Author Topic: New Electric Twin project back on track (Read 116351 times)

Larry Wong · « **Reply #400 on:** January 27, 2014, 08:49:45 AM »

Thanks I miss that part ,I guess water base paint would work ok.

Mike Ferguson · « **Reply #401 on:** February 14, 2014, 07:52:28 AM »

I blame Bob for the current Polar Vortex Snowpocalypse (TM) that's hit the Northeast.

Ever since you wrote that you were hoping to fly the twin testbed "in a week or so" in December, it's been nothing but snow, snow, snow ...

#kidding

Serious, hope you get to fly it soon, Bob ... and that good weather's around the corner.

Robby Hunt · « **Reply #402 on:** February 15, 2014, 10:01:29 AM »

Quote from: Mike Ferguson on February 14, 2014, 07:52:28 AM

I blame Bob for the current Polar Vortex Snowpocalypse (TM) that's hit the Northeast.

I blame all things vortex related on PJ.

wwwarbird · « **Reply #403 on:** March 25, 2014, 05:19:32 PM »

Any new news on the twin?

Bob Hunt · « **Reply #404 on:** March 29, 2014, 06:59:44 AM »

Hi Wayne:

Yes! There is some news to report on for both of my twins (counting the test-bed, I now actually have three of them here!). I'm just about done sanding the primer coat on the Second Wind (the first twin...), and I just installed the wing in the Wildfire twin. I'm attaching a few photos that depict how I install and line up the wing.

The top and bottom shells are also done and ready to install once the wing and tail are in place and the controls hooked up. The tail assembly is done and covered with .2 carbon, so the progress should go fast this week.

Later - Bob

john e. holliday · « **Reply #405 on:** March 29, 2014, 08:31:07 AM »

I bet your foam supplier loves you> Great idea on the lining up the wing and fuse.

Bob Hunt · « **Reply #406 on:** March 29, 2014, 08:37:13 AM »

Quote from: john e. holliday on March 29, 2014, 08:31:07 AM

I bet your foam supplier loves you> Great idea on the lining up the wing and fuse.

Yeah, they send me Christmas presents and everything...

Seriously, I am just small potatoes to them. I buy half billets several times a year. A half billet is 37 x 48 inches x 8 feet! That's half a billet... A full billet is 16 feet long! When I go to pick up foam I see hundreds of full billets lined up and curing. It's a big building!

Later - Bob

Bob Hunt · « **Reply #407 on:** March 30, 2014, 01:33:53 PM »

Got quite a bit more done on the new twin. I glued the bottom molded shell on yesterday and sanded it into the fuselage sides. The stabilizer went in today. I use a Johnson Angle Finder and custom fixtures to accomplish this very accurately. The fixture that holds the stabilizer is made from Lite-Ply and accepts different top plates to suit various stabilizers. It has fore and aft slides that are anchored with 4:40 screws and elastic stop nuts. I intend to make this fixture available in kit form as a new product from Robin's View Productions. I've used this fixture a few times now and I'm very pleased with how easy it makes a difficult job. I set the incidence in the stab to be about a half degree positive in the leading edge. I just don't want any negative incidence!

The photos below should tell the story well...

Later - Bob Hunt

Bob Hunt · « **Reply #408 on:** March 30, 2014, 01:58:44 PM »

Here are the custom made horn retainers that I make. They are fitted beforehand to insure that the horn will center on the stabilizer rear face. I make these retainers from 1/16-inch thick plywood. I install them after the stabilizer is glued in place.

Later - Bob Hunt

wwwarbird · « **Reply #409 on:** March 30, 2014, 08:45:36 PM »

Thanks for the update Bob, everything looks great. Waiting for some paint...

Bob Hunt · « **Reply #410 on:** March 31, 2014, 06:34:32 AM »

Hi Wayne:

Yeah, I'm anxious to see some paint as well. I spray my ships in Buddy Wieder's garage. Buddy "winters" in Florida each year and he is coming home this week. The Second Wind twin is virtually ready for the ChromaSeal coat, then bit of sanding and then the color coats. It should be finished by the end of April, but no promises... $:-\$

The big push now is to get the new twin caught up. As you can see from the photos, this one is coming along fast. It incorporates all the lessons learned from the building of the Second Wind, so there was not too much new "engineering" to do. It's coming together just as fast as I can build; no down time for thought...

The top shell goes on the new bird tonight, and then it's just a matter of details and the nacelles. The nacelles will be the last thing to be built and installed. Buddy and I built the test bed twin (photos earlier in this thread) to determine just where the thrust line should be located. Once that is resolved, the nacelles should take only a few days to build and mount.

I'm really enjoying this new build (so far at least). Everything is coming together as I had hoped and better.

Later - Bob Hunt

55chevr · « **Reply #411 on:** April 01, 2014, 09:05:33 AM »

Looks fast sitting still ... has a very "aero" appearance. Beautiful.

JD

Bob Hunt · « **Reply #412 on:** April 06, 2014, 06:12:44 PM »

Thanks, Joe!

Today I got a bit done. I punched holes in the top shell formers to allow airflow through the fuselage, and to lighten the shell a bit. The cooling air for the battery actually passes through the fuselage and out an opening in the tail cone. I've been doing this with the Crossfire series very successfully.

The cross bracing pieces went in earlier this week. I double checked everything in the fuselage and then installed the top shell permanently. Tomorrow I'll sand the top shell to match the fuselage sides and then the tail cone will be fit and installed. After that the front end blocks will be fit, carved and hollowed and the nose gear retract mount will go in, along with the battery mounts.

I also finished designing the nacelles today and will start on them tomorrow or Tuesday.

Later - Bob Hunt

Bob Hunt · « **Reply #413 on:** April 17, 2014, 06:01:39 PM »

Got a bit done this past week on the new twin. I was ready to take a bunch of photos of the ship as it sits now, but after one shot the battery in the camera went dead. So, here's just a teaser of what the nose of the main fuselage will look like. You just sort of have to picture it in your mind with my normal "Crossfire-Like" canopy.

By Sunday the ship should be ready for the nacelles to go on and then it's just a short bit of work until the finish goes on. This one has me excited!

Later - Bob Hunt

55chevr · « **Reply #414 on:** April 18, 2014, 06:02:07 AM »

Bob - I love the look of the "TwinFire". I want to this fly.

55chevr · « **Reply #415 on:** April 18, 2014, 06:16:38 AM »

Insert Quote

Bob - I love the look of the "TwinFire". I want to see this plane fly.

Bob Hunt · « **Reply #416 on:** April 19, 2014, 02:18:58 PM »

Yeah, me too, Joe!

Got some done today. I hollowed the nose blocks (top and bottom) and made a fin and rudder, The ventral fin (bottom fin) is just a silhouette to find the right shape; it may change a bit...

I taped everything together for a "hangar flying" session. Tonight the nose wheel retract mount goes in and tomorrow the bottom block goes on permanently. Then the fuselage will be sealed and carbon covered. After that it's just fitting the nacelles and we are into finish.

The tentative name for this beast is "Wildfire." That may change, too...

Later - Bob Hunt

Bob Hunt · « **Reply #417 on:** April 19, 2014, 06:30:12 PM »

Got a bit more done this evening. Here are a few photos of the front retract mount and how it fits in the front of the fuselage. The bottom cowl just fits over this assembly. Later tonight I'll seal all the wood in the front end with a very thin coat of Z-Poxy Finishing resin to ward off moisture.

Later - Bob Hunt

Mark Scarborough · « **Reply #418 on:** April 19, 2014, 07:05:06 PM »

Bob, those retracts are something huh,,

I have been reading some stuff on them,, it might be a good idea to make some form of strain relief for the wire exits,, I have heard of a few problems with wires fatiguing at the exit point,, MOSTLY on nose gear as a result of the steering portion from what I gather,, but it may be a good idea to be safer than sorrier,,

Bob Hunt · « **Reply #419 on:** April 19, 2014, 07:24:57 PM »

Hi Mark:

I'm not using the stock struts. I have had special ones made that are more robust. Also, I'm not using an actual E-Flite nose gear in the nose of this ship; it is a standard gear with no steering capability. I've researched these retracts quite a bit and am confident that they will perform well in this application. As a safeguard I might put "whisker skids" at all three gear points to protect the model in case of a malfunction. Of course these would only be used in practice; I'll remove them for appearance point judging and actual competition flights.

Thanks for your concern!

Later - Bob

Mark Scarborough · « **Reply #420 on:** April 19, 2014, 09:36:39 PM »

Quote from: Bob Hunt on April 19, 2014, 07:24:57 PM

Hi Mark:

I'm not using the stock struts. I have had special ones made that are more robust. Also, I'm not using an actual E-Flite nose gear in the nose of this ship; it is a standard gear with no steering capability. I've researched these retracts quite a bit and am confident that they will perform well in this application. As a safeguard I might put "whisker skids" at all three gear points to protect the model in case of a malfunction. Of course these would only be used in practice; I'll remove them for appearance point judging and actual competition flights.

Thanks for your concern!

Later - Bob

knowing how hard you work on your finish,, Just thought I would pass it on,,
I agree, they are pretty well made units,, and of course,, it makes sense not to use a steering retract,,
Aside from the minor issue with the servo wire fatigue,, ( not the strut wire) I think they are pretty darn reliable from what I have seen,, I too have a set in the drawer,, waiting,,,,,,

wwwarbird · « **Reply #421 on:** April 19, 2014, 11:12:48 PM »

Quote from: Mark Scarborough on April 19, 2014, 09:36:39 PM

Aside from the minor issue with the servo wire fatigue,, ( not the strut wire) I think they are pretty darn reliable from what I have seen,,

How about a little fillet of silicone around the servo wire lead to help support it?

Bob Hunt · « **Reply #422 on:** April 20, 2014, 07:49:16 AM »

Hi Wayne:

It is my understanding (please someone correct me if I'm mistaken...) that silicone emits a substance when it cures that will corrode wiring. Back when I was flying RC Pattern, I was told to never put any silicone anywhere near any electrical components.

I'd like to take this opportunity to say Happy Easter to everyone, to ask for God's blessings on us all, and to thank God for His gift of His Son, Jesus.

Bob Hunt

Bob Hunt · « **Reply #423 on:** April 20, 2014, 09:38:12 AM »

More to report:

One of the less glamorous chores to accomplish when building a twin -- but a very necessary one -- is to determine just how long the noses of the nacelles must be to achieve the proper CG range when the model is complete. This is made easier by making "dummy" profile nacelles that have an adjustment range for the motor mount positions. The nose gear retract must be put in place, along with the battery and the motors. I position the battery as far aft in its compartment as it will go, and then check the CG. More finish will go on aft of the CG than ahead of it, so I adjust the model to be slightly nose heavy during this test. If the CG shifts aft when the plane is done, I can simply adjust the battery forward a bit. There is one battery; a 4000 mAh 4S Hyperion. We might be able to get by with a 3300 mAh 4S, and if so, I'll have to shift it quite far forward in the battery compartment. This is all sort of a well-educated guess at this point, but by checking the approximate CG with the "dummy" nacelles, it's a more well-educated guess!

Here are some photos of the plane with everything taped in place for the CG check. The "real" nacelles will be built-up units and I'm starting on them just after I finish this post!

Later - Bob Hunt

Crist Rigotti · « **Reply #424 on:** April 20, 2014, 11:55:12 AM »

Bob,
Very cool. I would think you'd have the spinners and props installed also when doing this sorta check?

Bob Hunt · « **Reply #425 on:** April 20, 2014, 12:04:45 PM »

You're absolutely right, Crist; I just threw the motors in place for the photos and I'll add the props and the spinners and check the CG before starting the drawings of the actual nacelles. I just had a few moments to take those last photos before having to go carve the bird for dinner... Some things take priority!

Later - Bob

MarcusCordeiro · « **Reply #426 on:** April 20, 2014, 08:16:10 PM »

Fabulous!!!

Marcus

Crist Rigotti · « **Reply #427 on:** April 20, 2014, 08:26:39 PM »

Quote from: Bob Hunt on April 20, 2014, 12:04:45 PM

You're absolutely right, Crist; I just threw the motors in place for the photos and I'll add the props and the spinners and check the CG before starting the drawings of the actual nacelles. I just had a few moments to take those last photos before having to go carve the bird for dinner... Some things take priority!

Later - Bob

I hope you and your family had a very happy Easter and wonderful dinner.

RandySmith · « **Reply #428 on:** April 21, 2014, 02:51:35 PM »

Quote from: Bob Hunt on April 20, 2014, 07:49:16 AM

Hi Wayne:

It is my understanding (please someone correct me if I'm mistaken...) that silicone emits a substance when it cures that will corrode wiring. Back when I was flying RC Pattern, I was told to never put any silicone anywhere near any electrical components.

I'd like to take this opportunity to say Happy Easter to everyone, to ask for God's blessings on us all, and to thank God for His gift of His Son, Jesus.

Bob Hunt

Hi Bob

You can use Silicone but you need to "sleeve" the wire or part, just use a piece of plastic tube, or heatshrink will also do, the just put the silicone on the part the sleeve covers, let air dry in "OPEN" ventilated space.
The substance or gas it emits is acetic acid, or vinegar taken to the next step.
Randy

Bob Hunt · « **Reply #429 on:** April 22, 2014, 08:21:39 PM »

Thanks, Randy; I'll look into that...

New stuff: I designed the nacelles armed with the CG information from the "dummy nacelle" procedure outlined above. Since this model has a leading edge "cuff," the two nacelle sides are quite different where they attach to the wing. In order to get absolutely accurate shapes for the nacelle sides I made two ribs from the Lost-Foam fixture set from which the wing for this model was built. When I designed the wing I laid out a rib 1-inch from either side of the meeting of the inner and outer wing panels. By making another of each of these ribs, and then covering them with a layer of 1/16-inch balsa (which is what the wing is covered with...). I was able to achieve a perfect shape for the nacelles and insure that they will fit the wing and line up with each other at the front.

The next step was to make a template of the inner and outer nacelle sides and then use those templates to lay out the actual 1/32 inch plywood doublers. The balsa nacelle sides were then molded to the proper top view shape in custom cut foam fixtures. This process allows the sides to flow into the spinner shape without inducing an tension in the nacelle sides.

Here are a couple of photos. I'll try to get a few taken that depict the entire process described above.

Later - Bob

Bob Hunt · « **Reply #430 on:** April 23, 2014, 08:43:28 AM »

The nacelle sides came out of the forms this morning and I trimmed them and test fit them on the wing. All good so far!

Note the top view shot of one of the nacelle sides attached below; it clearly shows the curve that was molded into the side to allow it to flow into the spinner shape without having to draw the nacelle sides together with pressure.

Later - Bob Hunt

Bob Hunt · « **Reply #431 on:** April 24, 2014, 02:15:12 PM »

More done today:

The nacelle sides with doublers were removed from the molds and trimmed. The next step was assembly of the nacelle crutches. The accompanying photos should tell the story of how this was done.

Tonight I'll make the G-10 motor mounts and install them.

Getting close to completion of the construction! My target date for that is May 1. Looks like I'll hit it with a couple of days to spare...

Later - Bob Hunt

Bob Hunt · « **Reply #432 on:** April 26, 2014, 11:27:36 AM »

More done today:

I made a 1/32-inch thick plywood template of the desired motor mount plate and then used it to scribe two G-10 mount plates. The plates were cut from a sheet of G-10 using a motorized hand-tool fitted with a 1/8-inch diameter carbide bit.

The plates were brought to exact width dimension using a disk sander.

The plates were then fitted to the model using the nose ring as a fixture with which to perfectly position the mount plate. This is the same method as is described in my Hardnose Motor Mount Manual. That manual is available at no charge in PDF form. If you would like a copy, please email me at robinhunt@rcn.com

Once the mount was positioned properly, I used a small amount of medium CA glue to hold it in place. The plates will be more securely fastened to the plywood doublers with front and rear bracing that will be installed with long-curing epoxy and microballoons.

More later ...

Bob Hunt

Allan Perret · « **Reply #433 on:** April 26, 2014, 04:25:46 PM »

So what brand of long-curing epoxy do you use/like ?

Bob Hunt · « **Reply #434 on:** April 26, 2014, 04:52:01 PM »

Hi Allan:

Well, these days it is difficult to find any 3-hour epoxy; that's what I'd really like to use... I just loved the old HobbyPoxy Formula III 3-hour glue (24 hour complete cure). These days I'm using either a 45 minute epoxy from Great Planes, or the 30-minute Zap brand. I avoid using 5-minute and 15-minute epoxies; they just don't penetrate well. I always use epoxy glue with microballoons mixed in for gap filling properties and extra strength.

Later - Bob

Bob Hunt · « **Reply #435 on:** April 26, 2014, 09:04:06 PM »

Long day...

Here is the last stuff for tonight.

The first two photos show the filler piece that fits between the front of the motor mount plate and the nose ring. There will also be supports behind the mount.

The last photos depict the templating and installation of the nacelle bottom block. Tomorrow morning I'll tack the top blocks in place on the nacelles and begin the carving process. If all goes well I should be able to install the nacelles onto the wing late tomorrow or at worst by Monday evening.

Good night - Bob

Bob Hunt · « **Reply #436 on:** April 27, 2014, 02:53:33 PM »

Carving day!

Spent the afternoon carving and sanding one of the nacelles to shape. I'll tackle the other one after dinner. Lemon Chicken! Yum...

Later - Bob Hunt

Bob Hunt · « **Reply #437 on:** April 27, 2014, 03:37:07 PM »

Couldn't resist fitting the one carved and sanded nacelle to the wing just for a quick "hangar flying" session.

Oops; Marianne is calling me for dinner!

Bob Hunt

James Mills · « **Reply #438 on:** April 27, 2014, 04:00:48 PM »

Very cool Bob, look forward to seeing it in person.

James

Noel Corney · « **Reply #439 on:** April 27, 2014, 04:17:20 PM »

Bob , You are using micro balloons in your epoxy as GAP filler!!!! I didn't think that at your level of craftmanship you would have those, But as for making the epoxy stronger I have avoided using it except when absolutly necessary as my understanding was that it weakend the joint!!! TIA . Noel.

Bob Hunt · « **Reply #440 on:** April 27, 2014, 04:29:12 PM »

Hi Noel:

Actually a man I know that worked in the adhesive/chemical business told me to never use epoxy glue without a binding agent such as milled glass fibers or microballoons...

Later - Bob

wwwarbird · « **Reply #441 on:** April 27, 2014, 06:33:42 PM »

Quote from: Bob Hunt on April 27, 2014, 04:29:12 PM

Hi Noel:

Actually a man I know that worked in the adhesive/chemical business told me to never use epoxy glue without a binding agent such as milled glass fibers or microballoons...

Later - Bob

Hmm, really? How about when laminating?

Bob Hunt · « **Reply #442 on:** April 27, 2014, 06:33:44 PM »

Last stuff for today...

I carved and sanded the other nacelle and test fit them both to the airframe. Tomorrow I'll start hollowing the blocks and should be ready to install the nacelles by Tuesday or Wednesday. The next photos will be of the installation process.

G'night - Bob

Bob Hunt · « **Reply #443 on:** April 27, 2014, 09:14:40 PM »

Quote from: wwwarbird on April 27, 2014, 06:33:42 PM

Hmm, really? How about when laminating?

That seems to be the one caveat. But, then again, typically we don't use epoxy "glue" for laminating; we use epoxy-based finishing resin.

Later - Bob

Robby Hunt · « **Reply #444 on:** April 27, 2014, 10:59:10 PM »

Lookin' badass Bubba!

Noel Corney · « **Reply #445 on:** April 27, 2014, 11:41:24 PM »

Thanks Bob,I have been wary of using micro balloons in my epoxy, Makes it easier to use in my opinion. Are there any ratios recommended?? Noel.

Allan Perret · « **Reply #446 on:** April 28, 2014, 07:33:02 AM »

Good info at West Systems about use of fillers in epoxy:

http://www.westsystem.com/ss/filler-selection-guide/

http://www.westsystem.com/ss/adding-fillers/

Microballoons is a good filler for fillets/fairings, but there are better fillers for joint strength.
I have a container of the 410, the stuff is so light you have to be careful not to breath when you open it up.

Bob Hunt · « **Reply #447 on:** May 06, 2014, 05:32:11 PM »

That is good information, Allan; thanks!

Got a bit done over the weekend and today:

I covered the fuselage with carbon and installed the dorsal fin and rudder. I also doubled the carbon covering in the area on the wing halves where the nacelles will reside. Next I made the fixture that holds the nacelle crutches in proper alignment and taped them to the fixtures. The airframe was then slid into place and aligned in all axis. Finally, the nacelles crutches were glued to the wing. Doesn't seem like a lot, but it was quite time consuming.

The next step is to glue the nacelle tops in place and make the main gear retract mounts and install them in the nacelles. After that it is just a matter of fitting the lower nacelle blocks in place and installing hold downs for the lower access hatch on the nacelles.

Later - Bob

Larry Renger · « **Reply #448 on:** May 06, 2014, 05:57:02 PM »

This is the third one, actually, isn't it? Whatever became of the first one and the test one? Or am I losing track?

Bob Hunt · « **Reply #449 on:** May 06, 2014, 06:02:46 PM »

Quote from: Larry Renger on May 06, 2014, 05:57:02 PM

This is the third one, actually, isn't it? Whatever became of the first one and the test one? Or am I losing track?

Yup; this is the third one. The first one is in the finish process and I'm trying to get the new one caught up to it so that I can paint them both on the same day. The test bed was built to test motors, retracts, props, etc. It will fly next week. Dean Pappas just finished wiring up the harness for that ship. We will test all the harnesses in the test bed before installing them in the actual competition ships.

Yes, this has been a long project, but I'm not counting days... just knowledge and experience in making these things. I hope to very soon be learning about how they fly. I just thought that the building process of these ships might be of interest to the readers on this forum.

Later - Bob

Author Topic: New Electric Twin project back on track (Read 116351 times)

Robby Hunt

Robby Hunt