Page updated: 20 February 2010

Introduction

A trailer may be used only for winter storage or for slipping into a different river, lake or shore every week throughout the season. It may be towed hundreds of miles every month or never leave the marina. That means a trailer that is acceptable for one owner will not be for another and that many SeaHawks may now be on a trailer that was not supplied with the boat when new.

Marine Weld, of North Walsham, was the main, if not only, supplier of trailers to both Reedcraft and Moores. It now appears that they did not build to a standard design throughout production of the boat and slightly different versions were supplied over the years.

Those considering converting a conventional trailer with keel rollers should take note of the comments on conversions and particularly the function of bilge fin supports.

Key Measurements

There are two key features that define a trailer designed for a SeaHawk. The first is the central platform that replaces the rollers found on most other trailers and on which the central flat-bottomed keel sits. The second is the pair of rigid outriggers that provide a horizontal surface on which the bilge fins rest.

The measurements below are intended as a guide for those considering buying a trailer for their SeaHawk. They are taken from the trailer, shown here, that was supplied with the boat displayed at Earls Court Boat Show in 1992.

From bow support to front of platform	38"
From front of platform to start of outriggers	36"
Width of platform surface	9"
Width between outriggers	44"
Distance between outer edges of outriggers	53"
Length of outriggers	45"
Height of outriggers above platform	5¼"
Front of outrigger to wheel centre	26"
Height of platform above ground	13"

Purpose-Built Trailers

In contrast to the "show" trailer, above, the most popular design, known to have been supplied with new boats is that seen below. Apart from the generally lighter construction and different suspension arrangement, perhaps the most notable feature is that the winch position is fixed.

This example belonged to Hugh Illingworth when the photographs were taken. (Incidentally, the outline of anti-fouling on the central platform neatly shows the profile of the keel.) Hugh wrote saying:

"I am attaching some photos of the trailer before restoration. As you can see, the cross members were rotten.

With the help of a friend, we took the trailer apart, welded new twin cross members into it and it all went back together without problem. Also replaced the wheel bearings and painted the whole trailer silver but you'll have to wait until next year for a pic as I didn't take any photos after the rebuild.

This trailer works fine for launch and retrieval but sometimes it is a little tricky to line up the boat fore and aft to get the mini chines (don't know the technical name) to sit on the horizontal supports, particularly if there is a cross wind!"

[The term "bilge fins" has been adopted on the site as that is the expression used in the original Reedcraft brochure and all others since.]

Below is seen another example of this design of trailer, believed to be the original supplied with Penny, a 1985 boat.

Both these trailers use the same rubber sphere suspension units and have the same diagonal swinging arms attached to the chassis forward of the axle. All the strength of this design appears to be in the twin-sparred backbone between which the keel platform sits. It is also noticeable how the bilge fin supports form an integral part of the chassis, rather than just being brackets rising from the main chassis.

Converted Trailers

Converting a standard trailer requires that two key features are considered, how the main keel and bilge fins will be supported, and how to ensure the trailer runs nose-heavy when loaded.

The typical boat trailer supports the keel on rollers. Because of the short flat bottomed keel on the SeaHawk, the number and distance between the rollers is critical, to ensure the boat does not nose dive between the rollers as it is winched on to the trailer. Additionally, you will almost certainly need to make adjustments to the side-pads to provide adequate support for the bilge fins.

The owner of the trailer featured here needed to make adjustments to the rollers, axle position, and fin supports, to make it satisfactory. The one thing that could not be adjusted is the height of the rollers. This is a full ten inches higher than than the platform on the purpose-built Marine Weld trailers.

The Rollers

The supplier's catalogue describes this model as a speedboat trailer. As supplied, it had only three rollers, those that have the outer wheels fitted. Their separation was such that if the boat had to be drawn onto the trailer, the flat part of the keel would have left the rear roller before reaching the front roller, leaving the boat see-sawing on the central roller. It was, therefore, almost impossible to recover the boat using the winch. Instead the water needed to be deep enough to allow the boat to float over the trailer, as with the convention SeaHawk trailer, then boat and trailer drawn out of the water together.

To overcome this problem the previous owner had an additional cross-member and roller welded into the chassis. The cross-member was canted over at an angle but, originally, this was overdone and left the roller significantly below the level between the original front pair of rollers, as seen below on the left. In consequence when the boat was drawn onto the trailer, rather than ride over the front roller, it would drop onto the new, second, roller and the near-vertical leading edge of the keel would run into the front roller and stop dead!

Over the first summer with the new owner the cross-member was relocated and the roller raised. It was only as the photograph was prepared for the site that it was realised that the cross-member has been reversed. The roller is now on the leading, rather than trailing face, but luckily this has not caused any problem.

On other trailers, even if the rollers are set close enough together to provide adequate support to the hull, do check that they run level or have a means of adjustment. On this trailer the rear roller is mounted on bolts, which can be seen protruding beneath the chassis. These bolts allow the height of the roller to be adjusted by about two inches, so boats with a more conventional curved profile can be properly supported.

Axle Position

On purchase by the current owner it was found that the trailer was actually nose light with the boat in place. For safety's sake, it was necessary to remedy this as soon as the boat was in the water.

On this trailer it was simple to move the axle backwards six inches. The entire axle and suspension unit is separate from the chassis and secured only with a set of U-bolts. Moving the road wheels this small amount was sufficient to achieve acceptable nose-weight. On another trailer it might have been possible to adjust the position of the winch, but here, because of the limited number of rollers, this would have left the boat supported by only two rollers, so was not considered viable.

Bilge Fin Support

When bought, the original pads, designed to support the hull, were still in place. These were hinged and mounted on top of supports whose height could be adjusted. All this was a good design for securely hugging a conventional hull shape. However, for a SeaHawk, it proved impossible to tighten the pads sufficiently to stop them moving. Without the vertical sides to the pads that would be found on a conventional SeaHawk trailer, on taking the first corner the boat would drop off the pads. Such movement was clearly unacceptable.

Some heavy gauge angle-iron was obtained and this was welded on top of the supports. The carpeted pads were retained and re-fixed to the new fin supports. This work proved highly successful and there is now no movement in the boat while being towed.

As indicated above, apart from holding the boat upright, i.e. preventing the boat from rolling when going round corners, perhaps the more important function of the bilge supports on a roller trailer is to keep the boat from moving sideways, i.e. sliding off the trailer.

On the various purpose built trailer designs sideways motion is prevented both by the bilge supports and the bars in the chassis that hold the central keel in place. On those trailers the role of the bilge fin supports is primarily to prevent rolling.

With a roller trailer it is rather different. As no lateral support is provided to the central keel, the primary function of the bilge supports then needs to be considered as preventing lateral movement. In turn, the straps that hold the boat onto the trailer then have the primary anti-roll function.

Although the normal arrangement is to stop lateral movement by supporting the outside edge of the bilge fins, it is equally possible to stop any movement by supporting the inside edge of the opposite bilge fin. If the trailer is narrow this may be the only approach that is possible. The trailer seen below provides one such example.

On this trailer the bilge fin supports cannot be fitted between the wheels and bilge fins as the diagonal arm of the chassis, forward of the wheels, will provide no support for the front of the bilge fin supports, hence they are fitted inside the fins. It would appear, from the photograph, that the supports need to be moved outwards by an inch or so in order to be in close contact with the bilge fins and so prevent lateral movement. With the bilge fin supports set inboard in this way, the role of straps in preventing roll becomes more obvious.

Home-Built Trailers

Peter Stockley was converting an existing trailer to take his SeaHawk when the pictures above were taken. Working to a very tight budget, he had hoped to find a suitable sheet of steel to use on the central platform. Instead he made do with a heavy plywood sheet protected with a number of metal runners.

We await more information, from owner Austin Holden, on his immensely strong looking home-built trailer. Austin lives in Manchester and found the SeaHawk he bought in Glandford, a small village close to the north Norfolk coast.

Austin's boat was without trailer when he bought it and the "frame" in the picture below was part of the kit used by the Yard managers to lift it onto Austin's newly acquired trailer. He said:

"I was told that the boat could be lifted onto my trailer, and it was, using a frame, a pulley, a car jack and lots of wood blocks... an interesting exercise."

Design Considerations

Obviously, the some of the measurements above are critical to ensure that the boat sits securely on the trailer and that there is sufficient nose weight.

Those who have used a caravan or other trailer will be used to the business of adjusting the load in order to provide a suitable weight on the towing hitch. If the boat is too far back on the trailer there will not be sufficient nose weight for towing to be safe, the main danger being that the trailer can "snake" uncontrollably, in extreme cases causing the trailer to overturn.

The typical boat trailer offers two ways of adjusting the nose weight of the trailer: fore and aft movement of both the road wheels and the bow support. Balancing these two allows you to adjust the position of the centre of gravity so that it is just ahead of the road wheels.

Once the trailer is unhitched you also need to take care when climbing onto the boat or unloading any heavy items from the front of the cabin. Either action may be enough to shift the centre of gravity behind the wheels. The trailer will then tip smashing the stern on the ground! Always ensure that the trailer is propped to prevent it tipping before climbing onto a boat on its trailer.