Cradle project
I have no idea what I'm doing ... but somehow I've ended up with the responsibility of cradling my ship. Rationally I should probably just have paid a bit extra and gotten the boat up on land on a place that has cradles and supports and takes the responsibility, but if nothing else I've learnt a lot from this project. Welding is fun (though it may hurt a bit when working in T-shirt and shorts).
Status by 2025-09-24
Vocabulary
- "Support pipe" is the pipe(s) going in a straight line from the boat to the ground, taking most of the load from the boat. The "foot" of the pipe is near the ground.
- "Supporting legs" are extra legs attached from the lower part of the support and towards the ground.
- The "pads" are between the steel pipe and the hull, distributing the load a bit.* "scaffolding" is steel constructions intended to support the supports and keep them in place.
- "Support" includes the support pipe, pads and supporting legs (if any).
- "Ratchet strap" is a flat strap with an easy mechanism allowing to make it really tight (I do have some solutions for making ropes really tight too, but it's more complicated). "cargo strap" is a cheaper variant that can easily be made tight, but not very tight).
- A "partner" support is at the opposite side of the ship, a "neighbour" support is at the same side.
Summary
The boat is supported by 12 supports (six pairs). Some of them are very simple fixed-length steel pipes padded with a loose wooden block between the boat and the metal pipe (many of the pipes ending up perpendicular with the hull - I later identified this to be suboptimal), others are more elaborate constructions with adjustable reinforced supports with two extra support legs, a long diagonal pipe for anchoring the support with either a partner at the other side or steel anchorage points held in place by the keel, and slightly adjustable pads with rubber inserts.
Those supports are attached to each other by ropes, ratchet straps, simple steel sheets and steel corner profiles. All the supports are attached with the neighbour at 1m+ above the ground, and all supports are attached near the ground with the corresponding support at the other side of the boat.
I think one of the supports is going to fall down during the next month or two unless the setup is improved. However, three pairs of supports should suffice to keep the boat in place during bad weather, and I believe at least three pairs of supports are going to hold a storm.
Walk-through of the support pairs
First (stern) supports
The very aft pair of supports are adjustable support pipes. By the feet they are forced together with a cargo strap. Wedges are also hammered in by the ground. The starboard feet is missing protection against sliding to the left (aft), it may still be an idea to put in some steel going close to the ground towards the neighbour.
A bit further up they are stringed together with a simple flat belt of steel (I took what I had) 1n+ above the ground. This scaffolding will hold some tension when pullet, but it will flex if compressed. I should probably consider to reinforce it with a corner profile, or enhance it into a T-profile.
Some asymmetry here. It's two different kind of adjustable support pipes with slightly different minimum height, but also the starboard side is better attached to the neighbour support. That was mostly out of a concern that the neighbour support had a bad angle and needed some better scaffolding. It would still make sense to add some more scaffolding to make sure the support will not move or twist in any direction.
Those supports give quite a lot of vertical support, not so much horizontal support. I believe the support point is above the center of gravity, so anyway they do contribute to the sideway stability. Those supports are sort of supporting my bed. My earlier experiences (without such supports) is that my bed vibrates quite a lot in windy weather, I hope those supports will give me a better sleep.
The setup is very simple, a wooden block between the supporting pipe and the boat, and the supporting pipe is perpendicular to the hull surface, so the force from the boat goes parallell with the support pipe. I still came to think that this is a design flaw, for two reasons:
- If the top of the support or the wooden block is moved some few millimetres in any direction (which may easily happen as the friction between the wood and the hull is not so big, and when it's windy the boat will easily vibrate), the distance between the ground and the hull increases and the block may fall out.
- On a windstill day the angle of the force from the boat is perfectly opposite the stabilizing force of the support, so the block won't move anywhere - but the angle changes when there is wind in the air, potentially pushing the block up on the lee side and down on the windwards side, and the block may start moving. I've attached the blocks with some thinner rope to arrest any such movement.
Second pair of supports
The second pair of supports are more elaborate, with support legs, pads and they were also scaffolded together with a horizontal bar a metre above the ground and two diagonal bars before the boat came on land.
This proved to be a mistake, for two reasons: * Now there are seven contact points to the ground. It was fitting perfectly on the ground when it was welded together, but the groups was not even, so once it was moved it proved to be a disaster. For one thing, even after applying a lot of pressure on the support, the three legs on the starboard side was hanging in the air. I've knocked in a wedge to make sure there is pressure between the support pipe and the ground. * The support should not only tilt a bit outwards, but at the rear end of the boat it should also tilt a bit backwards (and in front forewards) due to the inclination of the boat hull. This was not counted for when welding the scaffolding between the partner supports. The line on the next photo shows where the main reinforced support pipe should have been going to catch the forces in the best possible way. The wrong angle may cause the support to twist to the left (stern). The diagonal corner profile has been put in place to prevent this from happening.
!(Full resolution)The holes on the support leg was not made by me. I had a guy helping me for a couple of hours, when I didn't manage to fix a good weld, he took over the welding machine and made those holes. I did the rest of the welding that day :-)
Things could have been made better. I think the scaffolding between the legs also should have a lower horizontal bar. The scaffodings between the first and second support on the starboard side is a bit of a mess.
But the scaffoldings on the port side is worse- with only flat strips of metal used.
On the port side, there is also a strap pulling the foot of the support towards the stern to keep it from rotating the other way. There should be something similar on the starboard side, but when I tried to make it I realized the main support foot was just hanging in the air and started moving as I was tightening it up ... so I aborted. Maybe it can work out now as I've tried hammering in some wedge.
Anyway, I'm pretty sure it will be good. The supports probably won't move anywhere. (It's a bit important, because those are one pair out of three "main pairs" that should not fail)
Third pair of supports
This is a very simple support - a simple non-adjustable support pipe padded with a loose wooden block on the top.
With dedicated corner profiles, some more experience and some helping hands I made some scaffolding preventing the support pipe from shifting to the left (aft) or right (fore) on the starboard side, it almost looks nice. It's not super-sturdy, but I'm not expecting very big forces on the scaffoldings. My original idea was not to avoid any welding on the pipes at all, but there are some few small weld points.
The feet are kept firmly in place with some ratchet straps. The middle of the support will not move sideways for sure. Things are worse on the top, with the support pipe going perpendicular - causing instability as soon as the block moves some few millimetres. I've attempted fixing this by some rope.
I made the port side first, due to lack of materials and lack of experience, the scaffolding on the port side is not as good.
The support pipe is perpendicular to the boat hull, with the above-mentioned problems. Some ropes are in place to prevent it from moving oo much.
Fourth pair of supports
The fourth pair is the most robust pair.
The feet are well anchored with steel bars going under the keel, to they will not slide out. A diagonal bar is also anchored, so the angle towards the hull stays stable.
In addition there is the very tight rope going under the keel also preventing it from flipping out. The supports are not supposed to experience any forces to the right/left (fore/aft), but there is also scaffolding towards the neighbours. Good pads with rubber towards the hull. Strong and reinforced adjustable pipes. Also stronger support legs than on the other supports. Only problem is that the steel under the keel may corrode completely before the boat is launched again. A neighbour told me that under heavy storms, the area may be flooded by salty water.
The anchoring arrangement could have been done better, and it's also less thoroughly done on the port side than on the starboard side. I had more focus on learning to weld than to design something nice when fixing those anchoring steel.
Fifth pair of supports
I have no faith in the starboard fifth support, it is going to fall down unless something is done with it.
The angle of the support is just wrong. The foot is too far out and/or the pad is too low on the ship. Hence over time the pad will move down due to vibrations etc, all until it falls. The strap holding the legs together is also too high on the starboard support.
The port side support is fine. More or less. The anchoring should probably be made better, and maybe the pad is a bit too hight up ...
... but it is probably good enough.
So it's needed to:
- Slacken up the straps and remove one of them (there is two of them)
- Push the rope on the starboard side further down along the feet (It's an assymmetric know - it should be possible to move the whole knot down the pipe. It should be non-trivial to move it upwards).
- Slacken the nut on the support pipe, lowering the pad and removing all tension. Most likely it can easily be done by hand - if not, use some pieces of metal
- adjust the angle slightly. The pad should go higher, the feet should probably be moved a bit in.
- It may be needed to tighten the strap a bit to keep the support in place
- Tighten the nut again, as much as it goes by hand and then a little bit more.
- The second strap should go from the top of the starboard support to the top of the port support. The angle of the port support seems good, so it's just to tighten it as well as possible.
Sixth (bow) pair of supports
This is also counted to be some of the "main" supports that should hold when all other suppors fall down. Things could have been done better, but it's probably "good enough"
One of the weaknesses is that diagonal pipe. The purpose of this pipe is to be anchored somewhere - but it's loose. And on the port side it's missing completely.
The starboard side is just a simple pipe support At least it's tightened up both below and on top with the one at the other side, with angles that allows it.
This support structure leaves something to be desired ... there should be at least one more small scaffolding support. I felt that something was amiss when constructing it, but was a bit too stressed to see the problem.
