SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jul 17, 2007, 12:25 PM
Registered User
Fresno, CA
Joined Jan 2005
32 Posts
Discussion
Why no giant scale prop jets???

With a power to weight ratio greater than 1:1 (3D airplanes) with light gas engines and now large brushless motors, why doesn't anyone market giant scale prop jets (tractor or pusher)? I think this could easily become a whole new segment to our hobby.
arp67 is offline Find More Posts by arp67
Last edited by arp67; Jul 17, 2007 at 12:59 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 17, 2007, 09:43 PM
Registered User
tailskid2's Avatar
USA, AZ, Phoenix
Joined May 2003
3,303 Posts
Interesting concept....never thought of that!
tailskid2 is offline Find More Posts by tailskid2
RCG Plus Member
Old Jul 18, 2007, 10:06 PM
Ldm
Registered User
Ldm's Avatar
United States, PA, Conestoga
Joined Jun 2006
8,222 Posts
its seems like the interest when they get larger reaches into e-flight , then , ducted , the turbine .
I agree with you but dont really know if there is a market .
Look at the ceremark line , reaching $400 for jet a retracts , larger would probably reach $600 ,
Vmar with there less then steller quality has there prop jets reaching $329 with no retracts
Ldm is offline Find More Posts by Ldm
Reply With Quote
Old Jul 21, 2007, 08:45 AM
LOWERRR!
MadMonkey572's Avatar
United States, TX, Roanoke
Joined Sep 2006
1,507 Posts
Prop jets would be waaaaay cheaper than a turbine though... hmm... my mind is clicking
MadMonkey572 is offline Find More Posts by MadMonkey572
Reply With Quote
Old Jul 21, 2007, 09:11 AM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,294 Posts
How about an enlargement of a '70s pattern ship with an ignition engine up front. Planes of that era looked very jet-like.

Tom
Trisquire is offline Find More Posts by Trisquire
Reply With Quote
Old Jul 21, 2007, 07:31 PM
Registered User
Fresno, CA
Joined Jan 2005
32 Posts
I decided I will take an A-4 Skyhawk I designed & built a few years ago and put it on steroids. I still have it in my CAD program. The model is all balsa and ply construction with the engine mounted at the rear in pusher config. For the giant sport scale version, I think it would be better to mount the engine up front. My plan is to use the DA-50cc engine. The A-4 has long landing gear with the nose pitched up at a high angle when sitting on the ground, so this helps tremendously with prop clearance.....a big issues when designing a prop jet model. To get the spinner to blend better with the nose of the jet, I will probably use the A-4D model as my reference. The latter skyhawks had longer, pointer noses. I plan to use fixed landing gear on the prototype.

Andrew
arp67 is offline Find More Posts by arp67
Reply With Quote
Old Jul 22, 2007, 04:21 PM
Registered User
Troutdale, Oregon, United States
Joined Oct 2003
288 Posts
turbo prop airliners

Why not go to turbo props?
Peter
peterpont is offline Find More Posts by peterpont
Reply With Quote
Old Jul 22, 2007, 08:10 PM
Registered User
Fresno, CA
Joined Jan 2005
32 Posts
After some additional research, I think I will switch from using the DA-50 gas engine to one of the large brushless motors now being offered from Hacker or one from Hobby Lobby. I will mount the motor at the rear of the fuse in pusher config. This will help out greatly with the scale appearance.

My goal/vision for creating giant scale prop jets is to have a model that is even larger than most of the turbine powered jets but costs significantly less and has a great power to weight ratio. I know if my giant scale A-4 Skyhawk is successful, many others will be interested in acquiring the plans and components to build their own. I want to design several other giant scale prop jets and sell the plans & components for them.

Andrew
arp67 is offline Find More Posts by arp67
Reply With Quote
Old Jul 23, 2007, 03:06 PM
Intermediate Multi
Trisquire's Avatar
Columbus, OH
Joined Mar 2005
3,294 Posts
A nose mounted engine might provide more prop clearance during take-offs and landings. Cosmetically, I don't have a problem with a prop (or engine cylinder) on the nose.

Tom
Trisquire is offline Find More Posts by Trisquire
Reply With Quote
Old Jul 23, 2007, 04:06 PM
Registered User
Fresno, CA
Joined Jan 2005
32 Posts
Tom....thank you for your input. Since I have chose to go electric with my giant scale Skyhawk, a builder could chose to mount the motor up front or at the rear.

My initial number crunching has produced the following specs for my A-4 Skyhawk project:

Motor: Hacker A60-14L brushless
Prop: 20" dia.
Fuse Length: 88"
Scale wingspan: 60"
Sport scale wingspan: 72"
Max. target weight: 18 lbs.

Andrew
arp67 is offline Find More Posts by arp67
Reply With Quote
Old Jul 24, 2007, 02:19 PM
Registered User
Joined Jul 2007
1 Posts
http://www.wrenturbines.co.uk/galler...ine=4&bypass=1
big geoff is offline Find More Posts by big geoff
Reply With Quote
Old Jul 24, 2007, 03:20 PM
Mr. ExperiMENTAL
Joined Apr 2004
1,715 Posts
Good Subject!!

Hey Fellas,

I agree, I think part of the reason it has not been thought about so much is because of the lack of technology. We have more recently seen a surge in so many areas of rc. I think we are now beginning to have electric motors and equipment that are fast enough and powerful enough to do the job "well" as in efficiently. Also there are more choices than there use to be. Then again maybe no one has really done it cause...no..one ..has...really...done it... LOL!
I have thought about this idea myself and mainly got held up on going all out when I started thinking about the number of batteries/weight and cost of Motor and ESC that would would be imminent for such a project. I ain't rich....lol. I myself would not be happy with a jet that only performed like a parkflyer so to get some decent performance we would need some higher end equipment...and that means $$.

It appears that most larger models run out runners or geared inrunners and have gobs of power but only moderate speed. Not that there are not a few out their but the choices are more limited. No one has been much looking for a super fast 3D plane or a mach 1 giant warbird. I think if there was a demand the industry will begin to produce more motors specificall designed to do this job. We need a few powerful but very fast motors that run props in the 7-15 inch range with pitch speeds in excess of 100mph. Or at least that is what would catch my eye.

Now I agree it is cheaper than turbine so I think it is a route that needs exploring and a few winning combos need to come to the surface.

I am currently building a Bobcat <Modified to be "ELECTRIC">.
Link here:
http://www.wattflyer.com/forums/showthread.php?t=14454

It will be running an AXI 4130-20
13X5 3 blade
45amp Castle HV
9 Cell Maxxamps

Sounds like a beast, should be a hoot. Should be ready by this weekend

I used what I had as far as equipment but I think there are better combos. On the thread are a few flights of this plane on various setups.


This is great stuff to think about.



Tips
Wingtips24 is offline Find More Posts by Wingtips24
Reply With Quote
Old Jul 29, 2007, 07:04 PM
Dunce!
v6focus's Avatar
Durham, UK
Joined Apr 2004
398 Posts
Simple answer

Because there isnt a market for them, nobody wants to buy them cause they cost too much and arent very good for 3D.

There are some out their though, the link geoff has posted however is just the Wren Turbo Prop engine.

The plane is a Turbo Raven and Somenzini aircraft also do a turboed bipe the Python.
v6focus is offline Find More Posts by v6focus
Reply With Quote
Old Jul 29, 2007, 07:25 PM
LOWERRR!
MadMonkey572's Avatar
United States, TX, Roanoke
Joined Sep 2006
1,507 Posts
Quote:
Originally Posted by v6focus
nobody wants to buy them cause they cost too much and arent very good for 3D.
Why would anyone want to 3D a prop jet?
MadMonkey572 is offline Find More Posts by MadMonkey572
Reply With Quote
Old Jul 29, 2007, 07:41 PM
Dunce!
v6focus's Avatar
Durham, UK
Joined Apr 2004
398 Posts
Cause thats what the turbo raven was best at that and vertical performance.
v6focus is offline Find More Posts by v6focus
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Why No Full Scale Pattern Planes? berryulson Modeling Science 2 Oct 04, 2005 02:57 AM
FYI.... Top Gun Pics In Jets and Giant Scale Thermalin Fuel Warbirds 0 May 02, 2005 10:03 PM
Why no prop damage on gearless planes? K-Man Beginner Training Area (Aircraft-Electric) 20 Nov 07, 2004 02:09 PM
Best giant scale prop??? GeeBeeMan21 Giant Scale Airplanes 2 Nov 11, 2003 10:13 AM
Why no 5x5 folder prop? kwilliby Power Systems 1 Sep 22, 2003 05:31 AM