fw190

My Feedback: (37)

This is something new to me, but it may be old for others... Instead of using fiberglass tape to reinforce the seam. I am trying to use carbon fiber tow. First, I lay up my fuse. Second, I cut of the excess fiberglass on the fuse halves (I do this just when the resin is somewhat cured).Third, I proceed to apply carbon tow and resin to the mating surface of the two halves ( I try and make sure that carbon is more into the fuse rather than the flange because it gets cut off anyways). Last, I close up the mold and dab on the seam.

So, would this method be strong enough instead of fiberglass tape or overlap method. I have done this on small parts such as wing tips and it worked rather well. I am however skeptical of using this method on larger fuses in the 1/5-1/6 scale warbirds.

Please let me know your thoughts and ideas, anyone use this method?

Thanks,

Vic

Here is the fin mentioned

davidfee

That looks interesting for making wingtips and such... a little more durable (and a lot stiffer) than just epoxy and microballoons/cabosil, etc. But for the fuselage seam I think you'd be better off with the fibers running across the seam, rather than along it. That is, use fused unidirectional carbon and cut it "across the grain." Or you could just use glass tape.

I don't think the overlap or step mold methods work well on really big stuff (especially if there is a sandwich involved) so taping the seam appears to be the way to go. Actually, a bias-cut tape would probably be the optimum.

-David

TOYMAKER

My Feedback: (6)

On the fiberglass seams running length wise just use the f.g. (you can use c.f but f.g.is easier work with) Where the c.f shines is in the area of the fuse that would normally have a bulkhead. Using just c.f cloth or c.f tow around the inside of the fuse in these areas will strengthen it tremendously.

My fuse on my pattern plane is made completely of c.f. and coremat laminate and has no bulkheads/formers anywhere. An extra layer of 8mil c.f 1/2" wide at the bulkhead areas gives it the sructural strength needed that a former would provide.


Wayne

FLYBOY

My Feedback: (11)

As stated, tow run along the seam will do nothing to keep the seam together. You need something running across it. Use carbon BID if you want to, but make sure it goes across, not just along the seam.

fw190

My Feedback: (37)

Thanks for the response guys!

What's a carbon BID?

I did some testing on the wing tips, I consistently slammed one of them to my wooden workbench along its edge and it did not break on the seam at all. It broke where there were no carbon fiber tow. It broke on the fiberglass parts, close to the carbon tow but did no harm on the tow until I kept on doing it and then it broke on the carbon tow as there where not much support from the glass tip structure.

So, why do we need it to run accross the length? I think the tape method does exactly the same thing, it runs across the length? Though have a wider area for joint. Do you think the carbon will sheer (separate) from each other?

I got this idea from looking at Yellow Aircraft kits, originally they used fiberglass tow and polyester resin ( this is where they usually break so I never would try this method). But now they are using the carbon tow method with their epoxy fuses.

Maybe I will give it a try and see how it will work on the big fuses.

Vic

winship

BID bi-directional or tow running in two directions within the cloth. The directions are refered to as the warp and fill. Warp is the long length as it comes off of the roll and the fill fibers are the ones that go across or side to side.

I agree with the posts above but give the tow method a try and keep us posted.

Winship

DanSavage

My Feedback: (5)

My Yellow Aircraft A-4 has all the fiberglass seams joined using a FG tow in the exact same manner as you describe. This includes the main fuselage seam, main and cockpit hatches. None of the seams are taped.

It's held together pretty well at over 200 flights and 3 crashes over it's 3-year lifespan.

I believe that all Y/A FG parts are built this way. I'm not commenting about the pro's or con's of the practice, only pointing out that this is used in a commercial product(s).

Dan

fw190

My Feedback: (37)

Dan, thanks for the response. I have only seen a few Yellow Aircraft kits. The P47, Spitfire both fiberglass tow and their new P40 using Carbon tow. Have not seen any jet kits. I did however see problems with the glass tow as they must have been in a rush putting the two halves together, where the glass tow was not sandwiched properly on the two halves.

Here is my test fuse with the carbon tow, its much stiffer in the seam area than using tape or the overlap method. I think that is a plus.

fw190

My Feedback: (37)

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fw190

My Feedback: (37)

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DanSavage

My Feedback: (5)

Hi Vic,

I'm getting ready to make some molded parts myself and I was thinking of using TOW instead of tape.

How did you apply the TOW to the seam area? I read your first post, but I'm not too clear what you do with the tow that's on the flange. Doesn't this prevent the mold halves from fully seating? Or, does the excess squeeze back into the fuse out from between the flanges?

Nice model, BTW.

TIA,

Dan

fw190

My Feedback: (37)

Dan,

I applied the tow on each half of the molds. I tried not to get too much of the tow into the flange area as it will get cut off anyways. Place the majority of the tow into the actual part. As you can see from my previouse pics that a lot of the tow are into the fuse not the flange. After putting the two halves together I press down on the tows to get them together and make a very good contact. If you can get tows to swirl together, it will be a very good bond, I don't think it will never separate in this area. The carbon tow is rigid compared to fiberglass tape, the glass fuse will have to break before the carbon tow will.

It is by far the easiest and cleanest method in seaming two parts together. Specially molded parts that you do not have access inside, just like the molded tips.

Vic

DanSavage

My Feedback: (5)

Hi Vic,

Thanks for the prompt reply.

I think I understand now. So, you generally try to keep the tow away from the seam (flange) until the two halves are joined, then you "slide" the tow into position over the seam. Right?

Obviously, you impregnate the tow with resin before applying it to the inside of the molds, right?

This method sounds like the way that I'll be joining my parts, too. I'm preparing to make the molds for a composite twin EDF Sukhoi SU-27 Flanker and it has a few places inside where laying down tape would be pretty hard to do. Thanks for the info.

What size tow did you use?

As an I took the time to go over to your web site. Your body of work is impressive. I especially like the P-38 project. What size engines is it designed to use?

Dan

fw190

My Feedback: (37)

Dan,

I try and get the tows just above where the glass was cut flush with the flange. This way when I put the two halves together they will already meet up. I just wet the tow with straight epoxy, currently I am using the west system 209, its slower and less viscosity, helping to wet out the tow better. You won't really need to play with the tow when you get the two halves together but just did it for unknowing securities. I am no expert and I am just playing with this stuff. I do put the two halves together within the 2-3 hour period before the epoxy hardens.
I wet the tow on the part but I am sure it can be done outside... BUT it gets 'HAIRRY' if you keep messing with the tow....

I don't know the strand number on my tow, I got it from a friend and he has no idea... but its about 1/8" diameter when rolled.


Thanks for your comments on the P38.... its coming along.... A pair of 91s 2-stroke will be good enough for this plane. I wanted to get the biggest engine in there so I went with a pair of G26. The prototype is weighing in at 22lbs. Engines are 8 lbs

Vic

Ricardo Aurelio

Dear Friends

I'm not familiar with the term "carbon tow". What exactly is that? A kind of a putty with resin and small pieces of carbon fiber?

Thank you

DanSavage

My Feedback: (5)

Hi Vic,

Thanks for the info. I can see how it would get a little "messy" to try to impregnate the tow before placing it on the parts.

Ola Ricardo,

As they say, a picture is worth a thousand words...



Carbon tow is individual strings of carbon fiber.

Dan

TOYMAKER

My Feedback: (6)

Why not just use a strip of 3/4 wide c.f. cloth? Thats what we use all the time on our fuse's. Much easier to work with and never had a seam split even on a hard crash.

fw190

My Feedback: (37)

Your right! a tape would be ideal. But how would you tape a wing tip? Even if you can access the mold internally, would still be difficult.

Vic

TOYMAKER

My Feedback: (6)

I see your point... I was just refering to the fuse joint.

The tow stuff would work great on wheel pants too.

WG

Tom Verstappen

Hi Vic,

Nice work you did there.

Cheers
Tom

Ricardo Aurelio

Hi Dan
Hi Vic

First, thank you Dan for the tow picture.

Well, Vic you may succeed with the tow job in the fuse just because we are talking about a low level loads, but since the CF strings goes along the seam and not across it, for sure the epoxy and some few strings that maybe occasionally across the seam will hold the two half of the fuse together.
If you really want the very best job done, then you should have a tape (CF or FG) with the filaments angled in 45* with the seam.

Good Look

DanSavage

My Feedback: (5)

Hi Ricardo,

You're welcome. This method of joining fuselages is stronger than it seems like it would be. True, it's not as strong as tape, but it works pretty well. Most all of the Yellow Aircraft models are joined using this method and they hold up pretty well to the types of abuses we heap on our models.

---

Hi Vic,

I'm sorry to pester you with questions, but I was looking at your P-38 page again and I noticed that you glued what looks like balsa strip stock on the splitter board around the perimeter of the plug and I'm wondering why you did this?

Thanks again,

Dan

Ricardo Aurelio

Dan

I don't know the Yellow Aircraft. Do they stand a YS vibration ?

Ricardo Aurelio

DanSavage

My Feedback: (5)

For the most part, Y/A makes and sells jets. I have an A-4 Skyhawk that ran with a K&B .82/Dynamax turning 22,500rpm for about 200 flights over 3 years until I blew out the bottom end of the rod. I'll be putting an O.S. .91/Ramtec in the model next. So far, so good.

Dan

fw190

My Feedback: (37)

For a while I had a Yellow P47 using the FG tow and never had any problems with it. This is why I asked this question if anyone had any problems with a tow seam method.

To make myself clear that I do not wait for the two halves to cure completely, its still tacky as I put the two halves together. Its still a chemical bond... not a physical bond.

The tow method allow me to put in bulkheads and formers while putting the two halves together ( something that I cannot do using tape ). I agree the tape method is the strongest and carbon tape is even better.

I must say though!!!!!! no model airplane is stronger than concrete at 80 MPH.

Dan, the balsa creates a channel to keep resin and glass within limits, also adds thickness to the flange. Questions... not a problem!

Vic