Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[tigertiger]

I am about to restart a model historic sail boat. Finished she will weigh about 17-20 kg, be about 1.5m long with bowsprit and 1.5m tall. For launching I am limited to a platform, with a 2.5m drop to the water from the top of the handrail, or hand-balling the boat 2m down a couple of large rocks. I want to avoid the latter if I can.
If I am going to modify the boat, it is better to do this before the deck goes on. Which is why I am asking now, before I continue.


Has anyone seen a launch and recovery system for a long drop?
Does anyone have any suggestions?


Considerations:
This is a sail boat, and booms will move about in the wind during launch and recovery.
There is a bowsprit.
There will only be a shallow drop keel, about 75-100mm max below the keel of the hull.
Recovery also needs to be done from 2.5m
I will need to be able to do this single handed.
Any derrick systems needs to easily portable.


All advice welcomed 

[Klunk]

Truck fan belts are quite large and heavy duty

[TailUK]

This might work but you might have trouble recovering the boat.

[TailUK]

Seriously.  I've seen some very good launching slings made if this stuff.  Stiffen the top edges with battens and used a rope or bars to lower and raise the sling.

[Stavros]

Strops are ok for a small drop but Tigertigers BIG problem is that it is a 2.5mtr drop which is 8 feet to the water and that's a long pair of arms to use strops sounds like he might need a lightweight engine hoist of some description,this a problem as it is not only a Historic sailing model but it has a bowsprit.


Whatever he constructs it has got to be strong enough to lift a full bag of spuds,so something like an engine hoist and a pair of strops are the order of the day and in my opinion this isnt really feasable due to the fact it would have to be allready 3m  above the platform before the 2.5 drop to the water so would really have to do a lift of 5.5 meters and protrude at least 2m out into the lake,so thus in fact the sheer strain at that distance would be rather big....I dont think it would really work in my opinion.


The only way I am sorry to say would be to handball down the rocks




Dave

[tigertiger]

I was thinking of using the hand winch from an engine hoist, and some kind of cradle supported on fold/twist out davits.
The problems then would be:

• design of the cradle, as the height of the cradle needs to be able to accommodate the mast
• securing the davits to some kind of base, there are 2 steps up to the platform, this means I cannot use the transport trolley as a base.

[Bob K]

Maybe it would make the sailboat somewhat not to scale, but how about a large diameter ring at the top of the mast, to act as a lifting eyebolt.  It doesn't need to be too thick, just enough to take the weight of the boat.
Next is an extendable Perch Pole (normally for fishing).  At our club they use them to hook onto broken down models up to eight feet out from the edge.  On the end of the line fit a large hook.
You can lower your sail boat using the pole and hook, then use the hook to catch the ring on the mast for retrieval. 

[tigertiger]

Interesting idea Bob.
I will have to see how the mast is stepped. The big issue is still weight, at 17-20kg, and the need for some kind of portable derrick. But at least that would mean only one boom/derrick needed, instead of two needed for a davit type arrangement.

[Bob K]

You did say the boat was about 1.5 m tall, I assume including the mast.  If you used the Perch Pole with hook the top of the mast is only a metre below you.   Obviously the mast needs to be strong enough, and securely set in the hull.  At "only" a metre below you maybe a more solid pole with hook would work.
Remembering that 20 Kg is close to a two-man lift, whatever the retrieval height.

[John W E]

Tiger - get in touch with Mr Colin Bishop - because a good few years ago he took part in the steering finals which were held at Ryhope pumping station and at the pumping station they use the cooling ponds for model boats to sail.   Its a fair drop from the side to the water - about 2 meters or so or less - I am wondering if he has any photographs, cos I cannot recall if they used the pulley lift system or if they had the pontoon at the time for lowering the boats in.    Now what they do though is have 2 tracks made from aluminium H girders with a trolley that runs in the track - on the trolley there is a cradle which the model boat sits in.   This is lowered over the side and the cradle is lowered into the water down the tracks using a rope.   The model boat is then driven away from the cradle and retrieval is just the reverse of putting the boat in the water.

Wondering if Colin has any photographs or maybe this wasn't around when he visited Ryhope.

John

[Colin Bishop]

Never been to Ryhope John, you must be confusing me with somebody else!

Colin

[tigertiger]

Thanks, Bluebird.


I can picture what you mean. It could be hooked over the hand rails. The lowering raising mechanism could still be done with a winch. The boat could then be push/pull maneuvered over the cradle with poles. The cradle would only need to catch the hull, no full height needed as the cradle would be pulled up the tracks to the side of the boat, and not from above.

[stringer]

HI Bin thinking
first does your platform have a side to it, if it does I have seen a cradle which holds the boat, the cradle needs to have two wheels attached sufficent in size to keep the boat away from the side of the platform, the whole thing looks like a tubeler sack truck, when out of the water it can be used to transport the boat back to your car, i will get on my ipad and make a sketch, I made one up for my schooner, worked a treat
Geoff

[stringer]

HI TIGER
I hope you are better at understanding my sketch than I am at drawing it, my schooner was about 27lbs with her ballest and it worked well, I have seen this idea used on pond launches before, I realize your boat is around 44 lbs, but the trolley needs only to be big enough to hold the boat away from the wall of the platform, let the trolley sink below water level and retrieval is the reverse action hope this helps

[ballastanksian]

Great idea 

[MikeK]

Hi TT, I have a similar system for my barge 'Will Everard' using a collapseable baggage trolley with a slotted cradle attached. At the lake I rig the boat and slide it onto the trolley stand then down to the water where it is lowered down the concrete side until floating, then the barge is pushed gently out of it's slot and off we go and at the end she is guided back into slot and hauled out ! You should be able to haul the boat up the steps with this cradle, but with the railing obstructing you I don't know how you are going to lift a heavy, unwieldy (especially if there is a wind !) model over the top using this type of gear, though


Mike

Just thought of another problem - the trolley stand being wood, wants to float up ! No problem with the boat on it but when it is time to go home it is a bit of a faffle to hold it vertical whilst 'docking' If you are good with aluminium construction then problem solved ! Oh, also the wheels are larger replacements from the DIY shop to give more clearance down the lake edge.

[tigertiger]

I have been and checked, sadly there is no wall.
If I did use a trolley, I would make sure it did not float. The same for any cradle I might make.
The handrail is only at 500mm height, a bit of a lift but do-able. No matter what the solution, I have to lift the boat, or boat plus cradle, over the hand rail.
Getting up the steps with the boat would need the boat to go fore and aft, or lift it above the rails, as the gap between rails is only 1.1m.

The rough layout of the platform is shown in the diagram below.

[MikeK]

Ah well back to the drawing board ! I like your computer drawing, though. Wish I was clever like wot you are 

Mike

[tigertiger]

It's only PowerPoint.

[tigertiger]

Just a quick note of thanks to all of those who have contributed so far

[Sonar]

I am about to restart a model historic sail boat. Finished she will weigh about 17-20 kg, be about 1.5m long with bowsprit and 1.5m tall. For launching I am limited to a platform, with a 2.5m drop to the water from the top of the handrail, or hand-balling the boat 2m down a couple of large rocks. I want to avoid the latter if I can.
If I am going to modify the boat, it is better to do this before the deck goes on. Which is why I am asking now, before I continue.


Has anyone seen a launch and recovery system for a long drop?
Does anyone have any suggestions?


Considerations:
This is a sail boat, and booms will move about in the wind during launch and recovery.
There is a bowsprit.
There will only be a shallow drop keel, about 75-100mm max below the keel of the hull.
Recovery also needs to be done from 2.5m
I will need to be able to do this single handed.
Any derrick systems needs to easily portable.


All advice welcomed 

Is this location the ONLY place you can go to sail your boat

[MikeK]

It's only PowerPoint.

Heard of it but never used it. Since retirement all such things, spreadsheets etc have become redundant, but I will certainly have a look see bye and bye


Mike

[Geoff]

Just as a suggestion, if the fence has horizontal rails with the right shape of davit they could interlock into the rails which would provide the support and take the weight. With a suitable cradle you may then be able to hand winch it down.


I think this is going to be very awkward. I've seen people use large diameter cam belts but I've also seen a model boat roll and drop into the water upside down from a height of 2-3 feet.


My belief is its essential to have a cradle which cannot let the boat roll or slide out one end and also to ensure that the actual lifting connectors are rigid and well above the centre of gravity to ensure a gust of wind can't topple the boat.


The problem is really that once you let go you have no easy way to stabilise the boat which really means a substantial cradle. Just as a thought think of a swing with a keel grove but rigid supports.


Goof luck with this but you may well find it easier, and less fraught to sail on a different pond.


Cheers


Geoff

[tigertiger]

Is this location the ONLY place you can go to sail your boat

 


Just about, yes. It is also walking distance from the house.

There is another far bigger lake very close, but there is still a problem of climbing up a 1m wall, with a 1.5 m drop on the other side, and then a 5m 30 degree slope to the waters edge.  If the police don't throw me off, then for most of the year, there is the blue green algae problem, which at the height of summer is really bad (see pic, not photo shopped that is the real color).
I could drive 3 km down to the other end of the lake, where there is a lake wall (hard bank) but then I could not park the car, the water is still polluted.
Unfortunately in China, most lakes and rivers with access to the public have a hard wall and usually a handrail (see pic). Most modern Chinese cannot swim and if they fall in they drown. The hard river banks are often 2m or more high.
The nearest cleanish pond with easy access is about 20km away, bear in mind that Kunming is a city with over 7m people and traffic is worse than London.

[Bob K]

In that case it sounds like your only option is the ring on top of the mast, and a one and a half meter pole with a hook on the end.  Can't see any other practical method of launch and recovery short of some very large and complicated davits system.