(Something Fast?) Delta Build Thread
 

Between my addiction to Deltas and my addiction to speed I kept thinking of what would make the perfect Delta. It seems that the Delta’s I am aware of all seem to have shortcomings so I made a list of what I would change. While a Delta may never win the German Speedcup, I have not seen any real attempts to be competitive. I may not be qualified to design a world champion speed plane but basic issues can easily be addressed.

This Delta is my design and my goal is to have a very clean airframe that will fly really fast or really slow. Most Delta models either have everything out in the breeze, weight too much or both. Deltas look good by default so making it look even better should not be hard. These were my goals during the design phase.

1. Reduce all drag. Drag is enemy #1 to speed so a clean design is important. (easy full engine cowl)
2. Low weight. Heavy airplanes do not fly well and it increases drag.
3. Build in a couple of days, not weeks or months.
4. Cost $100 or less to build.
5. Look good.

Specifications:
Wingspan – 32 in
Wing area – 475 sq. in.
Weight – three pounds with a 40-50 glow engine

RE: (Something Fast?) Delta Build Thread
 

I have built a few kits but scratch building is not my forte. I modified a copy of my plans and sent them to Top Notch Products for laser cutting. I was amazed on how well the parts fit together. I guess they should but I kept thinking I was over looking a big mistake but that was not the case. I gathered up the wood and parts listed on my material list and set everything out to start building. I liked the carbon fiber spars on the Dust so well I put out the couple of extra $ to go that route.

RE: (Something Fast?) Delta Build Thread
 

With a wing span of just 2" more then a clipped wing Dust the building area does not need to be very big. We will see if i can build it on a 30" x 40" dinette table.

For phase 1 of the building I gathered up the spars, ribs, engine mount, firewall, 1/4" dowel and two screws. The airfoil is a NACA 0006 but with the #1 ribs being over 22" long the maximum thickness is a little over an inch. The engine mount is just over 3" long so the engine can be set back far enough for a spinner to be close to the nose ring. I guess a rear intake fan engine would fit with a little effort.

I kept trying to think of a good way to attach the spars to the last rib and came up with a way I think will work well. I put a 1/4" dowel in the end of each spar with the long spar dowel cut off flush and the front spar dowel sticking out 3/16". The #4 rib height would not allow drilling a 1/4" hole and still be strong.

To make sure the airframe was straight I used two 1/2" hardwood rails with 3/16" supports as seen in the picture below. I just push down on the spars and everything aligned perfect. Thin CA glue on every joint except the last rib with a screw in it.

RE: (Something Fast?) Delta Build Thread
 

I like it!:D
Simple, efficient, cheap and fast that's exactly how it should be![sm=thumbup.gif]
I have never owned a or flew a delta but it looks fun!
I'll be watchin'
SJ

RE: (Something Fast?) Delta Build Thread
 

Thanks SJ, we will see if it flies.
There is a reason for several in this forum to have more then one Delta. It may be time to try one.

RE: (Something Fast?) Delta Build Thread
 

Mike

I like you build, looks good similar to my own delta.

Keep us posted.

Andre


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http://www.vimeo.com/clip:209833
http://www.vimeo.com/clip:209359

RE: (Something Fast?) Delta Build Thread
 

Mike- NICE WORK!

I will definitely buy one of these-

RE: (Something Fast?) Delta Build Thread
 

Thanks Razor,
Did I say I was going to sell them? :D
At this point it would be easy to put together a few kits but that may be a little premature. First it needs to fly well, fast and hold together in a 20G turn.

RE: (Something Fast?) Delta Build Thread
 

Next comes the leading edge, trailing edge and wing tips.

I did not want a blunt leading edge and first thought about using 1/4" bass wood. However, with the 48* wing sweep the hard wood did not have much mating surface on the ribs. After some testing I decided on mid weight balsa as it let me use firm pressure for the surfaces to fit well and the sheeting made it surprisingly strong. While it will take mild abuse I would not fly it into a tree and expect no damage.

Tilting the end ribs up I was able to see a perfect alignment before installing the trailing edge and then gluing everything including the end rib screw joint. I also install 1/4" tri stock on the trailing edge for the elevon to pivot on.

Wing tips are out of 3/8" x 2" balsa and cut as shown on plans after putting a 20* bevel on one edge with a small table saw. I marked the center on the edges and started sanding. An electric sander would have been nice.

The second picture shows the laser cut vertical fin support with spacers on the fin support and bottom sheeting for a 10* fin tilt. I hope the patch repair does not through off the lateral balance.

The sharp leading edge and the the wing tip design was discussed in the aerodynamics section and it seems I am not breaking any rules to create unwanted vortices's. Those guys are not afraid to point out problem areas if you have a bad idea I found out.

RE: (Something Fast?) Delta Build Thread
 

Before starting the component compartment and hatch I sheeted much of the bottom including the 1”strips on the leading and trailing edge. The hatch area has no predefined height but will be determined by the fuel tank and servos. There was plenty of room for an 8 oz. Tank but I am going with a 6-oz slant tank. Servo rails have been installed so a minimum compartment height could be determined.

At that point I took two sheets of 3/32” balsa and glued the ends together so I could work on them as a unit. I rested them on the spar on the outside of the #1 rib so I could mark the rib contour, servo rails and bulkheads. I also marked the height needed to clear the components inside. The balsa ahead of the firewall was left intact so it could be later pulled into the nose ring and glued. Any cutting in this area was kept square with building a full engine cowl in mind. The engine will be partially cowled just by design.

After forming the balsa I separated the two sheets. I then glued the two matched pieces to the inside of each #1 rib. I then glued tri stock so the hatch would have a resting place and room to round by sanding.

I really hate to add weight to balance a plane so I left access to the area behind the spar for the battery if tail weight is needed.

RE: (Something Fast?) Delta Build Thread
 

I dunno Mike, I have been reading your posts for years and you are a Whiz. If you are designing a delta, even for fun, it is going to rock- IF it becomes a kit I want one ;) If not then I want video!

You are a true speed-freak and you even apply like Aerodynamics and stuff to your posts, I can fly alright but I am basically a 4th grader com pared to you, Bob27, Flyboy dave and others when it comes to design/build/explain what we do.

Cheer to you my friend!

james

RE: (Something Fast?) Delta Build Thread
 

James,
I am flattered but there are a few pretty sharp guys in this forum. We all have our area and I just try to learn from others and make contributions when I can.

As far as my my design, time will tell. I am not reinventing the wheel here but taking proven concepts and putting all the good parts together.

RE: (Something Fast?) Delta Build Thread
 

Mike Looking good.

I have used 6 mm carbon rods in my delta's leading edge, and cut a half circle in the LE of the ribs to accept the carbon rod.

Also, I found a good 2" capstrip allong the leading edge helps when covering the wing.

But looking good.

My next version will have a smaller span and maybe a 3 mm carbon rod in the leading edge.

Andre

RE: (Something Fast?) Delta Build Thread
 

Mike, it looks like your are building a mini BTE Vortex. Where will the retracts go? Smile! Thanks for sharing the pics of your Vortex and attached a couple of pics of mine under construction, Ron H

RE: (Something Fast?) Delta Build Thread
 

Andre,
I have had two Diamond Dust with 7mm glass rods for leading edges and considered a smaller rod on my design. The good side to the rod is they are very durable. My reasons for not using a CF rod is weight, cost and I would have to add tri stock to get the desired sharper leading edge. The 3mm would not be too blunt though. Many model airplanes use balsa leading edges with sheeting and it is very light and surprisingly durable.

What is the span of your delta?

RE: (Something Fast?) Delta Build Thread
 

Hi airbusdrvr,
If we put them side by side I suspect "mini" would be a good word to describe mine. The distance from the bottom of the rib to the spar was less then 1/2" so I deceided not to install retracts on this one. :D

RE: (Something Fast?) Delta Build Thread
 

Hey Mike

Yep I agree with what you say, it does keep the cost down.

My delta is a 37.25 inch span and 21 inch chord.

Andre

RE: (Something Fast?) Delta Build Thread
 

That looks cool. Are you going to post PDF plans for this when done?

RE: (Something Fast?) Delta Build Thread
 

Thanks Troy, I may but want to see it fly well first. The guys that print the plans for me need PDF. The laser cutters wanted DWG and I work in TCW. During the build process I have made a couple of minor changes to the plans but not many.

My hats off to the scratch builders. I adjust my drawing .003" for laser kerf for the perfect fit and some guy makes it fit with a saw? My eyes work in tenths of an inch, not thousandths. :D

If it flies well the work is already done for throwing together a short kit with printed plans for not much money. I don't want to get ahead of myself though.

RE: (Something Fast?) Delta Build Thread
 

If this thing flies as fast as it builds then watch out. Since this is a prototype I am not going to put a $350 Jett 60 LX on it but will test the airframe with a TT 46 Pro.(I know I know) I am also experimenting with engine cowls and would hate to overheat an expensive engine. I have enough parts to build two airplanes and the second will be a different animal.

It was tempting to add more sheeting then my plans called for but I resisted. The open bays are not that big and bottom damage during landings should be less then my Dust. After applying the top center sheeting I put tri stock along the fuse area for a poor mans fillet. The nose ring was installed and the fuse sides that extended to the front were trimmed and pulled into the nose ring and glued. I also streamlined the bottom of the engine compartment.

The vertical fins were sanded but not glued in and the elevons were hinged. I think I will cover the plane before gluing the fins in because of the tight space between them and the hatch. The elevons will be installed before covering so I won’t have to reseal them.

I am going to reinforce several areas with fiberglass cloth and cut out what I would need. The large piece in the middle is actually going on the belly to protect it during landings.

The three most difficult things so far have been sanding the wing tips (razor plain on order), determining the sequence of assembly and not twisting the airframe while sheeting. Frequent checks for a straight airframe show it straight and the sheeting will now keep it that way.

RE: (Something Fast?) Delta Build Thread
 

You can see where the fiberglass was put down. pay no attention to the cowl in one of the pics. My second cowl attempt has wet paint on it and not shown. I used fiberglass and sheeting rather then kevlar thread to secure the leading edge. It seems like I use the wing tips for handles so I reinforced them and of course the belly for landing. It is ready to cover and the weight is 12.2 oz.

RE: (Something Fast?) Delta Build Thread
 

What about a thin piece of ply on the bottom to act as a skid and double as a grip to hand launch? Wouldn't add any significant drag but would save the covering and sheeting on rough runways. Still looking for a home for my 6.5 and this might be the ticket!

RE: (Something Fast?) Delta Build Thread
 

I would absolutely want a skid on a rough runway but it should be just fine on grass. I have hundreds of flights on belly lander with occasional tears in the covering being the biggest problem. A hand grip for launching would be nice. I was thinking about something rough textured on the side of the fuse just behind the engine may work.

Aren't you an electric guy? The plans show a back plate mount for an electric motor. The servos could be mounted behind the rear spar and there would be tons of room for a $500 battery behind a Neu 1509. If not a 6.5 would work. :D

RE: (Something Fast?) Delta Build Thread
 

lookin good Mike and very similar to my current project also..a fully sheeted/glassed DD..I used green florist foam to make the cowl moldings..(three piece)..shapes very easily but the sanding dust is a bugger to get rid of

good luck with it and I'll keeping checking in on the progress.

RE: (Something Fast?) Delta Build Thread
 

HB, that foam is an even bigger bugger (???) to get removed. I tried that stuff once and had a heck of a time getting out afterward. I use blue foam for cores now and acetone cleans out in seconds.;)