Konrad
Very Strong User
I built a Sig Sinbad 40 as a 12 or 13 year old. I was enamored at how different the model built compared to my much smaller 18" Guillow models. That crutch was an eye opener In how to build a fuselage that didn't look like a banana.
I flew the Sinbad 40 3 or 4 times as a Free Flight model. Each flight ended with the stab mount failing. Well, all but the last flight. On that flight I lost the SInbad to the thermal gods. I built my last Sinbad 40 as an RC single channel using a Mattel radio. All I recall of that was that the SInbad 40 was a lot faster, and was horrible to keep in trim with that huge decalage angle. Add to that the directional control/stability was wonky! Back then I blamed the Mattel radio.
I've been carrying around a Sig kit for the last 50 year. Even to a prepubescent kid I knew the design, while looking great was very poor.
I'm currently building a micro Sinbad, you can get one from Aloft Hobbies. Serendipitously the design of the micro Sinbad has some fuselage stringers that go aft under the stab. I've decided to take advantage of these stringer to use them as a much more stable stabilizer mount. As a result the stab now has 3 to 4 time more glue area that the original Sinbad of my youth.
This stab mount and the fact that I now know how to form a film fillet has reawakened my desire to relive my youth. Here I'm starting with a design study of the Sig Sinbad 40. The key is in the fuselage structure. I really need to thank Red Jensen for the design of the micro Sinbad with the placement of the rear stringers going aft under the stab.
I just re-read The Old Buzzard's Soaring Book and learned where that oversized stab came from. It was in all likelihood from Frank Zaic's Model Glider Design, this was a Free Flight handbook.
I also see where some of the stability issues I noticed as a child came from. While I love the character of that large bulbous nose. We all now know that side frontal area ahead of the center of pressure (center of gravity is a practical reference) is very destabilizing. So I'll be lengthening the tail boom to regain some directional stability. This will also allow me to cut down on the stab size to 60% maybe 50% of the as drawn stabilizer.
I will get rid of the rubber band wing hold downs. But will keep the tear drop wing mount for esthetics reasons. (Yes, I know about Hoerner's nozzles).
I was surprised that this Sig kit is a die cut kit (my kit has good cuts). Most Sig kits I recall being printed balsa. This means that I can't use most of the sheet wood in my kit. So I'll just use the plans as a reference guide. So I might still have this 50 year old kit when I'm done!
I flew the Sinbad 40 3 or 4 times as a Free Flight model. Each flight ended with the stab mount failing. Well, all but the last flight. On that flight I lost the SInbad to the thermal gods. I built my last Sinbad 40 as an RC single channel using a Mattel radio. All I recall of that was that the SInbad 40 was a lot faster, and was horrible to keep in trim with that huge decalage angle. Add to that the directional control/stability was wonky! Back then I blamed the Mattel radio.
I've been carrying around a Sig kit for the last 50 year. Even to a prepubescent kid I knew the design, while looking great was very poor.
I'm currently building a micro Sinbad, you can get one from Aloft Hobbies. Serendipitously the design of the micro Sinbad has some fuselage stringers that go aft under the stab. I've decided to take advantage of these stringer to use them as a much more stable stabilizer mount. As a result the stab now has 3 to 4 time more glue area that the original Sinbad of my youth.
This stab mount and the fact that I now know how to form a film fillet has reawakened my desire to relive my youth. Here I'm starting with a design study of the Sig Sinbad 40. The key is in the fuselage structure. I really need to thank Red Jensen for the design of the micro Sinbad with the placement of the rear stringers going aft under the stab.
I just re-read The Old Buzzard's Soaring Book and learned where that oversized stab came from. It was in all likelihood from Frank Zaic's Model Glider Design, this was a Free Flight handbook.
I also see where some of the stability issues I noticed as a child came from. While I love the character of that large bulbous nose. We all now know that side frontal area ahead of the center of pressure (center of gravity is a practical reference) is very destabilizing. So I'll be lengthening the tail boom to regain some directional stability. This will also allow me to cut down on the stab size to 60% maybe 50% of the as drawn stabilizer.
I will get rid of the rubber band wing hold downs. But will keep the tear drop wing mount for esthetics reasons. (Yes, I know about Hoerner's nozzles).
I was surprised that this Sig kit is a die cut kit (my kit has good cuts). Most Sig kits I recall being printed balsa. This means that I can't use most of the sheet wood in my kit. So I'll just use the plans as a reference guide. So I might still have this 50 year old kit when I'm done!
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