Transporting a boat on a roof or by a rod is a thing of the past, giving way to specialized boat trailers, but a standard trailer bought in a store often doesn't take into account the individual specifications of your boat or PVC boat with a hard bottom. slip-stack - a load-bearing frame that assumes the weight of the body and distributes the load evenly.
A homemade or modified slipway in a boat trailer solves several critical tasks: it prevents deformation of the bottom during prolonged parking and extinguishes vibrations at high speeds. Many owners underestimate the importance of correctly positioning the reference points, which subsequently leads to cracks in the fiberglass or ruptures of the seams of inflatable elements.
In this article, we will take a closer look at the design and fabrication of a slip that fits perfectly into the body of your trailer, and learn how to calculate geometry, choose the right steel, and protect the structure from the merciless water element.
Design features and types of slips
Before you take on the welding machine, you need to clearly understand what type of bearing structure your boat requires. Stack frame It's not just a set of pipes, it's an engineering structure that replicates the contours of a boat, and there are two basic approaches: a welded frame that is rigidly fixed to the trailer's long-rangers, and a modular system with adjustable stops.
For lightweight inflatable boats with plywood or aluminum bottoms, a simplified version with longitudinal beams and crossbars is often sufficient. nickel And side support is secondary to the overall support plane, but heavy fiberglass or aluminum boats require a complex system that takes into account the maximum stress points of the hull.
The key element here is kielson It's a central beam that runs along the axis of symmetry, and it takes the brunt of hitting rough roads, and if the quilson is too narrow or shifted, the boat will start to walk from side to side, which is dangerous when braking.
⚠️ Attention: Never use a thin-walled pipe (less than 2 mm) to make a slip; vibratory loads on the track at 80-90 km/h can lead to instantaneous structural collapse and loss of the boat.
The configuration also depends on the type of trailer. If you have a single-axle trolley, the center of gravity should be shifted closer to the drawer, so as not to overload the rear overhang. In biaxial versions, the weight distribution of the slip and the boat should be strictly between the axles.
Selection of materials and calculation of geometry
The basis of the durability of your slip is the correct selection of rolled metal, most often used profile pipe square or rectangular cross section. St3 structural steel 09G2CIt has increased corrosion resistance and strength.
For boats up to 4 meters long and weighing up to 300 kg, a 40x40 mm pipe with a wall thickness of 3 mm is quite enough. For heavier structures exceeding 500 kg, it is recommended to switch to a profile of 50x50 mm or 60x40 mm.
The geometry calculation starts with measuring the distance between the spars of your trailer. The slipway must fit into these dimensions with a margin of 1-2 cm on each side for ease of installation and dismantling. The height of the slip above the ground is also critical: too low a landing can lead to impacts on curbs, and too high will raise the center of gravity of the boat, making the trailer unstable.
Why is the thickness of the pipe wall important?
Many beginners buy pipes with a wall thickness of 1.5-2 mm, guided by the economy of weight. However, when welding such pipes burn, and in the welds, the metal loses strength. In addition, the thin wall quickly rusts from the inside, if the ends of the pipe are not sealed.
When designing crossbars (ribs) should follow a step of no more than 50-60 cm This will ensure the necessary rigidity of the structure to twist. To fasten the boat to the slip, pre-installed places for the installation of rump bolts or eyelets.
Assembly technology and welding work
The slip assembly process requires careful workspace preparation, you need a flat area, preferably concrete, to avoid skewing the frame during welding, first, the outer circuit is assembled, which must be strictly rectangular, and the diagonal check is a mandatory step: the difference should not exceed 2-3 mm.
Welding is best done with a semi-automatic protective gas (MIG/MAG) system, which provides high performance and minimal deformation of the metal. If electrode welding is used, choose electrodes 3 mm in diameter and boil in short stitches, allowing the metal to cool to avoid leashing the profile.
After welding the main frame, additional elements are installed: kilblocks, side stops and winch brackets, all welds must be cleaned with a petal-circle Bulgarian, which not only improves the appearance, but also removes slag, which is the focus of future corrosion.
| The slip-stick element | Recommended profile | Wall thickness | Appointment |
|---|---|---|---|
| Longerons (basic) | 50x50 mm | 3 mm | supporting frame |
| Cross-sections | 40x40 mm | 2.5-3 mm | Strength of construction |
| Kilblock (centre) | Pipe 60x40 | 3 mm | Boat's keel support |
| Winch brackets | Corner 50x50 | 4-5 mm | Fixing the mechanism |
Special attention should be paid to the places where the slip is attached to the trailer. It is recommended to use high-strength bolt joints (class 8.8 and above), not only welding, this will allow you to remove the slipway if necessary to service the trailer or replace rubber.
☑️ Preparation for welding
Corrosion protection and finishing
The boat trailer is operated in an aggressive environment: salt water, dirt, reagents on the roads. So the issue of corrosion protection is acute. Just painting the slip with ordinary enamel is dooming it to rapid rust. You need a multi-step protection system.
The first step is to sandblast or scrub the metal to shine, and then degrease the surface with a solvent. epoxyIt creates an impermeable barrier to moisture and oxygen, and an alternative is zinc-containing soil, which provides protective protection.
For finishing, alkyd enamels or special hammer paints are best suited, which hide small defects of welding and have high mechanical resistance. The paint should be applied in 2-3 layers with intermediate drying. Pay special attention to the inner cavities of the pipes - they must be treated with anticores (for example, "Moville" or specialized compositions for hidden cavities) through the process holes.
⚠️ Attention: Do not close the technological holes in the pipes tightly without pre-treating the insides with anticorcor, moisture that gets inside the pipe during rain or washing will remain there forever, causing the metal to rot from the inside.
A good addition to painting would be to install plastic or rubber linings at the contact points of the metal slip with the boat hull, which will prevent damage to the paint coating of the boat itself when vibrating.
Installation of winch and rigging
A slipway is unthinkable without a boat fixation system. The centerpiece here is a winch. For homemade slippers, hand-driven drum winches are most often chosen, although there are also ratchets. The power of the winch must be calculated with a margin: for a boat weighing 300 kg, the traction force must be at least 500-600 kg.
The winch is mounted on the front transom profile of the slipway. It is important to use larger diameter washers or additional reinforcing plates so that when the rope is stretched, the metal does not deform. The cable is better used synthetic - it does not rust, scratch the hands and does not injure the boat on a cliff, unlike steel.
For fixing the stern, straps with tension mechanisms (tretchers) are used. The number of fastening points depends on the length of the boat: for boats up to 4 meters, two belts on the sides are enough, for longer ones, four points are recommended (two sides + a central belt through a transom).
Use lock carbines to prevent the belt from unbuttoning on the bumps, and normal hooks can pop off when you're vibrating.
Don't forget the locking mechanism for the bow of the boat, which prevents the boat from slipping forward when the trailer is braking sharply, usually a welded arc or roller, which rests on the bow of the boat.
Tests and first operation
Once the paint is assembled and dried, the moment of truth comes, the boat is set up. The first landing is best done on a level ground in the presence of an assistant. The boat should be carefully keeled on the center stop and check the symmetry of the landing. The gaps between the sides of the boat and the side stops of the slip should be minimal, but without tension.
When you pull the rope of the winch, watch the behavior of the slipway. You should not hear the creaking of metal or visible deformations. If the slipper "plays", then there are not enough crossbars or too thin profile is used, in which case you can not continue operation - you need to strengthen the structure.
The first trip should be a trial: drive 10-15 kilometers on a familiar road at a speed of no more than 60 km / h. After stopping, be sure to check the tightening of all bolt joints and the condition of the belts. Vibration often weakens the fasteners in the first hours of operation.
The main criterion for the quality of the slip is the absence of backlashes and deformations after the first hundred kilometers of the run. If the frame is intact and the boat sits tight, then the calculations are correct.
Regular maintenance of the slip includes checking welds for cracks, lubricating the rubbing parts of the swab and updating the paint coating in the chipping areas. With proper care, the homemade slipper will last as much as the factory one, and often surpass it in reliability.
FAQ: Frequently asked questions
Can I use used pipes to make slips?
You can use old pipes, but only after a thorough defect. If the pipe has deep corrosion, especially through, or strong dents, its use is dangerous. (wall thickness) must be tested with a drill or visually on a cut. The savings on metal can cost you the boat.
Do I need to register a homemade slipway in the traffic police?
The slip itself as a removable structure does not require separate registration. However, if you radically changed the design of the trailer (for example, expanded the track or changed the dimensions), this may require changes in the trailer's PTS. In most cases, if the slip fits into the dimensions of the boat and does not project beyond the body, there is no problem.
Which profile is better: square or rectangular?
For spars experiencing bending load, a rectangular profile (e.g. 60x40) mounted vertically (60 mm up) works better due to greater inertia torque. A 40x40 mm square profile can be used for cross-sections and connections.
How to replace sandblasting?
If there is no sandbrush, use mechanical cleaning with a Bulgarian cord brush to pure metal, followed by treatment with a rust converter (if there are oxides left) and degreasing. The quality of surface preparation directly affects the service life of the coating.