The Prentice Baby Bipe - 1977
 

In 2003 I built a lovely little biplane for .25 power from a construction article in the July, 1977 issue of Model Airplane News - the Prentice Baby Bipe. Club members who usually ignore my small planes liked it and I enjoyed flying it until it was wrecked that same flying season.

I decided to build another Baby Bipe last year. The stock design had wings which were sheeted over two-thirds of their area which I thought was over-building such stubby wings. So in 2003 I re-designed the wings for an open framework structure with sheeting only at the center section in the first version. Airfoil and plan outline were unchanged. Now I am lightening the fuselage a bit by replacing plywood doublers with balsa.

RE: The Prentice Baby Bipe - 1977
 

Version I had a single aileron servo but now I am using two servos to make setting differential movement easier and to provide more useable space inside the fuselage. The servos are attached to 1/16"ply hatches with auto molding/trim tape which is more rigid than servo tape. It is tight fit getting 3 servos in.

RE: The Prentice Baby Bipe - 1977
 

Scratch-built biplanes are more than twice as difficult than building monoplanes. It is not just building a second wing, it is having to devise attachment methods for all of the struts and then trying to align both wings- in incidence, at right angles to the fuselage and equidistant from each other.

The photo at the left shows the evolution of a template to determine the precise length of an interplane strut. First, the upper wing position is held by a stick clamped with 2 clothespin clamps. Then a rough scrap wood template is made and it is then done in balsa to check the final dimensions. At the right is the finished lite-ply strut.

RE: The Prentice Baby Bipe - 1977
 

Things look up with some bright color on the fuselage and tail while my trusty test pilot, Tip Stahl, checks out the front office.

RE: The Prentice Baby Bipe - 1977
 

The completed model is covered in Ultracote and weighs 43.4 oz. with an OS .25LA engine. Wingspan is 32" and wing area is 425 sq.inches. Flight tests will await moderate weather.

RE: The Prentice Baby Bipe - 1977
 

You know, two days ago I went to a hobby shop in CT and got so friggin excited, I was buying stupid stuff we normally use that most people walk by, like koverall and paint, when I happened to look up, above the racks of parts to see a box, well, a few boxes! An ACE allstar bipe, THE M.E.N. piper cub, sig liberty sport, and a few other kits from years ago. I frantically went to the counter and asked if those kits were for sale, the answer I got was that the kit's were not in the boxes and it was just wood in them, I think the guy was lying, but you should have seen how nice and new these kit boxes were. I told him that he just pissed in my wheaties and I now have to continue with the scratch of my allstar bipe, I think anything you scratch build will be a favorite in the hanger. I don't think that bipes are twice as hard, just twice the impression at the field. I guess after building at least 8 bipes, you seem to think nothing of the extra work, it almost makes building a monoplane seem kinda 1/2 built in some ways:D

I know this is an old thread, but I've been building bipes recently and wondered how this flew? It looks terrific, and I would expect it to do well at that weight.

Jim