Stearman PT-17.

[davidchoate]

Got the laser cut kit last winter, and put it together to satisfy Dale that the lASER CUT PARTS WERE GOOD. nOW ITS TIME TO FINISH. I have the framw , hinges, and doped. I even have the aelerons hoked up. i'm doing it as an RC plane. I bought a Dumas peanut Curtis Hawk just to see how to align the top and bottm wing with a template as the Dumas kits do. If anyone has built this before, and knows how to align wings; please help.

[Bill Gaylord]

The Stearman build I posted here flew well. The gear placement set the CG dead on, with no ballast added. Some recommend giving the top wing a slight (1/2 to 1 degree) more positive incidence on biplanes with staggered wings. Just make sure that the bottom wing does not have more positive incidence than the top wing, as matched incidences will work fine. If the bottom wing has more positive incidence than the top, it will stall first and then the plane pitches up into a tail heavy stall, since the CG is now far aft to fly only on the top wing. I've flown a roller coaster biplane like this before, and it was not fun to fly.

Another thing you don't want is mismatched incidences between the panels. If you're going to have any, it's better for the left panel/s to have a hair more positive than the right, than vice-versa. The opposite scenario will cause the plane to bank hard left, as the p-factor already favors that direction. A slight mismatch can be trimmed out and the plane will fly reasonably well, but this is NOT much. It's that kind of precision settings that really throw people until they appreciate it. I had to go through that learning process when I started building, as I couldn't appreciate how precise wings have to be built, without seeing the results of wings that were not precise.

[davidchoate]

Thanks. For the warnings. It makes me want to do the little Dumas Hawk first. You must know what I'm talking about when I said that the Dumas Bipes kits have a light cardboard jig to align top and bottom wings;I want to adapt this to My Stearman.. It will be RC of course. I have a 350 motor, and all the gear.for it already.. My first bipe.

[tail spin]

Nice build David! I have had my eye on several Bipes at the LHS for future build for a display model only. But I see much more experience is needed & I am not ready for it quite yet I will be watching the build threads very closely . I Like the Guillows Stearman kit for several reasons, But also being they were built in my home town and the air museum & the old factory is a mile away from the house has one on display restored and flight ready on display in the Old air terminal .

[davidchoate]

The first Plane I built 30yrs ago was a Biplane. It flew remarkably well. I am sure it was luck. I have three Biplane kits . The PT-17 of course, a Tom Morse Scout(not Laser Cut), and a Curtis Hawk 14" Dumas. . Now I ike the jig for wing alignment, But have no clue as to how to find the balance point on a biplane. Anyone Know.? And Do you think I should keep the torque tube aeleron setup, or use a servo in each wing.? I have alot of plastic to paint yet before assy. As a matter of fact, I'm doing a cheap side project to keep Me busy as I wait for glue and paint to dry on the plastics. Its a free plan I got off Hippocket. I have all the radio gear, and a 370 brushless. I know shes gonna be heavy.

[tail spin]

Question, If Dumas has included a template for wing placement, Wouldn't it behoove Guillows to offer the same for their kits? Or maybe offer a free online down load template?

[Bill Gaylord]

Question, If Dumas has included a template for wing placement, Wouldn't it behoove Guillows to offer the same for their kits? Or maybe offer a free online down load template?

They're not going to want to add to the cost of the kit, since this would be a large part for biplanes, having to fit between the wing panels at assembly. The thing with Dumas is that they charge 5 million dollars for their tiny kits, so they have to throw parts like that in there to behoove their customers. The template would be something people could make themselves and be useful. Things like that could be put here. The piece would have to be something of higher quality that a piece of floppy cardboard to be useful. Irregardless a person would still have to tweak the strut lengths such that the wing panels would perfectly fit the template at assembly. If you're going to have to do that anyway, then there's not as much need for the template, since that can be done using rulers to check parallel alignment while fitting the struts to length.

A good method for ensuring wing alignment is to hold the model in front of you and slowly rotate it forward. The wing bottoms should expose themselves at EXACTLY the same rate. If you set washout, you will first see the underside at the tips, gradually moving toward the inner wing panels as you rotate the wing forward. The same goes for intentionally setting a hair more positive incidence to the top wing of a biplane. The point is that your eyes don't lie, and will pick up the slightest warp and/or incidence mismatch.

[tail spin]

Thank you Bill.