TimBle

CloudSkipper, the OS 55AX can swing a 13x6 or 13x7 with ease.

Often suggestions for props are too focussed on rpm and not getting the rpm into the correct band for an engine,in an unloaded airframe. the only to figure out which prop isbest is to measure static thrust and go fly the 3 best props. Ultimate rpm will produce more power but certain types of flying require more torque.
You also need to consider that although an engine can spin till 16,000rpm, the prop fitted to it may not like much more than 11,000rpm on a given airframe.
Noise reduction has benefits other than environmental. Prop noise is a loss of thrust. The more noise, the less efficienty that prop is converting rpm into thrust and for any plane, we want thrust. RPM dasta is nice to brag about, but thrust  is what we want.

Eganwp

My Feedback: (1)

I agree but disagree. Everyone is all gung-ho about "static" thrust, but in fact that's a very poor measurement to go by for our moving RC plane's application. What we need data on instead is DYNAMIC thrust as it applies to literally every manouver other than a hover/harrier. As soon as a prop is in forward motion, all static thrust is thrown out the window, and dynamic thrust fits the bill.

Once you look into prop engineering and thrust analysis, you'll come to the same conclusion. If it weren't, we'd all be running 16x1" props on our planes for REDICULOUS static thrust numbers, but as you know, that would be completely impractical for our application.

For example (and lets use a sport plane application for example):

Dynamic thrust (thrust at any speed higher than stationary), needs to have a greater thrust ratio than 0.6 as derived from many people much more intelligent than me... Ie. 11x4 prop = 4/11 = 0.3636 which is too low. The plane will have good slow/stopped vertical thrust (ie. excellent 3D), but very poor vertical with any speed. In this case something like a 10x7 would help with speedy verticals significantly. There's a reason guys with speedy little sport planes that aren't rediculously overpowered have such incredible top speeds and yet still have unlimited vertical... It all boils down to dynamic thrust. Now I'm not saying go throw on a 10x7 prop on this plane as it's the wrong application, but just be aware of the science behind it.

There are entire websites dedicated to dynamic thrust theory, calculations, graphs and testing as it pertains to RC planes, so I'm not going to even begin touching on their findings and results with RC planes.

This is one of the most highly misused calculations in RC today for general sport pilots IMHO.

For our application for those flying this plane in 3D, you're completely fine to break the 0.6 rule to maximize 3D thrust in a stationary (aka static) manouver.

TimBle

oh I agree, dynamic thrust is what we want but how many people have the tools to calculate or measure it?

the only way to do so is it to fit pitot tubes behind the propeller and fly the plane. The data recorders add weight and that skews the data somewhat. If you know of a simple way of measuring dynamic thrust please pm me or share on the thread. I would be very keen to build the necessary. I think theres a load of value in that since many propeller recommendations are based on what people perceive, not raw data.

ameyam

Again, every airplane and every flier will be comfortable with a different prop. Thats the idea behind suggesting a range of props. Someone flying the 300SP will need to keep an eye on speed as overspeeding will cause flutter. Therefore start with a 12x6 and then try one prop either side and see how it feels

Ameyam

elkiwi

My Feedback: (2)

Yesterday, a friend will fly for fist time an extra 300 whit a four stroke o.s. .52, when he told me that he would fly it whit this engine I told him that it`ll be a very pour powered, and what a surprise, It flies great I think is perfect whit 70 fs( sport fly not 3d)
I have a .46 rimfire and a 75 amps esc, 4s 3300 and now I thinking to use this stuf in a kit like this, because I love how this litle plane performs
Please share your coments and experience whit this setup, ( I dont want it for 3d, Ilike the sport and airbatic fly

IllinoisAviator

My Feedback: (7)

Hey guys, I have the whole plane without anything in it ready to sell, anybody that needs extra parts can email me at [email protected]

SU-31 flyer

I would like to know if anyone is flying a 40 engine? I have a K&B 4011BB 40 size engine and don't want to buy a new one. I'm not into 3D but fly aerobatics.

albsurfer

a .40 is a little small for this plane with it's wingspan and 5.5-6.5 lb weight for standard aerobatics. A .46 would be the minimum. A .50-/55 even better. A couple choices for inexpensive, reliable engines are available: TT .46 pro. Sig Aviastar .46 ($50.00) Sig Aviastar .53 ($70.00). An older OS, or any of the already mentioned engines used will work. Good luck

frankiev

hey guys been following this thread for a while now, and just received my extra from tower hobbies a couple days ago and will be powering it with a 55ax. i have a few questions.

i was thinking of going with nylon hinges or robart point hinges, is there any need for this?
also if using the ca hinges, is a pin sized gap sufficient?
my cowl is chipped just a bit around where the screws will go. does anyone know the color paint i should get to fix this? i need to touch up some blue and yellow.
for those of you with the 55ax, where did you end up mounting the rudder servo for proper balance?
are there any helmet head pilots that will fit the hatch/canopy?
are there any modifications/reinforcing i should definitly do?
does 3d hobbyshop still carry the carbon landing gear that will fit this plane?
how can i reinforce the landing gear?

sorry for so many questions i just want to buy everything i need before starting the build next week. thanx guys!

albsurfer

Frankiev,
1. Best place for the rudder servo is the servo deck. Takes a lot of counter-balance weight with the 55ax if you don't put it there.
2. I used the CA hinges with no problems. The pinned nylon hinges would be better in the long run. When I crashed, I rebuilt the tail
feathers with nylon hinges. The rudder hinges come loose after enough banging the tail, so it doesn't cause fuse damage.
3. Reinforce: a. the firewall with epoxy & the lg section of the fuse b. Thin out epoxy w/denatured alcohol (mixes better) and coat the:
servo deck; backside, bottom, and front of the hatch; the sections of the airframe that would be the battery mount and
where the hatch mates up to; the sides of the fuse where the wings attach.
4. I would use a 14 oz fuel tank with the .55ax for all around sport / aerobatics to get a full 10 min flight time. It gets windy here and
you have to keep the throttle on during 12-19 mph winds.

I do the reinforcements because if you have a hard landing, crash, or grab those areas too firmly with your hands, they can crack or break. You have a lot of open space in-between frames & ribs because of the aerobatic nature of the plane, and to keep it light for E Power.

Great flying plane. I lost mine due to a low altitude deadstick, but am considering getting another one. I may get a .61 size Extra or Edge, though. So.. I'm in a dilemma right now about that purchase. Read the posts on this forum for more advice.

Happy flying.
albsurfer

frankiev

thanx for the quick reply! so you mean to reinforce the firewall, just go over all the joints with epoxy? i noticed that there are cracks in all the landing gear blocks where the blindnuts were installed will a good coating of epoxy be enough to reinforce that? did you have to recess the control surfaces to get the proper gap when using the nylon pinned style hinges?

anyone else feel free to chime in. thanx again!

albsurfer

Thin CA all the cracks, anywhere, in the lg block, etc. If a crack goes all the way through & looks like it is compromising the airframe, consider replacing that piece of wood. You should be able to CA most anything you'll run into, though.
Epoxy the LG block after the CA dries. Use an acid brush to apply it so you don't get too much on & have the epoxy flow into the blind nut threads.

Put a thin coat of epoxy over the whole firewall to fuel proof it, in addition to the 4 edges that make up the attaching joints.

I didn't recess the hinges, which gave me a good enough clearance for the control surfaces. Also, use some clear covering or tape on the bottom sides of the ailerons & elevator, plus one side of the rudder, to seal the joints. You can also use clear packing tape instead, but plan on redoing the tape every now & then if you use it. It will help keep flutter out of them.

If you are going to do 3D, check the rudder for full deflection clearance to the elevator. You may have to shave a little off of the elevator if it won't clear on the full recommended 3D throws. The elevator & ailerons will be fine.

Using the 55AX, you should be able to do a knife-edge loop after the engine has been run the recommended number of break-in flights & re-propped. Don't be afraid to use a XOAR wood prop on this motor for your aerobatics later for stability & good power. APCs are great, but XOAR is definitely made for standard & 3D aerobatic performance.
Test-fit the exhaust on the 55AX & rotate the end of the muffler into the slot. It won't just bolt in & clear the fuse.

Oh, remember to put CA into the servo screw holes after you have installed & then removed the screws so it hardens the holes.

frankiev

hey are all of you guys happy with the tail wheel assembly that came with this kit? i was thinking of upgrading to a leaf spring style but am wondering if itd be a waste of money. i like the idea of the wheel assembly absorbing shock to the servos.

also ill be mounting my rudder servo on the servo deck, any suggestions for a good pul pull setup?

Rooster6

Hi frankiev, I haven't any problems with the supplied tail wheel steup.....works just fine for me. If you have a look on page16 there are some photos there of my pull-pull system, i think it was a dubro 4-40 setup, works flawlessly. Good luck with your build.

frankeldan

I think it's a great idea of installing a different tail wheel assy. Keep it light and small. I've found over time that a hard hit on any stock tailwheel will rip the rudder off the hinges.

a pull/pull isn't nessesary on this model. The rear servo setup is nice and direct. Mine balances out perfect with the servo in the tail

Dan

frankiev

if i do go with a pull pull how can i do it without using two elevator servos?

albsurfer

Yes. You are using a single, longer than stock, control arm
and installs just like a rudder pull-pull. But it's not really going to give you any real advantage on this plane.

TimBle

Considering the price of this ARF, if this is the amount of work you have to do before you even atart building then I'd rather stick to the Black Horse Extra 300s I currently fly. Its very well made and goes together super fast. I'm approaching 75 flights with it now and no signs of glue joints weakening of wood cracking and I snap roll her at 100% control throw every flight.

Rooster6

I think its just a question of personal modifications and how you like your planes setup, the GP Extra flys just perfect stock....I only done my mods because I had time to kill and had the gear just sitting around, its the way I like my planes. If I got the Black horse extra i'd would have cut it up as well so it was setup the way I like my planes. Just a personal thing I guess. My plane has no reinforcement and after 150+ brutal flights its still perfect.

albsurfer

Part of my mods are definitely "personal likes" to ensure it will stay together to my liking, and abuse. The hinge gap covering is standard to a lot of flyers who want to try and reduce control surface flutter and keep the air flowing relatively undisturbed over control surfaces during higher speed manoeuvres. Epoxying the LG block is a pretty standard requirement on GP arfs these days. Just read in the reviews and forums how many LGs come off on a mildly hard landing; even the .60 size planes like the 70" revolver.
The GP Extra 300SP is a great plane. The first time I crashed it, I bought a new fuse. The second time was a dead-stick. I haven't bought another fuse to fix it yet. Someone gave me another plane, so I'm going to fly it for a while, then resurrect my Extra 300SP again, only probably with a 4S. If I go .60 size, I'll probably go with the Phoenix Models Extra. Have a great day & happy flying.

frankiev

but i dont think the elevator servo will fit beside the pull pull rudder set-up where do i mount the elevator servo?

albsurfer

Don't put your receiver & battery on the servo deck. Relocate the servos in the deck to allow clearance for both of them to operate there. The Elevator rods can be bent some to accommodate the relocation, or as someone else did, they put a mini elevator servo in the tail.

Read the following 2 posts:
#86, P. 4 by clouddancer03; #145, P. 6, by kwboost;
Tells you what they did, but no pics.

frankiev

thanx a lot!

gleber

My Feedback: (10)

If you live in Central Florida, here is mine for sale

http://www.rcuniverse.com/market/item.cfm?itemId=729394

>keegan<

Hi does anyone know if you can fit a Saito -100 into this plane or would it be too big??