The Guppy is a really good airplane that everybody should build. I built one a long time ago, before I had a laser cutter, and powered it with an OS 26 Surpass. It would be equally at home with a Saito 30, but it really doesn’t need more power than that.
The plan shows flaps, but no ailerons. I built mine with flaps, and I added ailerons, and it was great. I’m offering your choice of ribs to build with or without the ailerons, so please specify when ordering.
The plan shows no plywood braces at the wing root. In the article the designer says to use Celastic to reinforce the center joint, and notes that if you do not want to use it you should build your wing with plywood braces. I’ll include a set of plywood braces and a dihedral gauge in your choice of either 1.5 degrees or 5.5 degrees per side. As I always say, if you’re flying without ailerons you need plenty of dihedral to get the plane to roll. The plan shows low dihedral and no ailerons, which I’m not a fan of, so you get your choice. Tell me which ribs you want (ailerons or no ailerons) and choose low or high dihedral.
I thought the Guppy’s chin was a very impractical design. If you think about it, building it as designed would be kind of tricky. You’re supposed to fill the corners with scrap, then sand them to the outline of the firewall. But the firewall is covered by the fuselage sides and the bottom sheeting. It doesn’t make sense to me. So I simply cut the bottom of the firewall off flush with the bottom of the fuselage side. Lay a piece of 3/4″ balsa on there, or two layers of 3/8″, and sand it to shape. This is the way I did it when I built one, and it was easy. Refer to a plan such as the Cloud Dancer to see what I mean about the chin block. Also note that if you do the chin like the Cloud Dancer, you can extend the block in front of the firewall all the way to the front of the cowling, or sand it flush with the firewall and add big balsa blocks on the front, which is what I would do.
One other important detail is that I’ve used lite ply rather than balsa for the aft bulkheads, tank floor, nose bulkheads, and the filler on top of the fuselage behind the wing. The reason for the change is because lite ply comes in larger pieces than balsa does, so you get the big parts all in one piece instead of joining them.