The Morgan body is built on traditional coachbuilding lines, using metal panels folded over and pinned or screwed to a wooden body frame.
The Morgan frame is relatively simple, at least for the so-called traditional models, and replacement of rotten or damaged wooden sections, or even the building of a complete new frame, should pose few problems for the average reasonably competent handyman. Be warned however that the process is labour-intensive and be prepared to pay accordingly if you farm out this work commercially, particularly where it involves removal and replacement of metal panels.
The timber traditionally used is European ash, and new cut to size framing sections are available from several sources for those not prepared to make them themselves. However, European ash has significant disadvantages as a framing timber - it is prone to rot, sometimes in surprisingly short order, and it also suffers from the problem of racking, that is sections such as at joints will tend to compress under load. While frames have been factory treated with a copper napthalene preservative since around 1986, this preservative itself only has a finite life, as little as two years in exposed situations. So don't assume just because your car is post 1986 that its wooden frame will be immune from rot.
Incidentally, while this timber has been called English ash, Belgian ash, European ash etc, it is one and the same timber, Fraxinus excelsior, and claims of differences when sourced from different locations, eg English ash having superior performance to Belgian ash for example, are absolute rubbish.
While in the UK there is little other suitable timber to choose from, there are far better coach building timbers available in some other countries and it is strongly urged that these be explored first. Australians, for example, are spoilt for choice with a range of coach building timbers vastly superior performance-wise to European ash. (See the section on Coachbuilding timber selection in "Technical" on the website of the Morgan Owners Club of Australia for test data). In choosing timber, look for long straight grained sections without knots and always ensure it is well-seasoned.
The easiest approach is to use the old wooden sections as templates, provided the car has maintained its original shape. It's a little more complicated if the frame has to be made without these reference points, but don't give up just because of this. Frame drawings are available from various sources for a number of the models and dimensions can also be referenced from other cars. Best to try to draw these up full size on drawing paper or cardboard if you can organise this. When cutting out the timber sections "hand" them to ensure symmetry, ie the side bits should be mirror images of each other. The doors are possibly the only tricky bits as the angles are a bit "unusual". It's best to make the rest of the frame first then make the wooden door sections to fit the aperture, ensuring the angles are correct. Remember that the section of door frame which carries the hinges should stand about 1/8" to 3/16" proud of the door hinge post to allow for opening of the door without the door panel fouling on the body. Note also that the angles of the joints in the door frames are compound in some cases, and need to be cut with care. In fitting the hinges, be careful to allow enough clearance so that the door skins, when fitted, don't bind on the tops of the hinge pins.
It is important, indeed absolutely critical, that all joints be glued and screwed. If using hardwood, screw holes will need to be pre-drilled, and it is recommended that only stainless or phosphor bronze screws be used. It is all too easy to twist the heads off brass screws in this application, and the oils in some timbers may attack and ultimately destroy the coatings on plated screws, with resultant rusting and possible wood rot. The glue used should be selected with care - some of the resorcinal boatbuilding glues for example have been found to crack and fail under use in a Morgan application. as have PVA glues. The preferred glue is Araldite, a Selley's product. However use the variety with the longer curing time, not the "instant" product.
The reason for glueing the frame is to ensure its stiffness and longer term integrity. The frame is a significant factor in Morgan ride quality as it acts as a stiffener for the chassis, ensuring that the springs do the work they are designed to do rather than relying on chassis and body flex as the primary means of shock absorption. Without glueing, the joints will work loose, particularly if the timber racks as aforementioned, and the car's ride quality will gradually deteriorate markedly as more and more of the suspension function is taken over by chassis and body flex. It may also lead to cracking and breakdown of both paintwork and the metal panelling at these stress points. The chassis in turn will also come under increased stress and be more prone to developing cracks. BE WARNED - No matter how well the joints are fitted and screwed together, the joints will work loose, sometimes in surprisingly short order, if they are not glued.
As a further background, the best approach for a curved wooden body section is one which uses a single piece of timber with linear grain structure. Long ago, boat builders assiduously searched for suitably shaped pieces of tree root to make curved stem sections to avoid the need for joints and they also sometimes grew saplings to a curve for use as ribs. This spreads the stresses/flexibility/recovery etc evenly along the length of the timber section. With timber shortages, this is no longer practicable, hence the use of joints. But joints are a compromise - they create a particular weak point as they break the linearity of the grain, and the stresses thus tend to focus on this point rather than spread out evenly. The joint thus needs to be constructed as far as possible to try to reduce this focus and ensure the stresses are spread, and given the tendency of some timbers, particularly European ash, to rack with screw holes consequentially widening and the joints working loose, the potential problems in not glueing the joints will be obvious.
There are some who apparently still advocate not glueing the joints. Disregard these people, as this runs directly counter to traditional long-established coach building practice for this type of body application. Should you arrange for someone else to do the frame, and they advocate this approach it is strongly suggested you run rapidly in the opposite direction.
Before panelling, treat the frame to several coats of copper napthalene or other anti-fungal treatment, and allow to dry thoroughly. When fully dry, paint the frame - the reason that some advocate not painting treated timber is to allow recoating with the preservative at periodic intervals, something you will not be able to do with your Morgan.
Finally, when repanelling, shape each panel for a proper fit, then thoroughly rust proof the inside before final fitting. Consider using tiny stainless steel screws for this process rather than the usual steel panel pins, which are prone to rust and also may cause electrolysis when using aluminium panels.
One of the weaknesses in the Morgan frame is the attachment point between the vertical inner rear wheel valance, which is made of plywood, and the short rear sillboard which bolts to the chassis. Two suggestions, which will also improve stiffness and durability : the first is to sheath each side of the inner rear wheel valance between two sheets of aluminium. These should be roughed on the sides chosen to face the valance, and, before gueing matched up and pre-drilled at around 6 inch centres to take small (ie 4 gauge 3/8") stainless steel woodscrews. Finally, the rough sides and the sides of the valance should be smeared with adhesive (once again Araldite is recommended) and the assemblies glued and screwed together. This should be done before the curved rear wooden wheel arch sections are screwed on. In fitting the valances to the rear sillboards, the latter should have a channel routed in them, about 1/2" deep to locate the valance (allowance for this needs to be factored into the size of the valance when making it). When these assemblies are screwed together, add a piece of aluminium angle bracket at each side to reinforce the join.
The following photographs show the pieces cut out and ready to glue and screw together, also in almost finished and then finished state. The curved wheel arch section is one of the two featured under the next heading in this section.
This shows the inner rear wheel valance cut out of marine ply, with one of the two outer aluminium sections cut to size. The front section of the one for the other side can just be seen to the right of the photo.
The two aluminium outer sections have now been glued and screwed on, and the curved wheel arch section added. The wheel arch section has still to be trimmed to size and the wooden chassis section added.
This shows the finished item taking its place in the (yet to be built) body frame.
This is the completed body frame - awaiting panelling after a little more preservative and paint. It is an early car, hence the rear-hinged doors, as per most of the first 78 Series 1 cars.
Making wooden rear wheel arches.
A suggested method, which ensures consistency and continuity, is to make up a steel former to inner shape of the arch. Note that the curve is not to a consistent radius. The curved section of the former can be bent up out of strip steel 1'' wide and 1/8" thick or similar. Once a correct curve is obtained it is reinforced by welding supports on it.
The wooden section is made by cutting four strips of 5mm ply slightly oversize. Use only marine or building grade ply made with waterproof glues for this. Glue the strips together, and pull them to shape by progressively clamping them to the former. Araldite again is the recommended glue. Allow to cure for at least 24 hours - on removal mark the top. The section will spread slightly on removal but will readily pull into shape again when glued and screwed to the inner wheel valance. Trim to size before doing this, but it is suggested that final shaping of the ends be left until the section is matched up to the sill boards.
The illustrations, which are for a Series 1 4/4, are self-explanatory.
In refitting the body to the chassis, a damp course is used between the top chassis rail and the bottom of the sill boards. Various types are available, the purpose of fitting the course being to prevent moisture transfer from one area to another, with resultant wood rot (the frame), rust (the chassis) or more probably both.
Various old car specialists sell this damp course in individual car rolls. However, as a suggestion, visit a local building supply specialist and take a look at the plastic dampcourse they sell for brickwork. It comes in various thicknesses and widths. Normally, the narrowest width will be too wide for the Morgan chassis, but it can be cut to size. In some cases, the rolls supplied by the specialists would simply appear to be this stuff cut to width and then onsold at an inflated price.
In fitting the damp course, the holes for the attachment bolts should be punched in first with the course matched up to the top chassis rail. With some types of damp course, this operation can be simplified by using an old electric soldering iron with a narrow tip. The damp course is clamped in place (raid the washing basket for a few pegs) the tip of the hot iron pushed up through the hole in the top chassis flange and the damp course melted to shape. The damp course is then removed, and two thin beads of non-acetic silicone sealant run along each side of this chassis rail. The damp course is then added, as necessary with a few bolts or studs up from underneath to aid alignment, and two further thin beads of the silicone run along the top of it before fitting the body to the chassis.
The use of the sealant is important. Otherwise capillary action is likely to draw both moisture and dirt into these areas.
While some people have experimented with other materials for dampcoursing, with varying degrees of success, It should be stressed that the material detailed here is specifically designed and marketed as a damp course, and the method outlined has been widely used for many years now in car restoration generally, not just Morgans.
In this context there would seem little point in searching for and using other materials not specifically designed for this purpose and whose use may prove to be below par or even lead to future problems.
Interestingly, in the hey day of British coach building, a strip of felt or other fabric was often used in lieu of damp coursing to help eliminate squeaks. This inevitably got wet, and quite often stayed damp, with the predictable results.