DHC-4 Caribou | 73" Span

[Pieliker96]

de Havilland DHC-4 Caribou
A 73" Span STOL Cargo Transport for Power Pack C Twin
​

Plans are out!

Build Guidance​

My build for this winter will be a 6.36% scale, 6-foot-1" span DHC-4 Caribou. If all goes well, it'll have reverse thrust capability, an actuating upper cargo bay door and lower bay ramp, retracts and their associated gear doors, monster double-slotted main flaps and slotted flaperons - all running, with some trickery, off a single 6-channel receiver. With two FT 2218's and a 3000mah 4s, my target all-up weight is 1900g (67 oz) for a wing loading of 17.7 oz/ft² and a cube loading of 9.1.

I'm pushing the boundaries of what I think I'm capable of. The wing is of traditional rib and spar construction, which, along with the flaps, have sharp trailing edges and tight, smooth sheeting - something that will likely take a lot of patience to get right. The flap hinges and linkages need to be strong and precisely located with minimal binding or actuation resistance - the potential for adverse tolerance stackup here is large. The wings will be removable for transport and have integrated connectors (one XT60, one MPX per side) and magnetically retained locking pins to make installation as easy as can be.

If everything goes well I'd like to try and "do the wheelbarrow", as it were: plant just the nosewheel on the runway while keeping the mains well off the ground. This maneuver should be facilitated by the massive flaps, 20% thickness root foil, and 2° incidence on the main wing. In any case, if it survives the maiden flight, it'll end up with a paint scheme somewhat like this

as the standard green camouflage, in my opinion, seemed too common and drab.

As the CAD model is pretty much finished at this point, I'm trying to gauge interest to judge how much effort I should put into the plans and documentation.

If you'd like to have a go at building this thing in a month or so, let me know by replying to this thread.

 

[Ligbaer]

View attachment 213299 My build for this winter will be a 6.36% scale, 6-foot-1" span DHC-4 Caribou. If all goes well, it'll have reverse thrust capability, an actuating upper cargo bay door and lower bay ramp, retracts and their associated gear doors, monster double-slotted main flaps and slotted flaperons - all running, with some trickery, off a single 6-channel receiver. With two FT 2218's and a 3000mah 4s, my target all-up weight is 1900g (67 oz) for a wing loading of 17.7 oz/ft² and a cube loading of 9.1.

I'm pushing the boundaries of what I think I'm capable of. The wing is of traditional rib and spar construction, which, along with the flaps, have sharp trailing edges and tight, smooth sheeting - something that will likely take a lot of patience to get right. The flap hinges and linkages need to be strong and precisely located with minimal binding or actuation resistance - the potential for adverse tolerance stackup here is large. The wings will be removable for transport and have integrated connectors (one XT60, one MPX per side) and magnetically retained locking pins to make installation as easy as can be.
View attachment 213300

If everything goes well I'd like to try and "do the wheelbarrow", as it were: plant just the nosewheel on the runway while keeping the mains well off the ground. This maneuver should be facilitated by the massive flaps, 20% thickness root foil, and 2° incidence on the main wing. In any case, if it survives the maiden flight, it'll end up with a paint scheme somewhat like this
View attachment 213301
as the standard green camouflage, in my opinion, seemed too common and drab.

As the CAD model is pretty much finished at this point, I'm trying to gauge interest to judge how much effort I should put into the plans and documentation.

If you'd like to have a go at building this thing in a month or so, let me know by replying to this thread.

ok

 

[Marzipan]

totally interested!!! but scaled down to something a wee bit more manageable for myself.

 

[FoamyDM]

I am Very interested. There are a number of new things to tackle here. (actuated Flaps mainly. ) Jumper Bay Fun,

 

[Pieliker96]

Nice! I'll be doing a fully-fledged set of plans then

totally interested!!! but scaled down to something a wee bit more manageable for myself.

I designed it for the scale of Power Pack C on 9" three-blade props - much larger and thrust-to-weight starts to suffer, smaller and wing loading becomes a concern. In any case you're welcome to scale down the plans to your liking once they're released - I personally won't be doing so since the design work is already done at the current scale

 

[FlyerInStyle]

Nice! I'll be doing a fully-fledged set of plans then


I designed it for the scale of Power Pack C on 9" three-blade props - much larger and thrust-to-weight starts to suffer, smaller and wing loading becomes a concern. In any case you're welcome to scale down the plans to your liking once they're released - I personally won't be doing so since the design work is already done at the current scale

It is designed for a ppc? Then I might oin in sometime later too.

 

[Pieliker96]

It is designed for a ppc? Then I might oin in sometime later too.

Yes, though you'll need extra servos and reversing ESCs if you so desire.

 

[FlyerInStyle]

Yes, though you'll need extra servos and reversing ESCs if you so desire.

I do not, tbh want the reversible esc's. too expensive. but the extra servos, I will have, and a 6ch receiver, if you show how you put it all into one, I can have too.

 

[Tench745]

Yes, though you'll need extra servos and reversing ESCs if you so desire.

What's the reversing ESC for?

 

[Ligbaer]

I do not, tbh want the reversible esc's. too expensive. but the extra servos, I will have, and a 6ch receiver, if you show how you put it all into one, I can have too.

simonk and blhelis are reversible in firmware so as long as youre running those your good

 

[Pieliker96]

I do not, tbh want the reversible esc's. too expensive. but the extra servos, I will have, and a 6ch receiver, if you show how you put it all into one, I can have too.

I should mention that the trick I'm using for getting extra functions out of a 6-channel is muxing several switches into a single channel and demuxing them on the plane side with an arduino. This way I can use a single channel to control landing gear, gear doors, cargo doors, flaps, and flaperons. Without that, your channel allocation would probably end up at the standard 4 plus flaps and gear.

 

[Pieliker96]

The full-scale DHC-4 had variable-pitch props and could put them into beta (negative angle of attack, reverse thrust) to reduce landing distance and backtaxi - something similar can be achieved by having the ESCs reverse the directions of the motor and drive the props backwards. It'll be interesting to see how it works at the model scale

 

[Tench745]

The full-scale DHC-4 had variable-pitch props and could put them into beta (negative angle of attack, reverse thrust) to reduce landing distance and backtaxi - something similar can be achieved by having the ESCs reverse the directions of the motor and drive the props backwards. It'll be interesting to see how it works at the model scale

Gotcha, I missed that it was going to have reverse thrust.

 

[FlyerInStyle]

I should mention that the trick I'm using for getting extra functions out of a 6-channel is muxing several switches into a single channel and demuxing them on the plane side with an arduino. This way I can use a single channel to control landing gear, gear doors, cargo doors, flaps, and flaperons. Without that, your channel allocation would probably end up at the standard 4 plus flaps and gear.

oh. I mean I have a arduino that i might use. if it ends up somwhere else, I can get one. are you using spektrum?

 

[Pieliker96]

oh. I mean I have a arduino that i might use. if it ends up somwhere else, I can get one. are you using spektrum?

I'm using Graupner but it shouldn't matter. I'll end up releasing the code once it's finished as well.
As far as the concept goes: I have three switches: one for the bay doors, one for the landing gear, one for the flaps. I mixed all of the switches to a single channel with different dual rates such that every unique switch combination results in a unique PWM output of the RX which can then be decoded by the arduino. Besides controlling the gear, gear doors, cargo doors, and flaps, I'm also using the arduino to do flaperon and differential aileron mixing since my 5th channel is taken up by a reversing signal for the ESCs.

 

[FlyerInStyle]

I'm using Graupner but it shouldn't matter. I'll end up releasing the code once it's finished as well.
As far as the concept goes: I have three switches: one for the bay doors, one for the landing gear, one for the flaps. I mixed all of the switches to a single channel with different dual rates such that every unique switch combination results in a unique PWM output of the RX which can then be decoded by the arduino. Besides controlling the gear, gear doors, cargo doors, and flaps, I'm also using the arduino to do flaperon and differential aileron mixing since my 5th channel is taken up by a reversing signal for the ESCs.

I am using spektrum but not sure that it can do that. if anything I will just cut out some functions.f

 

[Scotto]

This is going to be epic! So many cool things, but Im most interested in the double slotted flaps

 

[Marzipan]

@Pieliker96 I'm curious...you Canadian or just have a love for de Havilland Canada like me?

 

[Pieliker96]

@Pieliker96 I'm curious...you Canadian or just have a love for de Havilland Canada like me?

American, just have an interest in STOL and high-lift stuff

 

[Marzipan]

American, just have an interest in STOL and high-lift stuff

well, I'm Canadian and I love DHC, so lemme know if you undertake a DHC-5 Buffalo!