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Spruce Goose Foamie scratch build

Old 09-26-2014, 01:36 AM
  #51  
MononkBen
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Some more thoughts about the suggestion to add capacitors at the entry of the ESC as a solution...

Although the capacitance of the electrolytic reduces as the frequency raises (see pictures), adding more electrolytic capacitors in parallel at the entry of the ESC still increases the capacitance of the LRC circuit. This not only reduces the natural frequency of the circuit, but it also increases the damping factor. This is why it works.

Although this increase is not linear to the added capacity, this solution has its benefit, but the blocker remains the high frequency capacitance of the battery, which can not be changed. So the benefit will always be limited, and at some point, adding more capacitors at the ESC entry does not bring any value.

I am really looking forward to make these measurements on the parallel LRC compensation circuit... I will also measure the compensation circuit heat absorption with a thermal imaging camera to make sure my solution doesn't bring any additional overheating challenges...

Cheers!
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Old 09-26-2014, 02:49 AM
  #52  
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Hello Ben,
This is quite an undertaking as a entry level aircraft. Learning all the ins and outs of building comes with lots of time. One problem you are fighting with is trying to fit a large model by right into a small package. There will be a lot of challenges looking for space. I think a built up wing because of the wiring complex would have been more appropriate for working space. Wood frame and Depron foam skin with a 0.75 oz layer of glass epoxy or polyurethane and talcum powder to smoothen for painting.

I am including some information on motor wiring that could help you out. You could add a capacitor just behind naccelle mounted ESC's. I think 1 of thes hard wired for each motor would be more than enough. (8) total.
http://www.hobbyking.com/hobbyking/s...Search=voltage

The single was intended for direct plugin to a receiver. You could buy the 6 pack capacitor there also and re-engineer it also, They are big. You have to consider space with air flow also.

Here is a page link to a past build I did. Study it and read the electronics guru Ron Sommeron's articles too.
http://www.rcgroups.com/forums/showthread.php?t=952523


I also feel that you are applying to much engineering into your setups. Build the model and have fun and gain experience. You can also use APC 4- 5 inch props as a thought on collets. They make pusher and tractors. Although not specificatly for general flight. More for speed. Otherwise I do not know where you will find alternate rotations in other brands. Do not worry to much about the overlaps. The plane is small and you will never notice much effects.

Spar the wing as Chellie said in tapered wood I-beam or carbon arrow shafts. Not sure about house wires. There is a too stiff and feeding problem. But i like stranded silicone wires. Easy on epoxy. Learn how to use Gorrilla glue in small amounts. Cherish hot glue with foam in controlled amounts. Keep it light weight.

This is a page from one of my build logs. It has the answers. Hope this helps.
http://www.rcgroups.com/forums/showt...9#post21259157

KISS - Good Luck,
**Neons** Bob
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Old 09-26-2014, 03:20 AM
  #53  
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Originally Posted by MononkBen View Post
Some more thoughts about the suggestion to add capacitors at the entry of the ESC as a solution...

Although the capacitance of the electrolytic reduces as the frequency raises (see pictures), adding more electrolytic capacitors in parallel at the entry of the ESC still increases the capacitance of the LRC circuit. This not only reduces the natural frequency of the circuit, but it also increases the damping factor. This is why it works.

Although this increase is not linear to the added capacity, this solution has its benefit, but the blocker remains the high frequency capacitance of the battery, which can not be changed. So the benefit will always be limited, and at some point, adding more capacitors at the ESC entry does not bring any value.

I am really looking forward to make these measurements on the parallel LRC compensation circuit... I will also measure the compensation circuit heat absorption with a thermal imaging camera to make sure my solution doesn't bring any additional overheating challenges...

Cheers!
Ben your graff might mean something to others here but i will be truthfull when it comes to me ,i cant understand most to do with electrict setups or graffs ,i can read blueprints and figure out some wiring but i could not tell you why it works at all. I built nitro and gas planes most of 30 plus years and my first elecrict plane was a glider with a toggle switch from radio shack to turn the motor on and off with a servo hooked to the toggle ,no esc"s back then. I do however know many guys like Neons and others who build big seaplanes and do know a thing or two about the wirering of these big seaplanes i love so much and if it works for them it will work for me . Iam smart in other ways to make up for my lacking education about electric and i have done well by using street smarts to get by and my old carpenter hands to build them. joe
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Old 09-26-2014, 04:19 PM
  #54  
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Thanks Bob and Joe,

I highly appreciate every feedbacks and tips, and I enjoy every links to your builds. This is really helpful to me and has already prevented me from doing huge mistakes in my building plans. The long wires is only one of them.

I searched and read everything I could about ESC to battery long wires, including Ron's page. I am pursuing this analysis because I wish to understand it, and find a more efficient and convenient solution to this challenge, with less parts and lower weight. And I think it can be done.

Ultimately, this could become a significant contribution to many RC builders facing that same challenge, and for me, it is just as much fun as the rest of the built.

I am sharing this here, hoping that it may catch the interest of another RC builder that has an electrical engineering background like me. This may help understand the issue, and bring new ideas on how to solve it. At the end, the analysis will not need to be understood and mastered. The solution is meant to be as simple as a rule of thumb. That is my goal. And then, I will get back to the foam goose building.

Cheers!

(adding silicone wires to my purchase list: check!)
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Old 09-26-2014, 04:31 PM
  #55  
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Originally Posted by MononkBen View Post
Thanks Bob and Joe,

I highly appreciate every feedbacks and tips, and I enjoy every links to your builds. This is really helpful to me and has already prevented me from doing huge mistakes in my building plans. The long wires is only one of them.

I searched and read everything I could about ESC to battery long wires, including Ron's page. I am pursuing this analysis because I wish to understand it, and find a more efficient and convenient solution to this challenge, with less parts and lower weight. And I think it can be done.

Ultimately, this could become a significant contribution to many RC builders facing that same challenge, and for me, it is just as much fun as the rest of the built.

I am sharing this here, hoping that it may catch the interest of another RC builder that has an electrical engineering background like me. This may help understand the issue, and bring new ideas on how to solve it. At the end, the analysis will not need to be understood and mastered. The solution is meant to be as simple as a rule of thumb. That is my goal. And then, I will get back to the foam goose building.

Cheers!

(adding silicone wires to my purchase list: check!)
I have my ESCs in my fuse with short wires running to my battery from them . was faster for me to do it that way and they work just fine . Neons tuned me onto this wire .http://www.hobbyking.com/hobbyking/s...strSearch=wire later i found this gem for taming all those wires down to a few. http://www.hobbyking.com/hobbyking/s...er_1_set_.html
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Old 09-28-2014, 12:08 AM
  #56  
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Thanks Joe,

If I put the controllers in the fuse, then I have a lot of wiring in the wings (3*8=24), and this adds weight. I think I can fit the controller in the nacelles, assuming I can find a convenient solution to the spike issue.

Remember the first statement of this post: "This is a crazy idea..."... I know my aircraft is too small to conveniently have 8 motors... I think I should have said "insane"... Of course, I could have chosen to build a single engine scratch build without all these extra challenges, but I would have missed all this engineering fun, and I would not had the pleasure to discuss RC challenges with all of you..

The following ESC is 27mm long and weight only 9 grams: http://www.hobbyking.com/hobbyking/s...ontroller.html

I am currently prototyping the nacelles according to this ESC size. See picture (this is an experimental wing..). I cheat a bit.. the nacelle is a slightly larger than scale, but I am fine with that. The little wood block is the size of the controller so I think I can manage with the available space. I will also ensure the nacelle has air flow to allow the ESC cooling.

I will soon purchase a FlirOne thermal camera (350$) for my Iphone. I buy it for my house (to find cold spots - lots of cold weather here in Montreal winter), but it will be handy to verify the parts that are heating in my aircraft design and ensure appropriate cooling. For those who are interested in affordable thermal imaging, there is also a new product called "Seek Thermal" that works with any android phone for 200$. This is a very cool and handy gadget for your next RC design, and your house, so your wife should be ok with that expense... (note: I have no commercial interest in any of these products...)

Cheers!
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Old 09-28-2014, 12:21 AM
  #57  
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Originally Posted by MononkBen View Post
Thanks Joe,

If I put the controllers in the fuse, then I have a lot of wiring in the wings (3*8=24), and this adds weight. I think I can fit the controller in the nacelles, assuming I can find a convenient solution to the spike issue.

Remember the first statement of this post: "This is a crazy idea..."... I know my aircraft is too small to conveniently have 8 motors... I think I should have said "insane"... Of course, I could have chosen to build a single engine scratch build without all these extra challenges, but I would have missed all this engineering fun, and I would not had the pleasure to discuss RC challenges with all of you..

The following ESC is 27mm long and weight only 9 grams: http://www.hobbyking.com/hobbyking/s...ontroller.html

I am currently prototyping the nacelles according to this ESC size. See picture (this is an experimental wing..). I cheat a bit.. the nacelle is a slightly larger than scale, but I am fine with that. The little wood block is the size of the controller so I think I can manage with the available space. I will also ensure the nacelle has air flow to allow the ESC cooling.

I will soon purchase a FlirOne thermal camera (350$) for my Iphone. I buy it for my house (to find cold spots - lots of cold weather here in Montreal winter), but it will be handy to verify the parts that are heating in my aircraft design and ensure appropriate cooling. For those who are interested in affordable thermal imaging, there is also a new product called "Seek Thermal" that works with any android phone for 200$. This is a very cool and handy gadget for your next RC design, and your house, so your wife should be ok with that expense... (note: I have no commercial interest in any of these products...)

Cheers!
Ha Ha and i have no wife to ask ! The nacelles look good you might get everthing stuffed in them. joe
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Old 09-28-2014, 11:48 PM
  #58  
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Some Sunday morning fun, doing some nacelle building, preliminary assembly, envelope/sleeve experimentation (paper roll, and also aluminium... but the aluminium is a lot heavier than paper...), and getting ready to hot wire the fuselage..

For the fuselage, I will use 5 vertical layers of high density home insulation foam (1 inch). I plan to do some rough sanding to get the basic shape, then I will remove all unnecessary foam from the inner layers to keep the weight as low as possible, and also to make space for the RC gear. Then I will glue them together and do the final sanding and coating.

Cheers!
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Old 09-30-2014, 04:33 AM
  #59  
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Some fuselage inside space planning... By using 5 vertical sheet of 1 inch foam for the fuselage, it will be easy to cut out the inside space from the inner sheets before the final assembly of the fuselage sheets... I think this space of 3 x 16 inches should be plenty for the batteries and electronics, and enough room to play around for balancing the aircraft CG without the need of adding extra weight.

Cheers!
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Old 09-30-2014, 09:41 AM
  #60  
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Originally Posted by MononkBen View Post
Some fuselage inside space planning... By using 5 vertical sheet of 1 inch foam for the fuselage, it will be easy to cut out the inside space from the inner sheets before the final assembly of the fuselage sheets... I think this space of 3 x 16 inches should be plenty for the batteries and electronics, and enough room to play around for balancing the aircraft CG without the need of adding extra weight.

Cheers!
That Sounds like a Great Plan The wing is looking great too, Take care and have fun, Chellie
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Old 09-30-2014, 04:40 PM
  #61  
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Looks like a plan Ben ,the cowls are going to need some thinking on witch way to go . Mine were made from steamed rolled balsa then minwax water base hardwood flooring clear . 3 coats sanded in between made for a very hard cowl. I dont know if you could roll wet balsa that tight tho. Could roll foam then minwax or look for a round plastic tube to cut up. I have put in thin wall plastic pipe for underground cable that they sell in different sizes ,much lighter that pvc. joe
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Old 10-02-2014, 02:21 AM
  #62  
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Thank you Chellie and Joe,

Joe: your nacelles (very cool!) are a lot larger than mine... I don't think I can do it this way... My plan is to have a nacelle envelope that is not structural... my motors are only 17mm diameter, and my nacelle prototype envelopes are 36mm diameter, which is already larger than scale.

I will pursue the experiments with different materials, but at the end, my nacelle envelope will remain decorative, and will not be a structural element.

Cheers!
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Old 10-02-2014, 11:18 PM
  #63  
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Park flyers plastic might have something you could use http://parkflyerplastics.com/cart/in...index&cPath=58
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Old 10-04-2014, 07:40 PM
  #64  
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Saturday morning fun... paper coated comparative stress test with 6 Lbs weight, and first fuselage hot wire cut in my 5 layers of foam...

The suggestions I received to use 5x3 props will be adopted... According to the data I have, I should get a significant trust increase without consuming more power. I will therefore use 3 blades GWS 5030 and 5030R (alternate) as it appears they provide even more trust.

Because of this, I may need to cheat a bit for the water clearance and keep the wings on top of the fuselage as shown instead of having them integrated in the fuselage top... or maybe somewhere in between...

Cheers!
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Old 10-04-2014, 08:02 PM
  #65  
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Originally Posted by MononkBen View Post
Saturday morning fun... paper coated comparative stress test with 6 Lbs weight, and first fuselage hot wire cut in my 5 layers of foam...

The suggestions I received to use 5x3 props will be adopted... According to the data I have, I should get a significant trust increase without consuming more power. I will therefore use 3 blades GWS 5030 and 5030R (alternate) as it appears they provide even more trust.

Because of this, I may need to cheat a bit for the water clearance and keep the wings on top of the fuselage as shown instead of having them integrated in the fuselage top... or maybe somewhere in between...

Cheers!
Looks good Ben but you better cover that bike up before all the sanding starts . My solent has 5 degrees positive on the main wing and 1 degree negitive on the motors ,what is the goose going to have for the wing and motors? joe
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Old 10-05-2014, 12:25 AM
  #66  
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Rainy Saturday afternoon fun...

Some more hot wire cutting... the rough shape is getting there... Adding the aileron already gives it a cool look... Lot of space in there! Total weight: 330 grams... and the foam layers are currently assembled with lots of good old 2 inches wood screws... So my fuselage weight should remain on target once glued together and without these heavy screws. I may also dig additional channels to reduce the weight.

Haha! Joe! The bike, or should I say the scooter (Yamaha Majesty 400 2007 - lot of fun too!), is used to grab dust all winter here... I will give it a beauty wash next spring when the bike season is back!

I plan to use A1510 motors (18mm diameter, 17 grams) with these 5x3x3 props. According to the data I have, I should get 300g of trust with only 6 Amp... that is a total of 5.5 pounds of trust with 8 motors, and I should end up with a positive trust weight ratio. And this motor is the best size/weight/watt/trust ratio I can get for this small wingspan 8 motor RC model.

I have not determined yet the angles that I will use for the wings and motors though... I received many tips about that, and I will make my final choice later...

I am very pleased with the simplicity and the preliminary results of my multi-layer foam fuselage building concept. I may not be the first one to do that, but I have not seen any yet. But this building method means that my Foam Goose may not have a perfectly round tail... It will most likely have a rounded edges "squarrish" fuselage tail, and I am fine with that.

Cheers!
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Old 10-05-2014, 03:07 AM
  #67  
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Ben,

What's the diameter of the wood formers shown in the nacelle?

Don
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Old 10-05-2014, 03:48 AM
  #68  
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Hi Don,

The diameter of the wood formers shown is 33.5mm.
This picture shows a design prototype... the wood formers that I will use for the motors will be slightly thicker. Of course, I will ensure that the motor mount of the A1510 fits this diameter once I order them. I think it should be ok as long as the wood former is thick enough to support the mounting screws... if not, I will need to enlarge my nacelles...

Are you foreseeing any unexpected issue with this design?

Cheers!
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Old 10-05-2014, 05:01 AM
  #69  
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No, no problems, I was just thinking about the non structural covers for the nacelles. I've made circular cowls out of foam using a tubular form, generally thin aluminum for a form, and boiling water. Using 2 or 3mm foam might work out nicely for the nacelle jackets. Just sitting here thinking along....lol...my wife tells me that gets me into trouble...
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Old 10-05-2014, 05:26 AM
  #70  
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Originally Posted by DEG View Post
No, no problems, I was just thinking about the non structural covers for the nacelles. I've made circular cowls out of foam using a tubular form, generally thin aluminum for a form, and boiling water. Using 2 or 3mm foam might work out nicely for the nacelle jackets. Just sitting here thinking along....lol...my wife tells me that gets me into trouble...
Thanks Don!

Foam cowls are indeed an option, but in this specifically reduced size context, they would add too much size to an already oversized nacelle... so I must try to keep the cowls as thin as possible...

I already have 2 thin options that I can easily customize to my requirements: paper roll and aluminium... The final choice will depend on the requirement for extra nose weigh to balance the aircraft. I will be happy to consider any additional suggestions for an easily customizable thin nacelle cowls.

Keep the wife happy and stay out of trouble!

Cheers!
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Old 10-05-2014, 03:40 PM
  #71  
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Originally Posted by MononkBen View Post
Thanks Don!

Foam cowls are indeed an option, but in this specifically reduced size context, they would add too much size to an already oversized nacelle... so I must try to keep the cowls as thin as possible...

I already have 2 thin options that I can easily customize to my requirements: paper roll and aluminium... The final choice will depend on the requirement for extra nose weigh to balance the aircraft. I will be happy to consider any additional suggestions for an easily customizable thin nacelle cowls.

Keep the wife happy and stay out of trouble!

Cheers!
Dollar tree foam is around 3/16 thick but you can get 3 mm depron sheet .I dont think the weight of either foam or balsa cowls will change much so close to the CG ,its the weight of the tail that realy counts. I would cut out as far to the nose as you can for more battery positions. You also can use a bigger or smaller battery pack to get your cg correct . To get my CG on my solent i had to use two 3200 packs and my reciever / servo battery pack in the nose . There is alot of guess work till your alomst done on these scratch builds and thats half the fun. I bought a honda 250 reflex scooter this summer for jumping around town fast but i also have a 1997 Harley roadking a 58 cushman and i just bought a 56 bubble front vespa to restore. My second hobby is restoring old bikes and scooters and i sell some . joe
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Old 10-05-2014, 10:01 PM
  #72  
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Thanks Joe!

I understand now why the bike got your attention!!

Both paper roll and aluminium are 0.5mm thick, making the cowl 34.5mm diameter.
Using a 3mm cowl material will increase my diameter to 40mm and make it look a bit bulky, as they are already oversized.

Good idea to cut off further in the nose, but I need to be careful and avoid making the fuse too thin. I can go 3 inches further in the central layer without worry, and this should be ok for one of the batteries. I can also cut off the center layer in the tail up to a reasonable point, and lighten some of the tail elements a bit by making holes.

My 8 engines nacelles being in the front of the wing, they will also contribute to bring the CG towards the nose...

Cheers!
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Old 10-05-2014, 10:26 PM
  #73  
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Some sanding and fuselage parts ready for more work.

The round edges are ok, and I will keep this approach for the tail, even though the H4 had a round shaped tail..

Some of the fuselage parts look a bit fragile, but when assembled together with simple screws, the fuse feels very solid.

I have also done some experimental holes in the tail structure to reduce the tail weight. A long drill screwdriver covered with sand paper will allow me to enlarge them easily to the required diameter.

I don't mind keeping the flat bottom unless somebody tells me that the V shape boat bottom is extremely important.

The fuse parts will be glued together. I did an experiment with diluted white glue, and the parts I glued together were nearly impossible to separate until I snapped out half of assembly... I know that this is a water based glue, but the fuse will be covered and sealed. I will also experiment hot glue.. this could be very handy as it cures very fast. Maybe too fast.. I have large areas to glue and I am afraid that hot glue will not allow me to press and clean in a convenient time.

More fun every day!

Cheers!
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Old 10-05-2014, 10:35 PM
  #74  
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Ben,

You might look into this product. I've been using it for a while now. Handles just like white glue and it says it's waterproof.....
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Old 10-05-2014, 10:35 PM
  #75  
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Hi Ben The problem with a flat bottom on the fuselage, is that a Flat surface will want to stick to the water with suction, to where as a v shaped botton will take away that flatness and allow the fuselage to break free of the water easier, you might even want to incorporate a step in the fuselage bottom to allow air to get under the fuselage bottom to break free of the water.





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