Another ladder style fuselage jig illustrations from Tom Hallman and his Maxfliart videos from a screen shot.

Here's a similar technique by Dave Mitchell using Horizontal Keel construction. From FACN Mar/Apr 2013

BOX CONSTRUCTION UPDATE
Here's an update on fuselage box construction done with rectangle formers to align the sides
for the addition of the cross members.  I used the former patterns to cut out the foamboard/balsa/cardboard rectangles. I used this construction for the Ace Whitman Jack II plan.  I left off an additional 1/16" from the top and bottom of the rectangles to allow room for the cross members (1/16" SQ) so the glue doesn't stick them too, making it easier to remove them later.  The former pieces are then cut out to add to the box fuselage to give the fuselage some shape with stringers. 
I want to add that in making the rectangles I used steel machine squares (a good square will do) to make sure the sides are square or your fuselage sides won't be square to each other.  Then make sure you measure from the top of the side to the top of the rectangle on each side to make sure the fuselage sides are aligned accurately.  You can still build crooked fuselages if you don't take care to square up each rectangle to both side of the fuselage box.  Once you're satisfied it then becomes easy to add the cross members. 
One other note...make sure your cross members are flat with the top and bottom of the sides.  If they are twisted, when you add the formers it will tilt the formers at the angle of the cross members sides.  Don't ask how I found out that little jewel!! 
Here's a couple pics to illustrate the rectangle formers for side alignment.
Fuselage with formers added and rectangles removed.
Tom

THE HALF SHELL CONSTRUCTION...
They say a picture is worth a 1000 words... here's a picture of Thymekillers P-40 build on a CU (Cook Up) thread here on S&T...
As you can see this is very similar to the keel and former construction except that the formers are applied 1/2 a side at a time.  then the stringers are added and once the first side is completed, the  have shell is lifted from the board and the other side formers are added and  then the stringers to complete the fuselage.  Care must be taken to keep the fuselage from warping , giving you a banana shape!!!!

THIS THREAD HAS BEEN RECONSTRUCTED DUE TO THE PHOTOBUCKET SNAFU...SORRY FOR THE PICS THAT WERE MISSING FOR A WHILE.  I'VE TRIED TO REPLACE THE PICTURES AND SOME MAY BE A BIT OUT OF ORDER! THANKS FOR YOUR UNDERSTANDING EDIT AND REDO 23 JAN 2018.

Don't see why the thinner couldn't be sprayed.  The dunking saturates the foam quickly allowing the wood to be moved out of the thinner quickly.  It is possible that the super glue can be affected and possibly loosen joints with continued exposure.  I haven't experienced this. 

One other note.  The super glue will attack the foam unless it is the foam safe cyano.  So application of the super glue must be done carefully.

Tom

I would assume that's true but have never done the lost wax process.

I have enjoyed this process and am planing on doing another one for an upcoming build.

Tom

Fernando,

The lost foam is an interesting process. 

The foam is cut and sanded to a dimension that is just less than the desired size. I use reed for the formers and balsa for the stringers and sheet areas.  So if using 1/16 balsa over the reed formers the dimension of the reed (approximately 1/16 diameter) and the stringers. 

I use cyano glue (super glues) to glue the reed former and the stringers in place.  The nose plug was just tacked on for sanding purposes.  You must leave an opening large enough to remove the foam as it dissolves in the lacquer thinner.  Some builders split the structure and remove the foam and then re-glue the outer structure back together. 

I do prefer the lacquer thinner removal because it leaves the structure intact and you need not worry about the structure warping on the re-gluing process.

Depending on the size of the fuselage a pvc pipe filled with the thinner is used to soak the foam which will immediately begin to dissolve.  You may then pull the puddy-like disolved foam through the wing saddle area or the nose block area.

Strain the thinner and place it back in the thinner container for the next fuselage.

I hope this answered your questions.  I'll be happy to answer any other questions you may have.  The super glue is not affected by this lacquer thinner.  I use a dunking motion to soak the foam and remove it as it shrinks.

Tom

I never worked Lost Foam.
It seems a very interesting technique.
No problems with the thinner?
Can be used balsa wood?

Sorry for my bad english.