Primary Force

So, nachdem ich mich beschwatzen lassen habe von einem Stiletto Abstand zu nehmen, und meine Zeit momentan sehr begrenzt ist, habe ich mir einen Primary Force zugelegt. Vorgestern von Flight Depot abgeholt war ein Ausstellungsmodell, mit einem russischen 2,5er. Den 2,5er halte ich für einen Witz. Der Peter (Shoestring) rät den Einbau eines LA 25 wegen Schwerpunkteinhaltung. Im Lassogeier gibts einen Bericht wo hauptsächlich LA 40 eingesetzt wurden. LA 25 sowie LA 46 stehen zur Verfügung, ausserdem noch OS MAX 35 FP, OS MAX 35 S,
weiss jemand wo der Schwerpunkt sich befindet? Einen Plan habe ich nicht bekommen.
Gruss
Gerrit

Primary Force

Hallo Gerrit.

Warum versuchst du nicht mal mit dem 2,5er Russenmotor zu fliegen? Entweder er reicht aus und hebt ab oder nicht. Dann weißt du wenigstens, was an Motorleistung gefordert ist. Wenn das Modell nicht zu schwer ist und du nimmst ca. 16 m oder 17 m Leinenlänge (0,3er oder max. 0,38er Dicke), dann müßte das eigentlich funktionieren.
So kommst du auch mit begrenzter Zeit am schnellsten zum Fliegen.

Ich weiß nicht, wo der Schwerpunkt liegen soll, aber wenn du ihn bei 25 bis 30 % der Flächentiefe einstellst, bist du auf der sicheren Seite.

Gruß
Willi

Hallo !

also wenn der flieger mit 2,5er zusammen nicht über 750 gramm wiegt (was ich aber bezweifle) könnte man den 2,5er drin lassen. Ansonsten was ab 4 ccm aufwärts. 6,5er halte ich gewichtstechnisch für die Obergrenze, hat schliesslich nur 1,3m Spannweite.
Irgendwas gleitgelagertes um 5 ccm fänd ich optimal. Thundertiger GP28 oder Enya ss30. Oder nen ollen FOX 35 , dafür sind die Ami-kisten eh alle ausgelegt.

Wär schade wenn der Flieger wegen untermotorisierung in einer kritischen situation drauf geht, ausserdem macht etwas dampf unter der haube ja auch spass.

Grüsse, Sebastian

der Flieger liegt wohl eher bei 1100g, für einen 2,5er schlichtweg ungeeignet,

so, der LA 46 und der FP 35 gehen saugend rein, der LA 25 sowie der Enya SS30 und der Max 35S sind deutlich schmaler. der 2,5er Norvel fristet sein Dasein bereits in einem Eyas. Der Hersteller gibt als Antrieb LA 25 bis LA 40 an. mit dem FP 35 liegt der Schwerpunkt im ersten Drittel der Fläche, da der Hersteller keine Angabe zum Schwerpunkt macht sehe ich das erst mal als optimal an.
Ansonsten geh ich erst mal Eyas fliegen.
Gruss
Gerrit

Gerrit Voet schrieb:

So, nachdem ich mich beschwatzen lassen habe von einem Stiletto Abstand zu nehmen, und meine Zeit momentan sehr begrenzt ist, habe ich mir einen Primary Force zugelegt. Vorgestern von Flight Depot abgeholt war ein Ausstellungsmodell, mit einem russischen 2,5er. Den 2,5er halte ich für einen Witz. Der Peter (Shoestring) rät den Einbau eines LA 25 wegen Schwerpunkteinhaltung. Im Lassogeier gibts einen Bericht wo hauptsächlich LA 40 eingesetzt wurden. LA 25 sowie LA 46 stehen zur Verfügung, ausserdem noch OS MAX 35 FP, OS MAX 35 S,
weiss jemand wo der Schwerpunkt sich befindet? Einen Plan habe ich nicht bekommen.
Gruss
Gerrit

Zum Vergrößern anklicken....

Hallo Gerrit

INFO zur Primary Force.

Merry X-Mas and a Happy New Year.

Gruß Peter

http://stunthanger.com/smf/index.php?topic=20096.0

Hallo Gerrit

Fehlerteufel verjagt

Gruß Peter



Kim-

Mike e-mailed me that he had moved his c.g. back some from the 2" specified and liked it better on his prototype. This was several years ago, but I think he said something like 2 1/4" behind the root l.e.

Anyway, I felt that mine too, at 40+ oz, was not as responsive as other P-Forces and wondered whether I'd overloaded the wing or tail. Mine had quite a bit of sag between ribs for the 17% (measured) or 18% (specified by Mike) NACA sections. I had not turbulated the tail, something that seemed to improve another model's performance. You might try that.

I have used the LA .40 mostly, after starting with an FP .35 (pictured on plans). I had decided to redrill for an LA .25, since the heavier engines required 3/4 oz or maybe even more tail weight. However, the fuselage is now in 3 pieces, and rather than CyA it back together, I'll strip all finish and silkspan, add stub ribs, and make another lighter fuselage (and finish!) with a stiffer nose for the LA .25. At this point, I may just use the wing; I'm not sure that my round stab leading edge is the best way to go, even though I'm sure it works fine for the many P-Forces out there. Igor posted some thoughts on airfoil shapes and thicknesses at such low Reynorlds numbers, and I also noticed some NACA material that led me to sharpen the leading edges slightly on my other flapless LA-.25 stunter. The resulting stab on that one, whose plans you have, seemed to work well.

One thing I did notice was that using an APC 11" prop cut down to 10.5" worked pretty well, but the full 11" prop really damaged the model's turning performance. I think a less efficient, but much lighter, Zinger prop worked better, and I mostly used a 10" x 4" APC. If you're using a heavy 11" prop, you might try cutting back of the prop diameter and/or weight.

As usual, "for what it's worth."

Danke Peter,
aufschlussreiche Zeilen, kommen mir gerade recht.
Gruss
Gerrit

Danke Peter,
aufschlussreiche Zeilen, kommen mir gerade recht.
Gruss
Gerrit[/QUOTE]

Hallo Gerrit mehr "INFO"

OS LA 25 Setup

by Mike Pratt



After receiving a number of phone call and e-mails about how I was setting up the OS .25 FP & LA for the Primary Force I thought it would be a good idea to post it here on SSW. Please don't think I know all there is to no about these engines but I have found a few things that worked really well.

OS .25LA: I used the engine in stock form and was quite surprised how well it ran right out of the box after a short break-in. There were a few things about the engine I didn't like but the biggest thing was its lack of consistency (I am really fussy when it comes to engine runs but I believe that most sport flyers would be more than happy with the way the engine runs out of the box). I had to reset the needle before every flight and it was almost impossible get the same setting flight after flight. During some flights it would drop out of the rich 2-cycle and into a doggie 4-cycle for a few laps and then jump back to rich 2-cycle. In addition, the engine would go lean and almost quit in the second loop of the four-leaf clover (with plenty of fuel still in the tank).



I thought the rear mounted remote needle was the culprit and replaced the remote needle with a ST needle valve assembly (through the venturi). This was a little better but still far from what I wanted. I used different combinations of fuels, glow plugs, head shims, air filters, and muffler pressure with little or no change to the run. Completely frustrated, I switched to a tongue muffler and instantly most of the problems went away. The run was much smoother and more consistent cruising along at a rich 2-cycle but it still had a tendency to lean out in the four-leaf. Using a Bru-Line green air filter helped and almost stopped the leaning out at the end of the flight, but switching to a .250 dia. venturi (from Leonard at SSW) cured the problem completely. One other little change that I made was making a plug for the uni-flow vent that had a .050 hole drilled in the end to keep the engine from running a little fat (rich) at the end of the pattern.



Now the little .25 LA runs like a Singer sewing machine from the beginning to the end of the tank with a short power burst one lap before it runs out of fuel.



Listed below are the suggested changes and/or parts needed:



.250" i.d. Venturi.

S. T. needle valve assembly.

Tongue Muffler. Modified RSM or SSW

3 ounce Uni-flow tank (1" x 2" x 3") Brodak or GRW.

Props: APC 9" x 4"& *10" x 4" (*trimmed to 9-1/2").

Grisch 9" x 4" Black Magnum

Bolly 9-1/2" x 4-1/2" (re-pitched to 4").

Glow Plug: S-300 Sonictronics or Thunderbolt R/C.

Fuel: Sig Champion 10 or 15% ½ synthetic & ½ castor.

RPM: Set at 10,2 to 10,500 on the ground depending on your prop choice. It should be braking back and forth from a 2-cycle to a 4-cycle (more 2 than 4) and as it warms up it should be in a rich 2-cycle (by the time you reach the handle). After launch, the model should speed up during the first lap and as the engine cools a little you should hear it back off a little into a rich 2-cycle.



OS .25 FP: This was really easy to setup because the above modifications worked perfectly on the FP. There was no need to plug the boost port or angle the intake ports on the FP. It ran really sweet and I think it even has a little more power than the LA. The FP liked the Bolly 9-1/2" x 4-1/2" with the pitch set at 3.75".



One other thing that I will point out is I live at an altitude of 5000' so some of the changes and settings maybe a little different at lower elevations. When I travel to contests (at lower elevations) about the only changes I make to the engine is adding a Bru-Line green air filter and if it is really hot I switch to 15% nitro fuel.



I hope this helps,



Mikey