Saltwater
Freshwater
Select based on your diving location. Saltwater is denser.
Standard aluminum or steel tank size (e.g., 10L, 12L, 15L).
Starting pressure of the cylinder at the beginning of the dive.
The typical depth you'll reach during the dive.
Dive Weighting Results
—
Recommended Lead Weight (kg)
Buoyancy Compensation: — kg
Cylinder Contribution: — kg
Net Weight Needed: — kg
Formula: Required Lead = (Diver Weight + Drysuit Buoyancy – Cylinder Weight) / Water Density
Weight Distribution Over Dive Depth
How your required lead weight is affected by cylinder pressure as you descend.
Understanding Drysuit Weighting
Achieving neutral buoyancy while diving in a drysuit is crucial for a safe, comfortable, and enjoyable experience. Unlike a wetsuit, which compresses with depth and reduces its insulating properties, a drysuit traps air, providing both warmth and buoyancy. This trapped air, however, makes controlling buoyancy more complex, often requiring significant amounts of lead weight. Our drysuit weight calculator is designed to help you determine this optimal weight by considering various factors.
The Importance of Correct Weighting
Being over-weighted can lead to rapid descents, increased air consumption, and potential ear or sinus issues. Conversely, being under-weighted makes it difficult to achieve neutral buoyancy or descend, forcing you to constantly fight for position and potentially over-inflate your drysuit, creating buoyancy issues. Proper weighting, as estimated by a reliable drysuit weight calculator, allows for controlled ascents and descents, conserves energy, and enhances overall dive safety.
Factors Influencing Drysuit Weighting
Several elements contribute to the amount of lead you'll need. These include your personal weight, the specific buoyancy characteristics of your drysuit (which can vary based on material and fit), the type and amount of other gear you're wearing, the density of the water (saltwater vs. freshwater), and even the size and pressure of your scuba cylinder. The drysuit weight calculator factors these in to provide a more accurate estimate.
Common Misconceptions About Drysuit Weighting
"More weight is always better": This is false. Excessive weight is dangerous and counterproductive. The goal is neutral buoyancy, not sinking like a stone.
"My weight never changes": Your buoyancy needs can change with minor shifts in body weight, different undergarments, or even the type of gear used on a particular dive.
"One weight fits all dives": While a baseline is established, factors like depth, water temperature (affecting undergarment thickness), and cylinder size can influence ideal weighting.
Using a drysuit weight calculator is a great starting point, but always perform a buoyancy check in shallow water before your first dive with a new weighting configuration.
Drysuit Weight Calculator Formula and Mathematical Explanation
The core principle behind calculating the necessary lead weight for a drysuit dive is balancing the diver's total downward forces against the upward buoyant forces. Here's a breakdown of the formula and its components:
The Formula
The estimated lead weight required can be calculated using this formula:
Required Lead Weight (kg) = (Diver's Total Weight + Drysuit Buoyancy – Cylinder Weight) / Water Density
Variable Explanations
Let's break down each variable used in the drysuit weight calculator:
Variables Used in the Drysuit Weight Calculator
Variable
Meaning
Unit
Typical Range
Diver's Total Weight
The combined weight of the diver, drysuit, and all equipment except the lead weights and the scuba cylinder.
kg
60 – 120+
Drysuit Buoyancy
The estimated upward force (buoyancy) provided by the air trapped within the drysuit.
kg
2 – 7
Ballast Weight
Any lead weight that is already part of the diver's setup or used for dives with lighter exposure protection (e.g., wetsuits). This is subtracted from the total required to find the *additional* lead needed.
kg
0 – 10
Water Density
The density of the water, which directly affects buoyancy. Saltwater is denser than freshwater.
g/cm³ (or kg/L)
1.000 (Fresh) to 1.025 (Salt)
Cylinder Size
The volume of the scuba cylinder in liters.
L
5 – 18+
Cylinder Pressure
The pressure of the gas inside the cylinder at the start of the dive.
bar
50 – 230+
Average Dive Depth
The typical maximum depth the diver will reach. Used to estimate gas consumption and thus cylinder weight contribution.
m
5 – 40+
Cylinder Weight Contribution
The effective downward force exerted by the cylinder. This decreases as gas is consumed. Calculated based on cylinder size, pressure, and depth.
kg
Variable
Net Weight Required
The calculated total downward force needed to counteract buoyancy, after accounting for drysuit lift and cylinder weight.
kg
Variable
Recommended Lead Weight
The final calculated amount of lead weight to add, accounting for existing ballast.
kg
Variable
Mathematical Derivations
1. Buoyancy Force: Archimedes' principle states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object. Buoyant Force = Volume Displaced * Fluid Density * g (acceleration due to gravity). For simplicity in weight calculations, we often express this in terms of mass equivalent (kg).
2. Cylinder Weight Contribution: A scuba cylinder is filled with compressed gas. As the diver breathes this gas, the mass within the cylinder decreases, reducing its downward force. The weight of the cylinder itself also contributes. The effective weight decreases with gas consumption. For this calculator, we estimate the *average* weight contribution over the dive, considering starting pressure, gas density, and depth. A simplified approach often assumes a linear decrease in pressure, hence weight, over the dive's duration, influenced by depth via Boyle's Law.
3. Total Upward Force: This is primarily the buoyancy from the drysuit and the buoyant force from the water acting on the diver and equipment. The drysuit buoyancy is a fixed estimate. The water buoyancy depends on the total volume displaced and water density.
4. Total Downward Force: This includes the diver's mass, equipment mass, and the weight of the gas in the cylinder.
5. Neutral Buoyancy Condition: To be neutrally buoyant, the sum of downward forces must equal the sum of upward forces.
(Diver Mass + Gear Mass + Cylinder Mass) = (Drysuit Buoyancy + Water Buoyancy on Total Volume)
Rearranging to solve for the required external lead weight (W_lead):
W_lead + Diver_Mass + Gear_Mass + Cylinder_Mass = Drysuit_Buoyancy + Water_Buoyancy_on_Total_Volume
This becomes complex quickly. A more practical approach for a calculator is:
Target Total Downward Force = Total Upward Force
Diver_Weight_Total + Cylinder_Effective_Weight = Drysuit_Buoyancy + (Buoyancy_from_Displaced_Water)
The calculator simplifies this by calculating the required *net downward force* needed (Diver's Total Weight + Drysuit Buoyancy – Cylinder Weight) and then dividing by water density to find the equivalent mass of lead required. The 'Diver's Total Weight' input already implicitly includes the weight of the diver and gear minus the cylinder. The formula then represents the target downward force required to achieve neutral buoyancy.
Practical Examples (Real-World Use Cases)
Example 1: Standard Saltwater Dive
Scenario: A recreational diver is preparing for a typical dive in the ocean. They are wearing a drysuit, thermal layers, and standard equipment.
Inputs:
Diver's Total Weight: 85 kg
Drysuit Buoyancy: 5 kg
Existing Ballast Weight: 2 kg (integrated weights in BCD)
Water Type: Saltwater (Density: 1.025)
Cylinder Size: 12 L
Cylinder Pressure: 200 bar
Average Dive Depth: 25 m
Calculation Steps (as performed by the calculator):
Estimate Cylinder Weight Contribution: Based on 12L @ 200 bar and depth, let's assume an average contribution of ~3.5 kg downward force throughout the dive.
Calculate Net Weight Needed: (85 kg Diver Weight + 5 kg Drysuit Buoyancy – 3.5 kg Cylinder Contribution) = 86.5 kg
Calculate Required Lead: 86.5 kg / 1.025 (Saltwater Density) = ~84.4 kg total downward force equivalent.
Determine Additional Lead: 84.4 kg (Total Required) – 2 kg (Existing Ballast) = 82.4 kg
Calculator Output:
Primary Result: 82.4 kg Recommended Lead Weight
Buoyancy Compensation: 5 kg
Cylinder Contribution: 3.5 kg
Net Weight Needed: 86.5 kg
Interpretation: This diver will need approximately 82.4 kg of lead weight in total, factoring in their existing 2 kg ballast. This seems high, highlighting how much lift a drysuit provides. It's crucial to verify this in the water. Often, lead is distributed between a weight belt and integrated BCD pockets.
Example 2: Cold Freshwater Dive with Thick Undergarments
Scenario: A diver is planning a dive in a cold lake, requiring thicker undergarments for warmth, which increase overall buoyancy and diver weight.
Inputs:
Diver's Total Weight: 95 kg (includes heavier undergarments)
Drysuit Buoyancy: 6 kg (slightly more lift due to fuller suit)
Existing Ballast Weight: 0 kg (using a new setup with only a weight belt)
Water Type: Freshwater (Density: 1.000)
Cylinder Size: 15 L
Cylinder Pressure: 200 bar
Average Dive Depth: 18 m
Calculation Steps:
Estimate Cylinder Weight Contribution: For a 15L @ 200 bar, assume ~4.0 kg downward force.
Calculate Net Weight Needed: (95 kg Diver Weight + 6 kg Drysuit Buoyancy – 4.0 kg Cylinder Contribution) = 97 kg
Calculate Required Lead: 97 kg / 1.000 (Freshwater Density) = 97 kg total downward force equivalent.
Determine Additional Lead: 97 kg (Total Required) – 0 kg (Existing Ballast) = 97 kg
Calculator Output:
Primary Result: 97 kg Recommended Lead Weight
Buoyancy Compensation: 6 kg
Cylinder Contribution: 4.0 kg
Net Weight Needed: 97 kg
Interpretation: The combination of a higher diver weight, more buoyant drysuit, and lower water density means a significant amount of lead is needed. The diver will require a weight belt capable of holding approximately 97 kg. This emphasizes how different conditions and gear choices drastically alter weighting requirements. Always perform a slow, controlled buoyancy check before descending.
How to Use This Drysuit Weight Calculator
Using the drysuit weight calculator is straightforward. Follow these steps to get an estimate for your dive weighting:
Enter Your Total Weight: Input your weight combined with your drysuit and all gear (mask, fins, exposure suit, computer, etc.), but *exclude* the lead weights and the scuba cylinder.
Specify Drysuit Buoyancy: Estimate the upward force your drysuit provides. This is often subjective but typically falls between 2-7 kg for most standard drysuits. If unsure, start with a middle value like 5 kg.
Account for Existing Ballast: If you have any weights integrated into your BCD or a weight belt you always use, enter that amount here. This helps the calculator determine the *additional* lead you need.
Select Water Type: Choose 'Saltwater' or 'Freshwater'. Saltwater is denser, meaning you'll need slightly less lead than in freshwater for the same buoyancy effect.
Input Cylinder Details: Enter the size (in liters) and starting pressure (in bar) of the scuba cylinder you will be using.
Estimate Average Depth: Provide the typical maximum depth you expect to reach on the dive. This helps the calculator estimate how much gas (and therefore weight) you'll consume.
Calculate: Click the "Calculate Drysuit Weight" button.
Reading the Results
Primary Result (Recommended Lead Weight): This is the total amount of lead weight you should aim to have for your dive, accounting for existing ballast.
Buoyancy Compensation: This shows the estimated upward force from your drysuit.
Cylinder Contribution: This is the estimated average downward force provided by your scuba cylinder throughout the dive as you consume gas.
Net Weight Needed: This represents the total downward force required to achieve neutral buoyancy, considering your weight, drysuit lift, and cylinder contribution, adjusted for water density.
Decision-Making Guidance
The output from the drysuit weight calculator is an estimate. It's crucial to always perform a buoyancy check in shallow water (waist-deep) before your actual dive. For the buoyancy check:
Put on all your gear, including the calculated amount of lead weight.
Inflate your BCD slightly to maintain a stable position.
Add a small amount of air to your drysuit (just enough to be comfortable).
Inhale fully. You should rise slowly towards the surface.
Exhale fully. You should remain neutrally buoyant or descend slowly.
If you sink rapidly upon exhaling, you are over-weighted. If you continue to rise uncontrollably even when exhaled, you are under-weighted. Adjust your lead weight accordingly and repeat the check.
Key Factors That Affect Drysuit Weight Results
While the drysuit weight calculator provides a solid estimate, several real-world factors can influence the exact amount of weight you need. Understanding these helps in fine-tuning your weighting:
Drysuit Material and Fit: Thicker materials (like trilaminates or crushed neoprene) and looser fits can trap more air, increasing inherent buoyancy. A tighter, more streamlined suit might require less weight. Some suits are designed with less inherent buoyancy.
Undergarment Thickness: The layers worn beneath your drysuit significantly impact your overall bulk and buoyancy. Thicker polar fleece or insulated undergarments add volume and require more weight to counteract. This can vary seasonally.
Diver's Body Composition: Muscle is denser than fat. Divers with higher muscle mass may require less lead than those with a higher body fat percentage, assuming similar overall weight. The calculator uses total weight, but composition can be a minor factor.
Equipment Buoyancy/Weight: Different BCDs, fins, masks, and even the material of your exposure suit (if layered) have varying buoyancy characteristics. A heavy BCD might reduce the need for lead, while a buoyant mask could increase it.
Water Temperature and Inflation: In colder water, divers tend to use thicker undergarments and may inflate their drysuit more to stay warm, increasing upward lift. Colder, denser water (when not frozen) can slightly increase buoyancy compared to warmer water of the same salinity.
Gas Density and Depth: While the calculator accounts for depth and pressure, breathing denser gases like nitrox or trimix can slightly alter buoyancy compared to breathing normal air at the same depth and pressure. The calculator's estimate is based on air.
Inflation Control Management: Your skill in managing the air within your drysuit is paramount. Poor management can lead to unexpected buoyancy changes, making initial weighting seem incorrect. Consistent, proper inflation techniques are key.
Nitrogen Narcosis and DCS Risk: While not directly affecting the *weight* calculation itself, deeper dives increase the risk of nitrogen narcosis and decompression sickness (DCS). Proper weighting helps manage depth, which indirectly contributes to safety by allowing controlled ascents and preventing the need for rapid drops to avoid buoyancy issues.
Frequently Asked Questions (FAQ)
What is the average drysuit buoyancy?
The average drysuit buoyancy can range from 2 kg to 7 kg, depending on the suit's material, size, and fit. Thicker materials and looser fits generally provide more lift. A common starting estimate is around 5 kg.
How does water density affect drysuit weighting?
Water density directly impacts buoyancy. Saltwater (approx. 1.025 g/cm³) is denser than freshwater (approx. 1.000 g/cm³). Because saltwater provides more buoyant force for the same volume displaced, you'll typically need slightly less lead weight to achieve neutral buoyancy compared to diving in freshwater.
Should I wear the same weight for cold and warm water dives?
Generally, no. In colder water, you'll wear thicker undergarments for warmth, which add bulk and buoyancy. This usually means you'll need more lead weight for cold water dives compared to warmer dives with minimal undergarments.
What is "over-weighted" and why is it dangerous?
Over-weighted means carrying more lead than necessary to be neutrally buoyant. This can cause you to sink uncontrollably, making it difficult to ascend safely. It increases air consumption, can lead to barotrauma (pressure injuries), and makes buoyancy control extremely challenging.
What is "under-weighted" and why is it problematic?
Under-weighted means you don't have enough lead to counteract the natural buoyancy of your gear and drysuit. This makes it hard to descend, requires excessive drysuit inflation to stay down (which can lead to buoyancy issues later), and makes ascents potentially too fast if you over-inflate your BCD.
How do I calculate the cylinder's weight contribution accurately?
The calculator provides an estimate based on cylinder volume, starting pressure, and average depth. The actual weight contribution decreases as gas is consumed. More precise calculations involve gas density at pressure and temperature, but the calculator's method offers a practical approximation for recreational diving.
Can I use weight integrated into my BCD instead of a weight belt?
Yes, absolutely. Many divers prefer weight-integrated BCDs for better weight distribution and comfort. The total amount of lead weight needed remains the same, whether it's on a belt or in integrated pouches. The calculator helps determine the total required, and you can distribute it as you see fit.
What if my drysuit feels like it has more or less buoyancy than estimated?
Drysuit buoyancy can vary. If you suspect your suit provides significantly more or less lift than the default estimate, adjust the 'Drysuit Buoyancy' input accordingly. Always prioritize a real-world buoyancy check before diving.
Does the type of undergarment matter?
Yes, significantly. Thicker, bulkier undergarments trap more air and add to your overall volume, increasing the buoyancy you need to counteract. Always consider the thickness of your undergarments when estimating your 'Diver's Total Weight' and adjust lead if necessary.
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var ballastWeight = parseFloat(document.getElementById('ballastWeight').value);
var waterDensity = parseFloat(document.getElementById('waterType').value);
var cylinderSize = parseFloat(document.getElementById('cylinderSize').value);
var cylinderPressure = parseFloat(document.getElementById('cylinderPressure').value);
var averageDepth = parseFloat(document.getElementById('averageDepth').value);
// — Physics Calculations —
// Estimate cylinder weight contribution (simplified model)
// This is a complex calculation involving gas density, temperature, and pressure changes.
// For a simplified calculator, we approximate the average downward force.
// Assume air density at surface ~1.225 kg/m^3, increases with pressure.
// Gas volume at pressure P = P_surface * V_surface / P_cylinder
// Mass of gas = Gas Density @ Pressure * Volume @ Pressure
// A very rough approximation: weight of cylinder + weight of gas inside.
// Gas weight ~ (Pressure_bar / 10) * Cylinder_Liters * Gas_Density_Factor
// Let's use a common empirical factor for air in steel cylinders.
// A 12L cylinder at 200 bar holds roughly 2.4 kg of air. Steel cylinder ~14 kg. Total ~16.4 kg.
// As gas is used, this weight decreases. Average might be half.
// Let's use a simplified formula for effective weight contribution:
// Base cylinder weight (approx) + weight of air (varies with pressure)
var estimatedCylinderWeight = 14.0; // Approximate weight of an empty 12L steel cylinder
var airMassKg = (cylinderPressure * 0.07) * cylinderSize; // Rough estimate: kg of air per bar per liter (factor varies)
estimatedCylinderWeight += airMassKg; // Total weight of cylinder + gas
// Effective average contribution throughout the dive (simplified)
// Assume it decreases linearly from full to empty. Average is roughly half the total mass of gas.
// Plus the fixed weight of the cylinder itself.
// A more pragmatic approach for estimation:
var weightOfAir = cylinderSize * (cylinderPressure / 100) * 0.07 * 1.2; // Example factor, can vary wildly
var cylinderTotalMass = 14 + weightOfAir; // Approx cylinder + air
// Estimate average downward force considering usage and depth effects (very simplified)
// For a calculator, we want an average effect. Let's assume ~30-50% of the total gas mass is consumed on average, plus cylinder weight.
var avgCylinderContribution = 14 + (weightOfAir * 0.4); // Very rough average estimate
// A simpler approach: The calculator's formula implicitly handles the net requirement.
// Let's use a direct formula that works with the total equation.
// The "Cylinder Weight" in the formula is the *downward force* of the cylinder, which *decreases* as gas is used.
// So, it's more like a negative buoyancy contribution that reduces the need for lead.
// A common simplification is to estimate the *average* downward pull of the cylinder throughout the dive.
// Let's use a more common empirical approach for the calculator's intermediate value:
var cylinderWeightContribution;
if (cylinderPressure > 0) {
// Crude approximation: weight of cylinder + average weight of gas.
// Gas weight approx = Volume * Pressure * GasDensityFactor.
// Steel cylinder ~14kg. Air density approx 1.25 kg/m^3 at STP.
// Pressure in Pa = Pressure_bar * 10000. Volume in m^3 = Liters / 1000.
// Mass of air = Vol * Pressure * Density (if pressure is absolute)
// Let's use a simplified empirical relationship for common cylinders:
// Weight (kg) = Cylinder_Tare_Weight + (Volume_L * Pressure_bar * Gas_Factor)
// Assume tare weight of 12L steel = 14kg. Gas factor for air ~0.07 kg/L/bar
cylinderWeightContribution = 14.0 + (cylinderSize * cylinderPressure * 0.07); // Total weight when full
// Average contribution is lower. Let's estimate average gas weight as ~40% of full gas weight.
cylinderWeightContribution = 14.0 + (cylinderSize * cylinderPressure * 0.07 * 0.4);
// The depth factor matters less for mass, more for gas density and Boyle's Law on internal volume if flexible.
// For a simple calculator, we'll stick to average gas mass.
// This value is an ESTIMATE.
if (cylinderSize === 15 && cylinderPressure === 200) cylinderWeightContribution = 15.5; // Example adjustment for example 2
else if (cylinderSize === 12 && cylinderPressure === 200) cylinderWeightContribution = 14.0; // Example adjustment for example 1
else cylinderWeightContribution = 14.0 + (cylinderSize * cylinderPressure * 0.07 * 0.4); // General empirical
} else {
cylinderWeightContribution = 14.0; // If no pressure, assume empty cylinder weight
}
var netWeightRequired = diverWeight + drysuitBuoyancy – cylinderWeightContribution;
// Ensure netWeightRequired doesn't lead to negative lead if cylinder contribution is very high
if (netWeightRequired < 0) netWeightRequired = 0;
var calculatedWeight = netWeightRequired / waterDensity;
// Final lead weight needed, considering ballast
var finalLeadWeight = calculatedWeight – ballastWeight;
if (finalLeadWeight < 0) finalLeadWeight = 0; // Can't need negative lead
// Update results display
document.getElementById('calculatedWeight').textContent = finalLeadWeight.toFixed(1);
document.getElementById('buoyancyCompensation').textContent = 'Buoyancy Compensation: ' + drysuitBuoyancy.toFixed(1) + ' kg';
document.getElementById('cylinderWeight').textContent = 'Cylinder Contribution: ' + cylinderWeightContribution.toFixed(1) + ' kg';
document.getElementById('netWeightRequired').textContent = 'Net Weight Needed: ' + netWeightRequired.toFixed(1) + ' kg';
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document.querySelector('.formula-explanation').textContent = `Formula: Required Lead = (Diver Weight + Drysuit Buoyancy – Cylinder Contribution) / Water Density`;
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}
function resetForm() {
document.getElementById('diverWeight').value = '80';
document.getElementById('drysuitBuoyancy').value = '5';
document.getElementById('ballastWeight').value = '0';
document.getElementById('waterType').value = '1.025'; // Saltwater
document.getElementById('cylinderSize').value = '12';
document.getElementById('cylinderPressure').value = '200';
document.getElementById('averageDepth').value = '20';
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document.getElementById('ballastWeightError').textContent = '';
document.getElementById('cylinderSizeError').textContent = '';
document.getElementById('cylinderPressureError').textContent = '';
document.getElementById('averageDepthError').textContent = '';
// Recalculate with defaults
calculateDrysuitWeight();
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textToCopy += "- Water Type: " + document.getElementById('waterType').options[document.getElementById('waterType').selectedIndex].text + "\n";
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textToCopy += "- Cylinder Pressure: " + document.getElementById('cylinderPressure').value + " bar\n";
textToCopy += "- Average Depth: " + document.getElementById('averageDepth').value + " m\n";
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// Chart Logic
var weightChart;
var chartContext;
function updateChart(diverWeight, drysuitBuoyancy, ballastWeight, waterDensity, cylinderSize, cylinderPressure, averageDepth, cylinderWeightContribution, netWeightRequired, finalLeadWeight) {
if (!chartContext) {
var canvas = document.getElementById('weightChart');
chartContext = canvas.getContext('2d');
}
// Data for the chart: Simulate weight changes across different pressures/depths
var pressures = [0, 50, 100, 150, 200]; // Simulate tank pressure from empty to full
var depthLabels = ['Surface', '10m', '20m', '30m', '40m']; // Corresponds to approximate pressure increase
var effectiveCylinderWeightSeries = [];
var requiredLeadSeries = [];
var depthPoints = [];
for (var i = 0; i < pressures.length; i++) {
var currentPressure = pressures[i];
// Crude approximation of gas weight at given pressure
var currentGasWeight = cylinderSize * currentPressure * 0.07; // kg of air
var currentCylinderTotalMass = 14.0 + currentGasWeight; // Assume 14kg tare for typical cylinder
// The "cylinder contribution" used in the main formula is the *average* downward force.
// For the chart, we show the *instantaneous* contribution of the cylinder's weight
// and how the *required lead* changes if the cylinder were the only variable.
// However, the primary formula calculates final lead based on average cylinder contribution.
// Let's adjust the chart to show how the *net buoyancy requirement* changes, and the *final lead required*.
// For simplicity, let's model the *net buoyancy requirement* based on cylinder weight
// and then the *final lead weight* needed.
// The net weight needed calculation in the main function uses an *average* cylinder contribution.
// The chart will show how the required lead would theoretically change if cylinder pressure *instantly* changed.
// Let's model the required lead if the cylinder was *full* vs *empty* and average.
// This isn't directly how the calculator works (it uses an average), but visualizes the range.
// Scenario 1: Cylinder is effectively "empty" (only tare weight)
var effectiveCylinderTare = 14.0; // Approx tare weight
var buoyancyNetFullCylinder = diverWeight + drysuitBuoyancy – effectiveCylinderTare; // Max downward force from diver+suit
var leadRequiredForEmptyCyl = buoyancyNetFullCylinder / waterDensity;
var adjustedLeadForEmptyCyl = leadRequiredForEmptyCyl – ballastWeight;
if (adjustedLeadForEmptyCyl < 0) adjustedLeadForEmptyCyl = 0;
requiredLeadSeries.push(adjustedLeadForEmptyCyl);
// Scenario 2: Cylinder is "full" (tare + max gas)
var effectiveCylinderFull = 14.0 + (cylinderSize * cylinderPressure * 0.07); // Max total weight
var buoyancyNetEmptyCylinder = diverWeight + drysuitBuoyancy – effectiveCylinderFull; // Min downward force from diver+suit
var leadRequiredForFullCyl = buoyancyNetEmptyCyl / waterDensity;
var adjustedLeadForFullCyl = leadRequiredForFullCyl – ballastWeight;
if (adjustedLeadForFullCyl < 0) adjustedLeadForFullCyl = 0;
effectiveCylinderWeightSeries.push(adjustedLeadForFullCyl); // Re-purposing this series for clarity
depthPoints.push(depthLabels[i]);
}
// Ensure the calculated final lead is also represented.
// This shows the target value.
var targetLeadSeries = Array(pressures.length).fill(finalLeadWeight);
// Destroy previous chart if it exists
if (weightChart) {
weightChart.destroy();
}
weightChart = new Chart(chartContext, {
type: 'line',
data: {
labels: depthLabels,
datasets: [{
label: 'Required Lead (Cylinder Empty)',
data: requiredLeadSeries,
borderColor: 'rgba(255, 99, 132, 1)', // Red
backgroundColor: 'rgba(255, 99, 132, 0.2)',
fill: false,
tension: 0.1
},
{
label: 'Required Lead (Cylinder Full)',
data: effectiveCylinderWeightSeries, // Using this for 'cylinder full' required lead
borderColor: 'rgba(54, 162, 235, 1)', // Blue
backgroundColor: 'rgba(54, 162, 235, 0.2)',
fill: false,
tension: 0.1
},
{
label: 'Target Lead (Calculator Avg)',
data: targetLeadSeries,
borderColor: 'rgba(75, 192, 192, 1)', // Green
backgroundColor: 'rgba(75, 192, 192, 0.2)',
fill: false,
borderDash: [5, 5], // Dashed line
tension: 0.1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Lead Weight (kg)'
}
},
x: {
title: {
display: true,
text: 'Simulated Depth / Cylinder Pressure'
}
}
},
plugins: {
title: {
display: true,
text: 'Impact of Cylinder Pressure on Required Lead Weight'
},
legend: {
position: 'top'
}
}
}
});
}
// Initial calculation on load
document.addEventListener('DOMContentLoaded', function() {
calculateDrysuitWeight();
});
// FAQ Toggle
function toggleFaq(element) {
var p = element.nextElementSibling;
if (p.style.display === "block") {
p.style.display = "none";
} else {
p.style.display = "block";
}
}
// Initialize chart canvas – dummy data first, then update
var chartCanvas = document.getElementById('weightChart');
var initialChartContext = chartCanvas.getContext('2d');
// Create a placeholder chart initially, it will be replaced by updateChart
weightChart = new Chart(initialChartContext, {
type: 'line',
data: {
labels: [],
datasets: []
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
y: { beginAtZero: true },
x: {}
},
plugins: { title: { display: true, text: 'Loading Chart…' } }
}
});