Could someone outline the basic idea of crutch construction for me? Does the crutch actually become a permanent part of the structure or is it removed later? Pictures would be nice cause I ain't too bright!

Also what are the other basic construction methods used in scratch-building scale models?. I know a lot of WWI models use a "truss" construction which basically just involves building two sides and then turning them into a box. In some cases, then, formers are added to the sides of the box to make rounded sides.

A "crutch" assembly is 2 pieces of lite ply, over which, the balsa fuselage formers are slid on and CA in place. The sketch should provide an idea of what I am referring to.

Hope this answers your questions.

Thanks! What are the advantages (and disadvantages) of this construction method?

I don't have the same understanding of "crutch" as Campy has. If you take a round (approximately) fuselage with stringers down the horizontal center line of the formers. Cut the formers horizontally in half. Pin the horizontal stringers to the plan, then glue the former halves to the stringers. Complete this half of the fuselage. Remove this half of the fuselage from the board, turn it over, glue the other halves of the formers in place, and complete the fuselage construction. The original stringers that were pinned to the plan, are the "crutch". I will be building an OLD, redesigned (by me) Mosquito that uses this method and will try to post pictures, but it will be some time away. Advantages are that you can hold the "crutch" flat while you build, without having to worry about jigging up round fuselage formers.

Les

Les, that sounds like the classic Guillow's fuse construction.

Hi Abu,
I have built a couple of Ziroli designs. The crutch is the "backbone" of the plane. Ziroli usually makes this crutch stand on a number of building blocks. The crutch usually has cross braces too since this might also be banana shaped. The crutch is now laid on the building blocks and later the formers are passed through with the crutch being located on the inside part of the fuselage.
The formers are then aligned according to plan and then stringers are glued to the formers with the added advantage of fine tuning the position of each former according to plan.
It is a simple but an effective method of making a construction of a fuselage.

Hope this helps.

Reuben

Abu: Yes. That is my understanding. And it does not have to be a horizontal split as I described. I think the Guillows was a vertical split, but in their case, the stringers were complex in shape. With the horizontal split, the stringers are merely bowed to the correct contour. Both work equally well, when you have other than square fuselages.

Les

I believe when you split vertically, such as Guillows does, you are then building on the keel rather than the crutch. However, that's just symantics as the process is the same either way. Most, if not all, of the Top Flite scale kits are built on a crutch. When building on a crutch it usually is an integral part of the fuse but not always. I think some of Jim Ryan's electric warbirds are built on a crutch which is removed after the fuselage is sheeted. I prefer to build my fuselages on a crutch in upper and lower halves as Les described, actually pinning the crutch pieces to my building board rather than suspending them. I find it easier to build a straight fuselage this way but that is just my personal preference. I've gotten to the point that, if whatever I'm building is not designed to be built in upper and lower halves, I will often modify it so that it is. (Assuming it is not a box fuselage.) Once you get comfortable with a process why change it?