I always liked patriotic designs and went back to red, white and blue on my SV22 refinish. Sina was a huge influence on that refinish. I am also working with Sina on a patriotic finish on my new stunter,Voltron.

Here's Bruce Hunt with a flag-ish scheme:

I like it! Simple, elegant too.

Right ; Well Then ; Where were we . 

just wondrin how its doin , where its at . One thing with electric , theres no oil to hasten painting before flight . 

Hi Motorman (I'd sure like to address you by your real name, but it is not on your profile...):

The distance between the shaft center lines is approximately 15.5 inches. Not sure that's enough to allow the motor speed differential to make a difference, but it's worth a try... Just one more potential advantage of a twin and of electric power...

New stuff! This morning I laid in the fillets on the bottom of the Second Wind. I use the Super Fil product for fillets and have had great success with it. It is strong, easy to apply and sandable. Last week I applied the .2 carbon mat to the fuselage, applied a few coats of non-tautening nitrate dope and sanded the mat between coats. I'm hoping to have this model and my new Crossfire Extreme XLTC in primer by the end of the week. Then it will be a few days of excruciatingly detailed sanding before the ChromaSeal coat goes on.

I know this project has stretched out over a long period of time and some of you have questioned my commitment to finishing this ship. All I can say is, this project was not about reaching a speedy end; it was about enjoying the designing and building journey. This model was not slated to be a competition model for a specific season; it was something that I worked on when I felt like working on it. In the interim I've designed, built, finished and flown other models. I'm sort of looking at the twin as my masterpiece. I hope I can sustain that feeling all the way through the finishing process.

Later - Bob Hunt    

Do you think Super Fil would be a good compound for making propeller molds? Does it smell as bad as bondo?

Thanks,
MM

I think it is too soft a material to be used as a prop mold and expect any significant life from the mold. It has very little odor at all, however, and that's one of the good things about it. I think that an aluminum filled epoxy would be a better bet for a prop mold.

Later - Bob Hunt

 " it was about enjoying the designing and building journey " .

this makes it a SAGA , like ' Gone with the Wind ' ,   and all the better for it .
these young blokes are all in a rush these days .  

"  I hope I can sustain that feeling all the way through the finishing process. " !

at least it wont get oil all over it to impeed the paint adheshion , if you fly it before the graphics are applied . 

found with a bit of keel area , the inner outter bits not a lot of worry , running a booming 25 & a yapping 19 together .
At times the inner wants to chime in , or NEEDs to . Uphill Vertical in gusts .


one should avoid this effect though . with control line .

"in 1951 when he flew the ground attack version of the Meteor with a
demonstration of a new manoeuvre that he had developed and dubbed the 'Zurabatic
Cartwheel'."

a bit of tipweight can be usefull

Bob, did you mask for your fillets? Just curious...

Hi Wayne:

Yes, I do mask the model in the required areas for filleting. The following text and photos will, hopefully, show the technique that I (and many others) use to install fillets.

Photos 1 and 2 show the model (my new Crossfire Extreme XLTC in this case...) taped off and ready for the fillets. I place the tape on each surface back far enough to allow the full radius of the fillet to be formed.

Photo 3 shows a few of the many custom fillet tools that I have made. You can custom-size the radius that you want. I make these from 1/32 or 1/16-inch thick plywood.

Photo 4 shows the Super Fil material being rough formed. You need to "glop in" enough Super Fil to form the entire fillet before you do the final shaping.

Photo 5 shows the fillet smoothed to its finished shape with the fillet tool, but with the tape still in place.

Photos 6 and 7 show the tape removed

I install all of the fillets on the bottom of the plane and let them cure. Then I install all the fillets on the top of the plane.

Hope this helps.  

Later - Bob Hunt
  

Doc,
I've been using Super-Fil for about 15 years now. Bill Werwage got me on to it. Bobby explained the application perfectly. I used other items for fillets in the past but Super-Fil is the only one that is trouble free.

The quantity is good for at least 4 or 5 stunters, so it is really cheap.

Bob,
Can't wait to see the airplanes coming out of the production spray booth this week. I also think the twin will be very competitive.

Randy Powell's progress on his fantastic new electric ship has shamed me into getting back to work on my Second Wind Twin (Don't want to rush into these things...).

Yesterday I made the trip to Buddy Wieder's spray booth (his garage) and shot the primer onto the airframe. Note in the photos that I masked off the open bay areas so that no primer could get onto them. The primer I use takes a bit of effort to sand off, and I didn't want to "go through" on the silkspan covered  areas when sanding. Those areas have been sealed and sanded using dope and Aero-1 filler. They are ready for the Chroma-Seal coat to be applied.

I plan to sand a few hours each week on this thing until it's done. Rushing at this point would be foolish.

The ship is coming out very light and I have high hopes that it will fly well.

Later - Bob Hunt  

Hi Bob:

They are cooling air outlet holes. You can't see it in the bottom shot, but there is a cooling air inlet hole in the bottom of the nose cone on the fuselage. I needed a way to get that air out...

Yeah, taping off the open bays was a Homer Simpson moment for me... Doh! 

Later - Bob   

Way cool!!!

Marcus

Looks awesome Bob!!

Wow! Thanks to everyone for the kudos!  

I still think it will look like a boxcar if placed next to Randy Powell's new electric machine (Check out the "New Build" thread on the building forum here if you haven't seen Randy's masterpiece yet...).

I was concerned about the "numbers" in this one for a while. It was mostly designed by peering over my thumb at the end of a deftly outstretched arm while repeating the phrase, "That looks about right" over and over. Hey, it's a time tested method... I had the chance to fly Gordan Delaney's Pathfinder Profile Twin while at VSC one year and was amazed at how well it flew. Really, that is one of the finest flying models it has ever been my pleasure to put through a pattern!

Having flown Gordan's amazing ship I was very concerned that my twin would not fly nearly as well because it just had to be "different" in numbers due to my design method. I recently called Gordan to get his twin's "numbers" in order to start again and build a "proper" twin. He got his twin down and started measuring. Each dimension he gave me was checked against my twin to see just how far I was off. I won't keep you in suspense; my twin was within 1/8-inch all the way around!   Talk about being relieved! That's the main reason behind my sudden surge of energy on this project. I'm now convinced that it will be a great flying ship. Buddy Wieder has been telling me that since he saw the initial side view drawing...

I'm going to attack the sanding of the primer this weekend and hopefully have it ready for the Chroma-Seal coat next week. After a detail sanding of the Chroma-Seal coat (Most of it will come off...), it will be time for a whisper-coat of white Chroma-Base paint and the canvas will be ready for whatever Sina Goudarzi and I come up with for a trim scheme. Wayne, trust me, it will not include anything in the copper/bronze/metallic brown family...  .

Sina asked me to send him top view and side view photos. He used them to come up with a two-view drawing on which I could sketch out some  ideas with which he could start work on a new trim scheme. This is a tough assignment; don't want to miss the opportunity to have something "special" for this one. I'm attaching Sina's two-view so that you can see what he's done. Perhaps this might help you in trimming your next plane.

Later - Bob Hunt

    

Bob,

Your model is really shapping up, you do good work. "SO." Standing ovation!

Posted a 2-view ta boot. What a guy!!

Plans? Kit in the works?

I'm looking forward to your progress.

Charles

Is the color scheme settled yet?

As long as you get it done before the Joe Nall. I want to see this plane fly!

Derek

P.S. I would like to take it for a spin too!

Progress report?

 What's the latest Bob?

On the multi engine equivalent issue it could have something to do with the smaller the engine the more HP per CI.  Also the tip of the prop does most of the pulling.  On a multi engine setup you have increased the prop tip area.  It's the same reason sale plains have long skinny wings. increases the efficacy. I should ask my Son - he is a real engineer.

Thanks guys, I did realize that you can't simply add up the displacement, hence my question on how to work out what sort of power you need for multi-engine models. Larry's point on the prop swept blade area is also valid. In my next life I need to do an engineering degree! It will be interesting to see what motors, props and batteries Bob ends up with.

Keith R

I've always believed that the "artificial" airspeed provided by the prop disk is what makes our planes fly the way they do. Not only does the air blast from the prop make the wing more efficient, but the elevators as well. How do I know this? I once made a canard with the prop aft of the elevator. I needed to more than double the size of the elevator to get the model to perform properly. The elevator was only seeing the air flow provided by the airspeed of the model; it was not getting the benefit of the additional prop blast. The light went on...

Since that time I figured that a twin was the optimum platform for CL stunt... if only I could get consistent engine runs. Let's face it, it's difficult enough to get one engine to run perfectly all the time; two engines running perfectly all the time is both a dream and a joke. With the advent of electric power I realized that all those sketches I made of twins over the years were suddenly practical possibilities.

As mentioned earlier in this thread, I had the opportunity to fly Gordan Delaney's Pathfinder Profile twin. That ship is powered by two 15's and is fitted with two 8.5-inch diameter props. It has effectively 17 inches of prop disk span providing a huge amount of that (as I call it) artificial air blast. Gordan's model was among the very best flying models that I've ever had the pleasure to pilot. It had plenty of line tension (but not excessive) everywhere; it flew at virtually one speed everywhere, and it was easy to fly anywhere on the hemisphere. I was sold at that point.

I know my twin has taken a long time to reach completion; I have had no time schedule for this one. It will fly in the spring. I've learned tons during the building process about engineering a model to be light, strong, and accurate. There were lots of challenges and that was the fun part. With what I've learned, we've already begun work on a totally new, and larger, twin design. In fact, we have a test bed almost ready for flight and it should fly later this week. I'll throw in a few photos of the testbed twin at the end of this response.

Power system? Well, we originally were going to use E-Flite Power 10 motors. The Kv was a bit high on those and so, my friend Will DeMauro did a bit of research and found the Cobra 2820-14 motor, which is a bit lighter than the Power 10, has a much larger main bearing and a lower Kv (850). Both of these motors - and the retracts - will run off one 4S 4,000 mAh Hyperion battery. Two Phoenix 35 ESC's are being used and a Castle Creations BEC is being used to power up the retracts. Will Hubin has provided a brand new Twin Timer that has separate ESC ports, a retract port and a pot with which one motor can be made to run faster or slower than the other motor. That promises to be a great trim tool...

The Cobra motors will be fitted with either 9-inch or 10-inch (Obviously we will try both...) props. We have obtained a number of matched sets of tractor/pusher props and will try all possible permutations to determine which setup works best. If the 10 inch props end up being the choice, that will yield 20 inches of prop disk span, covering a great deal of the span of the model. The wing should be lively... If we use the 9 inch props, we will only have a paltry 18 inches of disk span.  

I'm making no predictions, but if this project reaches fruition anywhere near my hopes for it, I'll have a weapon like I've never had before.

Enjoy the photos of the new testbed... This model has 672 square inches of wing area and looks to be ready to fly with battery on board at 63 to 65 ounces. Buddy Wieder and I have put about a month of work into this one.


Later - Bob Hunt

That ship is powered by two 15's and is fitted with two 8.5-inch diameter props. It has effectively 17 inches of prop disk area..

Just being picky.. The disc area of 2 x 8,5" props equals disc area of one 12" prop.



Lauri

This is beyond awesome.   Is the Blue Foam Molding bucks or will they be glassed?

I've got bad news for you, Marcus... You're going to be singing soprano from now on. Those blue foam blocks are the actual blocks that are attached to the plane; this one will not have molded shells.

Okay, I sort of sprang this one on everyone without proper explanation. This is a testbed model designed to allow us to try different thrust line placements. There are two sets (so far...) of nacelle front ends; one with the thrust line on the wing's centerline, and one with the thrust line 1/2 inch lower than the wing's centerline. The rear halves of the nacelles are permanently attached to the wing and the front halves are removable/interchangeable.

We used the same technique to build the wing for this testbed model as we did for the Joe Nall Cadet models. We call this construction the  "Lost-Sheeting method." There is no balsa sheeting on the wing. The wing is a solid foam core made from 1-pound density foam. There is a slot cut in the center of the wing cores to allow the leadouts to get to the tip and have some adjustment. There are slots cut into the top and the bottom of the wing at the high point to accept 1/2 x 1/8- inch basswood spars. The spars run the full span of the wing. There are several shear webs imbedded in the core between the spar slots to prevent the spars from "racking." That is the technical term for what the spars want to do on either side of the wing during maneuvering. In an inside maneuver the top spar in in compression and the bottom spar is in tension. If there were no webs between them, they would try to "clap hands" under stress. The webs prevent the spars from trying to move and hence impart a tremendous amount of strength. Enough not to break under maneuvering loads by themselves? Not quite. After the spars are glued into the slots and are firmly glued to the vertical grain shear webs, we apply .2 (two tenths ounce per square yard) carbon mat using water thinned Titebond wood glue. The carbon is first applied from the back of the spar on the top, around the leading edge and ends at the back of the spar on the bottom. A thin carbon strip reinforces the trailing edge area, and an additional piece strengthens the entire center section area. Even the flaps are 1 pound foam covered with two layers of the .2 carbon mat. They are extremely rigid and absolutely straight.  

This process yields a wing that is extremely strong and yet quite light. Can this method be used in a "front line" model and have a front row finish? No; it is great for trainers and testbed models, however. If you have an idea for a new design that needs testing before you invest a lot of time and money into it, then this is a great way to test your theories quickly and cheaply.  

We wanted to have a model that had the correct fuselage volume and "looks." A profile fuselage would have been prone to twisting and we wanted a model that would look and fly like a real front line ship. To quickly and cheaply achieve this goal we used Dow Flotation Foam for the blocks on the top and bottom, and for the hatch areas as well. This is NOT the type of foam you might find at one of the home improvement houses; it is a very special type of foam and is quite difficult to find. It is used in making floating docks. This foam carves and sands like butter. We normally use it for the mold bucks on which we mold our fuselage shells. This time we carved and sanded it to shape, and then hollowed the blocks to about a 1/8-inch wall thickness. All the blocks carved and hollowed in this manner together weighed about an ounce. To finish the surface we brushed on a coat of Z-Poxy finishing resin and then let it sit for a few minutes to soak in a bit. Then we wiped off all the excess. When the epoxy had cured, we sanded the surface smooth with 220 no load paper. There will be no additional finish applied to the testbed. We believe that this method could be used in a front line model with the addition of a coat of .2 carbon, so long as the paint used did not affect the foam. There are a number of finishes that we intend to try on this floatation foam and we will report the success or lack thereof somewhere down the road. You could produce quite exotic shapes in an extremely short amount of time if this works out...

All the exposed balsa has been sealed against moisture with a thin coat of polyurethane clear. The exposed foam is being left raw; there is no fuel residue to worry about. Again, all of this was proved out in the Joe Nall Cadet models that we built to teach new modelers with at the Joe Nall Fly-In.

The testbed is fitted with E-Flite 10-15 size retracts, and it is a tricycle gear system. We wanted to know just how much differently a twin would fly with the gear up...  

This testbed will allow us to do a lot of propeller experimentation and motor run experimentation before putting the system into our new front line competition twin designs. Better to find out potentially bad things with a model that doesn't have a competition finish...    

This model is almost ready to fly and our target is sometime next week. We're hoping for a fairly warm and calm day for the test hops.

Later - Bob Hunt