Dr J and Mr Hyde Method

Someone asked me about my "no jig" fuselage design. I was going to write an article some day, as these planes have lots of cool tricks in the design. I guess that is some time away (after I win a few Nats I suppose) so I guess will post here.

My fuse is 100% CAD designed and laser cut. Even all the parts (except the 1/64" ply) used in the motor crutch are laser cut.

The fuse is built on a flat table (mine is glass). The top crutch is glued to the table using the laser cut relief holes shown in the cutouts (the relief holes are only held to the crutch by short uncut sections).
Use only slow CA here so as to not wick across the glass table. See the Kicker stains on the circles?

Then the crutch is added and all of the formers (they snap into slots in the crutch).

The sides are added and tacked to the formers and engine crutch with thin CA (use epoxy at the crutch). Then the bottom crutch is slid into place and it tacked into place.

Everything is tacked together, and then the cutouts for the bottom crutch are removed to allow access to the cuttouts in top crutch.

The fuse is then cut away from the tabs in the top crutch.

The "buck" of the cutouts are still left glued to the table. Done.

I built two fuse shells this way in less than two hours (the doublers were done the night before). They weigh 5 oz each with 1 oz aluminum pads attached, they are also VERY, VERY, VERY, strong in torque and straight as an arrow. No jig needed!

Brad,
Very cool. Thanks for sharing with us. Sure beats waiting for the article. Yeah, this forum is great.

Great post!

And beautiful design and workmanship. Thanks for sharing it, Brad.

Accuracy (laser cutting) really pays, doesn't it?

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"To find fault is easy; to do better may be difficult." -Plutarch

With CAD drafting you can get all the precision of laser cutting right off your jigsaw. Intricate little cuts may not be practical, but I've found that I can print stuff right from the CAD program and use it as a cutting template. With a little care in sawing(just kissing the line with the saw blade and keeping track of which side of the line is "outside") you can get parts in the range of .005. Plenty good enough for self jigging alignment.

So instead of spending hours fitting and trimming parts on the plane you spend hours laying them out in CAD!!

>With CAD drafting you can get all the precision of laser
>cutting right off your jigsaw. Intricate little cuts may
>not be practical, but I've found that I can print stuff
>right from the CAD program and use it as a cutting template.
> With a little care in sawing(just kissing the line with the
>saw blade and keeping track of which side of the line is
>"outside") you can get parts in the range of .005. Plenty
>good enough for self jigging alignment.
>
>So instead of spending hours fitting and trimming parts on
>the plane you spend hours laying them out in CAD!!

I have done this also. You do not need the laser cutting.

The method works either way...

Brad, what is the wing area , approximate weight, and recommended engine for this plane??

Bigiron aka Marvin Denny

> Brad, what is the wing area , approximate weight, and
>recommended engine for this plane??
>
> Bigiron aka Marvin Denny

The current Hr. Hyde and Dr. Jekyll are based on the Impact wing which is 685 squares.

Of course, I run the Siato 72 four stroke.

This fuselage box could easily accomodate several other designs. A box is a box afterall. I have used almost the identical design for all of my airplanes since I came to Texas except, for kit planes of course.

Dr. Jekyll has an 18 3/8" tail moment, and an 8.75" nose moment. The fuse sides as shown are 3" tall. this gives me advantage of using the foam cores (also made from 3" stock) for jigging up the assembly.

Thanks. That is somewhat larger than I want to work with.
That looks like a good construction method.