DHC-4/C-7A Caribou Nears Completion - RC Groups (2025)

I started on this project October 2014 and I am now ready for taxi test and maiden flight, which I will be doing before final finish details. I still need to put some scoops, exhaust, side door hinges and pitot tubes on the aircraft, and will do that after I am sure it fly's. This is a Sparc Lazer short kit, with redesigned flaps, Lado retracts, E-flight power 60's on a pair of 5000mah, 65c, 6s Graphene batteries for main power and a 2200mah, 65c, 3s Graphene battery for auxiliary power for the brakes, lights, and Mr. RC sound system. I have 21.8 lbs. of thrust for the 26 lb. 14oz all up airframe, at a max of 132 amps at full throttle. I am up to 14 channels on my Fr Sky Taranis X9D radio. I am set up to do LAPES cargo deliveries with this bird. LAPES is an acronym for Low Altitude Parachute Extraction System, so, I open the cargo door and ramp to release my pilot chute, and have a parachute release for the main chute, and a LAPES sled release for my cargo sled. The scale sled is loaded with 12 boxes of 105mm artillery rounds and 24 cartons of C-rations, a classic beans and bullets load. My main chute is a 17 inch parachute flare chute. I also have a practice sled that is just a box structure simulation of the cargo sled covered with international orange trim monokote for visibility. I will be releasing the practice sled at altitude to see how the aircraft handles with the chute out before doing a simulated LAPES just inches off the runway to see if my sleds will slide or tumble.
The flap set up is compliments of Robin Fowler's (Eye For Wings) posts on his Caribou build. After 3 concept models and about 3 weeks of fiddling, I ended up with a working set up. I only did a build log for a few of my modeling friends, but have a huge photo file of the process.
I used a T-rail down the center of the cargo bay to guide the sled out upon release. I hope it works without crashing my aircraft. I have never heard of anyone doing LAPES with a scale model, but, I may not be the first to try it.
I may need to do multiple posts for photos.

That is a good looking model

Wow that is absolutely stunning, a plane to be proud of well done, please keep us up to date on the maiden, Ken

Absolutely AWESOME! I love the Caribou!

Very cool!! Can you show a more detailed close up of the double slotted flaps?

Post the build photos!

Here are more build photos of the flap set up. Again, I got all the info for these flaps from Robin Fowler's (Eye For Wings) foam Caribou build log. He said he finished that one about 2 years ago.
I would still like to know if anyone knows of another Sparc Lazer DHC-4 Caribou that has been finished and flown.
Thanks guys for all the compliments!
I will have to start another big project soon, as I am retired and need to keep busy to stay happy! One of the most rewarding parts of this project after completing my concept model of Robin's flap set up was the reassembly after painting.
Well, I noticed that after reassembly, my left outboard flap is coming down too far and needs adjustment, which is done with the tie bar link. I need to lengthen that one to keep it from pulling down too far. I have lots of photos and will post more as requested for specific parts of the build. I was hesitant to do a full build log because of the time involved.

Here is a photo of an outboard wing panel with the servo linkage and a Viet Nam photo of a Caribou after landing at some of the mud hole dirt strips at the special forces combat bases. This is true natural camo!
Bob

just awesome!!!!!! well done!

Robin is right, these models are very different construction. This one is a conventional wood short kit. I think that it was developed from the 1985 plans from Frank Smith. I have a set of these plans. They were sold by M. C. Beaulieu Plan Service of Presque Isle, Maine. I doubt if they still exist. These plans were three 8 foot by 3 foot sheets for a 98" span, fixed gear model with barn door flaps, with a 1/64th ply overlay that made them look like segmented flaps. I only used the overlays on the ailerons. The plans were helpful as the Sparc Lazer short kit only came with a build book and no full size plans. I looked for this kit for about a year, online, before locating one. I have really enjoyed this project, working out all the small engineering details. There is one problem I am still trying to work out with programming on the Taranis transmitter. If the flaps come down too far, the rear flap segment tie bar can go "over center" on the rear pylon and cause the rear flap the pull further down instead of coming back up. That could cause a crash, so, I just want to limit total flap movement short of that critical point. I would not expect to be able to use full flap on this model, anyway, without needing more down elevator. The webmaster of the Caribou Association (former Caribou pilot) informed me that in full STOL mode the horizontal stabilizer comes up about 10-12 degrees at the leading edge to compensate for the extra needed down elevator to be able to land. Had I known this before I finished that part of the build, I could have included that feature in my model, making it even more scale. However, I was beyond that part of the build when I found this out.
Programming the Taranis radio has been a challenge, and I am still watching videos on the subject, and trying things on my own to turn the flap adjustments around. My throw adjustments only seem to affect my "flaps up" or home position, not flaps down. I will persist until I get what I want. I used to be a test engineer, but am very rusty on any programming issues.