Estes Spitfire x8 (one of these days)

[kullas]

One of these days if i ever make it to my 3rd cert i want to build my bird from scratch i was messing around on rocksim and came up with a upscale version of a Estes Spitfire. I built the estes version many years ago and still have it has 20+ flights on it and i like the looks of it. I would like to get some input from others. What could i do to make it better or does it look ok the way it is.

View attachment Spitfire_x8.rkt

 

[MartyAMC]

I like it.

I did notice the third fin is made from balsa and weighs less than a pound. I think you were planning on using plywood based on the other two fins. You'll also want to mass override some weight for you avionics bay for stability planning purposes.

Good luck with your level III when you get there. The M2000 looks like an impressive flight in the simuation.

 

[Handeman]

One of these days if i ever make it to my 3rd cert i want to build my bird from scratch i was messing around on rocksim and came up with a upscale version of a Estes Spitfire. I built the estes version many years ago and still have it has 20+ flights on it and i like the looks of it. I would like to get some input from others. What could i do to make it better or does it look ok the way it is.

For the many of us that don't have or use Rocksim, could you post just the .jpg?

 

[kullas]

I like it.

I did notice the third fin is made from balsa and weighs less than a pound. I think you were planning on using plywood based on the other two fins. You'll also want to mass override some weight for you avionics bay for stability planning purposes.

Thanks for the input thats why i wanted someone else to look at it i will go back in and change it and add the weight maybe 5 lbs for the electronics and hardware?

For the many of us that don't have or use Rocksim, could you post just the .jpg?

let me see if i can get one posted

 

[kullas]

Here is the pics

 

[Handeman]

Very kewl!!!

Is that weight right, 40+ lbs?

 

[kullas]

Yep right at 40lbs, 11' tall, and right 4.5 feet wide

 

[GuySmith]

Very Nice!

A couple of things to watch out for though. The forward swept fins can present two issues. One would be the forward sweep induces a yaw instability that gets worse the faster you go - the third fin looks like it is large enough to overcome this effect but keep an eye on the yaw stability when you fly it the first time. Second would be that the forward sweep also induces an adverse lift effect on the tips. This also gets more pronounced the faster you go. This can be mitigated by added stiffness in the forward swept fins, but I would not fly it in the transonic range (say above 800fps). I would suggest that you increase the fin thickness from 3/16" to 1/4", this would add stiffness and provide better landing impact resistance. The fins have a fairly large surface area so the first few flights should be in low to no wind conditions until you are comfortable with its flight characteristics.

Cool project - let us know how it goes.

 

[kullas]

I think i will glass the tube and the fins but i cant find a way to to that in rocksim. 1/4 ply and glassed should stiffen it up some. or i could sandwich the ply with foam and then glass the whole thing that way i would have enough room on the fin so i could bevel the edges.

 

[GuySmith]

Sounds good. One layer of 6oz is all you should need. Keep it light - it will give you a much wider selection of motors to play with.

To simulate the fiberglas layers just superimpose fins of fiberglas on the plywood fins or override the weight of the fins with the total weight of the fiberglass, epoxy and plywood. You can do the same with the body tube.


NOTE: Adding fins even imaginary ones does impact rocksim's stability calculations.

EDIT: I just figured out how to add materials to the materials list. Assuming you know the density of the composite material (in this case a layer of 6oz glass and epoxy on each side of a 1/4" plywood sheet) you can add it to the materials spreadsheet in the data folder and mark each of the columns you want the material to appear in and you are good to go.

 

[kullas]

Thanks i will have to give it a try when i get home