I have been out of control line flying for some time and recently got back into it thanks to my brother. I have a question about engine selection for the Brodak Strega. The plans say 51 to 60 and I bought a Super Tigre 51 for it. I noticed how nice my Nobler flies with a OS 46 and I looked at the wing area on both the Nobler and the Strega. The Strega has a whole lotta wing area, so I got to thinking this engine doesn't look big enough. Should I have the engine re-worked for more power or just buy a larger engine? I haven't started building yet but I want to be prepared if I need to make a change.
Thanks!
Russ

A 75 sounds too large? The way engines can be modified I thought a good shop could build some real power into the ST 51 and there would be power gains and weight savings. The kit says .51 to .60 but the wing area is a lot so maybe it is a slow flyer and something fun to fly. I'll get started on it when the wife runs out of summer projects. Thanks for the input.

I am ashamed to admit this but I don't know what a PA engine is or where to get one. I have been out of CL flying for some time as you can tell. Can you direct me to a good source for the engine. Thank you for the advice!

Will do, thanks again!

Russ,

A phone call to Randy Smith at Aero Products (as mentioned by Pete) will prove to be your best "next step".  He can answer any question you may have about his products; specifically, what will work for your application and what won't.

Cheers,
Jim

A 75 sounds too large? The way engines can be modified I thought a good shop could build some real power into the ST 51 and there would be power gains and weight savings. The kit says .51 to .60 but the wing area is a lot so maybe it is a slow flyer and something fun to fly. I'll get started on it when the wife runs out of summer projects. Thanks for the input.

   I don't think anyone is "building more power" into ST51s as an aftermarket tweak. Almost all aftermarket tweaks *reduce* the power to make the engine more tractable for stunt.

     I agree with the others, an ST51 is very marginal for this application. I would look more in the 60-75 region. I have had very good results with PA61 or RO-Jett 61 BSE (special "Brett" version - (yes, you can order it that way and Dub knows what to do) engines. The airplane was designed around an ST60, which would also serve well, as would a Saito 72. The nice thing about a PA or RO-Jett rear exhaust engine is that you will not be limited in the future - there's really nothing better. You can run it on a header muffler until you want to get in to tuned pipes. The only downside is the cost - ultimately it's a bargain since it runs forever and requires no fiddling, but the initial cost is high.

   And it can' be overlooked - make sure that the leading edge of the wing is as blunt as you can make it. Presuming this is an ARF/ARC, carve/sand the leading edge until you have at least about 1/4" radius. You can't go too far because the leading edge wood is 1/4" square hardwood of some sort. Stock, the leading edge comes to what is essentially a point, and this causes violent stalls in even benign summer conditions.

    Brett

I am one of those who have had great success with ST .51s.  I have used them in several planes including a SV 11 at 64 oz., and a USA-1 at 54 oz.  The engine flew both, in rough winds, with absolutely no problems.  While it is not as strong in a stunt run as my PA .51, it is plenty.  A high RPM 4-2, and using Tom Lay's suggestions on prop and fuel.  I like them, a lot.

    I think they are pretty decent, too, but the Strega is *a lot* more of a load than either of those. The weight of the ARFs is always in the upper 60's/70's (and borders on the .021 lines in some cases) and its much larger and much draggier than an SV-11 (which is a *far* better design). Ted and I flew his with a Rustler/Merco 61 Metamorph and while that has a lot more ponies than an average ST51, it was certainly not overburdened with excess power. Maybe you and I could make it work, but I fear that it will take a pretty delicate touch to keep it out of trouble.

     But I think you have an even better idea lurking in there - instead of switching engines, switch airplanes! An SV-11 with a good ST51 is a far more potent combination than a Strega with any engine.

   Brett

I'd unload the Strega for an SV-11, Impact or Legacy. Ditto the G.51 and go with the Enya .61CX rear exhaust.  Steve

I think many people built the Strega ARF/ARC or even the kit with the stock flaps and most certainly it didn't fly well even with rounded LE, specially if power with a detuned stunt engine. This thing needs some serious power to drive it through the corners and against the wind.

Stregas got a bad reputation down here. Having 3 ARC in stock and no body buying I decided to built one the right way, put a powerful and properly setup engine on the nose and show how's this business is done. My initial idea was to show and sell, but the darn thing flew so well that exceeded my own expectations, it quickly became my No1 competing model for now.

     After Unknown Pilots #1 and 2 flew an ARF Strega at the first International ARF-Off (coming in 1 and 2, by the way) shortly before the 2007 TT, I took the opportunity to check the airfoil on the Silver/Red Strega that  Kent flies. The critical part of the airfoil (i.e. the first inch or so) was COMPLETELY different from the ARF version. The ARF came to a point and complied with the usual "45 degree departure" angle people have been using since 1951 to fair the leading edge into the sheeting. Kent's was much more blunt and couldn't have been achieved with a standard square LE on it's side. I think that's a pretty critical difference.  The basic Patternmaster-type design isn't great by Impact standards but it's perfectly competent if executed correctly. I think that's were the ARFs seem to have missed the boat.

   I agree that lots of power is required -that's why I am concerned about ST51s. The ARFs are pretty heavy as they come and the airfoil (despite difficulty generating lift) is pretty draggy. Plus it's just big. As long as people want to use 4-2 break motors or 4-strokes, the old rules about size/weight/engine size still applies. 35-sized=525-575 squares and <45 oz, 46-sized=620-660 square inches and <56 oz, ST60=700-750 and <65 oz. The Strega is clearly in the ST60 range (not surprising since the basic Patternmaster was designed around the ST60) and first flew with that. You might get away with a Saito 56 (snice you can run 4-strokes gutted out to the max without them getting jumpy) but I certainly wouldn't try anything less than that. I am sure that you could overcome a lot of the issues with a RO-Jett or PA61 on a pipe and just use brute force to keep the speed up in the corners, but if you have those you probably ought to build a better airplane for it.

   Once the airfoil on the ARF-Off champion model was blunted (in 10 minutes, at the field, with a hand rasp and a positive mental outlook), it was reportedly flyable. I expect it has all the usual Patternmaster/Cardinal type response (slow/heavy around neutral, explosion corners, massive control loading - which is about how it flew with the pointy leading edge, except you add abrupt stalling in even soft corners and some round maneuvers) but that's clearly a matter of preference and is probably intentional. Fix the stalls and the ARF-Off airplane was flyable enough.

    But in comparison, and sticking to ARFs - the Vector is clearly in a different time zone in terms of performance. Reasonable control linearity (a little "exponential" compared to Impact/TP/Infinity but easy enough to adjust to), even control pressures throughout the travel. Of course the handle loads are much less just because it's smaller but it's much more consistent and doesn't take two hands to get out of level flight. That's one reason the Strega was so hard to keep from stalling with the pointy LE - it takes tremendous force to get it to do anything, but only a tiny bit more and it's cranks up into a very tight corner. Same with all the Patternmaster/Cardinal-type airplanes - actually, the ARF Cardinal as it comes is even more like that, but the LE is blunt and it's light enough to not stall when it happens. The fix to the Cardinal is to take about 1/2-3/4" of the TE of the flap, and I expect that you might get the same thing on the Strega.  It might make it more prone to stalls but I think the flap or lack thereof is not the issue- it's separation at the LE, and putting on big flaps isn't going to fix that.

   Brett

Hello Bill,
  You are a lucky man to have a first class ST 51. I have tried just about every reported tweak on my ST 51 and it just will not work for me. The ring is decent, but the engine just runs away in any sort of wind. Used just about every fuel mix that has been recommended and the usual prop and venturi mods. Some work better than others, but the same basic problem is still there. In the end I gave up and put one of my old Merco 61s in the plane and all the problems went away. Its old and it is ringed, but my, it is still a good stunt motor!
  The newer Merco Belko Metamorph is even better and it is cheaper than a PA or Rojett. If you can live with the weird exhaust, it is a cracker! I must ask Santa for one!

Regards,

Andrew.

Save the ST 51 for a Profile Cardinal. Patternmaster-ships take a minimum of a 1 H.P. Go big or go home!

   Maybe it's the same thing with different interpretations. What I was unable to do (and this is common with the Pattermaster/Cardinal models) is crisply start and stop maneuvers. Trying to get it out of level flight takes so much effort than you just can't get it started properly into a round loop, for instance. The same effect also makes it "wrap up" into the corners, because once you get it out of a straight line, you have applied so much force that you can't stop it from going further. These are all characteristics that we have spent many hours designing and trimming out of our airplanes (Impact, TP, Infinity). And David reports that Orestes' airplane is about like that around neutral, too (although it does have the exponential response).  That's one of the consistent errors I see from the "giant flap" crowd - swooping into the round maneuvers, particularly, but also the explosion-type corners. None of the competitive airplanes I have flown have that to any great degree. You certainly don't need that for straight-line tracking.

Brett
   

Would it be going too far afield here to ask what causes the exponential response?
Thanks.

But I think you have an even better idea lurking in there - instead of switching engines, switch airplanes! An SV-11 with a good ST51 is a far more potent combination than a Strega with any engine.

   Brett

Hi Brett,

Thanks for the kind words.

Even though I have flown with Kent several times, I have never flown his Strega (or any other Patternmaster derivative!).  Kent has worked many years on the Strega.  He kinda followed Ted's advice and took one design and kept using it.

I do not think the ST 51 would be a good choice at all for the Strega, Arf or otherwise.  I misplaced my comment to Andrew about having some really good ST .51s.  The ST .51 IS a good stunt engine for some applications, I think.  Not as good as my PA engines, though.

Kent started with the ST 60 in his Strega and has gone through several different powertrains.  Even a RoJett .76, IIRC.  He is familiar with the plane and does well with it.  Windy is in the same category in that he had flown the PM wing, basically, for so many years.

I would go with a SV plane myself.  My favorites have been the SV wing, and the Saturn wing, so far.  Going to use the Imitation wing before long.  Those wings, along with Billy's Geo Bolt wing (used one in Aaron's Geo XL), seem to be very "forgiving" in a sense.

Bill

Brett,

This video shows my friend Henry with his Strega and the same Enya 61CX that is with me  now. I think he is using  0% nitro and 25% all castor fuel and a Bolly 12.5x5.5.



This Strega had the leading edge rounded to the max and a better flaps then the stock ones, but he taper it. His Strega can not make corners as tight as mine by a good amount.  Both Stregas were built from an ARC kit and mine end up 40g heavier. Henry is a veteran who is known to be very knowledgeable about trimming and he is always on the top 7 here.

This is me flying my Strega with Engine no2, which is not running as strong as engine No1 and I was taking it easy on these corners.  I am using 3 blade prop, with a 2 blade prop and engine no1 corners are even tighter.



All I can say is that the way I have been making flaps makes a big difference. Perhaps it makes more difference in heavier models and not so much in lighter models with better airfoils.

I should correct my statement, Al Rabe does not make “thick”  flaps nor Howard. What I meant to express is that Howard show the way to make flaps extremely twist resistant and Al Rabe also felt the benefit it makes.

Martin