders of magnitude.
- Raker spacing along the run, and the tributary strip each one takes — A regular run gives a tributary width equal to the spacing; an end raker takes less and a raker either side of a blockout takes more, and neither is covered by one figure.
- Attachment height on the strongback, measured not assumed — Connecting at mid-height rather than near the top doubles the axial force and the vertical pull without anything else changing.
- Raker angle, agreed against the deck space it consumes — Steep saves floor and costs anchor capacity; the multipliers on both run away above 60 degrees.
- Slab age, thickness and edge distance at every anchor position — Brace anchors sit near slab edges in young concrete, which is where breakout capacity is lowest and where the datasheet embedment may not fit.
- Raker length and its rated capacity at that length — Timber loses critical load with the square of length; an adjustable prop's rating falls as it is wound out, and only the manufacturer's table gives that curve.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.