01-02-2013, 04:24 PM
I've been looking at motors, lipo's, and other similar model specs to get an idea of wing loadings and all up weights. I'm thinking along the lines of retaining about the same weight as the original or a similar model and seeing what sort of performance can be obtained with relatively inexpensive parts. Mostly Stuff from HK.
Here is a bit of a list I put together in xl of
The first sheet has motors that could be made to fit the Airframe I'm sure there are many more than in this list but I think it's going to be hard to go past the NTM 2836 3000 or the 2700 version of the same motor. Frank is running the 2200 version in his RareBear and it slips along quite well.
It's lighter than the original motor, a speed 400 motor weighs about 95 grams and this one weights 87 and for $17.00 plus postage I think that clinches the deal. I'll be getting one of the 2700 KV and one of the 3000.
The second sheet in the file shows a comparison of Lipos
Because the model needs to fly for about 2 mins (I'll accept 115 seconds at a pinch) I've worked out how long each pack will last at various amounts of current draw. and also what their max continuous current rating is.
So it looks like it's a choice between the ZIPPY Compact 4S 35C 1600providing 50A for 115 seconds this would suite the 3000KV motor (with the right prop of course) and the Turnigy Nano 4S 45-90 1300 providing 40A for 117 seconds. The weights are 178g and 155g respectively. For comparison 7 2/3A nicad cells would weigh 140 grams with out wires or leads. We must be in the same ballpark weight wise so far.
As far as all up weight goes I don’t want to exceed a wing loading of 20 oz per sq ft to that gives a maximum all up weight of around 570 grams. I hope to be well under this perhaps as low as 450 grams this should give me a wing loading of around 15 oz per sq ft. which will make it a lot friendlier to fly !!
So far with out the airframe we are looking at 346grams and counting so we’ll have to see how we go.
Here's a Pic of the MH 33 Airfoil I'm going to use to develope the templates to hot wire cut the foam wing cores.
Here is a bit of a list I put together in xl of
The first sheet has motors that could be made to fit the Airframe I'm sure there are many more than in this list but I think it's going to be hard to go past the NTM 2836 3000 or the 2700 version of the same motor. Frank is running the 2200 version in his RareBear and it slips along quite well.
It's lighter than the original motor, a speed 400 motor weighs about 95 grams and this one weights 87 and for $17.00 plus postage I think that clinches the deal. I'll be getting one of the 2700 KV and one of the 3000.
The second sheet in the file shows a comparison of Lipos
Because the model needs to fly for about 2 mins (I'll accept 115 seconds at a pinch) I've worked out how long each pack will last at various amounts of current draw. and also what their max continuous current rating is.
So it looks like it's a choice between the ZIPPY Compact 4S 35C 1600providing 50A for 115 seconds this would suite the 3000KV motor (with the right prop of course) and the Turnigy Nano 4S 45-90 1300 providing 40A for 117 seconds. The weights are 178g and 155g respectively. For comparison 7 2/3A nicad cells would weigh 140 grams with out wires or leads. We must be in the same ballpark weight wise so far.
As far as all up weight goes I don’t want to exceed a wing loading of 20 oz per sq ft to that gives a maximum all up weight of around 570 grams. I hope to be well under this perhaps as low as 450 grams this should give me a wing loading of around 15 oz per sq ft. which will make it a lot friendlier to fly !!
So far with out the airframe we are looking at 346grams and counting so we’ll have to see how we go.
Here's a Pic of the MH 33 Airfoil I'm going to use to develope the templates to hot wire cut the foam wing cores.
“The knack of flying is learning how to throw your machine at the ground and miss.”
"When once you have tasted flight, you will forever walk the earth with your thoughts turned skyward, for there you have been, and there you will always long to return." ~Leonardo Da Vinci