120" Powerhouse - RC Groups
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Aug 04, 2008, 01:01 PM
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120" Powerhouse

Looking for some engine advice...

I am building a 120" WS Powerhouse, don't have any idea of the weight yet and I know at least a few of these this size have been built before. Anyone have any information on what the powered with? Mine will be 3 Ch RC.
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Aug 04, 2008, 06:37 PM
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Weight of the Big Powerhouse

There is an easy way to estimate the weight when you scale up.
Weight is proportional to volume assumiming the density of the building materials remain the same. (reasonable)
Volume is the cube of linear dimensions.
Soo.... lets say the standard power house is 84 inch span and weighs 4.5 pounds. The new one is 120 inch span so the new weight is 120 cubed divided by 84 cubed times 4.5 pounds = 2.92 times 4.5 = 13.12 pounds.
Area goes up by the square of linear dimension so it doesn't keep pace with weight so the wing loading goes up too. This is one of the reasons full size aircraft have much higher loadings than our models.
In this case the standard model has a loading of 72 ozs /(84 x 14/144) = 8.8oz/ft sq. The 120 inch model has a loading of 210 oz /(120 x 20/144) = 12.6 oz/sq ft.
This is still a very reasonable loading and will produce a gracefull slow flying model. Even though it is more heavily loaded it will probably glide better than the original in my experience. Big models just go better, something to do with Mr Reynold's number, but that is another story!.

Hope this helps and look forward to seeing the big one, Awesome!

Aug 05, 2008, 04:51 AM
Registered User
I use roughly the same approach to Allan and in addition I keep the power weight ratio the same.

So in this case the engine size would be 3 times original powerhouse size.

I am not sure of the original power but think that the 84" would fly nicely on a modern 30 or 40 4 stroke. So this would suggest a 120 4 stroke would be Ok.

I have a 108" scaled up version of Vic Smeed's Mam'selle and it flies nicely on a clapped out Magnum 90 4 stroke. loops only if you give a bit of down elevator first. Takes off in no time at all, and flies very nicely on fast idle.

Weight of Mam'selle is 11 lbs - I build light
I am considering a 120" southerner and will put a 120" 4 stroke in that.

same calc as Allan's but not getting such big nos to handle

scale up = 120 / 84 = 1.43

wing area increase = 1.43 x 1.43 = 2

weight increase = 1.43 x 1.43 x 1.43 = 2.92

power increased by 2.92 from original

attached photos show the original 36" free flight model and an intermediate scale up to 72" with an early saito 30 4 stroke. the above formulae held quite good for the scale ups

enjoy your building and flying the powerhouse
Last edited by John38; Aug 05, 2008 at 12:57 PM.
Aug 05, 2008, 07:23 AM
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Big plane , lovely model , which is your actual favorite?, now you are talking my language I love big planes, far more efficient, please post pic's of your big powerhouse build I might be tempted.
Aug 05, 2008, 09:31 AM
Registered User
Bill Northrup had an 84" Powerhouse on floats powered by a K&B 40. It would get off the water fine but it took a bit of a run. A Senior Telemaster at 96" is built somewhat heavier than a Powerhouse, and they fly fine on a 2 stroke 60, and are said to fly on a 45. Maybe a 4 stroke of 70 to weak 90 would work well, or any sport 60 2 stroke would give more than enough power.

In the old days the big birds like the Valkyrie, Lanzo Record breaker, etc, were flying on Browns, Super Cykes, and, if you were lucky, Anderson Spitfires. These were probably as good as a sport 40 2 stroke at best.

Again, depends on what you want to do with it.

Aug 05, 2008, 11:30 AM
RC is relaxing. Repeat.
Good morning,

Thanks you all for the very informative answers. I am currently building a 84" Quaker and I know they fine nicely with a .56 FS. I have a Saito ready to go into that. For those interested, the 120" Powerhouse in a Holman plan and he has a short kit for it. Very nicely drawn plans and quality wood for the short kit. Unfortunately, he has only sold a few of the scaled up Powerhouses and doesn't recall what they have flown with power wise. I just sold a 1.50 Saito FS that I should have used. I am thinking of using a 26 or 32 Evolution Gasser as they have the same mounting as a 2 or 4 stroke, but I really do like gas. Even at todays $, the gas is a heck of a lot cheaper than the nitro. I really like the FS sound though... Thanks again, when I get started on it, probably next week, I'll post some pictures.
Sep 11, 2008, 11:49 AM
RC is relaxing. Repeat.

120" Powerhouse

Hi, I am finally making some progress on the Powerhouse. I had to complete my 86" Quaker first. All you pursists please put on your sunglasses now. The Quaker is transparent green and cream monocoat. I have laid the Powerhouse horiz stab on it to show the scale. I did not do a build tread, but wanted to update the build. I am going to start the wing tonite or tomorrow. I have not flown the Quaker yet so no pics or video for you. When I maiden them, probably the same day, I'll try to post some footage.
Sep 11, 2008, 01:02 PM
Chad H Fly`n Farmer
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Man Tim that is one awesome Powerhouse dude! I think the rain forests will be depleted of trees after you get that sucker done.

Just a beautiful job man, and on your Flying Quaker. Nice photos too, but we need someone or something in there for a size reference.

Send us more photos when completed and of the big day for both.

My hats off to you for such a big project, just dwarfs the Powerhouse I want to start this winter.

Good stuff..................Chad

PS...............love the Rod in the garage and your Vette, I have a old 68 RS-SS Camaro 4 speed, so I like the old cars too!...........bye.
Sep 11, 2008, 01:09 PM
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Thanks Chad,

I'll try to put some scale in next time. The wheels on the Pwerhouse are 6 inches...maybe that helps. CU
Sep 11, 2008, 05:10 PM
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WOW..... beauty Tim, my Quaker 84" also flys on a 56. Very good combo although a little overpowered really. The Powerhouse is very nice and you should have a ball with that one. The small 84" version flys extremely well yet tough to bring back home. Floats and floats and a real looker in the air. Good luck with your maidens.
Let us know how the gasser works out, I think it's a cool combo and the Evo looks right in there. Chad and I both would like to do a small 4 stroke twin in something. Maybe this winter something will come of it.
Last edited by williame3590; Sep 11, 2008 at 10:45 PM.
Sep 12, 2008, 11:11 AM
RC is relaxing. Repeat.
Nice looking planes you have there. I guess you guysd just don't fly the old timers... I am really envious of your flying situation. I drive about 130 miles one way to fly. I read with interest the blog on your club. We have a great field in the middle of the desert, good group, a lot of guys put a lot of work into it and now I get to enjoy the efforts of their work. We can fly 12 months out of the year if you don't mind a little heat.

I started the Powerhouse wing last night, but that will be it until Sunday night when I get back from the desert. I'll post a pic of the bones when they are glued up.

The EVO looks a little big, the pilot has to look around the motor to see forward. I have a 17x6 on there to break it in, and I will probably prop it up quite a bit so the prop size will look more appropriate to the size of the plane, and also I don't think I will need all those revs to keep it in the air.

Until next time, don't rekit anything!
Sep 12, 2008, 11:21 AM
RC is relaxing. Repeat.
Hey Chad or Williame,

How do I keep air in those Trexlers. I have tried the stuff between he hub and tire, toothpicks, twisting and they still leak out. I mean in less than 30 minutes. What is the trick?
Sep 12, 2008, 03:17 PM
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Tim, just cut the plastic point off those nylon hinges and shove that in the end. Never twist the rubber or you will regret it. The tube will seal never to take air in or out again. Regards Bill

I wonder if the heat down there is expanding the tire, air inside getting pretty warm and just being forced out Really don't have any trouble with mine and actually just bought a pair of six inch. Bill
Last edited by williame3590; Sep 12, 2008 at 04:19 PM.
Sep 23, 2008, 02:46 PM
RC is relaxing. Repeat.
Here is a picture of the assembled wing - less covering. I bult it as 1 piece and now have cut it in half ( two 5 foot wing panels). I have actuially covered 1 panel but I did not sheet the center section, and now I am having second thoughts about that...the wing seems strong but the leverage may be too great for the wing to handle without the sheeting. I'll figure it out tonight.
Sep 23, 2008, 03:44 PM
Gravity gets me down.
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I love the idea of a giant Old Timer.

Will start a new thread with questions about resources.

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