Look at the low end of the fin and you can see the lighter wood tip.
Some kit wood is pieced together from smaller strips. The problem is the differences in the different wood densities. It becomes a concern when you are shaping the fins.
The fins are set over the full size instruction sheet drawing and the bevel lines are drawn in pencil with a straightedge.
You'll never get a sharp diamond fin profile by using little squares of sandpaper shown here in the instructions.
I've used the Great Planes sanding block many times before on the blog. The block is perfectly flat and the sandpaper is self adhesive. If you don't have one yet - trust me and buy one!
Please note that there is more than one model of this tool from Great Planes -- the flat surface tool is available in 5.5", 11", 22" and 33" sizes. There is also a model with contoured surface too.
ReplyDelete5.5" model: http://www.greatplanes.com/accys/gpmr6169.html
11", 22", 33" models: http://www.greatplanes.com/accys/gpmr6170.html
contoured: http://www.greatplanes.com/accys/gpmr6190.html
Hi Naoto,
DeleteI'm aware there are larger sizes available, thanks! I have found for LPR rocket use, the 5.5" block handles most everything.
I was mainly mentioning the sizes for the benefit of folks reading this blog. If you order through a hobby shop dealing with R/C aeroplanes, they're apt to give you the 11" or longer and not the 5.5" (as you noted, this size would be what you want for LPR rocketry use).
DeleteYou can also find similar "tee-bar" sanding tools, though I find those to be less comfortable due to the narrower grip.
How did you get the bevel angle so consistent?
ReplyDeleteHi Unknown,
DeleteIt my sound like an easy answer, but its lots of practice! I've done a fair share of beveled fins over the years.
Practice on scrap balsa, not the fins supplied in the kit. Buy one of the Great Planes Easy Sander blocks shown above - they are the best for this type of work.