Head Hunter 15 (oz7651)

About this Plan

HeadHunter 15. FAI competition power model for .15 powerl.

Quote: "Because so many contests specify eight and ten second motor runs with three-minute maxes, the designer presemnts a good case for the smaller, faster climbing design with a carefully chosen airfoil for en easy, slow glide.

The HeadHunter represents my first significant departure from the design philosophy I have been using since the original Bounty Hunter (oz8543) was conceived in 1962. There is a noticeable family resemblance, primarily because i have been using swept back wings since 1957, but the similarity ends there.

Our ace in the hole with the Bounty Hunter was its glide, but with the HeadHunter it is a combination of both climb and glide, with strong emphasis on the CLIMB. This becomes obvious when the two designs are viewed side by side. Except for about four inches more wingspan, the HeadHunter is slightly smaller than the Bounty Hunter, but the HeadHunter is powered by a .15 displacement engine, and the Bounty Hunter uses an .049!

I decided on this drastic revision of philosophy at the end of last year's contest season, not because the ships I flew hadn't done well; rather, I merely felt there was a better answer to the new short-engine-run contests which have become the standard in the Southwest and East. It is not unusual to arrive at the contest and be told engine runs have been reduced to eight or ten seconds, with three-minute maxes. This can get monotonous when you are flying a big, slower climbing ship, such as the Bounty Hunter, the Trigger, or the One Grand. Of course, these ships will still win their share of competitions, but I prefer using something I feel is better suited to the situation, to regain the original advantage I would have had before the contest director lowered the boom.

As luck would have it, the HeadHunt-er 15 has turned out to be superior in all respects, under any rules. As a result of the 15's performance, a 1/2 A and a B-C version are being used this season. Area for the 1/2A is 260, for the B-C, 650. The 15 version shown in this article has 454 sq in of wing area (projected). A total projected area of 616 squares puts the HeadHunter in the FAI gas class at slightly under 28 oz. Thus, although it was designed primarily for unlimited AMA rules, the HeadHunter 15 is a formidable threat in both classes.

HeadHunters built for unlimited only have weighed between 15 and 18 oz. ready to fly. I have done my testing for FM with lead added to the unlimited ship and, while performance in the air was great, the added weight made DT landings rough on the light airframe. Thus, if you are planning to fly both unlimited and FAI, I would advise you to build with heavier wood, and shoot for 21-24 oz without lead. This is a compromise, especially for unlimited, but it should still be tough to beat. For pure FAI work, shoot for 26-27 oz. Because a serious FAI'er usually puts a couple of hundred flights on his ships during a season, it is essential that toughness be built in. I am in the process of building my
FAT HeadHunters now, with these modifications: a 1/8 plywood pylon core sheeted with 3/16 balsa; spruce wing leading edge and main spar; rock-hard balsa wing trailing edge; 1/8 diameter wire nose skid; cast aluminum pan motor mount; 3/16 fuselage sides; and silk covering. Many other small touches are necessary for pure FAI work, but each modeler has his own pet methods, so I won't elaborate.

The lightest HeadHunters are not flimsy. In fact, they are tougher than most unlimiteds. They have to be because they are so much faster in the climb. The prototype HeadHunter was buried up to its timer on its second test flight (not enough decalage - it dove in vertically on the glide) with no damage except a broken prop, which proved two things: 1) it is rather tough at 18 oz; and 2) I am a wild man when it comes to trimming new designs.

In going, for a wild climb, besides increasing the normal sweep angle of the wing and stab, I mashed the airfoils down to a little more than 7%. Such thin airfoils also allow shortening of the tail moment..."

Article pages, text & pics from RFJ.

Direct submission to Outerzone.

Supplementary file notes

Article pages, text & pics.

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