KaP2011

My Feedback: (17)

Thanks for that answer Zor.

I understand the answer so I must not understand the question. What hp range do I need to be in to get a 1 to 1 thrust to weight ratio? I realize the prop will have a great deal to do with the ratio but I'm not sure how to get to the answer I'm looking for. I am only high school educated and that was 35 years ago. I'm not sure we went over that in class, if we did I must have been asleep that day.
I know that if I took an engine and rigged it up on a test stand with a scale and got a result of 8lb of thrust, I would have a 1 to 1 thrust to weight ratio on an 8lb airplane. I'm just not sure how to do the math to come to the answer.

Zor

KaP2011,

I do not know how much I can help you with your inquisition.

I understand that you would wish to calculate the horse power needed to produce a specific thrust from the engine-prop combination.

As you indicated the no-math method is to make a static test with a good scale rigged up to measure the thrust. I think that most fliers just go by the general reported usage of others.

To try to figure this by mathematics is not simple nor easy.
Horse power is the ability to do work.
One horse power can lift 550 lbs a distance of one foot in one second.

Some of the difficulties to use calculations for us modelers are ___
1- We do not know precisely and sometime not at all what is the horse power rating of an engine.
2- The engine is turning a propeller to convert the HP into thrust.
3- The thrust will depend on the propeller size (diameter), on the prop pitch (which varies along the radius of the blades), on the prop airfoil (which can also vary along the blades).
4- We do not have manufacurers figures telling us the statcic thrust of their prop versus rpm; we have to do our own tests as mentioned above.
5- We do not knowany specificprop efficiency.

It all seem to boil down to using a recommended engine range (size) for a model and play around with different props.

I think the best you can do is browse around until you develop a feeling for types of models, their weight, the engine installed, the prop used and is it a 3D capable model and to what extend it is (how much thrust it has versus weight).

Watch for other postings coming up by ohers. You may get this general infomation of model, weight, engine and prop and vertical flight performance.

Good luck,

Zor

KaP2011

My Feedback: (17)

Thanks Zor. What you are saying is pretty much what I thought.
I'm not out to fly 3D with my US60 but I do want it to fly vertical until I pull back on the throttle. I don't think a .61 or the .75 is capable of that on an 8lb airplane no matter what prop I put on it. I also don't think the FS .95 would do it either. The .95AX may be capable but I can't go larger than a 14" prop.

I have been told by some of the guys in my club that I'm barking up the wrong tree without a paddle 

Gordie M

Kap,

Trymeasuring the thrust with the plane tetheredto afish scale and engine / prop full throttle, you'd want to see the fish scale reading more than 8lbs (at a quess I'd say about 30% more) to get 1 to 1 thrust.

The95AX is going to give you all the vertical you need for sure. I would see the down sides as prop diameter and torque roll. When you snap the throttle open, I'm picking the plane will want to roll around the engine a bit. My Tower Kaos at just over 5lbs with a 55AX does this, especially on a landing overshoot from a slow air speed / low throttle to instant full throttle, upsets the plane a bit if you bang the throttle in to fast. It's not an issue at higher air speed.

I've also bend my own 3/16 wire gear and lengthened it 1 inch even for the 13 inch props I usewiththe trike gear configuation. The 3/16 diameter is way stronger than the kit 5/32 wire gear.

Cheers,

Gordie.

thom25

Kap,
My US60 with OS-.75AX,APC 14X8, Spring air main gear retracts with 3/16" struts, weighs 8.125#. I can fly straight up until I pull the throttle back! A larger engine may give more power but the prop diameter will be limited by the gear length. A larger engine may also add nose weight that may require tail weight to balance, thus increasing over all weight and reducing thrust to weight ratio. Try the OS .75AX/APC14x8 combo you will like it.
Thom

KaP2011

My Feedback: (17)

Ok, I'm convinced, I'll order the .75AX. I have been worried that the .95AX would make it too nose heavy and prop clearence for a larger engine will be an issue. My landing gear is 5" from the bottom of the wing to the axle which should give me about an inch of clearence with a 14" prop. 

prgonzalez

My US60 has a Tower Hobbies 0.75 engine with 12x6 APC. Last time I checked, it was pulling over 9 lbs of static force (WOT) checked with a fish scale at the tail wheel . With a dry weight of 7.0 lbs even, she goes unlimited vertical at 3/4" throttle. An US60 at 8 lbs would not be a problem either.

Zor

Hello Gordie,

The following is written more for the general reader.
You probably know this already.

The speed of the human being nervous system communication is such that reaction time is typically one half (1/2) second. The fastest ever measured was one quarter (1/4) second.

For that reason it is best to apply the throttle smoothly in about a two second motion so that if unexpecedmodel motion takes place then the pilot is able to react fast enough.
Instannt full throttle is not recommended.

Comparing 3/16" dia wire to 5/32" dia wire, the 3/16 is 1.440 times stronger if made of the same material and heat treated with the same procedure.

Have a great day all.

Zor

JNorton

My Feedback: (2)

Interesting reading about reaction time. http://www.humanbenchmark.com/tests/...time/stats.php
John

Zor

Hi JNorton . . . long time no see you.

There is a reaction time testor on that site.
I had seen this site a long time ago or a similar site which is from where I remembered some values.

Just tried this site from your posting and I averaged between 250 and 300 ms.
Perhaps typical for an old fellow .

Zor

KaP2011

My Feedback: (17)

Haha, fun game. best I could do was 231ms after 10 clicks.

corch

My Feedback: (1)

LOL, 205.3 avg of five clicks...must be all the video games of my youth.

Zor

corch,

Nice to see you in the spirit of being a real modeler again.

Zor

fly2fly

My Feedback: (3)

A couple of months ago the battery came loose in my US1000 and the plane was destroyed. I was so depressed, I didn't fly for a month and almost quit the hobby.

However a couple of weeks ago I was luckey enough to buy another 1000 that I found on this site.I'm gonna stick with the OS 1.08 from the first plane.

I have flown many plane but the Ultra Sport is my favorite. Flys like a pattern ship and lands like a trainer. I'm not a builder but I love thewse planes andwould be honored to join the brotherhood.

The blue one was my first one :-(. The white one is the new one.

scottrc

Both your old one and your new one are mighty nice looking planes fly2fly.

fly2fly

My Feedback: (3)

Thanks, I'm kind of partial to thetwo tone scheme of the blue and white. It reminds me of the classic pattern ships of the 70's. It was beautiful. I couldn't find out who built it but Iwould like to shake his hand. I stillhave the shattered pieces in a big box. Imight try to seeif someone can rebuild it for me. I just can't do it.

The white one with the blue, yellow and red trim was built by Dennis Sarette (hope he doesn't mind) of NH. This guy is a master builder and coverer. To say it looks factory would be an insult.I hate to admit it but this is actually a better plane than the old one. It has wing filets, pull/pull rudder, oversized landing gear, and some other goodies that the other one didnt have. If you buy a plane from this guy, it's going to be top quality. I'll try to post some more photos in my gallery.

Yours are nice also. I would love to have a 40 or 60 in my hangar that Icould fly when I dont feel like lugging out the big guy.

tschuy

My Feedback: (1)

Okay....

You all are forcing me to clear my bench and get back to building my US1000...

Nicely done...

Cheers,

rglgatortail

My Feedback: (7)

Your in Yak13.

1. Ken Isaac - RCKen
2. Mike Buzzeo - Minnflyer
3. Alex7403
4. Dash008
5. AH1G
6. tschuy
7. MILDBILL-RCU
8. Box car
9. Top Gunn
10. SeaJay
11. Crash Campbell
12. SKYHI1
13. ChuckW
14. RhyanO
15. landeck
16. Ilikebipes
17. airbusdrvr
18. Insanemoondoggie
19. daisy shoot
20. prgonzalez
21. BelAirBob
22. hrrcflyer
23. rastus1
24. tony0707
25. *JCB*
26. Redback
27. bigugly
28. MetallicaJunkie
29. Gordie M
30. Jim_Purcha
31. rcsws
32. jeffsend
33. fireman7875
34. 72
35. ser00
36. Oly
37. cpeisher
38. donzhere
39. SKYHI1
40. kbarko
41. pgilbert
42. rambler53
43. rcjets_63
44. dschroeder
45. Quikturn
46. blueapplepaste
47. green river rc
48. SushiSeeker
49. VCScott
50. FallDownGoBoom
51. ccp10
52. Deadeye
53. Eganwp
54. carlosponti
55. Navy18
56. MineBurg
57. Cdallas2
58. loopyrc
59. Sled
60. Bernard
61. jrbmoto
62. Bubba153
63. Alfredbmor
64. FentonFlyer
65. Sneakywrist
66. BLW
67. smkrcflyer
68. gabarber
69. Amishwarlord
70. JPMacG
71. kamakazie frank
72. RussianFlyer
73. RoyR
74. Red Jeepster
75. Fallingleaf
76. Yukonflier
77. rcjim000
78. goonybird1
79. rglgatortail
80. Latebreaker
81. Tango juliet
82. Saito18
83. hafidy
84. RR24
85. mechdrew
86. siko_flyer
87. Kit
88. n7188u
89. gerryndennis
90. JNorton
91. misterv
92. Mustangman40
93. OntAeronut
94. proptop
95. scottrc
96. scirocco14
97. pt19 flyer
98. Doug47
99. b.bixel
100! bikerbc
101. weezle
102. Mtthwacrss
103. matadco
104. rickbrad
105. GaryHarris
106. Roary m
107. P47Tbolt
108. jp boud
109. arrdee
110. KaP2011
111. HFrank
112. custombuiltrc
113. jquid
114. dasquirrelisme
115. KC10Chief
116. _Tommy D
117. Do328jet
118. sirzepp
119. mrshea
120. AJsToyz
121. svenska3
122. I FLY
123. turnscrew
124. SteveW
125. Super08
126. ma_mulcahy
127. digital_trucker
128. ARTP47
129. us020140
130. Profiled
131. kgibson4
132. r/coldie
133. Tubthumper
134. JH313
135. TWIN FLYER
136. Fliegerboy
137. Doug Robinson
138. thom25
139. Yak13

richwill11

OK guys, I wana be in too! I guess I would be #140. I own a US40 that I built and flew a lot back in the early 90's. What a great flying plane. But back then I also purchased a 1000, ST2500, and acquired OS108. I've just decided to finally build the 1000. But from what I've read, the engines I have may be a little small. So I've been looking at an OS160FX. It's the same weight as the ST2500 and puts out 1hp more. So please tell me what you guys think. I wanna do the right engine and retracts too. Happy I found your group. Rich

72

Rich, I'm planning a 1000 with the OS160 too. Don't know about the retracts or not yet but I think the OS will be a great engine for this.

richwill11

That's great! Maybe we can keep in touch to compare notes. I'm planning to take my time and start my build either before or after xmas. Don't know about retracts either other than they'd be nice, but may also cost more that I wanna spend. Rich

72

I'm thinking maybe a fuselage mounted carbon fiber gear taildragger.

richwill11

yeah mine will be a tail dragger also.

Twin_Flyer

My Feedback: (4)

72, is the two or four cycle OS 160?

I was thinking of going to a 160 twin, but not in the mood the cut and redo the front so maybe a Saito 150 or YS 140 instead.

I'd still like gas (DLE 30?) but havent found any real feedback from anyone who has done that plus not sure if I have enough prop clearence with the exisiting gear.

Bill S.

72

I have an OS 160fx 2 stroke. I also have a dle 20 and 30 but I think the gas engines will require too much of the nose to be cut away to fit around the gassers and it just wouldn't be an Ultrasport anymore. Love my gassers but the Ultra needs to keep its lines I think!!
The dle 30 swings a 19/8 prop so clearance would be bad also. I am running this engine in an EF Yak 74" and it has long gear so no problem there.