Thread Tools
Jan 10, 2019, 05:44 PM
Registered User
slow_flier's Avatar
subed in

Tom K
Sign up now
to remove ads between posts
Jan 10, 2019, 05:45 PM
EB-66C Team Member
J Morgan's Avatar
Quote:
Originally Posted by parkcityskier
I think that you really have got something started here, J. Like you say, a squadron soon.
I'm still working on my plans, correcting mistakes and adding some details that were glossed over on the original plans. I'm also doing some calculations to give me targets to shoot for. Based on the relative sizes of J's and my plane I will try to have all my build weights about 65% of his. With J posting weights as he goes along this will give me a good idea on how I am doing using a new technique that I have never tried before. I also ran some numbers to give me some target weights for the AUW. I estimate the heavy stuff (prop, motor, ESC, battery, and retracts) to be
3 1/2 Lb. so I am going to shoot for an AUW of between 6 and 8 Lbs just for a start. I've done one quick motor run with a 16x6 two bladed prop and a 4S pack and was getting about 1000W. I want to build a four bladed prop and continue more tests with both props and with different size battery packs. The wing area of the plane is about 733 sq in. So, with my target weight range I would expect a power loading of 125-166 W/Lb, and a wing loading of 19-25 oz/sq ft. For an airplane of this size I would have a Wing Cube Loading (WCL) of 8.4-11.1 which puts me in the lightly loaded category. This is all guesswork at this point because I haven't even started to build but it gives me confidence that a good flying airplane is possible at the end. Hope to start building soon.

Jim
I've got to give your weight plan some more thought Jim, but here is a quick shooting from the hip rundown of what I think. Not sure you can equate the weights ratio with the different size builds. For instance, my old 48" ws Me-263 ( now with Scotty)weighs about 35+ oz. I doubled the size with my new one and it is 10 lbs. As you go up in size, weight in not necessarily proportional. Another example is my prop/motor/two batts/rec batt/esc is about 6.5 lbs. If you take 65% of that= 4.25 lbs.
Now I'm shooting for 20 lbs AUW. It looks really good so far but I do know from experience that as you go up in size, weight starts to shoot up at an alarming rate and a lot of times you can't control it. I think I can make 20 lbs, maybe even a little less. But the devil can be in the details and I want several cool details so....... we'll see.
I'm thinking a better comparison on our builds might be comparing wing loading.
Example: Ziroli has on the plans, 30-35 lbs AUW. That is a 49.7 oz WL and that's fine with a wing this big, no problem, been there , done that.
Mine at 20 lbs AUW is a 25.6 oz WL. Absolute floater at this size.
I'm thinking a more reasonable goal for you would be trying to keep the wing loading around 17-18 oz/sq ft. By the way, what is the WA on your plan?
And I might be all wet on this, welcome all input, if someone has compared other different size builds, the info only helps the build.

J
Jan 11, 2019, 12:47 AM
Parkcityflier
parkcityskier's Avatar
Thread OP
J, thanks for all that. It’s not very encouraging though. My WA is 733 sq in so I would have to get down to a six pound airplane to get to a 19 oz/sq ft WL. With the 3 1/2 pound weight of the heavy items that would only leave me 2 1/2 pounds to build the plane and I don’t think that’s going to happen. I’ve got a lot of motors but not sure if I have more than one that would turn a 16” prop. That battery pack is the big weight and it might be hard to have a lighter one, depending on the motor. I think that at this point I’ll have to see if I can find a better motor/prop combination to reduce the battery weight required and then pretty much just build a fuselage to see where I’m at. I think that an eight pound airplane would be possible if, as you say, with the bigger airplanes the weight really goes up fast and with a WCL of 11.1 it should fly but it’s not going to be floater.

Jim
Jan 11, 2019, 12:55 AM
Registered User
Subbed,

CR
Jan 11, 2019, 07:28 AM
EB-66C Team Member
J Morgan's Avatar
Quote:
Originally Posted by parkcityskier
J, thanks for all that. Itís not very encouraging though. My WA is 733 sq in so I would have to get down to a six pound airplane to get to a 19 oz/sq ft WL. With the 3 1/2 pound weight of the heavy items that would only leave me 2 1/2 pounds to build the plane and I donít think thatís going to happen. Iíve got a lot of motors but not sure if I have more than one that would turn a 16Ē prop. That battery pack is the big weight and it might be hard to have a lighter one, depending on the motor. I think that at this point Iíll have to see if I can find a better motor/prop combination to reduce the battery weight required and then pretty much just build a fuselage to see where Iím at. I think that an eight pound airplane would be possible if, as you say, with the bigger airplanes the weight really goes up fast and with a WCL of 11.1 it should fly but itís not going to be floater.

Jim
I think I might approach your plane differently. Build it and then when you have a good handle on the finished weight, select your motor/batt/ prop combo.
I already had a good idea ( from previous models) on what I would need for mine. Plus I already had that high $ 4 blade prop and big honker Turnigy 6364 motor sitting around idle. Birger ran some numbers for me and it looks like 2000+ watts on 8s which should be perfect for my plane if I come anywhere close to 20 lbs AUW. Although I'm hoping for 18 lbs.
I'm not looking to discourage you, yours will still fly well I'm sure. I find it's easier to get a good scale type flying plane the larger you go up in size.

J
Jan 11, 2019, 10:51 AM
Parkcityflier
parkcityskier's Avatar
Thread OP
J, don’t worry about discouraging me. It just makes for a bigger challenge. I agree with you about building the airplane first. I just happened to have a motor that would turn a 16” prop and factored it in because I had it. It weighs 342g and could be a little overkill in the power that it produces. About 1000W would be ideal. There’s not a huge selection on lighter weight motors that can turn the big prop but there are some so, as you say, I can wait until I have a plane before I really have to have a motor. My big interest in this plane, besides having a new Spad, is really to see how light that I can build it using a new technique for me.

Jim
Jan 11, 2019, 04:43 PM
71% of the world is runway . .
Bart83's Avatar
Good to see you've started the thread. Looking forward to see what you make of the Spad

Cheers,

Bart
Jan 11, 2019, 05:14 PM
Watch out for that planet....
Shane McMillan's Avatar
Will be watching with interest Jim.

Subbed!

Shane.
Jan 11, 2019, 05:42 PM
Registered User
W. X. Davis's Avatar





Woody
Jan 11, 2019, 07:00 PM
Parkcityflier
parkcityskier's Avatar
Thread OP
Thanks, guys. I'm still working on the plans that I picked up. They have been good for some profiles and airfoils and a general layout but my construction technique will be entirely different. I've been impressed with what J is doing with foam on his bigger A-1 so I'm going to try to adapt as much as I can of it to my own version. I think that spending time brainstorming ideas before I actually get to start cutting and gluing will be time well spent. My primary goal will be to end up with an A-1 that is as light as I can possibly make it so a lot of J's techniques will no doubt be also used here. An exception will be that rather than building the fuselage in two halves as J as done I will be using a box frame and build from the inside out. Doing it this way allows me to build it in a jig and I can leave the bottom of the fuselage open to allow things like control linkages and a retractable tailwheel installed easily before closing the bottom skin. At the front end I really like J's idea of the sliding motor/battery tray but probably will not use it unless I need the extra weight up front. Rather, I am thinking of building a removable upper section of the cowling to provide access to the motor and battery replacement. There is plenty of room behind the motor to do this. On the full scale A-1 the entire middle section of the cowling was made removable, in sections, to provide access to the engine so the cutlines on my removable section of the cowl will fit right in as if they were the cutlines on the full scale A-1. I'm also thinking about a building technique for the wing but I'll get back to that later. Any and all suggestions on what I am planning will be welcome.

Jim
Jan 11, 2019, 08:38 PM
EB-66C Team Member
J Morgan's Avatar
Sounds like a plan.

J
Jan 12, 2019, 03:52 AM
Registered User
balticS2's Avatar
On station

Alec
Jan 12, 2019, 11:34 AM
Registered User
Following, got a soft spot - my Dad flew A-1E's in the 1st Air Commandos at Pleiku and NKP, 66-67. Looking forward to watching the build.
Jan 12, 2019, 01:22 PM
AeroDan
On Station. Dan
Jan 12, 2019, 04:07 PM
Parkcityflier
parkcityskier's Avatar
Thread OP
Rofldrone, that's interesting about your dad. I was flying the A-1H on Rescaps in 1966 but I was up north off the Intrepid and he would have been down south somewhere so I guess that we would never have been in the same sky on a day.

Jim


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Electric A1H / AD6 Douglas Skyraider Skyraider Bill Scale Kit/Scratch Built 967 May 30, 2019 05:22 PM
Video The Electric Turd " the movie" NoT aNoThEr BiXlEr 2 mod videO? stsguy The Builders Workshop 0 Dec 15, 2015 10:07 PM
Discussion A-1 Skyraider 1.6m Electric Miraj Electric Warbirds 6 Sep 25, 2013 06:24 AM