Hi Bertrand,
I've been too busy beavering away to upload my latest photos... so I'm doing that right now - 171 new pics to pour over! They'll take an hour or so to upload, but you'll find them here, eventually:
www.ihpa.ie/carbon-dragon/index.php/cd-b...hil-lardner-s-cd#new
Horizontal Stabiliser Front Spar:
You're right - you can't build the H-stab in carbon as you would in wood, and I had to have a good think about it before I tackled that problem. My solution was to fabricate the front spar in one piece on an A-shaped mold (rather than the gentle curved shape of the original wooden spar) with a single carbon rod in each of the four spar caps. You can see the 'A-shaped' mold I used to shape the front spar in the photos below.
I then cut the H-stab ribs at the correct angle to allow the front spar to be bonded to the cut ribs. The 'nose' sections of the ribs were then bonded onto the spar to give the final shape. This worked very well. I also used this method when constructing the vertical tail.
H-Stab Rear Spar:
All my spars are fabricated from two layers of 195gsm carbon twill cloth cut at 45degrees to the long axis, with the carbon rods sandwiched in between the two layers, at the edges of the spar to form the spar caps and flanges. For all but the 'bent' front spar on the H-stab you can use continuous lengths of carbon rod in the spar caps. There is no need to cut them at the center / root. The carbon rod can easily be bent to accommodate the slight bend in the spar caps. I only discovered this after making my first H-stab spar with a double-taper. My elevator spar was made with continuous lengths of rod and turned out perfect!
H-Stab Attachment points:
Like Rick Mullins I used two metal attachment fittings for the rear attachment points and just a single V-shaped fitting for the front mounting. The two rear fittings will slide onto fixed metal pins attached to a horizontal bar fixed to the tail boom (as per the original plans) and the front fitting will be secured by a single, spring-loaded pip-pin to facilitate quick assembly and removal.
I'll show you how I made the carbon hinges in the next post... the system is limiting me to 8 attachments per post!...