FTFF 2015 Scratch Build: Sikorsky S-39

[willsonman]

The problem is your climate. Hardware stores will carry what is typically used by contractors. It never gets cold enough in AZ to justify the use of 2" thick stuff. You will probably have to laminate several sheets to get the thickness you need. Super 77 works in a pinch but will not hold forever and will let you hotwire through it. I've heard good things about Glidden Gripper thinned out working well here but I've not tried it myself.

 

[smithhayward]

I'm going to go over to my local Home Depot and just ask someone if they can order it. Worth a shot. I'm not willing to buy a case of it just yet, but if they need me to order 3-4 sheets I'll have to consider it.

They do have 1" pink stuff here. I'll look into the Glidden Gripper. I was going to ask about the best way to laminate multiple pieces anyway. I assume the goal is to have a thin film between each layer without dry spots if possible right? Any chance that simple Mod Podge would work if skimmed on? The plan would be to do a layer of brown or tissue paper with the WBPU to seal it all together, so maybe the Modge Podge would work...

So much to test, so little time.

 

[willsonman]

Yeah, see the thing is everyone sees Peter with the brown paper and everyone thinks its the ONLY way to cover foam. Its a fantastic solution but look at his airplanes. They have ZERO compound curves. Once you get to those, the paper becomes useless. This is not a Pinata that we are covering. Even 2oz. autobody glass would be better than brown paper. Been saying it for years now. I was covering my airplanes with tissue and WBPU on these forums before Peter was even a member of FT, But only on surfaces WITHOUT compound curves.

Ok, off the soap box and calm down. The easiest thing to do is to buy some thinner foam that is currently available to you and start figuring out what works for you to laminate them. I used Super 77 on this project because its what I know... and I've heard that Glidden Gripper needs a full 24 hours to cure out. Impractical for the timeline of this project. Mod Podge dries hard so probably not. That's the thing, it has to remain fairly pliable after its dry.

 

[Craftydan]

I'm going to go over to my local Home Depot and just ask someone if they can order it. Worth a shot. I'm not willing to buy a case of it just yet, but if they need me to order 3-4 sheets I'll have to consider it.

They do have 1" pink stuff here. I'll look into the Glidden Gripper. I was going to ask about the best way to laminate multiple pieces anyway. I assume the goal is to have a thin film between each layer without dry spots if possible right? Any chance that simple Mod Podge would work if skimmed on? The plan would be to do a layer of brown or tissue paper with the WBPU to seal it all together, so maybe the Modge Podge would work...

So much to test, so little time.

For foam lamination glue, I've had great results from WBPU -- Water based polyurethane. Paint on each surface, bond and press for a few hours. Tests I've run show good results after 2 hours (1.5 hrs still had a fairly weak shear bond), but I generally let it sit overnight. Repeat until you've built up your desired thickness.

Keep in mind the foam you bond will need to be fairly clean and free of any skin -- strip the paper for DTFB and peal the skin on the pink stuff.

 

[wilmracer]

Something that is also worth testing for laminating is Foam-tac. I've used it on my last few projects for laminating. I'm using it on the Beta build for Nerdnic's P-38 as well. It is a contact cement so it bonds quickly, it sands MUCH easier than GG, seems to bond better than 3M77 and the one test I did showed it could be hotwired through, at least vertically through the layers, without any trouble.

Just make sure you have a good skim coat over the whole surface, put the parts together and pull them apart a few times until it gets stringy, wait 10-30 seconds, and put the parts together where you want them to be forever.

 

[smithhayward]

Thanks all, this is great. I'll let you know what works - perhaps in a thread of its own.

I'm trying to figure out what I can use to form the airfoil on the Sci-Fi Cylinder build (see my signature). I need to form some curves and then sand/shape them into the top/bottom sections. Still trying to figure out what I'll use to reinforce the main cylinder structure, maybe I can curve a few pieces of 1mm steel wire and embed it into the shape somehow. If anyone has ideas please post them over in that thread. Thanks!

 

[willsonman]

Depending on the thickness of the foam you may be able to wire cut sections and curve them into shape.

 

[smithhayward]

Yeah, I think for the Sci-Fi project the 1" foam will be perfect. I'll be able to fit it to the inside and outside of the basic cylinder shape, and form it from there.

It'll be for other projects that I'll want to laminate multiple together for fuselages and large wings.

Again - Thanks so much to all of you!

 

[willsonman]

UPDATE:

I recently had a hard landing which really took a toll on the landing gear. The little eyelets on the bottom mounts all need to be replaced. To help alleviate the stress from this I have ordered small oleos that I will incorporate into the main upper strut to give some relief from the stress. I will update here when I get to working on this solution.

 

[Spastickitten]

Aw, that sucks man, hope to see them gear in ship shape!

 

[willsonman]

Its all very frustrating but then again, these are the problems faced with a model I have found VERY little information on. I've not found a single build thread on it using these plans so issues like this are bound to come with experience over time.

Basically what will be done is to entirely remove the upper strut mount eyelet. I will cut off a portion of the strut and braze on the oleo strut. I will fabricate a mount from brass sheet to connect the strut to and that will receive multiple screws to secure to the fuselage. Then, a simple cotter pin will be used to pass through the mount and the oleo to secure it. This will allow the struts to be fastened elsewhere for possible snow flying

 

[willsonman]

Oleos arrived from China today. I immediately started work.

First, here are the struts. There are two grub style set screws in the top where the "axle" normally would go. This will be my mount at the top of the fuselage. The other end also has two grub screws that would normally attach to a retract pin of some sort but here it will connect to the leg of the gear.


First I made some brackets from the hard brass sheet I used to make the tail gear hardware. I cut the pins shorter and the whole thing is secured with the grub screws at the top so the pin will not move out.


Here is the completed setup for one leg. I added a segment of brass tubing to the outer portion of the strut to make up some of the gap inside the oleo. Secured using the two grub screws.


I'll affix the brass mount to the fuselage using 3 or 4 screws to spread the load out. The springs are quite stiff but I'll evaluate clipping the springs back after an initial flight report with the modification.

Now, I did factor that the struts could be set manually into the oleo further to raise the wheels for possible snow flying. We will see how that goes but I do not think it will be sufficiently short enough. Again, we shall see.

 

[willsonman]

Finished it up tonight. Got the new parts painted and mounted it all up. To answer the question... no. The wheels do not raise high enough to clear the pontoons for snow. Fortunately, All of the landing gear can be removed with a single allen key.

Now, I do have a VERY small pond fairly close. If I can persuade my wife to drag along the kids I may try to have some taxi time on the water and see how she does. No promises though. Especially since the weather is turning again.

 

[AkimboGlueGuns]

Nice! It'll take hard landings a bit better I presume?

 

[willsonman]

Thats the idea... It'll work... probably.

 

[AkimboGlueGuns]

I hope you get it on the water soon. That'll add a whole new dimension of awesome.

 

[earthsciteach]

Bring it up to my place, Josh! There are plenty of spots on the river that would be nice to fly from.

 

[willsonman]

RIVER?!?!?! Wow, that would be scary.

 

[Craftydan]

RIVER?!?!?! Wow, that would be scary.

That's what the whitewater Kayak is for

 

[willsonman]

Took her out for a casual Sunday flight yesterday afternoon. The landing gear is now perfect. No adjustments to the struts needed and the little bit of bounce on landing was perfect. I am very happy with it and she still is such a dream to fly.