Interlake
Customflex · designed by Francis Sweisguth · 1933
centerboardBermuda rigUnited States
The Interlake is a 18-foot bermuda rig sailboat designed by Francis Sweisguth and built by Customflex, first launched in 1933.
General
| Builder | Customflex |
|---|---|
| Designer | Francis Sweisguth |
| Years built | 1933 |
| Hull type | centerboard |
| Rig type | Bermuda rig |
| Construction | fiberglass |
| Origin | United States |
Dimensions
| LOA | 18.00 ft5.49 m |
|---|---|
| LWL | —— |
| Beam | 6.25 ft1.91 m |
| Draft (max) | 4.58 ft1.40 m |
| Displacement | 650 lb295 kg |
| Ballast | —— |
| Sail Area | 175 ft²16.3 m² |
Design ratios
Computed from the specs above using the standard formulas. Try the sailboat calculators with your own numbers.
SA / Displacement 37.31 Performance / racer — powered up
Capsize Screening 2.89 Better suited to coastal use (> 2.0)
How these numbers are calculated
- SA / Displacement
SA ÷ (Disp ÷ 64)^(2/3)— Power-to-weight. < 16 under-canvassed, 16–20 cruiser, > 20 racer.- Ballast / Displacement
Ballast ÷ Disp × 100— Stability/stiffness. Higher carries sail better.- Displacement / Length
Disp(lt) ÷ (0.01 · LWL)³— < 100 ultralight, 100–200 light, 200–300 moderate, > 300 heavy.- Comfort Ratio (Brewer)
Disp ÷ (0.65 · (0.7·LWL + 0.3·LOA) · Beam^1.33)— Motion in a seaway. Higher = more comfortable offshore.- Capsize Screening
Beam ÷ (Disp ÷ 64)^(1/3)— ≤ 2.0 favored for offshore; > 2.0 better for coastal use.- Hull Speed
1.34 · √LWL— Theoretical max displacement speed in knots.
Estimated price
$7,500 typical range $6,000 – $9,000
⚠ Rough estimate only — not market data. Derived from a simple model based on length and hull age; actual asking prices vary widely with condition, equipment, engine hours and location.
