Another "Screamin Demon" Delta build
 

Never one to rush into things, I have finally started to build a kit I got from Mike Connor back in August 2007,when he first designed and produced the kit before selling the business. Originally I had thought of powering it with either a OS .40 FSR (still in the box) or with a large out runner like an Axi 4120 and fly it using a larger high pitch prop. My current budget constraints (none) have made necessary to go a different route and use what I have on hand which is an Ammo 28-56-3200Kv motor similar to the HET 2W23 I used in my PQ stingray (which I have yet to get back into the air with what I hope is a better prop for it). The motor is rated for around 700 watts continuous and 1.5 kilowatt burst which gives it a current range of 45to 75 amps, with the cooling system and a heat sink added to the motor I may be able to get a bit better performance out of it but it is what I have to use so that's what the plane is going to be powered with.
With that in mind construction then started with building the motor mount and cooling duct, as they are needed in the preliminary stages of the airframe construction. I made up the cooling tube using the old plank method for construction with a plumbing piece as a mold that just happened to be the exact size to fit the motor with the additional heat sink into.
Then I made up some blanks for the cooling inlet/motor mount and cowl. With the blanks for the cooling tube and mount made up they had carbon fiber veil applied to reinforce them before they were turned then assembled into the complete assembly which makes up the motor mount and nose of the airplane. These blanks were then turned forming the inlet/mount and cowling shapes so they could be mounted onto the aft portion of the cooling duct which has it supports fastened to the sides so it fits into the bay between the ribs were to original plywood mount for a glow engine would normally go. The leading edge of the wing also attach to the motor mount, I am hoping this will really tie everything together and make a very rigid and stiff airframe time will tell but it seems to be the way to go with it. As I have very limited power it is important to keep the weight of this airframe as low as possible to make up for the lack of power, so every thing is being looked at in the build process with an eye to minimizing weight. The ribs had lighting holes cut into them to reduce a lot of weight, where this is plane is going to be powered with an electric motor I don't need the mass to counter the vibration of the engine and it can be a lot lighter construction then it normally would be with an a IC engine.
As mike did I made supports to hold the carbon fiber spars in place, these were then fastened in place over the plans and the ribs and motor mount then fitted onto the spars and fastened into place. Then I progressed to shaping the leading edges and wingtips and added them to the airframe the added the leading edge sheathing to tie everything together. Once they had dried I then applied the sheathing to the trailing edge at this point the weight is around 7 ounces so I hope that my target of a 2 lb all up weight can be achieved. I am currently in the process of adding a shear web around all of the sheathing on the leading and trailing edge, and will add the balance of the sheathing after the shear web has been completed.

RE: Another "Screamin Demon" Delta build
 

Yahoo another delta build! About time for another one of these. Love your ideas IE, will be watching this build.:D:D

RE: Another "Screamin Demon" Delta build
 

That center section looks really good IE...!!

RE: Another "Screamin Demon" Delta build
 

Thanks guys!
Well I almost have the shear webs done just a few more inches to go. The nice thing about the shear webs is that you can remove any sags or bows in the sheathing so it is straight and true with the wing, the leading edge in particular. Boy did it stiffen up the airframe!

I have tried to keep the center section as tight as I could and am going to be blending it into the wing as much as possible. I still have a bit more to do to the center section, one thing that is going to happen is that all of the control linkages will be contained within it, including the control horns to the torque rods for the elevons. It's going to get interesting making that all up along with the hatch cover, the center section is going to be 2 1/4 inches high at it highest point so all I have to blend into the wing is the 1/2 inch difference on the sides. Part of the two center ribs you see will be removed to allow for space in the hatch area but the remaining part of the ribs will make up the hatch and frame for the belly if you follow what I am doing. It was easier to locate them using the carbon fiber spars with the plan to carve them out after most of the frame is completed to keep the shape true. This should keep the amount of frontal area to a minimum on this plane...

RE: Another "Screamin Demon" Delta build
 

After installing the shear web around the inside perimeter of the sheathing I started to sheath the wing. Normally I do this in one large piece and call it done, but because of the modifications I am making for this electric SD I decided to install more spars and shear web to make up for the fact that the forward carbon fiber spar will have the center removed. One of the reasons I decided to do this is that the 1/32 balsa I used for the shear webs added little weight the weight of the glue is probably more than than the materials used. Here are a couple of shots to show the progress...

RE: Another "Screamin Demon" Delta build
 

What size batteries will you be using? I am considering this plane for an electric motor I have laying around.

RE: Another "Screamin Demon" Delta build
 

It is designed to fit from a 3 cell to 5 cell lithium polymer battery in the 3 to 4 thousand mah range as well as a 100 amp castle creations Ice Esc. The center bay is 2 3/4 inches wide and the only limiting factor for the battery is the forward carbon fiber spar. I am adding a couple of wood spars with shear webbing to make up for that modification to allow space for the battery to fit within the wing itself so I dont have a battery compartment sitting on top of the wing instead of in it.

RE: Another "Screamin Demon" Delta build
 

After the tedious process of adding the shear webbing and doing the sheathing the wings are finally done! Hopefully in the next couple of days I can finish up the wingtips and get started on the center section and hatch. Well all of the work seems to be worth it, the wing is very rigid. It doesn't twist much which was a concern for me where I am going to be using the winglets and having swept the wingtips as well. This aspect of it was the primary reason for the added shear webs. Another reason for adding the shear webs is I am worried about the sheathing ballooning and distorting with the large bay area and thin sheathing. Well I can say that's not a problem at this point and the weight isn't too bad at just over 10 oz.
At this point I am still trying to figure out how to exactly do the torque rods and mounting for them. With the center section I am going to have to shorten up the elevon span a bit. Somehow I have to compensate for shorting up the elevon span so I am planning to give the root of the elevon's a bit more cord, at least that way I maintain the same volume of control surface area even with the reduced span.

RE: Another "Screamin Demon" Delta build
 

A quick update...

After getting the sheathing finished on the wings it was time to move on to the center section or the fuselage if you will. The firs thing was to add the supports for the belly pan. These were added to stiffen the sides of the center section and the sheathing on the belly pan (no landing gear on this one). After sheathing the belly here is the fist look at inside the "fuselage", lot of room in here compared to most hotliners or other "speed planes".
After getting the hatch ends frames and sheathed it was time to cut out the front spar's center section. (I sure hope the provisions I made for this is adequate!) After cutting out the spar I added the side supports for the hatch. Then I framed up the hatch in place for this application the hatch as to not only be airtight but a perfect fit as I want it to be able to carry the compressive force on the top of the wing that the front spar would normally carry. With this one battery size isn't going to be much of an issue the compartment size is roughly 10.5 inches long, 2.5 inches wide and 1 5/8 inches deep. Even adding the ESC and two servos there ought to be lots of room, and with a 10 X 2.5 hatch access to the internals it ought to be pretty easy to set up.

Edit to add pictures and:
While I have really compromised the ability for this plane to tolerate negative g's it still should be able to handle upwards of 50g's under positive load.
Here is a look of how the center section looks from the front. Next I have to start to blend the center section to the wing and build the outlet tube/linkage housing.

RE: Another "Screamin Demon" Delta build
 

Who says you need a forward spar...? The main spar at the rear is all you need.

RE: Another "Screamin Demon" Delta build
 

Cp, I hope your right that rear spar is going to have a lot more of the load on it. Although the added spars and shear webs ought to carry a bit of the load the front spar would have carried, it will be an interesting experiment. I started to blend in the forward part of the center section last night and had to give up before I screwed anything up too bad, I had some issues with bending the sheathing and getting it to stick. Hopefully tonight I can get some better results with what I am trying to do. I'm still trying to figure out the exhaust duct and the torque rod setup, on of the major problems will be having access to the linkage connections to the torque rods. At this point I pretty much decided that for the most part the torque rods are going to have to be built into the end of the exhaust tube. This airframe is too small to allow for the tail cone to be detachable, and it is going to have to have the blending for the root of the elevons into it as well.

RE: Another "Screamin Demon" Delta build
 

From what I can see, you could lay some tristock in the steps that you created in the sheeting. Mask off the sheeting that you don't want to nick with duct tape and then sand or scrape the tristock flush with the surrounding sheeting.
I use new formula Bondo [ez sanding] to blend in the edges and voids.
With a credit card you can wipe on a very thin layer that doesn't need much sanding and it usually takes me about 3 Bondo sessions before all the low spots are leveled and blended good enough for covering or primer.

RE: Another "Screamin Demon" Delta build
 

Originally I had intended to do it that way but I have since decided I wanted to go more for a full on BWB type of construction. I figured that the lower I got the interference angle between the wing and the body the lower my interference drag should be. Hopefully it going to be worth the effort and weight for doing it this way. After a couple of hours work this is what I got for tonight's effort.

I've got to try out that new bondo... how is it to work with?

RE: Another "Screamin Demon" Delta build
 

That looks very good..!
The compound curved sheeting can be done in one piece, though.
Make patterns out of file folder paper and transfer that to the balsa skins.
I've done this on .10-.15 sized deltas, but haven't tried it yet with a 40 sized yet.
This ASP .12 delta is surprisingly fast [133 mph] with .4 HP. The wing is as thick as the engine at the root chord but tapers down real quick to a typically thin section.
Dip the wood in straight ammonia and use thin CA while it is still damp to force it down to the framewoork.
It's easier to just try stuff like this, to just dive in and do it than it is trying to explain....;)

The new Bondo doesn't gum up the paper as quickly as the old stuff. The old stuff had a sticky glaze on the surface that needed to be cut through. You can use 80 grit as your first "knock down" paper. Just always be aware of gouging the balsa. Like anything else, there is a skill to acquire but it's pretty easy to work with if you apply it judiciously. Don't ever think that the first application / coat will be the last. I find that the second coat is close to perfect, but a third skim coat is used to fill the 80 grit scratches and then I don't touch the third coat with anything heavier than 150 grit, usually finishing up with 220 grit. 150 grit can make minor contour corrections and feather the bondo / balsa. 220 is just to polish the wood and Bondo, not to make contour corrections.
The Gator paper they sell at Lowes is worth the extra money, too.

RE: Another "Screamin Demon" Delta build
 

Thanks!
I bet that little sidewinder really hauls... That plane was part of the inspiration for what I am doing to this poor SD.
I wasn't having a good night with balsa last night. (Even with the ammonia.) The grain orientation I was trying to use just didn't work, plus a bit less stiff balsa helped.

That new bondo sounds like a lot better product, my memories of bondo go back to using a cheese grater to take off the glaze then start sanding. As far as fillers, the most part I use micro balloons and epoxy but it's a bit harder to sand, I've got to try some of that new bondo.

I think it will be interesting to see if this has any real effect on a .40 size airframe even though my power may be marginal.

RE: Another "Screamin Demon" Delta build
 

Unless you are building similar planes in large batches for spec class competition or for formal speed trials it's pretty hard to figure what is worthwhile and what is a waste of time.
Usually it takes a bunch of little things to add up to a collective good effect.
Regardless, what you are doing is artistic and it should fly as good as it looks.
BTW, Bondo is really good for feathering the edges of fiberglass to wood if you just lay a patch of cloth down, but don't want to glass the whole plane.
It's also great for feathering layers of cloth as well, like with a lost foam cowl [where you skip making an actual mold].

RE: Another "Screamin Demon" Delta build
 

Hopefully keeping the weight down as much as possible and keeping the airframe as clean as possible will help to mitigate the low power a bit. Well it's not that low I can get 1500W in a burst that's about 2 HP so it should move fairly well. I not going to glass this airframe, but do plane to use a composite finish to compliment the stressed skin aspect of the build. With all of the control linkages out of the airstream I am hoping it's clean enough to get some performance out of it. So far the real issue I have found is the props, but I don't have to tell you that, you make your own...:D
Well time to get some glue on the fingers...
Edit to add some photos (it doesn't look as awful without the flash)

RE: Another "Screamin Demon" Delta build
 

Her are a couple of shots to show how the blending has progressed. At this point two thirds of the center section has been blended, so now it is on to making up the torque rods for the elevons. After I have the torque rods finished I can move on to building the linkage tunnel/cooling exit and tail cone section. I have go t to have this all ready to go before I can blend in the last several inches of the center section and the wing, as well as the root section of the elevons. At this point the major part of the construction is finished leaving only the wingletts and elevons yet to be built up. Even though a lot of sanding and filling needs to be done I think the airframe is getting to the point that you can see it's final shape starting to emerge.

RE: Another "Screamin Demon" Delta build
 

She looks gorgeous..!

If you could make the fins the fairings for the linkage that would kill 2 birds with 1 stone.

Otherwise it's going to be tough to avoid coming up with a design that doesn't have a blunt aft end...?

RE: Another "Screamin Demon" Delta build
 

Lookin awesome!! It's going to look fast just sitting on the table!

RE: Another "Screamin Demon" Delta build
 

;) Great idea, giant canoe covers...
I gain a bit of drag over the winglets but...
I got to think about that, thanks that may make things a bit easier than what I had intended.
As far as the aft end I was thinking along the lines of the x47b type of look.

RE: Another "Screamin Demon" Delta build
 

Thankks Smokn, it just another "Screamin Demon" like you guys have already built I'm just trying to blend a few ideas into it, hopefully not screwing a good plane up.

Combatpigg just made an interesting suggestion for another idea to incorporate as well...

RE: Another
 

A bit of progress ...
While the first picture may not look like much, it is a part I have needed for some time, these are the torque rods for the elevons. Now all I have to do is make up the top of the control horns the pushrods go through and I can proceed with enclosing them in the cooling duct inlet. I have got to build the torque rods into the trailing part of the wing and cooling duct once they are mounted to the trailing edge of the wing in their mounting tubes.
I gone around and around several times on how I was going to enclose the control linkages. I was going to either use blisters, or scrap the winglets and go back to the two fins mounted near the center of the fuselage so I could use them as a canoe covers for the elevon linkage. I really wanted to use the winglets over the fins for the reduction in interference drag and a couple of other reasons. Because the control horn have got to fit inside the cooling duct they are a bit shorter than I would like. Because I can't give the servos the mechanical advantage I would like, I had to go to a stronger servo than I would have used. Just to throw a bit higher level of difficulty into the control linkage I am using push rods in what would normally be a pull/pull configuration so I have push/pull action on the elevon torque rods. (see sketch- It shows the torque rods in the cooling exit)
I have also redesigned the winglets using a 3/16ths thick built up construction rather than the 1/8 slab construction, as well elongating them, and raking them a bit more. Doing this I reduced the overall frontal area by about 3/8ths of a square inch by lowering their profile by just over an inch. Because of the swept wingtips on this plane I also was able to move them back from the neutral point by 2 inches.
Well now back to building instead of drawing...

RE: Another
 

I've had someone take a look at my selections of materials and proposed method for using the torque rods and the setup I am using should work. (Thanks again Brooks!) Because of the limitations in the dimensions of the control horns for the torque rods I had to go with 100 oz servos for this plane. I have just finished cutting out the pockets for mounting the servos. I really wish I had done this before I had the sheathing on but this part of the design was still in a state of flux until recently. Now having gotten that sorted out the build will start to progress again.

RE: Another
 

Tight quarters in there isn't it.
I'm loving your build IE! My next one may be a lekkie also now that I've been watching this.:D