Sunday 7 May 2023

Trailer | Measuring Up For PocketShip

One of the first things I did when restarting the build was to investigate what sort of trailer we will need to transport, launch and retrieve PocketShip.

The manual provides some guidance in the shape of a drawing on page 282, which is a useful starting point. It also recommends that we get an extended tongue so we can leave the bowsprit in situ while towing.

This is the drawing.

So I sent the drawing to SBS Trailers, who were highly recommended by the suppliers of the kit.

They asked for some dimensions which I provided and a quotation duly arrived.

However, I was concerned about the location of the winch and the height of the winch post, so I visited their factory in Wolverhampton to examine the options and talk to their specialist.

I am glad I did, because it immediately became apparent that a standard winch post would not be suitable for PocketShip.

The winch has to be horizontally in line with the bow eye in order to pull it safely and securely onto the trailer.

A standard winch post has the winch located at the top, which is fine for most boats which have their bow eye at the top of the stem. The winch pulls the boat onto the trailer until the stem meets the snubber, which is also located near the top of the winch post.

PocketShip is different, though. The bow eye serves two purposes. It braces the bowsprit with the bobstay, so it has to be located at the bottom of the stem. It is also used to retrieve the boat onto the trailer, so the winch cannot be at the top of the post. It has to be much lower in order to pull horizontally on the bow eye.

A custom winch post was required, and I was sent off to provide detailed measurements of the front of the boat.

I used a level to extend a line along the bottom of the keel out to the stem. Like this.

Then using a variety of methods, including a plumb bob and a laser level, I measured off all the key dimensions.

Here I am enjoying a Gin & Tonic after a taxing day scratching my head and remembering the principles of basic geometry.

This was the final output.

The specialist at SBS Trailers told me that the snubber should meet the stem about two thirds of the way up, so that's where I pencilled it in.

The winch post should be 60 degrees from the horizontal, so I pencilled that in too.

The broken line shows what the winch post should look like, theoretically.

I sent this off to SBS and they quickly recommended the next size up for the winch post, with a custom top member with the winch mounted underneath, in line with the bow eye.

So that's what we are going for.

It is inevitable that the bobstay must be uncoupled while towing, otherwise it will be in the way of the winch post. Which would not be good.

I did ask on the CLC PocketShip forum about winch post configuration, and some builders said that they had modified their trailers to have the snubber meet the stem below the bow eye, so they could keep the bobstay connected while towing.

It turns out that this is a really bad idea. With the snubber so low down on the stem the boat could potentially jump forwards out of the trailer in the event of a collision or sudden stop. That's why the guy at SBS Trailers told me that the snubber must be located up towards the top of the stem.

That means that the bobstay has to be disconnected whilst on the trailer. That's OK.

The SBS guy also confirmed my suspicion that the winch line is not a restraint. Its only function is to retrieve the boat, which must be separately secured to the trailer.

I was in New Zealand recently and saw quite a few boats being hauled out and towed with just the winch strap holding them in place. Also a really bad idea.

I've learned a lot about trailers in the last few weeks. Mine is now being built. Feels like a milestone event!

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