Some thoughts on this subject.
1 MiniMax air-frame is basically much heavier than some others like the SkyPup. So it is more difficult to make Pt 103 weight on a Max because you have less wiggle room when it comes to making weight. ( I don't know much about HiMax )
2 To make weight, look for big ticket items than looking at small savings here and there. Not that small savings do not matter, they do. But monitoring the big things will yield huge savings. Or rather, try not to make weight altering mistakes in major components.
To cite an example : I used domestic birch 1.5 mm ply in my spar webs. Big mistake, because that added straight 1.25 lbs to my build. Use only Finnish birch, which though is also 1.5 mm, is a tad thinner and also much lighter. Spar web is a big item as there are 4 long pieces. Mistakes made in big items are difficult to make up with small savings like using thinner gussets etc.
Use 1.0 mm ply for the wing's leading edge wrap (especially for 103 version which has the least wing loading).
3. Go for the low hanging fruit first, if you want big, easy savings.
3a Paint is the lowest one. My paint job came out about 8.5 lbs. Add about 7.5 lbs for fabric plus cement. That makes it about 15 to 16 lbs for fabric + paint. A good paint job plus fabric weight can easily be north of 30 lbs.
When I did the empennage, I measured weight on each item before covering , after covering and after each coat of of filler or paint. Then I extrapolated the weight addition on one component ( say elevator ) and multiplied that weight addition to the total painted area, and that is how I got the figure of 8.5 lbs for Ekofill plus paint. I agree more paint adds more UV protection, so I am prepared to re-cover after 6 or 7 years. But to some extent, using a dedicated UV barrier like Ekofill off-sets reduction in longevity caused by using less coats of paint. Paint also has UV barriers, but I suspect they may not be as effective as a dedicated and purpose-made UV barrier.
3b I did not cover the fuselage box with fabric. Another saving of about 30 sq ft of fabric plus some cement.
4. Customization is another major grief-aggravator when it comes to weight addition. The more you customize your plane , the more convenient and comfortable it becomes for your dedicated use, but it also comes with more weight penalty. Those who stick to plans have the upper hand in keeping weight low. The plans look spartan for a reason. The more basic and bare bones you make your plane, the more you will be rewarded with better performance for the same engine you have chosen. Keeping it FAA-legal is just an added bonus ( though practically I know it is perceived the other way around ).
This is a comprehensive topic and I just wrote what came to my mind. I am sure others who know better will chip in. |
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