Author Topic: Electric Crossfire (Read 8565 times)

Bob Hunt · « **on:** June 12, 2011, 07:06:10 AM »

Since I ran out of time to do a proper job on my new "Second Wind" twin and get it ready for the Nats, I decided to finish up the Crossfire that I started last year instead.

Here are a couple of photos of it during the painting process. I've since added the name and numbers using painting stencils that Phil Granderson made for me. They were perfect and incredibly easy to lay on the model. I am using Chroma Base Dupont paints on this one, and this paint covers so well that the edge produced by the stencil is almost imperceptible. I'll try to take a few shots of it just before the clear goes on this week.

This one will have an E-Flite 25 motor and a Phoenix 45 ESC. I'll use Hyperion 4S 4000mAh battery packs and, of course, a Hubin timer. The estimated weight will be 58 to 59 ounces with the battery on board. That is equivalent to a glow model without fuel at 52 to 53 ounces! The wing area is 670 square inches, so this one should be plenty light.

Later - Bob Hunt

john e. holliday · « **Reply #1 on:** June 12, 2011, 07:24:13 AM »

That is awesome.

Bill Little · « **Reply #2 on:** June 12, 2011, 09:41:29 AM »

The "look" is incredible, Bob. I am sure that you will be competitive with this set up!

Bill

Crist Rigotti · « **Reply #3 on:** June 12, 2011, 09:46:40 AM »

Wow, looks good Bob.

Bob Hunt · « **Reply #4 on:** June 12, 2011, 10:30:09 AM »

Thanks, guys for the nice comments. I have been told by many for years that the Genesis (rudderless) look was very dated (outdated really...) and that I needed to go to a design with a rudder. Years ago I took a long sabbatical from CL Stunt and flew a bunch of RC pattern. I designed a ship for RC that used a lot of my CL thinking and called it the Crossfire. The name came from the crossfire of technology from CL to RC.

I came back to CL in 1987 and brought some of what I had learned in RC back to CL, and again built a ship and called it Crossfire. Only this time it was a reversal of the theme... I had found the value of a rudder!

That first Crossfire was the first dedicated piped CL stunt model and was built in haste to get it ready for the 1987 Nats. I had lost a bit of my light-weight building touch those years in RC and the original Crossfire weighed in at 64 ounces! Ouch! It flew okay, but it did show its weight. It turned very equally, however and I decided to strip the finish off of it and put it on a diet. I made built-up movable surfaces for it and revamped the look of the bottom block. I hogged out the vertical fin and put ribs in it and made a built-up rudder. I was very careful in applying the paint and came up with a net loss of nearly nine ounces!

That ship sat on the front row in appearance at the 1990 Nats and flew to a fourth place finish. It was a very good airplane. It was actually built around the wing and force arrangements that I used in my 1980 Genesis. That ship finished in 2nd place at the 1980 World Championships (Silver Medalist) and also in 2nd place at the 1980 Nats (Both times just behind that Les McDonald guy…). I really liked the way that the swept forward trailing edge worked and just opted to re-design the fuselage shape when I came up with the Crossfire. Not sure why I moved away from that wing design; it really worked well!

Last year I decided to re-design the Crossfire as a dedicated electric model and used the same wing as the 1980 Genesis and the 1987 Crossfire. Only I added a couple of inches of span to give it a higher aspect ratio look. I also revamped the bottom block shape (again) and added a curved ventral fin. I really like this one aesthetically and may build a couple more with slight style changes. I’m fairly sure it will fly well, as it is light, straight and is built on a proven set of “numbers.” We’ll see…

Plans will be available, as will wing and tail sets and molded fuselage shells.

Attached are photos of the RC Crossfire and the first CL Crossfire.

Later - Bob

Bill Little · « **Reply #5 on:** June 12, 2011, 10:53:26 AM »

Any link to Stevie Ray Vaughn in that "Crossfire" name Bob?

Bill

Bob Hunt · « **Reply #6 on:** June 12, 2011, 10:57:44 AM »

Sorry, Bill, but not a chance. I came up with that name before Stevie or Chrysler!

Bob

Mike Scholtes · « **Reply #7 on:** June 12, 2011, 11:09:39 AM »

'Fess up Bob, there's a little SRV in any guitar player!

I don't see any obvious venting on the model; do you have a shot that details your thinking on inlet and outlet venting on this one?

Bob Hunt · « **Reply #8 on:** June 12, 2011, 11:16:20 AM »

I not a big fan of slack tuning, Mike... I'm more of an Al DiMeola fan... Stevie was good, but just not my cup of tea.

You are very perceptive about the cooling. There is a large chin scoop that has a bifercator that directs the air onto the motor. The big thing about this one is that the entire internal fuselage is opened up to allow the exhaust air to go through the fuselage and out the back where there is an outlet! There is a low pressure area aft of the outlet and this should "pull" the heated air through and out.

Later - Bob

Bob Hunt · « **Reply #9 on:** June 20, 2011, 07:23:04 AM »

Well, the clear is on and rubbed and the flaps and elevators are on for good. All I need to do now is serve the leadout ends and paint the spinner (which, by the way, is a pre-production sample of one of the new E-Flite electric spinners. It has slots cut for reverse rotation props).

Target date for trim flights is Thursday, June 23rd. That's a record for me for having a new ship done in time to put a bunch of practice flights on it before the Nats. Usually I'm testing them the day before I leave home!

Here are a couple of shots at this stage.

L:ater - Bob

Bob Hunt · « **Reply #10 on:** June 20, 2011, 07:26:24 AM »

Here are two more shots...

Bob

john e. holliday · « **Reply #11 on:** June 20, 2011, 07:41:18 AM »

Bob, I think you have out done yourself on this one. I like it.

Bob Hunt · « **Reply #12 on:** June 20, 2011, 07:51:02 AM »

Thanks, Doc! I'm very pleased with the "look" and think that painting the spinner will only help the illusion. Hopefully it will fly as well as I hope it will. It should, as it is light and straight. It is certainly the most shiny model that I've ever turned out! My arms are aching from rubbing all weekend long...

Later - Bob

Allan Perret · « **Reply #13 on:** June 20, 2011, 09:20:34 AM »

Looks great. What did you use for clear coat, dope or auto 2-part ?

Would like to get a set of the plans as soon as available, the plan will be for a dedicated electric, right ?

Bob Hunt · « **Reply #14 on:** June 20, 2011, 09:33:55 AM »

Hi Allan:

Thanks! I used Dupont Chromabase paints and clear. The clear I used is the G2-7779S Multi-Mix, with the 7775S catalyst.

Plans will be available sometime after the Nats, and yes, it will be a dedicated electric ship right from the get go. If someone wants to modify the nose for glow, that's okay by me, but there will be no plans from me for it. I'm now totally committed to electric power, except for Classic Stunt.

Later - Bob

Derek Barry · « **Reply #15 on:** June 20, 2011, 09:46:30 AM »

Looks great Bob! However, I am a fan of the no rudder Genesis

Dad built one for Bob Shaw and I got to fly it a few times, it was a lot of fun.

C-ya in Muncie

Derek

Matt Colan · « **Reply #16 on:** June 20, 2011, 10:50:08 AM »

Bob, that is just too cool!!!!!! I really like it!!

Looking foward to seeing it in Muncie!!

John Miller · « **Reply #17 on:** June 20, 2011, 12:10:06 PM »

Sun of a gun, I thought you'd finally run out of Bronze paint, but the clear coat changed the tint.....

Hey, it looks really great. It will fly just as good I'm sure. Don't forget about the twin when you get back from the Nat's though,,,, please.

Allan Perret · « **Reply #18 on:** June 20, 2011, 01:52:59 PM »

Was looking at the first two pictures at top of thread.
Thats really cool the way you faired the struts into the pants.
Would like to see a "How To" on that..

Bill Little · « **Reply #19 on:** June 20, 2011, 02:31:36 PM »

Brother Bob! It does look fantastic, as I would only expect from you. And as such I also expect it to be a great flier. Best of luck at Muncie!

Big Bear

Ward Van Duzer · « **Reply #20 on:** June 20, 2011, 02:35:35 PM »

Bob,

When you are done with this one, just drop it in the mail

I'm sure it'll get to the right address!

W

Crist Rigotti · « **Reply #21 on:** June 20, 2011, 04:27:22 PM »

Glad to see you are entering Open with that one! Sweeet!

An Advanced entrant,

Bob Hunt · « **Reply #22 on:** June 20, 2011, 09:04:48 PM »

Hi Wardo: I know that you've always liked the Crossfire look and have built a few ships that had a lot of CF influence. For that reason, you will receive the first copy of the new Crossfire Extreme plans!

Crist: What makes you think I'm not going to fly in Advanced? I haven't been to a Nats in years. Don't I get to start over in Advanced?

Derek: Alas, you've seen the last Genesis from me... Except, maybe if I decide to fly some Nostalgia 30. Heck, I'll build a Juno or a Stiletto for that...

John M: Yes, my plan is to crank hard on the twin when I get home from the Nats. I really think that is the future...

Allan P: I guess I should have taken some photos of the fairing process huh? I will build another Crossfire Extreme, but it just might end up with retracts... No fairings then. $:-\$

G'night - Bob

Tom Niebuhr · « **Reply #23 on:** June 20, 2011, 09:35:09 PM »

Bob,
Glad the "Crossedwire" is finished. I see that you made a HUGE change to your paint scheme... you added stripes on the flaps! And you know that I like the rudder.

The CF is certainly up to your usual fantastic standards. I guess you will have to fool Crist and take another FIRST.

Then on to the twin.

wwwarbird · « **Reply #24 on:** June 20, 2011, 09:52:09 PM »

The plane looks awesome Bob, great lines and super sleek. I really like the "non-copper" maroon color too, what is it?

Wynn Robins · « **Reply #25 on:** June 20, 2011, 10:03:17 PM »

the through the fuse venting is COOL! love it.......how did you keep the structure free through the back and still keep it stiff?

kits Bob?

??

Bob Hunt · « **Reply #26 on:** June 21, 2011, 05:04:31 AM »

Hi Wayne:

The "Maroon" color you are seeing in the photos is actually a dark metallic brown that contains a lot of red flake in it. I used to use Cadillac "Firemist" brown paint on my ships. The ship that I used to make the 1978 World Team and the WC winning Genesis had that color as the main trim, as did the two Genesis models that I built for the 1980 World Championships. The first Crossfire had the lighter copper color as the main color trim on its first paint job, but I went to the darker color for the repaint. The color in the photos that I posted don't really reflect (pun not intended...) how the color presents in real life. It really looks like a dark metallic brown with red highlights. Photos can be deceiving...

Hi Wynn:

Yes, the fuselage is "open" at the rear to facilitate venting. I used various diameters of sharpened brass tubing to cut "vent" holes in each fuselage former and in the formers that are in the molded top and bottom shells. I used diagonal "sticks" in the fuselage crutch to maintain stiffness and also relied on the carbon mat that was applied over the entire model to add to the stiffness. Trust me, it's rigid! Dean Pappas explained to me that the opening at the rear is in a low pressure area and it will tend to "suck" the hot air through the fuse and out the back. We'll see... I also made some cooling outlet holes in the bottom block just in case...

Attached is a photo of the original Crossfire in its original paint scheme and also one of it in its second paint scheme (I posted this photo above as well, but I'll put it here for comparison).

Later - Bob

Bob Hunt · « **Reply #27 on:** June 21, 2011, 05:35:03 AM »

What the heck, I'll throw in one of the new Crossfire Extreme without any image correction for brightness. This may give a better sense of the actual color (then again, maybe not...). - Bob

Crist Rigotti · « **Reply #28 on:** June 21, 2011, 06:18:27 AM »

Quote from: Bob Hunt on June 20, 2011, 09:04:48 PM

Crist: What makes you think I'm not going to fly in Advanced? I haven't been to a Nats in years. Don't I get to start over in Advanced?

I laughed out loud on that one Bob!

Tom Niebuhr · « **Reply #29 on:** June 21, 2011, 03:36:09 PM »

Bob,
That is one fine looking airplane. As to the talk about advanced. Yes , you are an advanced Expert! Crist has a lot to fear.

Tom Niebuhr · « **Reply #30 on:** June 21, 2011, 03:38:48 PM »

Bob,
Your RC Crossfire had anhedral tail surfaces. Is there any reason that you did not use that on the CL Crossfire?

Bob Hunt · « **Reply #31 on:** June 21, 2011, 04:00:17 PM »

Hi Tom:

Thanks for the comments I really, really appreciate them!

As for the anhedral, well, I'm getting lazy in my old age. It sure looks cool, but it's just too much trouble and it may add too much weight to the aft end of the model in structure and linkage. But, again, it does look cool!

Looking forward to flying with you in Tucson in March.

Bob

wwwarbird · « **Reply #32 on:** June 21, 2011, 05:47:29 PM »

Quote from: Bob Hunt on June 21, 2011, 05:04:31 AM

Hi Wayne:

The "Maroon" color you are seeing in the photos is actually a dark metallic brown that contains a lot of red flake in it. Later - Bob

So then, in a way, you could call it another shade of copper.

Bob Hunt · « **Reply #33 on:** June 21, 2011, 06:07:22 PM »

Well, not copper perhaps, but certainly in the bronze family...

Bob

John Miller · « **Reply #34 on:** June 21, 2011, 07:23:36 PM »

DOH!!!!!

Bob Hunt · « **Reply #35 on:** June 21, 2011, 07:28:18 PM »

Got a lot done today! My flying buddies, Tom Hampshire and Buddy Wieder came down to help and lend moral support... but I got a lot done anyway!

(Only kidding Tom and Buddy; you guys were a tremendous help!)

I wanted to finish off the "electronics bay" (Formerly known as the tank compartment...) without a mess of unsightly wires. I thought long and hard on this and came up with a solution that I think will work fine and look tidy.

I decided to mount the ESC and the Hubin timer on a plate that would rest on formers that would fit the shape of the bottom block. I wanted to keep this plate as light as possible, while still having a very secure mount. Iused light ply for the formers and cut them out to save weight. The 1/16-inch thick plywood plate is glued to the top of these formere and the entire unit fits very nicely into the bottom of the ship. The ESC is rubber banded to the plate and the Hubin timer will be screwed to the plate.

I was able to eliminate a lot of the ESC wiring, a good bit of the signal wire, and also the wire that runs from the timer to the start button was shortened to only 3-inches. Wire weighs a lot!

I'm attaching a couple of photos of the mount without the ESC or timer mounted, and in another post I'll post a couple with the ESC in place. I just brushed a coat of resin onto the mount to protect it from humidity and it will go into the ship tomorrow morning.

Later - Bob

Bob Hunt · « **Reply #36 on:** June 21, 2011, 07:29:49 PM »

Here are the photos with the ESC rubber banded in place...

Bob

WhittleN · « **Reply #37 on:** June 22, 2011, 09:21:30 AM »

Bob
Having built 3 purpose build electric stunters now I can really appreciate your efforts in a clean electronics bay construction. Your approach is very good. I would like to see if you refined your battery mounting. I have been practicing 6 flights (I have 6 batteries) back to back. I really don’t have a system that:
1. Doesn’t require tools to change the battery
2. That keys the batter into an exact position every time.
Norm

Bob Hunt · « **Reply #38 on:** June 22, 2011, 09:42:02 AM »

Hi Norm:

Thanks for your comments on my ESC and timer mount. Yes, keeping everything tidy and all wires separated is now the focus.

I don't have photos yet of the battery mount in the Crossfire, but I do have several of the mounting system in my Genesis Extreme that I will post here. The system that I will use on the Crossfire is essentially the same as this one. It has worked very well for me for quite a while now, and others have been using it with great success also. It absolutely puts the battery in the same place each time, but it does require that you remove and reinstall a 1/4-20 nylon nut each time. For me that is no biggie as I like the security and it doesn't take more than a few seconds to change batteries.

Hey, I need to speak with you about the SN project we have discussed. I'd like to move forward with that as soon as we can...

Later - Bob

WhittleN · « **Reply #39 on:** June 22, 2011, 10:55:01 AM »

Thanks for the pictures Bob. I would like to remove the hatch and the battery without tools but you have added some good ideas to my collection.
I will send you an e-mail about the project. I'm quite far along on it.

Norm

Dean Pappas · « **Reply #40 on:** June 22, 2011, 07:57:42 PM »

Hello Norm,
You need to look at the belly-pan latches that the Japanese hardware outfits sell to the Pattern guys. I'll go look for pictures and sources.
I dummied up a cheap copy for one of my E-RC ships, and it can be made to look very tidy.
Regards,
Dean

Wynn Robins · « **Reply #41 on:** June 22, 2011, 08:45:42 PM »

Quote from: WhittleN on June 22, 2011, 10:55:01 AM

Thanks for the pictures Bob. I would like to remove the hatch and the battery without tools but you have added some good ideas to my collection.
I will send you an e-mail about the project. I'm quite far along on it.

Norm

hey Norm - here is my take on Bobs design - no need to unscrew anything and it works a treat

http://stunthanger.com/smf/index.php?topic=20144.0

Tom Niebuhr · « **Reply #42 on:** June 22, 2011, 09:56:16 PM »

Bob,
Do you have a means to move the battery forward or aft for CG adjustment?

Bob Hunt · « **Reply #43 on:** June 23, 2011, 04:59:49 AM »

Hi Tom:

Yes, I can easily adjust the position of the battery in the "electronics bay" by making mount plates that position it fore or aft as required. Initially I make a location/mount plate that puts the CG slightly forward (Like the saying goes, a nose heavy ship will be sluggish, but a tailheavy one might not get a second flight...) of the point where I think it will ultimately reside. I can then make plates that hold the battery progressively further aft. When I find the "sweet spot," I duplicate that battery plate and mount all my batteries in that design plate.

My mount system also allows me to move the battery up or down a good bit to allow for vertical CG adjustments. This is one of the many advantages that electric has over glow.

As for the "screwless" mounting... I'm not a fan of it. I'm a belt and suspender kind of guy when it comes to mounting the battery and the battery cover (cowling or canopy...). It takes me just slightly longer to remove and install screws, but the peace of mind is more than worth it. I've seen two batteries "exit" models in mid air so far, and, thankfully neither of them exited from my airplane. Believe me, that can ruin your day. It sure did for those two electric enthusiasts. I'll bet their batteries are held in now with bolts... The worst way is with Velcro. Velcro picks up dirt, loose grass blades, etc and not only loses some of its holding power, but it also look awful. Stick to bolts, or a nut atop a threaded stud.

Later - Bob

Allan Perret · « **Reply #44 on:** June 23, 2011, 07:27:55 AM »

On the Crossfire, did you still use the rear motor support like you did in the Genesis ?

WhittleN · « **Reply #45 on:** June 23, 2011, 08:54:14 AM »

Oh Bob! you're killing me with that no Velcro stuff. I like a little grass on my Velcro. But I must admit you are correct. I didn’t realize you built a frame for each battery – this could expedite the battery change out process.

Wynn copied your pictures to my idea folder they are certainly worth considering. Thanks.

Dean I will hunt the electric Pattern forum for the latch pictures but if you run across them please post.

Jose Luis Oterino has some good ideas on his MG 10 stunter. I like the car pin hold down and the use of circuit board material.
http://stunthanger.com/smf/index.php?topic=21161.0

Norm

Bob Hunt · « **Reply #46 on:** June 23, 2011, 12:51:48 PM »

10-4, Norm, glad to help...

Allan: Well, we never did even fly the Genesis with the yoke and rear bearing. We decided that since we were firewall (Electron wall?) mounting the motor, we had effectively solved the cantilever problems. We have not had problem one with the front mount in respect to bearing life. So needless to say, I didn't use it in the Crossfire either.

Later - Bob

WhittleN · « **Reply #47 on:** June 23, 2011, 01:22:12 PM »

Guys
I too have removed the rear bearing support and now have 87 flights on Sultan-e #2. No problems so far. I must admit every once in a while I do worry about the bearing going out.
One side benefit of having a rear bearing mount is that you can use threaded rod ¼ -20 and a ply plate to act as a paint stand rod holder.
Norm

Dean Pappas · « **Reply #48 on:** June 24, 2011, 08:14:06 PM »

Hi Norm,
Here are a few, but still not the one I was thinking of when I lsat wrote.
Dean
http://www.centralhobbies.com/building_materials/hatch%20acc/hatchacct.html

Mark Scarborough · « **Reply #49 on:** June 24, 2011, 10:58:32 PM »

here is another option
http://www.3dhobbyshop.com/Canopy-Latch-for-40-72-ARF-Kits_p_15453.html
Bob, I likethe Crossfire, RC Pattern version as well.
did you ever do formal plans for that one?