Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Patriot XL--Questions for the Experts

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Old 11-15-2005, 01:58 PM
  #1  
Rcpilot
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Default Patriot XL--Questions for the Experts

This will be my first speed plane with retracts. I'm an accomplished kit builder.

I got questions. I've read a lot of posts (search function) about this plane.

Reducing frontal area to make it faster:
What are you guys talking about? It looks like a bullet to my untrained eye. Are you eliminating the side intake scoops over the wings? What are ya doing to "reduce frontal area"?

Retracts:
Lots of controversy about air and mechanical. I've never had retracts before--so I'm having a REALLY hard time with this. The air system is VERY expensive. Mechanicals are cheaper--but where can I get a decent set? Those el-cheapo hobbico retracts aren't going to cut it for my tastes.

Is it really worth the $200 for the air retracts?

I don't mind modifying the kit to some degree. I haven't built a "stock" kit yet. They ALL end up getting re-engineered in a couple places.

Engine:
2-stroke for me. I really can't afford a Jett engine--although it would be nice. And I'm NOT slapping an OS 91FX[:'(] in this plane---not a chance. I've had one of those.[:'(]

I'm flying at high altitude--and a 1.00 engine doesn't seam to be rediculously overpowered. Maybe a 1.20?

Help a wanna-be speed freak out and give me all the hot tips on making this bugger fast and clean. [8D]

Thanks
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Old 11-15-2005, 02:31 PM
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SitNFly
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Default RE: Patriot XL--Questions for the Experts

See notes below. I was a little disappointed overall with my XL. Takeoffs were a joke until you modify the gear for a more noseup attitude. The retract install was a little cluttered. Also comes out very noseheavy.

ORIGINAL: Rcpilet

Reducing frontal area to make it faster:
What are you guys talking about? It looks like a bullet to my untrained eye. Are you eliminating the side intake scoops over the wings? What are ya doing to "reduce frontal area"?

I didn't install the side scoops just because I didn't like the looks. Seems like they would be a pain to install and paint. Same with the plastic tail fairings. I made new ones out of balsa. Ditto tailcone.

Retracts:
Lots of controversy about air and mechanical. I've never had retracts before--so I'm having a REALLY hard time with this. The air system is VERY expensive. Mechanicals are cheaper--but where can I get a decent set? Those el-cheapo hobbico retracts aren't going to cut it for my tastes.
Is it really worth the $200 for the air retracts?

If you want to go fast, it is. With the angle of the gear on this plane, I don't think mechanicals would work. Don't know if you could rig up a servo and linkage.

I don't mind modifying the kit to some degree. I haven't built a "stock" kit yet. They ALL end up getting re-engineered in a couple places.
Engine: 2-stroke for me. I really can't afford a Jett engine--although it would be nice. And I'm NOT slapping an OS 91FX[:'(] in this plane---not a chance. I've had one of those.[:'(]
I'm flying at high altitude--and a 1.00 engine doesn't seam to be rediculously overpowered. Maybe a 1.20?

I've got a Jett 90L in mine and fly at 5300'. Already thinking about a 1.20. This is a fairly big plane and should handle more engine easily. You wind up hacking most of one side of the cowl out anyway, might as well stuff a bigger mill in there.

Help a wanna-be speed freak out and give me all the hot tips on making this bugger fast and clean. [8D]

Thanks
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Old 11-15-2005, 03:03 PM
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rmenke
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Default RE: Patriot XL--Questions for the Experts

RCpilet:
This is a very deep area, some in dispute. Put simply, drag is the enemy of speed. Anything you can do to eleminate drag will increase speed assuming all other factors remain the same. Power is king in almost all design assumptions. Ok, lets make it fast, whatever it is. Start in front and work back. First thing drag hists is the engine area, a spinner helps direct the air into the prop and around the frontal area. The more frontal area, the more drag. A extreem example would be a yak 54, large drag area and the lets say SR- 71 that has a long spear in the front. The tip of the spear is the start of the design streamlining. As drag moves back, any obstruction or redirection of the air flow creates additional unwanted drag. When you get to the wing, tradeoffs start to take place dependant on intended uses and lift needs. The Yak wants lift at slow speeds, thus a thick large wing area. The 71 wants speed, thus a thin sharp frontal area and as small as possible. Landing gear, imagine landing gear hanging down on a 71 doing 3,000 mph. The additional power needed to get to speed would be substantial. So, retract the gear. How about the wing holes for the wheels and system. Yes, doors would help a bunch and a must in the 71's case. Look closely at the wing of a P-51 and the majority of modern aircraft. The joint from the fuse to the wing is filled to deflect the fuse airflow down over the wing in a unbroken fashion, filled,= fillet. Is the filet worth the work, yes if you need the extra mph. Every little drag reduction will increase the speed of your aircraft, to a point. The point is weight. The more weight you add, the slower your aircraft will become. Lighter aircraft will turn better. The trade offs start again. Note pylon racers have the gear hanging off generally. Also note the thin wheels and the front of the gear is sharpened to a near point in a well detailed racer. Attention to datails in raceing flat rules. Look at the Q-500s, all almost exactly alike. The fastest are the lighest and best streemlined, plus power. All races are not won by the fasest airframe in the race as you should know. All things equal, the pilot with the additional 100 rpm will come out on top. The heavy airframe with 200rpm more may be way in the back. Detail suddenly becomes king. Hope I have given you some general basics, its a very long and complex quesion and answer. You may see knife sharp leadilng edges on a 71, pure speed, the fighters are much blunter, they must turn to survive in combat. Trade offs. Best kept speed secret=watch the fast guy/winners, generally the older farts. Hang out, look listen, question and help as much as possible. There may be a kid at the sticks, but the knowledge may be in the pit. Most racers will help you along and answer your questions, to a point. Same sweet guy will be the first to kick you between the legs if you are getting too close. Why do you think they keep the pilots 10' apart during a race? ENJOY
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Old 11-15-2005, 03:21 PM
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Default RE: Patriot XL--Questions for the Experts

Frontal area - if you look at the plane from the nose on - that 'profile' you see is the frontal area. That in a large way determins the drag of an airframe. The inlets provide a little more area - but not much.

If 115 mph is fast enough, rather than 120, build the plane as designed. There is little you can do (easily) to get a substantial amount of drag out of it. Its just a big plane, with a somewhat thick wing.

Retracts....
Air is easier to install. In the XL they are somewhat required. Mechanicals in this setup will require two retract servos. Dave Brown, B&D, Robart mechanicals are good. Hobbico gear are unsuitable for this plane (it is BIG and heavy). Air gear wise, Spring Air, Robart, B&D are very good. Retract servo for air can be any old servo you have laying around.

As noted, get the ground angle right!! The plane has to sit level or slightly nose high. Make sure this is right during construction. Ensure the CG is per the plans.

Engine....

The plane is designed for a "60" size engine. It comes out nose heavy as it is. Anything phyically larger or heavier its going to cause you grief. Squeezing it into the cowl is not a big issue. So, a word of caution if you are hedging toward a 120 powerplane. The 'lite weight' 120 engines like the jett BSE-120 and the new OS-120 coming out are low rpm engines - big props. Ground clearance is at a premium.

My experience with the OS91FX has been pretty good. The Thunder Tiger 90 is very good too. (use a jett-stream muffler or a full pipe on either and the power and reliability will be there). The Evolution 100 and MVVS 77 engines are worth looking at. The ST90 is a real nice engine, but at altitude its going to be marginal. A real good piped pattern engine would be excellent ..... An old YS61 long stroke with a 12x12 on the front ... Maybe even a good ole Rossi 60 or 65.

IF you want the best performance at higher altitudes, keep the plane light. Do what you can to get another 1/4 lb out of it.
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Old 11-15-2005, 06:35 PM
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Default RE: Patriot XL--Questions for the Experts

Alright:
I gotta go with mechanical retracts. First plane with retracts--and I just can't bring myself to spend the big $$ on the pneumatic setup.

I found a set at Robart. The combo set with the mains and the nose gear is $65. It's the 608 mains and the 610 nose.

Will this work?

This gear rotates 90*. Is that the amount of rotation that I need? Or do I need an 85* set?

Robart says that you can use ANY servo--and I got plenty of high torque servos lying around.

So, how can I reduce the frontal area? Do you guys do away with the fake air scoops on the side of the fuse?

On the engine:
Tower lists the plane as suitable for a 60--91 engine. Either 2-stroke of 4-stroke. I'm a 2-stroke luver. And I want a 90 size engine. You guys said it takes HP to go fast and overcome the drag--right?

Is there any reason why the plane WON'T handle the power of a 90 size 2-stroke?

What about the Tower Hobbies .75? It's my favorite engine--but I want a rocket--not a sloth. I just don't know if I can get the speed I crave from anything less than a 2-stroke 90.

Bob27s:
You mention a Thunder Tiger 90. Are you talking about the 91 4-stroke engine? Or do they make a 90 size 2-stroke? I haven't ever seen it.

As for the weight--I can hack some weight out of it somewhere. I can always find a place to get rid of some weight. Any pointers would help. WHERE can I drop a couple ounces on this airframe?

Sorry if all these questions seem silly. I'm primarily an aerobatic/IMAC--3D type guy. This will be my first go-fast plane, and I want to do it right.

Thanks for your help.

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Old 11-15-2005, 06:50 PM
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Default RE: Patriot XL--Questions for the Experts

How about the ST G-90 engine with a tuned pipe?

The engine:
http://www2.towerhobbies.com/cgi-bin...?&I=LXFV79&P=0

The pipe:
http://www2.towerhobbies.com/cgi-bin...7&I=LXZ563&P=K

The header:
http://www2.towerhobbies.com/cgi-bin...7&I=LXZ627&P=K

Thanks
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Old 11-15-2005, 07:12 PM
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kamakazie frank
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Default RE: Patriot XL--Questions for the Experts

I agree with sitnfly! The XL is not what it seems. Mine is loaded with all the goodies including the Jett 90L and it does not impress me with speed. Don't take me wrong it flies like a pattern ship, great roll rate, only weighs in at 8.5 lbs, it is a big ship, ............but no speed. For speed I enjoy my Kangke F3D!!! Hot razor with only a 32SX.
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Old 11-15-2005, 08:50 PM
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Default RE: Patriot XL--Questions for the Experts

You can use a 90, in fact, its about required for any decent speed. Kamakazie speaks the truth; big bird needs big engine. As far as mechanical retracts, I think you will need three servos, one for nosewheel and two for mains. The angle is just fubar for the mains (see the attached photo). You will also need about a mile of servo extension to get from the wing retract servos back to the receiver in the tail. See Kamakazie's build post for an idea of the spaghetti in the tail of this plane. I saved a little balance weight by putting three ounces of lead weight in my balsa tailcone before gluing it on. Probably could have used 5 as I am still adding weight to balance. Don't know for sure, but the wing might get in the way of a tuned piped unless you have a long elbow off the exhaust flange.

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Old 11-16-2005, 08:50 AM
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Default RE: Patriot XL--Questions for the Experts

I get mid 140's (average speed) out of my Pat XL with a Jett 90LX. This is on the high end of what you'll get out of a 2 stroke 90. I suspect with lower power 90's, you'd still get 110s to 120s. If that's not fast enough, you'll need to go to another airframe.

Yeah, and mine has the nose down stance. No big deal. Just dial in some flaps on take off and it comes up as easy as spittin' off a log. Looks cool. Sticks on landing.
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Old 11-16-2005, 09:04 AM
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Default RE: Patriot XL--Questions for the Experts

As these guys pointed out... you need air gear in this plane. It ends up costing about the same in the long run anyway. (if you are looking for some budget air gear, look at the KMP retracts).

The plane is BIG. Its fat. No way around that. You will see some of the photos with the inlets removed. As I noted earlier - that is your choice, but it doesnt do all that much.

The fastest Patriot XL I have any information on was from Jon - his is Jett 90LX powered - moved at around 135-140 on average (tuscon at 2500 feet). One other XL with FIRE 90 in it reported about the same speeds.

The Thunder Tiger 90 is a 2-stroke. Seems not to be available here in the US for what ever reason. The newer ASP and Magnum 90x engines are similar, but do not seem to have the power that TT90 had.
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Old 11-16-2005, 09:47 AM
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Default RE: Patriot XL--Questions for the Experts

Cheif aircraft has the Thunder Tiger 91 pro listed, does not come with a muffler though
http://www.chiefaircraft.com/cgi-bin...nderTiger.html
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Old 11-17-2005, 06:50 PM
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Default RE: Patriot XL--Questions for the Experts

I've mothballed the project for now. I've got the kit, but thats all.

I'm just too interested in Giant Scale aerobats at the moment. I'll have to wait and get my speed fix another time.

Thanks for all the help.
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Old 11-17-2005, 10:06 PM
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Default RE: Patriot XL--Questions for the Experts

I recently got the speed-bug and am in the process of building a PatXL. I appreciate the talk about what engine is best and I still haven't decided-- what do you guys think of putting a YS .91FZ in this plane? I thought four-strokes were "forbidden" in prop-jets!

Anyway, I agree completely with the comments about making the plane lighter and to that end I would really like to hear opinions about what servos to use:

(a) What is the smallest servo I can *safely* get away with in the wings (I want to build with the flaps option and this, as you know, results in four servos in the wing-- on what seem like fairly small control surfaces). What about four HS-81's (either nylon or metal-gear)? Using four "standards" here seems like a bit of extra weight!

(b) The rudder is fine, but do I really need one servo on *each* elevator half? Could I *safely* use mini's here also?

I understand that this is a "speed plane" and using the appropriate servo is necessary to maintain safety. I just wonder if I couldn't save quite a bit of weight by being careful in my selection of those servos. Any thoughts are appreciated!
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Old 11-18-2005, 09:47 AM
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Default RE: Patriot XL--Questions for the Experts

You can probably use the YS91 in there.... just keep in mind that you are pretty much limited to a 12" dia prop, and set it up accordingly.

If I ever actually get around to BUILDING my XL kit, I plan on using Hitec HS225 (or the digitals of the same size) all the way around. That is going to save at least 4-5oz out of the plane. NiMH 600-800 battery. HS81 on throttle and retract valve. (my guess is HS81 servos would be adequate for the flaps too...but I hate mounting any flight control with only 2 screws...) Central hobbies aluminum wheel axils (maybe titanium gear struts - im not sure if those are still available).

And watch, when i get all this weight out, its going to be nose heavy Flying where I am the weight is not that critical, but for those flying at 4000-6000 ASL stuff like I listed above may make all the difference in the world.

In looking at the plans, it does not appear difficult to rework the main gear geometry so it is moved forward another 3/8" or so when extended.
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Old 11-26-2005, 07:16 PM
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Default RE: Patriot XL--Questions for the Experts

Hi

I read your post and here is the set up I have and is most likely the chepest too. Check my Patriot http://www.rcuniverse.com/forum/m_3587738/tm.htm

First, mec retracts are the chepest and reliable if you know what you are doing. Take the rodsand clevises and throw them away. go with a least 4/40 rods and Dubor locking clevises. Cost is less than $4. GWS makes a retract servo that is awesome power. It is a little slow but man what power. Very low cost for a 100+ Torque. servo

second, drag. she is fine. if you tamper with the front you will lose tank space and she is fast any ways.

Third, engine. Rossi, MVVS, and Jett are all super engines, but if you need a less $ engine and OS is out ( not a OS person myself) I would say get a Super Tigre 75. Run the ST with 15% and a 11x7or 8 and she will still make you smile.

I have had all the engines servos, and exe out there. this is the less $ and still have an awesome bird.

Freebird
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Old 11-26-2005, 07:18 PM
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Default RE: Patriot XL--Questions for the Experts

Sorry, I do not have a ST, I have a Jett 90 on board. Did not want to lie!
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