Prop Jets
07-23-2002, 09:51 PM
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Prop Jets
I am looking to get a prop jet to replace my Patriot. I am thinking about the Cermark F20 60 size ARF but I can't get any info on how fast will it go? I am planning on using an OS .91 FX. I would like to get a prop jet that will go about 100MPH - 130 MPH what do you guys think?
Jimmy
Jimmy
07-23-2002, 11:04 PM
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Search!
Try a search on "propjet" or "Patriot" etc. There are many threads about these high performance beauties!!
I have a Patriot ARF with an Irvine 53, should have a maiden flight this weekend!!
Why not try the CBM F-16N?
I have a Patriot ARF with an Irvine 53, should have a maiden flight this weekend!!
Why not try the CBM F-16N?
07-24-2002, 01:05 AM
#3
Prop Jets
I am 3/4 through my 60-90 size Cermark. I stripped the Red off completely and recovered in Monokote "Charcoal" with white underneath. I installed the Jett .90 in mine. if you go with the 91fx, you ought to install the Ultra thrust muffler also.
* I have the Little F-20 also and it is in the 120mph range. The bigger Cermark with the right engine will be around the same. There are a few modifications which are a must or tthe plane may only last a few flights before the damage show itself.
* I have the Little F-20 also and it is in the 120mph range. The bigger Cermark with the right engine will be around the same. There are a few modifications which are a must or tthe plane may only last a few flights before the damage show itself.
07-24-2002, 01:16 AM
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Prop Jets
Originally posted by Cyclic Hardover
I am 3/4 through my 60-90 size Cermark. I stripped the Red off completely and recovered in Monokote "Charcoal" with white underneath. I installed the Jett .90 in mine. if you go with the 91fx, you ought to install the Ultra thrust muffler also.
* I have the Little F-20 also and it is in the 120mph range. The bigger Cermark with the right engine will be around the same. There are a few modifications which are a must or tthe plane may only last a few flights before the damage show itself.
I am 3/4 through my 60-90 size Cermark. I stripped the Red off completely and recovered in Monokote "Charcoal" with white underneath. I installed the Jett .90 in mine. if you go with the 91fx, you ought to install the Ultra thrust muffler also.
* I have the Little F-20 also and it is in the 120mph range. The bigger Cermark with the right engine will be around the same. There are a few modifications which are a must or tthe plane may only last a few flights before the damage show itself.
Jimmy
07-24-2002, 01:25 AM
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They make several pushers including the F-16N the FA-18 Hornet, smaller F-15 Eagle and the A-10 also..
I got the ARF Patriot from WARJET (right here on RCU..) I have seen a couple on e-bay also..
Keep us posted!
and yes, use the JETT!!
james
I got the ARF Patriot from WARJET (right here on RCU..) I have seen a couple on e-bay also..
Keep us posted!
and yes, use the JETT!!
james
07-24-2002, 01:31 AM
#7
Prop Jets
The engine mount area is already built. Instead of installing the traditional engine mount, it is already their using hardwood rails. This is okay I guess but I epoxy glassed the entire inside of it all.
*Two of my close buddies have this engine on DC F-18s. It will flat tear right off from torque if you do not glass it up. Retract mounts again won't last long at all. My guess is only a couple flights unless you beef up the mounts.
*Elevator servo. is a single servo attached to the stab with little blocks. Very stupid. A guy somewhere here had one which crashed on a maiden flight because the servo broke lose. I expoxied my servo right to the stab itself, then glassed around the bottom also. That sucker is not coming off! Not much room in their either. Get some sort of a low profile high torque servo.
* Since i decide to recover , I also dabbed a little epoxy on each rib just for aggravation. Overall it is a good plane. I just don't like red. Also our stats here at 5000ft fall short of what you'll get in Florida. I boast 120mph for my DC F20 but that is as best you'll get here with a 17% overall loss in peformance. I know guys at sea level with the same setup getting 150mph.
*Two of my close buddies have this engine on DC F-18s. It will flat tear right off from torque if you do not glass it up. Retract mounts again won't last long at all. My guess is only a couple flights unless you beef up the mounts.
*Elevator servo. is a single servo attached to the stab with little blocks. Very stupid. A guy somewhere here had one which crashed on a maiden flight because the servo broke lose. I expoxied my servo right to the stab itself, then glassed around the bottom also. That sucker is not coming off! Not much room in their either. Get some sort of a low profile high torque servo.
* Since i decide to recover , I also dabbed a little epoxy on each rib just for aggravation. Overall it is a good plane. I just don't like red. Also our stats here at 5000ft fall short of what you'll get in Florida. I boast 120mph for my DC F20 but that is as best you'll get here with a 17% overall loss in peformance. I know guys at sea level with the same setup getting 150mph.
07-24-2002, 02:52 AM
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How fast are we all going
This seems to be on most guys minds, so here's a really easy formula to guestimate air speeds without any measuring device at all. It is: RPMxprop pitch in ft. ( ie a 9" pitch prop would be .75ft instead of just 9) x60 divided by 5280.
Example: Say your engine turns a 9" pitch prop at 20,000 rpm
Using the formula:
20,000x.75x60/ 5280= approx. 170mph.
These numbers deal directly with the theoretical max speed based on prop pitch only and tend to be a little low since motors unload in flight raising rpm's and twisting of the prop causes pitch increase. (Although the pitch increase in usually negated by loss of efficiency due to changes in prop dynamics.) I hope this helps most of you guys out there that are tired of guessing the speeds of their planes. Drag is also not figured in the above calc...
Dan, Aerojet Composite Models
Example: Say your engine turns a 9" pitch prop at 20,000 rpm
Using the formula:
20,000x.75x60/ 5280= approx. 170mph.
These numbers deal directly with the theoretical max speed based on prop pitch only and tend to be a little low since motors unload in flight raising rpm's and twisting of the prop causes pitch increase. (Although the pitch increase in usually negated by loss of efficiency due to changes in prop dynamics.) I hope this helps most of you guys out there that are tired of guessing the speeds of their planes. Drag is also not figured in the above calc...
Dan, Aerojet Composite Models
07-24-2002, 09:18 PM
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Prop Jets
Originally posted by Cyclic Hardover
Back in the early 80's the Thunderbirds were using T38's i think. Not sure if you are aware the T-38 is the 'Grandpa" of the F-20.
T-38, F-5, F-20. Anyways, go find a picture of it to go by.
Back in the early 80's the Thunderbirds were using T38's i think. Not sure if you are aware the T-38 is the 'Grandpa" of the F-20.
T-38, F-5, F-20. Anyways, go find a picture of it to go by.
Jimmy
07-25-2002, 01:00 AM
#14
Prop Jets
Heres another "diddy" for you. Like I said earlier, first was the T38 which was a trainer in the late 50's, Then they thought it would be a neat fighter, so with a bit of cosmetics it became the F-5. Then in the early 80's Northrop wanted to compete with the F-16. They turned it from a twin engine to a single. The ass end gives this away*
This brings us to R/C. The DC F-20 is really an F-5. Although a sport scale plane, again look at the backend. The Cermark is the true F-20 with a single exhaust. Nothing wrong with either one. Just food for thought.
This brings us to R/C. The DC F-20 is really an F-5. Although a sport scale plane, again look at the backend. The Cermark is the true F-20 with a single exhaust. Nothing wrong with either one. Just food for thought.
07-27-2002, 04:04 PM
#15
JimmyA
Look in this forum, under Patriot Drivers...
Look at the elevator mod...
I'm the guy who's F-20 crashed on the first flight when the elevator servo came loose.
Also, I'm sorry to say this...but you will be Disappointed in the performanc of the plane with the O.S. .91FX. They just "don't crank". If money isn't a problem...get the Jett 90.
Also, the retracts that come with the plane are junk...Get the Robart #609 H.D. mechs., their only like $40. The stock ones have prob. with the "axles"...they twist all the time, and you'll be dragging the wheels side-ways all the time.
The Robarts come "long", and you have to heat, and bend the strut for the axle, the cut off to size for the wheels.
However, the struts are thicker, and eliminate all the twisting problems.
Also...check in the back where the elevator torque rods fit onto the stab.
Look at the elevator mod...
I'm the guy who's F-20 crashed on the first flight when the elevator servo came loose.
Also, I'm sorry to say this...but you will be Disappointed in the performanc of the plane with the O.S. .91FX. They just "don't crank". If money isn't a problem...get the Jett 90.
Also, the retracts that come with the plane are junk...Get the Robart #609 H.D. mechs., their only like $40. The stock ones have prob. with the "axles"...they twist all the time, and you'll be dragging the wheels side-ways all the time.
The Robarts come "long", and you have to heat, and bend the strut for the axle, the cut off to size for the wheels.
However, the struts are thicker, and eliminate all the twisting problems.
Also...check in the back where the elevator torque rods fit onto the stab.
08-08-2002, 01:46 AM
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08-08-2002, 02:22 AM
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Wicked!
That SU looks wicked, but I need more info. Any reviews or pics out there...?
Call me when they make an ARF, or when you build it and wanna sell it..
james
Call me when they make an ARF, or when you build it and wanna sell it..
james
08-08-2002, 03:39 AM
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Prop Jets
I am still debating, it cost close to US$150.00 landing it to the U.S. and then building it. This is going to take some effort. I don't think they are going to ARF it :-(!!!
08-08-2002, 04:48 AM
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I have a F20 but not quite impress with the look due in part its not a very scale looking plane. But scratch build don't sound fun to me either, what a dilima :-0 ???
08-08-2002, 03:22 PM
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To go that kind of speed, I think you should go get a Q40 and a Nelson and a big field with 20/40 eyesight and a very good pilot. Its also good to become an AMA member first!
