CAP 21 – from an old Model Tech kit
10-13-2011 | 09:11 AM
#1
CAP 21 – from an old Model Tech kit
I’ve had some great first flights today with this simple model.
It’s a pleasure to fly. Very smooth and stable. OS 45 FSR, 2390 gr. AUW.
Here are the mods that I made, some of which probably contributed to the relatively low weight:
I used Kevlar pull-pull for the large rudder in place of a heavy single pushrod.
The tail-wheel assembly provided is nice, but more suitable for use on a 1/5-1/4 scale Cub from the weight and design aspects, so it will be used for that in future, while for the CAP I installed a simple 40-size t/w assembly instead. This saved a ‘ton’ of weight at the back end.
For the wing attachment, some strange and questionable H/W was provided. I changed that into a laminated ply plate across the fuselage above the T.E. position, drilled and tapped for ¼-20 nylon bolts. That always works well.
The kit provided canopy was not very clear, heavy, and rather ugly. Here is where I was happy the LHS carries so many ARFs – for they also carry many replacement cowls and canopies too, so I easily found a cheap alternative canopy that could be made to work reasonably well.
The engine per the instructions should be installed inverted or side mounted. I don’t particularly like inverted two strokes, and didn’t have a Pitts muffler for the other option, so opted for the funny angle you see in the pics. It is almost upright, allows use of the standard muffler, and actually the muffler is more or less in the position of the ‘scale’ cheek cowl, so the model’s silhouette should be acceptable I think.
The kit also includes wheel pants. They are very heavy so they were left off. I may add lighter ones in future.
The foam wheels I used are not the prettiest wheels I could find but weigh next to nothing, and on a sport model of this size I think they do the job.
Finally – the l/g is shown attached to its mounting blocks with tiny self-tapping screws. That may be OK for attaching a small plastic fairing etc. but it’s not the way to attach an u/c to a model IMO, so I installed heli-coils into the hardwood blocks and then bolted the gears on with proper 6-32 Allen bolts (4 for each leg).
I set up the controls with ~40% exponential on the ailerons and elevators, and about half of the rudder throw shown in the instructions. This adds to the control smoothness I believe. I also set up the strip ailerons to have a significant differential, and such that the dual rate selection affects only the amount of “up” travel of the ailerons and not the “down” travel. It really does fly as if “on rails” and far better than what I expected.
In summary, a very nice and simple model that was quick and fun to put together, and is a lot of fun to fly. If you can still find one, I recommend it, but do keep it light and avoid any temptation to over-power it and “beef it up”.
It’s a pleasure to fly. Very smooth and stable. OS 45 FSR, 2390 gr. AUW.
Here are the mods that I made, some of which probably contributed to the relatively low weight:
I used Kevlar pull-pull for the large rudder in place of a heavy single pushrod.
The tail-wheel assembly provided is nice, but more suitable for use on a 1/5-1/4 scale Cub from the weight and design aspects, so it will be used for that in future, while for the CAP I installed a simple 40-size t/w assembly instead. This saved a ‘ton’ of weight at the back end.
For the wing attachment, some strange and questionable H/W was provided. I changed that into a laminated ply plate across the fuselage above the T.E. position, drilled and tapped for ¼-20 nylon bolts. That always works well.
The kit provided canopy was not very clear, heavy, and rather ugly. Here is where I was happy the LHS carries so many ARFs – for they also carry many replacement cowls and canopies too, so I easily found a cheap alternative canopy that could be made to work reasonably well.
The engine per the instructions should be installed inverted or side mounted. I don’t particularly like inverted two strokes, and didn’t have a Pitts muffler for the other option, so opted for the funny angle you see in the pics. It is almost upright, allows use of the standard muffler, and actually the muffler is more or less in the position of the ‘scale’ cheek cowl, so the model’s silhouette should be acceptable I think.
The kit also includes wheel pants. They are very heavy so they were left off. I may add lighter ones in future.
The foam wheels I used are not the prettiest wheels I could find but weigh next to nothing, and on a sport model of this size I think they do the job.
Finally – the l/g is shown attached to its mounting blocks with tiny self-tapping screws. That may be OK for attaching a small plastic fairing etc. but it’s not the way to attach an u/c to a model IMO, so I installed heli-coils into the hardwood blocks and then bolted the gears on with proper 6-32 Allen bolts (4 for each leg).
I set up the controls with ~40% exponential on the ailerons and elevators, and about half of the rudder throw shown in the instructions. This adds to the control smoothness I believe. I also set up the strip ailerons to have a significant differential, and such that the dual rate selection affects only the amount of “up” travel of the ailerons and not the “down” travel. It really does fly as if “on rails” and far better than what I expected.
In summary, a very nice and simple model that was quick and fun to put together, and is a lot of fun to fly. If you can still find one, I recommend it, but do keep it light and avoid any temptation to over-power it and “beef it up”.
10-13-2011 | 10:14 AM
#2
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From: Rangiora/Kaiapoi, NEW ZEALAND
RE: CAP 21 – from an old Model Tech kit
u r to be congratulated for all the fore thought that u put into it I,m trying to do somi;iar with an Astro Hog converting it to electic with 6 cell batteries if I can get them ,bit of a short supply here and at Hobbyking seems to be plenty in the states but postage is prohibitive ,,,I really hope ur plane gives you hours and hours of fun ,,thats what big boy toys are meant to do aye
