For fear of straying off topic again, I'll post my way of launching torque monsters. I hold them by the top and give full throttle and heave them STRAIGHT UP! They will climb straight torque rolling all the way and then run out of steam and level off. simple and effective and it takes the ground out of the equation.
Now back to the 38..........................

J

Here is what I ended up doing. It turned out pretty good. I glassed the inside of the fuselage at key structural areas with 2oz and West systems epoxy resin such as the inside nose section forward of the inlets all the way to the nose gear mount, and inside the fuselage from the inlets all the way back past the wing mounting area's. That way I didn't have to worry about how my novice glassing skills would look. But to make the outside dent resistant I used Styrospray 1000 from Industrial polymers. I got a half gallon of the stuff for $30 + $10 shipping. It can be sprayed on or brushed on, I did the brush on method. I think this is the same stuff as wow planes but a half gallon of wow planes would cost $160.
Sooo long story short just building with 1" thick foam alone you get a pretty strong airframe due to the thickness of the foam then along with glassing the inside sections where it's needed and then apply an easy hard plastic shell for dent resistance and added striength with not much sanding and fuss you get yourself a real strong as well as ding resistant airframe.

Here is the web site for Stryospray 1000


http://www.industrialpolymers.com/pr...st/styrospray/

If you aren't glassing, what are you going to do for fuse strength? Is there a ply keel or anything?

how much weight did the hard shell add? ...and 2oz cloth wont be enough strength...at least in my mind ..but im not there to feel it .i would have used 5.8 oz. in the nose gear ,fan ,wing mount ....you can still add cloth if needed i guess.if that hard shell epoxy does'nt add a lot of weight that is a great way to do it ...the price is good for 1/2 a gallon

You've done a great job so far but your worrying me about your approach to avoid glassing! There are so many available demos around here for how to glass...its really not hard. Foam is great for getting a shape but you need some strength besides the surface hardness. That A & B stuff wont get you there IMO.

Originally Posted by falcon5

Here is what I ended up doing. It turned out pretty good. I glassed the inside of the fuselage at key structural areas with 2oz and West systems epoxy resin such as the inside nose section forward of the inlets all the way to the nose gear mount, and inside the fuselage from the inlets all the way back past the wing mounting area's. That way I didn't have to worry about how my novice glassing skills would look. But to make the outside dent resistant I used Styrospray 1000 from Industrial polymers. I got a half gallon of the stuff for $30 + $10 shipping. It can be sprayed on or brushed on, I did the brush on method. I think this is the same stuff as wow planes but a half gallon of wow planes would cost $160.
Sooo long story short just building with 1" thick foam alone you get a pretty strong airframe due to the thickness of the foam then along with glassing the inside sections where it's needed and then apply an easy hard plastic shell for dent resistance and added striength with not much sanding and fuss you get yourself a real strong as well as ding resistant airframe.

Here is the web site for Stryospray 1000

I am inspired by this thread so I've started a not as large 80" A-4 SkyHawk based off JS44 intakes and the JS44 Skyhawk thread, I'm 1/3rd way through gonna post pics this week when I get a chance.

I did my experiments with StyroSray and pink foam and found with 2oz glass and one coat it's just as strong or stronger than Epoxy and doesn't stAnk up the joint. With 2 coats only (no glass) it's about as strong as 1.5oz glass and epoxy, they do 3 coats in the LS2 vid. I used HKs 18gm2 glass and SS and it was around the strength of 2 coats of SS without glass and very tap resistant no fingernails. With HKs 48gm2 I used one coat and it did self settle on a flat surface like it said it would do but I think it was the HK glass that didn't have the strength of the 2oz but it was no doubt stronger than the 18g glass

With the 2oz glass and one coat of SS I can drop a sharp pointed knife on it from 8" high and not puncture the foam. All these test were done without my A can hardener properly mixed. Called the folk who make SS and they said you have to stir A real good first then mix A and B, I never stirred A first so all those test could be made harder

In the Wow Planes video the guy does 3 coats of the stuff and after seeing an A-10 in person done with 3 coats of LS2\SS1000 it felt like it was a composite plane it was a fairly hard shell. LS2\SS1000 is the heat and there's little to sanding involved...no doubt noob friendly stuff.

I'm still going to glass my wing bottom with 2oz and 2 coats of SS, but for the rest of the plane it'll be SS only except for a couple of structural places were I'll use the 48gm2 HK stuff

Originally Posted by falcon5

One of the main gear struts arrived today. I am told by Robart it will be another 4 weeks for the nose gear and other main strut to be made. They asked if I wanted them to send just the one strut and I figured it would help with the setup of the nose retract so I told them to go ahead and send it.

So these were custom made? Was it reasonable, $$ wise? The lead time seems odd to stagger the completion of them like that - obviously I don't run a model airplane hardware and gear company so I wouldn't know but it would seem to make sense (to me) to complete them all at once!

Originally Posted by erh7771

I did my experiments with StyroSray and pink foam and found with 2oz glass and one coat it's just as strong or stronger than Epoxy and doesn't stAnk up the joint. With 2 coats only (no glass) it's about as strong as 1.5oz glass and epoxy, they do 3 coats in the LS2 vid. I used HKs 18gm2 glass and SS and it was around the strength of 2 coats of SS without glass and very tap resistant no fingernails. With HKs 48gm2 I used one coat and it did self settle on a flat surface like it said it would do but I think it was the HK glass that didn't have the strength of the 2oz but it was no doubt stronger than the 18g glass

With the 2oz glass and one coat of SS I can drop a sharp pointed knife on it from 8" high and not puncture the foam. All these test were done without my A can hardener properly mixed. Called the folk who make SS and they said you have to stir A real good first then mix A and B, I never stirred A first so all those test could be made harder

In the Wow Planes video the guy does 3 coats of the stuff and after seeing an A-10 in person done with 3 coats of LS2\SS1000 it felt like it was a composite plane it was a fairly hard shell. LS2\SS1000 is the heat and there's little to sanding involved...no doubt noob friendly stuff.

I'm still going to glass my wing bottom with 2oz and 2 coats of SS, but for the rest of the plane it'll be SS only except for a couple of structural places were I'll use the 48gm2 HK stuff

Strength is not just a measure of dent & puncture resistance. I doubt foam with this hard shell will have very good strength in tension. That is what glassing would be for. Without glass, flight and landing loads will cause flexing that will create cracks that would start as finish blemishes, and over time could allow structural failure. If there are other structures, such as ply keel or stringers, you could just go with the hard shell. A fuselage need structure the same as a wing - either you need a spar/beam or a strong skin for strength.

Originally Posted by pdawg

You've done a great job so far but your worrying me about your approach to avoid glassing! There are so many available demos around here for how to glass...its really not hard. Foam is great for getting a shape but you need some strength besides the surface hardness. That A & B stuff wont get you there IMO.

Originally Posted by AIR SALLY

how much weight did the hard shell add? ...and 2oz cloth wont be enough strength...at least in my mind ..but im not there to feel it .i would have used 5.8 oz. in the nose gear ,fan ,wing mount ....you can still add cloth if needed i guess.if that hard shell epoxy does'nt add a lot of weight that is a great way to do it ...the price is good for 1/2 a gallon

Awww no worries guys..Fuselage is super strong. About 75% of the inside of the fuselage is glassed with West systems and 2 oz cloth. The Styrospray 1000 on the outside is just for dent resistance. The thing feels like it's built like a tank.
Rodger the weight of the Styrospray 1000 feels like the same as epoxy resin. Kicking myself for not weighing the fuselage before I put it on but it dosn't feel much heavier. The glasssing of the inside feels like it added a bit of weight though.

Originally Posted by Eddie P

So these were custom made? Was it reasonable, $$ wise? The lead time seems odd to stagger the completion of them like that - obviously I don't run a model airplane hardware and gear company so I wouldn't know but it would seem to make sense (to me) to complete them all at once!

The struts I kind of got the runaround from Robart a bit and got three differant answers from three different Robart people but I think what it was is they had one strut already in stock and they will have to manufacture the other two. I had them send me the one they had just so it can be an aid to help me install and line up the nose gear mount. They are $81 per strut so kind of expensive.

Can you use the styrospray over WBPU and fiberglass? Or even as a replacement for WBPU?

Originally Posted by jetcaptain

Can you use the styrospray over WBPU and fiberglass?...

Yes, it comes out very rash resistant and gives good structure.

... Or even as a replacement for WBPU?

That's how I will use it over EPO, EPS, pink and blue foam...it's relatively cheap and can use a ton of to cover....no stAnkin up the joint either.

I don't know what the structural properties of it by itself, single or multiple coats are...I have not really tested that yet but I've bent pink foam with it and without it to get an idea of the tensile strength and there's definitely a different...don't know how much compared to LS2\ss100 with glass though

What type of foam is it? If it's anything like fan fold foam (15psi) then just a single layer of 5.8oz cloth isn't going to do much if anything for strength. The strength of the glass and foam composite is directly proportional to the ability of the foam to resist compression. Weak foam = weak composite. You might as well not even have the foam at that point. The guy in the videos from Industrial Polymers is a good friend of mine.

Originally Posted by SteveC68

What type of foam is it? If it's anything like fan fold foam (15psi) then just a single layer of 5.8oz cloth isn't going to do much if anything for strength. The strength of the glass and foam composite is directly proportional to the ability of the foam to resist compression. Weak foam = weak composite. You might as well not even have the foam at that point. The guy in the videos from Industrial Polymers is a good friend of mine.

I use half in pink board, 2 inch blue board both are 15ps but is relatively strong

Wow I had no idea not glassing the outside of the bird would generate such a buzz. Good to get opinions on all sides, I like it. Glassing is great I guess but in the past I never used it as a structural component. I relied on carbon/aluminum rod, ply wood, and other reinforcing techniques. I guess I like to use what has worked for me in the past.
In preparation for the T-38 I did do a test airplane prior to the start of this build built out of 1” blue foam to see how the 1” foam would perform and what kind of stress a box structure airframe built out of this stuff could handle. I also wanted to see how foam wheels on a semi heavy airplane would perform, and a few other things. So I built a 96” long sport scale Euro fighter that weighs 18.5 pounds built all from 1” blue foam. I put two Hayoe 5” fans in it with about 17 pounds thrust total. I flew the snot out of it for two and a half months, testing everything from full deflection rolls at high speed, to high speed dives with hard pull ups along with stalls, spins and a host of other maneuvers. I really tried to put the 1" blue foam thru it paces and stress it to the max. The airplane performed flawlessly, and didn’t have any structural issues not being glassed, It was and still is a great structurally sound airplane to go yank and bank out at the lake bed with because of solid structural reinforcing using aluminum rod and ply, balsa leading and trailing edges, and so on. The rest of the foam structure just goes along for the ride.

Due to this T-38 being heavier and bigger then the test Euro I did choose to glass reinforce much of the inside fuselage as a token but I will mainly rely on my tried and true methods for the main structural integrity of the airframe and step up those methods as needed to be sure I have a structurally sound airframe to handle what the plane will be designed to do.

I think you guys are under estimating the strength of a foam structure like this. The foam is strong and has the ability to absorb quite a bit of energy without breaking.

F5, thanks for a heads up on that new coating. Lots of potential. I`m thinking it may be good for making quick plugs for prototype glass structures.

Another idea might be to apply glass cloth, using spray contact cement like 3M 77, to the outside of a structure like your fuselage, and then coat it with the Stryospray to fill and smooth it. Just a thought.