FTFF 2015 Scratch Build: Sikorsky S-39

[willsonman]

Its been quite awhile since I've done any updating here. Reason is: I've not done anything. My work schedule has turned for the worse as of late so I've just not had the time. I set a goal to complete this by September and the month is already half over.

Last night I separated the fuselage/pontoons from the wing/booms. I gave the underside a good spackling to clean it up and started to apply tissue and WBPU to the tail. Only about 30 minutes worth of work but its a start. The top of the wing is ready for glass so I may proceed there before too long. The V-stab needs to be reinforced with a small piece of styrene tubing where the struts connect. The balsa was a little crushed and I'm afraid it will get worse over time. May as well do it now and do it right. Once I get the tail surfaces coated I need to look into why the rudder has issues in one direction. I am hoping that stiffening things up with the tissue/WBPU in addition to a second set of struts will give the control I need on the rudder. This coming weekend looks to be a bit of a bust for long stretches of work time but I need to push on and get this one done.

 

[willsonman]

Huh, Just realized that I started this thread EXACTLY one year ago today.

 

[Spastickitten]

Really, that's a lot of work put into this build. Glad to see you are still working on it.

 

[willsonman]

Its the price you pay when you go "scale" and want a plane that does not come as an ARF or a kit. Even if it does come as an ARF or a kit, it is far more cost-effective and ups the "pucker factor" on maiden. For me, scratch building is my adrenaline rush. This is the third model this year for me and I am more than pleased with the results. She will make an appearance at FTFF 2016 for sure. I cannot think of a better venue to show what can really be done with foam.

 

[Spastickitten]

I might just be able to go to ff2016 if I can get enough people that want to go, or just go hide in Fred's car.

 

[willsonman]

A bit more work yesterday. Took the servo covers off the bottom shaped and painted them. Also sanded the spackle I had applied previously. Now, to fill the gap in the wing joint. Apply spackle liberally. Cover the wing panel in saran wrap. Install the wing and let dry over night. You have to press them together to get the spackle to ooze out and then look for voids but you get the idea from the pictures.

 

[wilmracer]

Looking good (as always!)

 

[Spastickitten]

Awesome

 

[willsonman]

Got home from work and separated the wings. Inside needs to cure out still.

 

[willsonman]

UPDATE! But a small one. I did get time to sand down the joints on the wings. I just put a heavy coat of WBPU on to make the spackle harder. I did a LOT of troubleshooting on the rudder. So, first off, the sullivan rod is harder to move than I would like, which is part of the issue. Centering becomes a big problem with that. On top of it I realized that the pocket I carved out become paper thin toward the trailing edge, which gives when the servo is used. To alleviate this, I placed a piece of 1/32" balsa with GG into the base of the pocket. The top of the servo just barely sits flush with the bottom of the wing. I will make posts for the servo to screw into and affix them with epoxy. I also used the air compressor to blow a bunch of talc (baby powder) up the sullivan rod. It helped a bit but I think I will work on that more. The bend at the tail is as shallow as I could make it but I have my concerns with this over time. A dead rudder servo will not crash the plane but a MG full-size servo is NOT in my budget for this. I have over a dozen on-hand so I really do not care if it fails. With the v-stab stiffening I think I will at least have SOME deflection to the left, whereas before I only had right deflection.

 

[willsonman]

More of the same old tonight. WBPU cured out on the wing joint so I glassed the top of the wing. Continued on with the tail treatment of WBPU. Painted the top of the wing hatches. I've got pictures but its really all stuff that has been covered before.

 

[willsonman]

Posting pictures of yesterday's progress. Also got the bottom of the wing glassed last night.

 

[wilmracer]

Nice! It is crazy how long it can take to wrap up a model like this. Keep it up!

 

[willsonman]

Well, to be honest I've only really put about another 20-30 hours in. If I had an entire week at FTFF and the weather cooperated I could get it ALL done there. I still have to glass the leading edge of the wing. No biggie. I'll wrap up the tail today as well. Then comes the WBPU/BP fill coat on the wings. Need a new can of primer. If I push hard I can have her done by next weekend. Still need to do the engine nacelle. We will see.

 

[willsonman]

So, I had some warm afternoon weather and figured it would probably be the last of it. I took advantage of the sun and knocked out the wings. Applied the leading edge glass. While it cured in the sun I mixed up the WBPU/BP slurry. By the time it was mixed the glass was sufficiently cured to apply the mix. I did the wing top and bottom in about 20 minutes. I started on one side and worked toward the other. I also applied it to the balsa to fill the grain. By the time I got to the other end the starting side was dry to the touch. The brush was getting gunked up so I went inside to rinse the brush. By the time I got back out the entire wing was dry to the touch. I flipped it over and applied the fill to the other side in like manner. Rinsed the brush again and I was ready to start sanding on the first side.

The pictures tell the story. Using 80-grit paper on a BLOCK I knock off the ridges from the brush. The progression shows the ridges quite well in the sun. Once the ridges are knocked down then I use 220-grit to get the finish surface and kill the swirls made from the 80-grit. I got one side of the wing completely done. In all about 30 minutes of work... and I smelled baby-fresh afterwards. I should really do a video of this entire process to demonstrate how quickly you can do this process. The UV light from the sun REALLY helps you out a lot.

 

[willsonman]

Paint is on. I assembled the styrene nacelle and it will not work so I started on a foam one. The diameter was .25" too small. Oh well. I think it was all of $4.

 

[AkimboGlueGuns]

Nice work. I'm still eagerly awaiting her flight in full colors.

 

[willsonman]

ME TOO!

 

[earthsciteach]

I get to fly it!!!

 

[willsonman]

Ok, BIG progress today. I repaired a balsa wing for a fellow club member and plowed right into this after I wrapped that up.

Just teaser shots but I completed the vinyl application to the wings and tail. I re-glued a loose magnet in one wing joint and installed a styrene tube in the V-stab to prevent the soft balsa from crushing from the struts being screwed in. Still need to affix the rudder servo and button down those hatches. I started carving the bottom portion of the engine nacelle. It was tricky since I had to carve around the airfoil but I knocked it out in about 30 minutes. They both need glass, fill and paint. The bottom one will be attached permanently then I can re-assemble the plane and worry about how to lock down the top of the nacelle. I need to make three more struts. Two more for the V-stab and one that goes across the booms at the same attachment points as the two struts that go from the booms to the tail of the fuselage. Lots of little bits left to wrap up but I may just keep my September deadline.