I recently built Sig's Jenny JN4 ARF (HERE – look under "ARF Scale Models") and have been flying it for about two months. This review includes what I did to strengthen the Jenny so that it could take a more powerful motor. My initial setup used a Hobbyzone 3 channel tx/rx/servos recycled from the Super Cub with the stock SIG 180 motor, almost immediately followed by an upgrade to Spektrum DX6 rx/tx/servos, an E-Flite Park 400, Thunderbird 18 Controller and 1320 Lipo.
My second Jenny after substantial re-inforcing
I got to like the Jenny so much that I bought two more (I made a deal at my lhs) so I could apply the lessons I learned (the hard way) for strengthening subsequent builds. I'll get into more detail about flying characteristics after the build review.
Kit Contents
The kit features die-cut plywood and foam parts:
The foam wings/tail is about 3/32" thick and the yellow color is only on the top surface; the wing has no dihedral or washout. Note that the wing has under-camber:
- this is when the bottom of the wing is concave. An under-cambered wing is a high lift design and may perform extremely well at slow speeds but may become unstable at higher speeds – something to consider as you read on about the motor that comes with the Sig. The motor is, well, barely adequate:
It's geared down to 4.4:1; the problem I had with it is that it did not last more than an hour, if that – the gears wore quickly and stripped – not worth dealing with it.
Based on my experience with the my first Jenny, I reinforced the fuse with carbon fiber strap running its length and fiberglass cloth in high stress areas – the firewall and landing gear slots.
An inside shot of the CF strap and fiberglassing:
I also used CF strap to beef up tail surfaces, including inserting a strip inside the vertical stab:
I beefed up the fuse wing struts with CF strap:
{mospagebreak}
Due to the motor change, I also beefed up the firewall (one good smack and it will push in):
The kit's firewall does not fully cover the fuse, so this overlaps it; I fiberglassed the inside firewall for added strength
I mounted the Lipo behind the firewall, using foam to hold it in place:
The DX6 servos fit perfectly in the kit's servo tray:
The kit features a small plywood piece for the tail dragger – I used a nylon wing saver instead:
Also note that epoxied a small CF tube for the control rod's exits:
Finally, this wing is from the first kit – it's been extensively reinforced as it went suffered through forces for which it was NOT designed:
I managed to fold the wing in flight during some maneuvers that put a LOT of stress on them – fortunately it was over grass:
Based on what I learned, the second wing is reinforced with carbon fiber tubes embedded in its leading edge:
Flying
Flying with SIG's 180 was, well, uninspiring and I thought difficult – it's underpowered and has no real punch to get out of trouble, let alone do a loop. Best to figure replacing it and use the 180 for a paperweight – I did not get more than about an hour out of the 180 before it self-destructed (gears chipped and wore down very quickly).
I indicated above that the under-cambered wing has no dihedral or washout – it's not very forgiving. However, I found that I could slow-fly it very nicely in tight circles with the E-Flite 400 throttled back and a light hand on the stick. With more power, the Jenny will do loops and rollovers nicely, although it will pick up speed quickly – lots of height recommended!
With the under-cambered wing, as speed increases drag increases exponentially; this can lead to some funky flying. In truth, the Sig Jenny is not really designed to be much more than a slow-flyer, so pushing it as I did can sometimes result in unpredictable behavior – use LOTS of altitude when you rev it up.
CONCLUSIONS
Overall this is one of my favorites – it's a fun plane to fly, looks great in the air and will slow-fly nicely. When pushed, however, I did not find it at all forgiving – not unexpected as it really was not designed for high speeds. I think I like this so much because it can be quite a challenge sometimes.
NOTE: HobbyZone is releasing their E-flite Jenny JN-4 Slow Flyer ARF in March – this looks very similar to the Sig Jenny and I would speculate that it's an "updated" version of the Sig, with very much the same flight characteristics.
NOTE: This is a new site so please consider it a "work in progress". I would greatly encourage readers to send in articles for posting on AmpAviators. In contrast to a forum, finding articles of interest will be TONS easier here.
Sig Jenny JN4 ARF
Attractive WWI biplane slow flyer, with mods to strengthen
Key Specs:
I recently built Sig's Jenny JN4 ARF (HERE – look under "ARF Scale Models") and have been flying it for about two months. This review includes what I did to strengthen the Jenny so that it could take a more powerful motor. My initial setup used a Hobbyzone 3 channel tx/rx/servos recycled from the Super Cub with the stock SIG 180 motor, almost immediately followed by an upgrade to Spektrum DX6 rx/tx/servos, an E-Flite Park 400, Thunderbird 18 Controller and 1320 Lipo.
I got to like the Jenny so much that I bought two more (I made a deal at my lhs) so I could apply the lessons I learned (the hard way) for strengthening subsequent builds. I'll get into more detail about flying characteristics after the build review.
The kit features die-cut plywood and foam parts:
The foam wings/tail is about 3/32" thick and the yellow color is only on the top surface; the wing has no dihedral or washout. Note that the wing has under-camber:
- this is when the bottom of the wing is concave. An under-cambered wing is a high lift design and may perform extremely well at slow speeds but may become unstable at higher speeds – something to consider as you read on about the motor that comes with the Sig. The motor is, well, barely adequate:
It's geared down to 4.4:1; the problem I had with it is that it did not last more than an hour, if that – the gears wore quickly and stripped – not worth dealing with it.
Based on my experience with the my first Jenny, I reinforced the fuse with carbon fiber strap running its length and fiberglass cloth in high stress areas – the firewall and landing gear slots.
An inside shot of the CF strap and fiberglassing:
I also used CF strap to beef up tail surfaces, including inserting a strip inside the vertical stab:
I beefed up the fuse wing struts with CF strap:
Due to the motor change, I also beefed up the firewall (one good smack and it will push in):
The kit's firewall does not fully cover the fuse, so this overlaps it; I fiberglassed the inside firewall for added strength
I mounted the Lipo behind the firewall, using foam to hold it in place:
The DX6 servos fit perfectly in the kit's servo tray:
The kit features a small plywood piece for the tail dragger – I used a nylon wing saver instead:
Also note that epoxied a small CF tube for the control rod's exits:
Finally, this wing is from the first kit – it's been extensively reinforced as it went suffered through forces for which it was NOT designed:
I managed to fold the wing in flight during some maneuvers that put a LOT of stress on them – fortunately it was over grass:
Based on what I learned, the second wing is reinforced with carbon fiber tubes embedded in its leading edge:
Flying with SIG's 180 was, well, uninspiring and I thought difficult – it's underpowered and has no real punch to get out of trouble, let alone do a loop. Best to figure replacing it and use the 180 for a paperweight – I did not get more than about an hour out of the 180 before it self-destructed (gears chipped and wore down very quickly).
I indicated above that the under-cambered wing has no dihedral or washout – it's not very forgiving. However, I found that I could slow-fly it very nicely in tight circles with the E-Flite 400 throttled back and a light hand on the stick. With more power, the Jenny will do loops and rollovers nicely, although it will pick up speed quickly – lots of height recommended!
With the under-cambered wing, as speed increases drag increases exponentially; this can lead to some funky flying. In truth, the Sig Jenny is not really designed to be much more than a slow-flyer, so pushing it as I did can sometimes result in unpredictable behavior – use LOTS of altitude when you rev it up.
Overall this is one of my favorites – it's a fun plane to fly, looks great in the air and will slow-fly nicely. When pushed, however, I did not find it at all forgiving – not unexpected as it really was not designed for high speeds. I think I like this so much because it can be quite a challenge sometimes.
NOTE: HobbyZone is releasing their E-flite Jenny JN-4 Slow Flyer ARF in March – this looks very similar to the Sig Jenny and I would speculate that it's an "updated" version of the Sig, with very much the same flight characteristics.
NOTE: This is a new site so please consider it a "work in progress". I would greatly encourage readers to send in articles for posting on AmpAviators. In contrast to a forum, finding articles of interest will be TONS easier here.