This is the first time I have posted anything on this forum, but after reading all the various threads on Plank design I thought that my project might also be of interest.
I have always liked the simplicity of the Plank aircraft with its promise of good performance. This goes back many years, when back in the 1970’s Al Backstrom wrote several articles in Sport Aviation giving all the important parameters for a successful design. Being professionally an aircraft structures man and only an amateur aerodynamicist, I have designed my plank following his guidelines, while also taking into consideration the many words of wisdom gleaned from Home Built Airplanes.com.
A few years ago the UK CAA allowed what was called a single seat de-regulated (SSDR) class of aircraft. The requirements are similar to FAR103 with a max empty weight of 115 Kg 252 Lb. I attempted to design an enclosed convention aircraft to meet this requirement using simple construction suitable for the average home builder but they were all too close to the weight allowance. The Plank offered the best option including the added bonus of the intellectual challenge involved.
The aerofoil is Fauvel 14%, chosen because of its similarity to the Abrial used by AB. It is highly reflexed with a good +Cm putting the CG location at 20% C which agrees with AB. The Cl does suffer but with the low wing loading I think should be satisfactory.
The elevons are 27% C within the limits specified by AB. I read Norman’s last article suggesting 17% C to be the optimum length to alter the angle of attack of the wing with minimum loss of lift. It makes much sense. Unfortunately the wings have been built. I was aware that the flare out would need care and I would appreciate a briefing on the best techniques from anyone who has flown a Plank. I am hoping the mid wing and broad chord will provide a good ground cushion effect, with not much pilot input needed during landing. Similar to the MW8
The wing chord has been increased by 12 inches compared to the WBP1, this is to meet the wing loading requirements and also provide more pitch damping. I have fitted large fixed tabs to the elevons to relieve the stick loads caused by the reflex at higher speeds. Al Cleve did this in his Plank glider. I also notice that Jim Marske had them on his early glider
The propeller thrust line is angled to be within 10% C of the vertical CG as recommended by AB.
It is proposed to make the nose leg height adjustable to find the best take off angle for the wing during hop tests. It is hoped to retract the nose wheel later for more speed.
If the aircraft looks Cri Cri around the front, that is because I propose to fit a Cri Cri canopy.
I would appreciate any helpful comments, although the wing is built and difficult to change now. I hope to try hopping the basic aircraft later this year.
--------------
In answer to the encouraging replies so far.
I haven't calculated the drag curve for the aircraft because in my experience it is a lot of work with usually a doubtful result. I prefer to do a comparison with similar designs. However I have fed the parameters of my Plank and AL Backstrom's aircraft into the LAA quick performance calculator which shows good correlation with the figures in AB's articles. Assuming my aircraft is similar in drag to the WPB-1 and with the Koenig 430 engine rated at 24 BHP, the calculator indicates a cruise around 80 MPH which I will be well pleased with. Al used a Kiekhaefer 440 engine running at 5400 RPM max. The power curves for the similar Rotax 477 show 30 BHP at this RPM. AB reports a max speed of 95 Kts (105 MPH) which agrees with the LAA calculator. It is worth noting that the WPB-1 is some 100 Lbs heavier than my Plank with less wing area.
-------------
|
MW Plank |
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|
ESTIMATED PERFORMANCE WITH AN ENGINE OF YOUR PROPOSED RATED POWER |
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|
Selected rated shaft power |
24.0 |
BHP |
||||||
|
Effective flat plate area |
3.44 |
ft² |
||||||
|
Take off run |
294 |
feet |
||||||
|
Rate of climb at 1.3 Vs |
881 |
feet per minute |
||||||
|
Max level speed |
93 |
mph |
||||||
|
Cruise speed at 75% power |
85 |
mph |
||||||
|
Flaps up stall speed |
36 |
mph |
||||||
|
Glide descent rate at 1.3 Vs |
396 |
feet per minute |
||||||
|
WPB-1 |
||||||||
|
ESTIMATED PERFORMANCE WITH AN ENGINE OF YOUR PROPOSED RATED POWER |
||||||||
|
Selected rated shaft power |
30.0 |
BHP |
||||||
|
Effective flat plate area |
2.50 |
ft² |
||||||
|
Take off run |
544 |
feet |
||||||
|
Rate of climb at 1.3 Vs |
732 |
feet per minute |
||||||
|
Max level speed |
111 |
mph |
||||||
|
Cruise speed at 75% power |
101 |
mph |
||||||
|
Flaps up stall speed |
48 |
mph |
||||||
|
Glide descent rate at 1.3 Vs |
495 |
feet per minute |
||||||
The WPB-1 take off speed is given as 50-55 MPH. taking Vs 48 x 1.1= 53 MPH again shows good agreement with the calculator
The fuel tank initially will be a plastic bottle in the fuselage. The first three wing ribs have a 6 inch dia lightening hole forward of the spar. If the aircraft proves worthy of full development, the plan is to insert two 15 Litre tubular tanks into the wing with a 5 litre bottle header tank in the fuselage.
I attach another photo showing the wing centre join tube which will be bolted across the fuselage. The wing spar tubes slot into an eccentric FG bush on the centre of the fuselage tube and are pinned near the wing root.
The wing spar is reinforced internally with another split tube as required, with the ply ribs attached by a fillet of Chopped strand mat and polyester resin. I tested these joints until the rib disintegrated without failure of the joint. Because the spar is built in all round at the join tube it does not need a drag brace on this aircraft. The diagonal tube is there to provide a root fitting but also provides some redundancy at the wing spar joints. Ie the ribs are supported at two points and if one joint is iffy the rib load will be supported by the two adjacent ribs.
---------------
The performance calculator is available on line. Go to LAA Home. Aircraft & Technical. Designing Aircraft. Preliminary Design. Performance Estimate. Unfortunately it askes for the drag coefficients. For the Plank I entered the values shown in the worked example which seemed to be about right for the WBP-1. I then used them for my Plank assuming similarity. It would be useful if they produced a graph of Cd values for various aircraft from a Cassutt to a Microlight with a selection in between, then you could select the nearest to your aircraft and obtain a rough performance estimate. Probably as good if not better than trying to calculate it.
---------------
The performance calculator is available on line. Go to LAA Home. Aircraft & Technical. Designing Aircraft. Preliminary Design. Performance Estimate. Unfortunately it askes for the drag coefficients. For the Plank I entered the values shown in the worked example which seemed to be about right for the WBP-1. I then used them for my Plank assuming similarity. It would be useful if they produced a graph of Cd values for various aircraft from a Cassutt to a Microlight with a selection in between, then you could select the nearest to your aircraft and obtain a rough performance estimate. Probably as good if not better than trying to calculate it.
Here is the page Mike refers to: Welcome to the Light Aircraft Association
Below find a quote from Neal Willford's Performance Estimate Spreadsheet. The estimated drag areas may prove useful.
Other useful spreadsheets by Neal are found here: Software & Design
|
Approximate aircraft drag area estimates |
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|
Drag area is estimated from published performance figures from a wide variety of sources, so accuracy cannot be verified |
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|
For all aircraft propeller efficiency and 'e' are assumed to be equal to .75 |
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|
Values are given to provide a qualitative feel for drag area only |
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|
Aircraft |
Gross Weight (lbs) |
Empty Weight (lbs) |
Useful Load (lbs) |
Max Rated Horsepower |
Wing Area (sq. ft.) |
Wing Span (ft) |
Max Speed (mph) |
Drag Area (sq. ft.) |
Wing Loading (lbs/sq ft) |
Power Loading (lbs/bhp) |
Span loading (lbs/ft) |
Weight/span^2 (lbs/sq ft) |
|
Quickie |
480 |
240 |
240 |
20 |
53.0 |
16.7 |
126 |
0.9 |
9.1 |
24.0 |
28.8 |
1.73 |
|
American Eagle |
360 |
150 |
210 |
12 |
72.0 |
36.0 |
110 |
1.0 |
5.0 |
30.0 |
10.0 |
0.28 |
|
KR-1 |
750 |
375 |
375 |
35 |
62.0 |
17.0 |
141 |
1.1 |
12.1 |
21.4 |
44.1 |
2.60 |
|
Cri-Cri |
375 |
159 |
216 |
24 |
33.4 |
15.8 |
124 |
1.2 |
11.2 |
15.6 |
23.8 |
1.51 |
|
Moni |
500 |
260 |
240 |
22 |
75.0 |
27.5 |
120 |
1.3 |
6.7 |
22.7 |
18.2 |
0.66 |
|
Vari-Eze |
875 |
458 |
417 |
65 |
53.6 |
22.3 |
162 |
1.6 |
16.3 |
13.5 |
39.2 |
1.75 |
|
DWJA |
650 |
380 |
270 |
40 |
77.0 |
24.0 |
135 |
1.7 |
8.4 |
16.3 |
27.1 |
1.13 |
|
Van's RV-3 |
1100 |
750 |
350 |
125 |
90.0 |
19.9 |
195 |
1.7 |
12.2 |
8.8 |
55.3 |
2.78 |
|
KR-2 |
800 |
420 |
380 |
65 |
78.0 |
20.7 |
150 |
1.9 |
10.3 |
12.3 |
38.7 |
1.87 |
|
Wittman Tailwind |
1425 |
863 |
562 |
160 |
86.0 |
23.0 |
217 |
2.0 |
16.6 |
8.9 |
62.0 |
2.69 |
|
Mooney Mite |
700 |
460 |
240 |
25 |
95.1 |
26.9 |
105 |
2.1 |
7.4 |
28.0 |
26.0 |
0.97 |
|
Sonerai II LTS |
1150 |
540 |
610 |
76 |
84.0 |
20.3 |
150 |
2.1 |
13.7 |
15.1 |
56.6 |
2.78 |
|
DWJ |
640 |
398 |
242 |
32 |
77.0 |
24.0 |
112 |
2.2 |
8.3 |
20.0 |
26.7 |
1.11 |
|
Thorp T-18 |
1600 |
1030 |
570 |
180 |
86.0 |
20.8 |
203 |
2.3 |
18.6 |
8.9 |
76.8 |
3.69 |
|
Van's RV-6 |
1650 |
1080 |
570 |
160 |
110.0 |
23.0 |
202 |
2.3 |
15.0 |
10.3 |
71.7 |
3.12 |
|
Sonex |
1100 |
570 |
530 |
80 |
98.0 |
22.0 |
150 |
2.3 |
11.2 |
13.8 |
50.0 |
2.27 |
|
Cougar |
1400 |
700 |
700 |
100 |
80.0 |
20.2 |
155 |
2.5 |
17.5 |
14.0 |
69.3 |
3.43 |
|
Jodel D9 |
595 |
353 |
242 |
25 |
97.0 |
19.2 |
94 |
2.6 |
6.1 |
23.8 |
31.0 |
1.62 |
|
Culver Cadet |
1305 |
750 |
555 |
75 |
120.0 |
27.0 |
140 |
2.7 |
10.9 |
17.4 |
48.3 |
1.79 |
|
Avions Roitelet |
462 |
231 |
231 |
25 |
65.6 |
22.9 |
96 |
2.8 |
7.0 |
18.5 |
20.2 |
0.88 |
|
Sorrell Guppy |
575 |
330 |
245 |
18 |
129.0 |
21.3 |
80 |
2.9 |
4.5 |
31.9 |
27.1 |
1.27 |
|
Prest Baby Pursuit |
700 |
450 |
250 |
45 |
83.0 |
22.6 |
115 |
2.9 |
8.4 |
15.6 |
31.0 |
1.37 |
|
Scorpion |
670 |
350 |
320 |
35 |
90.0 |
24.0 |
105 |
3.0 |
7.4 |
19.1 |
27.9 |
1.16 |
|
ABC Robin |
680 |
415 |
265 |
35 |
97.0 |
25.3 |
105 |
3.0 |
7.0 |
19.4 |
26.9 |
1.06 |
|
Jodel Bebe |
598 |
356 |
242 |
26 |
96.8 |
22.9 |
93 |
3.0 |
6.2 |
23.0 |
26.1 |
1.14 |
|
Eklund TE-18 |
695 |
420 |
275 |
37 |
60.0 |
24.6 |
103 |
3.3 |
11.6 |
18.8 |
28.3 |
1.15 |
|
Cessna Airmaster |
2250 |
935 |
1315 |
145 |
182.0 |
34.2 |
162 |
3.4 |
12.4 |
15.5 |
65.8 |
1.92 |
|
Rose Parrakeet |
675 |
410 |
265 |
37 |
116.0 |
20.0 |
100 |
3.4 |
5.8 |
18.2 |
33.8 |
1.69 |
|
Druine Turbulent |
572 |
341 |
231 |
26 |
80.7 |
22.5 |
87 |
3.7 |
7.1 |
22.0 |
25.4 |
1.13 |
|
Ryan STA |
1600 |
1035 |
565 |
125 |
124.0 |
30.0 |
150 |
3.7 |
12.9 |
12.8 |
53.3 |
1.78 |
|
Luscombe |
1200 |
720 |
480 |
65 |
140.0 |
35.0 |
120 |
3.8 |
8.6 |
18.5 |
34.3 |
0.98 |
|
Thorp T-211 |
1250 |
720 |
530 |
90 |
104.0 |
25.0 |
132 |
3.8 |
12.0 |
13.9 |
50.0 |
2.00 |
|
Irwon Meteorplane |
475 |
275 |
200 |
25 |
105.0 |
20.0 |
85 |
3.9 |
4.5 |
19.0 |
23.8 |
1.19 |
|
FL600 |
748 |
458 |
290 |
20 |
147.6 |
35.1 |
78 |
3.9 |
5.1 |
37.4 |
21.3 |
0.61 |
|
Ercoupe |
1175 |
716 |
459 |
65 |
142.6 |
30.0 |
117 |
4.0 |
8.2 |
18.1 |
39.2 |
1.31 |
|
Little Dipper |
700 |
425 |
275 |
53 |
105.0 |
25.0 |
110 |
4.1 |
6.7 |
13.2 |
28.0 |
1.12 |
|
Davis DA-2A |
1150 |
620 |
530 |
65 |
82.5 |
19.2 |
110 |
4.1 |
13.9 |
17.7 |
59.9 |
3.12 |
|
Piel Pinocchio |
595 |
390 |
205 |
26 |
97.0 |
23.9 |
84 |
4.1 |
6.1 |
22.9 |
24.9 |
1.04 |
|
Wittman Buttercup |
1290 |
817 |
473 |
100 |
132.0 |
29.5 |
135 |
4.1 |
9.8 |
12.9 |
43.7 |
1.48 |
|
EAA biplane |
1023 |
640 |
383 |
85 |
120.0 |
20.0 |
125 |
4.2 |
8.5 |
12.0 |
51.2 |
2.56 |
|
Dart Kitten |
742 |
500 |
242 |
36 |
129.0 |
31.8 |
95 |
4.2 |
5.8 |
20.6 |
23.3 |
0.73 |
|
Scorpion II |
750 |
450 |
300 |
35 |
108.0 |
25.8 |
91 |
4.4 |
6.9 |
21.4 |
29.1 |
1.13 |
|
Lincoln Sport |
600 |
370 |
230 |
35 |
108.0 |
20.0 |
90 |
4.5 |
5.6 |
17.1 |
30.0 |
1.50 |
|
Dormoy Bathtub |
425 |
235 |
190 |
20 |
85.0 |
24.0 |
75 |
4.6 |
5.0 |
21.3 |
17.7 |
0.74 |
|
Powell Racer |
475 |
310 |
165 |
32 |
76.0 |
15.8 |
85 |
4.8 |
6.3 |
14.8 |
30.1 |
1.90 |
|
Baby Ace |
950 |
575 |
375 |
65 |
112.3 |
26.5 |
110 |
4.9 |
8.5 |
14.6 |
35.8 |
1.35 |
|
Aeronca C-3 Master |
1006 |
569 |
437 |
40 |
142.2 |
36.0 |
93 |
4.9 |
7.1 |
25.2 |
27.9 |
0.78 |
|
Cessna 120/140 |
1450 |
890 |
560 |
85 |
159.3 |
32.9 |
120 |
4.9 |
9.1 |
17.1 |
44.1 |
1.34 |
|
DH Hummingbird |
500 |
310 |
190 |
22 |
120.0 |
30.1 |
76 |
5.0 |
4.2 |
22.7 |
16.6 |
0.55 |
|
Cessna 150 |
1600 |
1129 |
471 |
100 |
160.0 |
33.3 |
125 |
5.0 |
10.0 |
16.0 |
48.0 |
1.44 |
|
HM14 Flea |
485 |
275 |
210 |
20 |
140.0 |
19.7 |
70 |
5.0 |
3.5 |
24.3 |
24.6 |
1.25 |
|
Porterfield |
1160 |
675 |
485 |
65 |
168.8 |
34.8 |
109 |
5.1 |
6.9 |
17.8 |
33.4 |
0.96 |
|
Wee Bee |
410 |
210 |
200 |
30 |
44.0 |
18.0 |
83 |
5.1 |
9.3 |
13.7 |
22.8 |
1.27 |
|
AG-14 |
1400 |
850 |
550 |
90 |
121.7 |
34.6 |
120 |
5.3 |
11.5 |
15.6 |
40.5 |
1.17 |
|
Ryan SCW |
2150 |
1395 |
755 |
145 |
202.1 |
37.5 |
140 |
5.3 |
10.6 |
14.8 |
57.3 |
1.53 |
|
Acro Sport |
1350 |
733 |
617 |
180 |
116.0 |
19.6 |
150 |
5.3 |
11.6 |
7.5 |
68.9 |
3.51 |
|
Loughead S-1 |
640 |
375 |
265 |
24 |
195.0 |
28.0 |
75 |
5.3 |
3.3 |
26.7 |
22.9 |
0.82 |
|
Interstate Cadet |
1200 |
700 |
500 |
65 |
173.8 |
35.5 |
107 |
5.3 |
6.9 |
18.5 |
33.8 |
0.95 |
|
Starduster II |
1704 |
1000 |
704 |
180 |
165.0 |
24.0 |
148 |
5.5 |
10.3 |
9.5 |
71.0 |
2.96 |
|
Taylorcraft |
1200 |
700 |
500 |
65 |
169.0 |
36.0 |
105 |
5.6 |
7.1 |
18.5 |
33.3 |
0.93 |
|
Sayers HP-22 |
430 |
250 |
180 |
10 |
157.0 |
36.0 |
55 |
5.7 |
2.7 |
43.0 |
11.9 |
0.33 |
|
Fly Baby |
925 |
605 |
320 |
85 |
120.0 |
28.0 |
115 |
5.8 |
7.7 |
10.9 |
33.0 |
1.18 |
|
VP-1 |
650 |
450 |
200 |
50 |
100.0 |
24.0 |
95 |
5.9 |
6.5 |
13.0 |
27.1 |
1.13 |
|
Rearwin Junior |
999 |
569 |
430 |
45 |
179.5 |
36.0 |
91 |
5.9 |
5.6 |
22.2 |
27.8 |
0.77 |
|
Aeronca C-2 |
672 |
308 |
364 |
30 |
142.2 |
36.0 |
80 |
5.9 |
4.7 |
22.4 |
18.7 |
0.52 |
|
Heath LN4 parasol |
700 |
450 |
250 |
25 |
135.5 |
31.2 |
73 |
6.1 |
5.2 |
28.0 |
22.4 |
0.72 |
|
Pietenpol |
1200 |
622 |
578 |
65 |
145.0 |
29.0 |
100 |
6.2 |
8.3 |
18.5 |
41.4 |
1.43 |
|
VP-2 |
1040 |
640 |
400 |
65 |
130.0 |
27.0 |
100 |
6.3 |
8.0 |
16.0 |
38.5 |
1.43 |
|
Aeronca Champ |
1220 |
710 |
510 |
65 |
169.0 |
36.0 |
100 |
6.5 |
7.2 |
18.8 |
33.9 |
0.94 |
|
Pober Pixie |
900 |
527 |
373 |
65 |
135.0 |
30.2 |
100 |
6.6 |
6.7 |
13.8 |
29.8 |
0.99 |
|
Wren |
420 |
232 |
188 |
10 |
150.0 |
37.0 |
52 |
6.8 |
2.8 |
42.0 |
11.4 |
0.31 |
|
Taylor E-2 Cub |
925 |
525 |
400 |
37 |
184.0 |
35.2 |
80 |
7.0 |
5.0 |
25.0 |
26.3 |
0.75 |
|
Aeronca C-3 |
877 |
466 |
411 |
40 |
142.2 |
36.0 |
82 |
7.2 |
6.2 |
21.9 |
24.4 |
0.68 |
|
Piper PA-12 |
1750 |
950 |
800 |
100 |
178.5 |
35.5 |
110 |
7.3 |
9.8 |
17.5 |
49.3 |
1.39 |
|
Se5A |
1935 |
1410 |
525 |
200 |
244.0 |
26.6 |
138 |
7.5 |
7.9 |
9.7 |
72.7 |
2.73 |
|
Woody's Pusher |
1150 |
630 |
520 |
75 |
130.5 |
29.0 |
98 |
7.8 |
8.8 |
15.3 |
39.7 |
1.37 |
|
Flaglor Scooter |
625 |
390 |
235 |
40 |
115.0 |
28.0 |
80 |
7.9 |
5.4 |
15.6 |
22.3 |
0.80 |
|
Aeronca K |
1040 |
590 |
450 |
40 |
146.4 |
36.0 |
78 |
8.0 |
7.1 |
26.0 |
28.9 |
0.80 |
|
Anderson Kingfisher |
1600 |
1092 |
508 |
115 |
185.0 |
37.1 |
113 |
8.1 |
8.6 |
13.9 |
43.1 |
1.16 |
|
Aerosport Rail |
730 |
446 |
284 |
60 |
81.5 |
23.3 |
90 |
8.2 |
9.0 |
12.2 |
31.3 |
1.34 |
|
BAC Drone |
640 |
390 |
250 |
31 |
172.0 |
39.7 |
73 |
8.2 |
3.7 |
20.6 |
16.1 |
0.41 |
|
AV Roe 560 |
470 |
285 |
185 |
22 |
138.0 |
36.0 |
65 |
8.3 |
3.4 |
21.4 |
13.1 |
0.36 |
|
Sopwith Pup |
1225 |
856 |
369 |
100 |
254.0 |
26.5 |
106 |
8.3 |
4.8 |
12.3 |
46.2 |
1.74 |
|
Praga B |
660 |
440 |
220 |
41.7 |
142.0 |
22.0 |
78 |
8.3 |
4.6 |
15.8 |
30.0 |
1.36 |
|
Piper J-4 |
1400 |
880 |
520 |
75 |
183.0 |
36.2 |
96 |
8.3 |
7.7 |
18.7 |
38.7 |
1.07 |
|
Sopwith Camel |
1455 |
930 |
525 |
130 |
231.0 |
26.9 |
115 |
8.4 |
6.3 |
11.2 |
54.1 |
2.01 |
|
Fokker Dr1 |
1295 |
895 |
400 |
110 |
200.9 |
23.6 |
105 |
9.0 |
6.4 |
11.8 |
54.9 |
2.33 |
|
SE5A replica |
1150 |
690 |
460 |
85 |
146.0 |
23.3 |
95 |
9.2 |
7.9 |
13.5 |
49.3 |
2.11 |
|
Wing Ding II |
310 |
120 |
190 |
12 |
97.0 |
16.0 |
46 |
9.4 |
3.2 |
25.8 |
19.4 |
1.21 |
|
PDQ-2 VW |
600 |
350 |
250 |
50 |
77.0 |
20.5 |
80 |
9.5 |
7.8 |
12.0 |
29.3 |
1.43 |
|
Volmer Sportsman |
1500 |
1000 |
500 |
85 |
185.0 |
36.5 |
95 |
9.7 |
8.1 |
17.6 |
41.1 |
1.13 |
|
Birdman |
310 |
120 |
190 |
12 |
136.0 |
34.0 |
50 |
9.8 |
2.3 |
25.8 |
9.1 |
0.27 |
|
Piper J-3 |
1100 |
680 |
420 |
65 |
178.5 |
35.2 |
87 |
9.9 |
6.2 |
16.9 |
31.3 |
0.89 |
|
Stits Skeeto |
465 |
265 |
200 |
18 |
150.0 |
30.0 |
55 |
10.4 |
3.1 |
25.8 |
15.5 |
0.52 |
|
PDQ-2 JLO |
430 |
230 |
200 |
36 |
77.0 |
20.5 |
70 |
10.5 |
5.6 |
11.9 |
21.0 |
1.02 |
|
Curtiss CW-1 Junior |
975 |
555 |
420 |
45 |
176.0 |
39.5 |
75 |
10.6 |
5.5 |
21.7 |
24.7 |
0.62 |
|
Fokker DVII |
1874 |
1540 |
334 |
165 |
217.4 |
29.3 |
114 |
10.8 |
8.6 |
11.4 |
64.1 |
2.19 |
|
Spirit of St Louis |
5135 |
2150 |
2985 |
223 |
319.0 |
46.0 |
120 |
11.0 |
16.1 |
23.0 |
111.6 |
2.43 |
|
Kolb Firestar |
650 |
325 |
325 |
40 |
140.0 |
27.7 |
70 |
11.5 |
4.6 |
16.3 |
23.5 |
0.85 |
|
Republic Seabee |
3150 |
2100 |
1050 |
215 |
196.0 |
37.7 |
120 |
11.8 |
16.1 |
14.7 |
83.6 |
2.22 |
|
ACE |
600 |
375 |
225 |
40 |
215.0 |
28.3 |
65 |
14.6 |
2.8 |
15.0 |
21.2 |
0.75 |
|
Bleriot XI |
600 |
25 |
150.0 |
25.6 |
50 |
15.8 |
4.0 |
24.0 |
23.4 |
0.92 |
||
|
Quicksilver Sport |
525 |
254 |
271 |
40 |
156.0 |
28.0 |
59 |
19.7 |
3.4 |
13.1 |
18.8 |
0.67 |
|
Curtiss JN-4D |
1920 |
1430 |
490 |
90 |
352.3 |
43.6 |
75 |
20.0 |
5.5 |
21.3 |
44.0 |
1.01 |
|
Quicksilver Sprint |
525 |
254 |
271 |
40 |
156.0 |
28.0 |
54 |
25.5 |
3.4 |
13.1 |
18.8 |
0.67 |
|
Curtiss |
735 |
735 |
30 |
272.0 |
32.0 |
45 |
26.8 |
2.7 |
24.5 |
23.0 |
0.72 |
|
|
Wright Flyer |
745 |
605 |
140 |
12 |
510.0 |
40.3 |
29 |
28.9 |
1.5 |
62.1 |
18.5 |
0.46 |
|
Farman |
990 |
50 |
432.0 |
32.8 |
50 |
33.1 |
2.3 |
19.8 |
30.2 |
0.92 |
||
|
Antoinette IV |
1146 |
50 |
430.0 |
41.0 |
46 |
43.1 |
2.7 |
22.9 |
28.0 |
0.68 |
||
|
Antoinette XI |
1058 |
50 |
300.0 |
40.0 |
46 |
44.0 |
3.5 |
21.2 |
26.5 |
0.66 |
Norman geeft volgende link http://www.homebuiltairplanes.com/forums/general-experimental-aviation-questions/8762-aircraft-efficiency-tool-list-equivalent-flat-plate-areas-various-planes.html
This is what I was looking for. I have checked the figures for the Cri Cri :-
Cd0 = DA/S = 1.2/33.4 = 0.036
Feeding into the LAA performance calculator gives answers which compare very favorably with those shown in Jane's All The World's Aircraft at 30 BHP
|
Selected rated shaft power |
30.0 |
BHP |
|||
|
Effective flat plate area |
1.26 |
ft² |
|||
|
Take off run |
527 |
feet |
|||
|
Rate of climb at 1.3 Vs |
1399 |
feet per minute |
|||
|
Max level speed |
137 |
mph |
|||
|
Cruise speed at 75% power |
125 |
mph |
|||
|
Flaps up stall speed |
60 |
mph |
|||
|
Glide descent rate at 1.3 Vs |
586 |
feet per minute |
|||
|
|
----------------------------
Topaz comments:
"Planks" have their problems (and, believe me, I've investigated in-depth), but an inherent lack of static stability (stick free or fixed) isn't one of them.
LINKS NAAR FLYING PLANK ARTIKELS
The links below will likely be of interest to those reading this thread.
------------------------------
Following on from post 126. After a year of building, the project is beginning to look more like an aircraft. The fuselage and wing are basically complete, with the fins and rudders the only major item left to build, plus of course many details. However it is hoped to do hopping trials early next year. If satisfactory the top decking and engine cowling's will then constructed to finish the aircraft.
After looking at a metal fuselage with a mass of brackets and fittings, also wood where the thin ply would likely deform between frames, I decided to build a composite design using 1 inch thick polyurethane foam and polyester resin with carbon fibre and Kevlar reinforcings. From design experience with pilot-less aircraft at BAe, I found there to be considerable strength scatter on test specimens produced under non controlled conditions. Therefore very conservative stress allowables have been used. Even so, although the wing spar has already been load tested to 4.0 g, the complete airframe will also be proof loaded before going to any altitude.
The composite design results in more pleasing lines with rounded corners which are also better aerodynamically, whereas with sharp edges, as with aluminium construction the flow could separate creating more drag.
I have used a control mixer as shown previously on this site, incorporating push rods attached to the stick at 45 deg. It works well.
A friend and MW6 pilot Andy Lewis has built a 1/4 scale radio controlled model of the aircraft to give some confidence in the design and look for problem areas. This has now flown and aggressively aero batted, including inverted flight and appears to be complete vice less. Although not dynamically scaled, a quick check on the easier to work out parameters has show it to be very close. Only one curious thing happens. During level flight with full up elevator (12.5 deg) no stall occurs, but the aircraft wallows laterally dropping one wing then the other about 10 deg with a period of two seconds. I haven't found any explanation in Tailless Aircraft in Theory and Practice. Does anyone have any ideas? It doesn't look dangerous but will be something to watch out for.
Andy's video can be found on YouTube http://youtu.be/YyJl2X5yV-w Or type in MW10 First Flight
------------------------------------
Performance information is shown in this thread No 130. This is calculated from the LAA performance calculator and assuming the drag is similar to Al Backstroms Plank WBP-1.
From this the L/D ratio is 10.5. I don't know what it is on the model but would guess it is similar, allowing for scaling, Re number, etc.
Thanks Nickec. Will do my best.
The fins are removable and so could be modified if necessary. The front attachment will be capable of adjustment so that the fins could be toed in to improve the directional stability if needed.
The construction is too far advanced to consider diffuser tips and horizontal drag rudders. I have a feeling in my water that a straight wing without vertical surfaces just relying on horizontal drag rudders could be hard work. I notice that in most pictures of the B2 bomber, that the dragerons seem to be deployed and this is a self stabilising in yaw swept wing.
The model was flying with a CG location at 22%. Al Backstrom's aft limit. The ideal 20% location should improve stability. Location confirmed by slight down trim required on the model at 22%. The wallow at full up elevator is not shown on the video, but isn't that severe, however it is something to be aware of during stall tests.
Personally I think the late Al Backstrom had all the best answers in his EPB-1.
Mike
---------------------------------
The oscillation referred to in the previous update when flying slowly with full up elevator, was diagnosed as Dutch roll. Normally caused by too much dihedral and low fin area. Not having a wind tunnel or the necessary expertise in this area to work out a solution. The only way open was to copy a similar successful design.
The tip mounted fins were obviously increasing the effective dihedral and needed to be lowered as much as possible. I looked at the Backstrom plank, being the nearest to my aircraft and calculated the vertical tail coefficient Vv, which was 0.021. The MW10 with original fins was 0.0172. Extra area was added to the aft of the fin and the assembly was lowered to give some under fin similar to the WPB-1 to reduce the dihedral effect. Vv is now 0.021 and has cured the problem.
Out of interest as best I could measure them, I looked at several other plank aircraft.
Opel Vv 0.015
Marske Monarch Vv 0,011
Pelican Vv 0.017
This suggests that with inboard fins a smaller vertical tail volume is possible.
For conventional aircraft I use a Vv of around 0.03 which seems to work satisfactorily.
I have had a major setback with the konig engine. Upon internal examination the engine was a mess looking as if something has gone through it, probably a bearing retention strap. Barrels pistons and the rotating inlet port all deeply scored. I have borrowed a KFM 107 engine which is slightly heavier but would need major modification of the airframe to mount it. Luckily I have now been lent another Konig 430 by the LAA chief engineer, who just managed to buy it before I got there. It is an earlier version and is not compatible with the reduction gear from my engine. It has a 42 inch dia prop, direct drive. However at the moment I intend to use it in order to avoid delays to early flight trials. I would be interested in a low cost late Konig 430 engine if anyone knows of one.
We now have a new video on You Tube showing flight trials with the revised fins. See MW10 Second flight. Full up elevator is applied from location 1.35 to 2.
I am at present making the fins and honeycomb rudders.
Other pictures show a Mini Max type canopy now proposed due to doubts about finding a Cri Cri canopy and load testing the seat with self moving weights. The aircraft is supported off the ground on a tube through the wing attachment stub spar, with a prop at the engine mount putting the fuselage in representative bending. The wing attachment structure is also tested.
--------------------------
In answer to BigBens question re Al Backstroms plank article which shows a higher thrust line is possible on a tractor aircraft. Possibly this could be due to the prop wash hitting the wing reflex and causing a higher nose up pitch, thus requiring more down thrust to counteract it, where as with a pusher this would be much less or none existent. Just a thought.
Mike
---------------------------
All the major airframe components are now made, leaving the many finishing off jobs. Such as Fuel system, brakes, covering and many more. However the end is in sight and hoping for flight trials in the spring. Although my impending hip joint replacement may slow things somewhat.
The original plan was to try the aircraft before building the top decking to see if we had any major problems before going too far. But flight trials with the model, minus the cockpit assembly but fitted with an on board video camera, indicated greater pitch change with power. This was probably due to the lower CG and drag centre, so I decided to build the upper assembly which is now complete.
The direct drive Konig engine propeller thrust line is some five inches higher than my damaged engine when fitted with a belt reduction gear. To correct this I made an adaptor to increase the down thrust in line with Al Backstrom’s guidelines.
The Mini Max canopy skull cap didn’t quite suit the canopy line and so I made my own custom molding.
--------------------------
I have attached a sectioned drawing of the Plank with a dimension scale. Allowing for steering mechanism the forward fuselage is as short as it is possible to make it. I need to use the tip of my toes to apply full lock as on the MW8, this is because my Chief test pilot Eddie Clapham has long legs with his hip joint six inches above mine. He is coming for a trial fit in the New Year, I hope there will be no problems.
The propeller is six inches from the wing trailing edge and just about level with it.
I had a thought that the nose wheel might have a destabilizing effect, so Andy Lewis who built the model flew it with a representative nose wheel assembly, luckily things were satisfactory.
The videos of Dutch roll on You Tube, with the exception of a Russian jet with a defective autopilot, which is really rolling and yawing, don't show genuine Dutch roll, only pilot induced examples. It would be useful if Andy were to make a video of the early Plank which shows the phenomenon to good effect and then show flight with the fin modifications which eliminated the problem.
-------------------------------------
The aircraft was originally designed to the UK SSDR requirements similar to FAR 103 with an empty weight of 105 Kg or 253 Lbs. One of the reasons of going tailless was the difficulties of designing a conventional aircraft within this weight limit, while keeping the structure simple. So lop off the tail. Of course when the design was well advanced in order to keep the Trade happy, the Authorities upped the requirements to an all up weight of 300 Kg. Anyway due to my age this will probably be my last project, so I thought, why not go for something more challenging.
Now that all the major components are made and weighed the total comes to 113 Kg or 249 Lbs. Just about on target.
Mike