|May 16, 2003, 07:59 AM|
Pulqui II Project
Pulqui II Project
And here we go again, and this time with a complete new EDF model!
After two months of R&D I already have the figures and the draw of my Pulqui II N°5, I am starting to build it next week. I am assuming to spend 6 months in this project.
The initial spec. are based in a modified 1:14th scale:
Wingspan: 800mm, 31.5”
Length: 840mm, 33.7”
Gross Weight: 1112gr, 39.2oz (estimated)
Wing load: 56.5gr/dm2, 18.8oz/sqinch
Airfoil: Symmetrical, 12.4%
Fan diameter: 92mm, 3.6”
For the people who don’t know the Pulqui II, here are some photos.
You also have a good summary about the history of Pulqui in:
|May 17, 2003, 02:45 PM|
Danged if I know how you're gonna fit a 92mm fan and cells into a 31.5" span Pulqui II. I began drawing up a 40" span version for a 90mm Midifan some time ago, and here's a pic of the drawing.
There's not a lot of space remaining outside the ducts, even at that size
|May 17, 2003, 09:42 PM|
The scale you chose (1:13) is the same I have for the fuse (1:14 modified).
At these sizes there is always a little space for the power plant and RC stuff, particularly in EDF models .
Four ways to gain space:
Choosing a bigger scale e.g. 1:11, but it needs a bigger power plant, is a trade off solution.
Using RC glider’s gear, good if you can afford it
Making the fuse wider, good for me
Cheating the fuse’s shape, awful but practical
I will hide the Rx, battery and Aileron servo in the canopy. The elevator servo will be upside between the rudder and the canopy, and it will be horizontally mounted.
The fan and power plant will as be some where between the CG and the tail. Here we have a compromise, in one hand the fan should be near the tail to be more efficient, in the another hand we have to balance the model (CG) and try to have the smaller momentum we can. The batteries will be then forward the CG and in the lower part, they have to copy the rounded shape of the fuse (customized pack). Or you can put the pack forward the fan’s hub inside a tube. If you have a glow engine, it will be over the CG and the fuel tank behind the engine (beware, to calculate the CG, in this case we have to consider the tank full, because it is behind the CG).
Anyway the accurate position of the power plant should be trimmed with the model in the hands.
Here are the figures for three different scales and the modified ones, all in meters.
|May 19, 2003, 08:03 AM|
I will construct it all from scratch.
First I cut the wings and the fuse from white foam (20kg/m3) with a hot wire. To do this, I needed to build the airfoils and the fuse shape in balsa cover with ciano in order to admit the hot wiring. I have to admit that it is better to shape in aluminum that in balsa, particularly the airfoils. Regarding the foam, it was the best I could get.
Here are the 3 views of the model I used to cut the foam (hot-wire), the main modification made to this plans was the enlargement of fuse’s diameter, I need 92mm inside plus the RC equipment space.
|May 20, 2003, 08:19 PM|
I covered the foam with pre-molded glass fiber + epoxy the wings. I pre-molded the fiber glass in a window glass. Summarizing, cut the fiber, covering the window glass with the epoxi and after that put the fiber. Wait until the epoxi gets no liquid and put the lamina over the foam which should wetted with epoxi.
Previously I practiced the same technique with the rudder. Very good idea!
|Jun 02, 2003, 09:29 PM|
Yesterday I finished to cover the second half wing. As the first was bad, this time a tried a different mix. I used 2 parts of epoxi for each part of fiber (48g/m2). This time I think it would be great, for this low weigh 1 to 1 proportion is too few epoxi.
I will try to take some photos for the next post.
PS thanks Kevin!
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