ryley

working with carbon fiber and making some parts

Recommended Posts

I've got some experience working with glass and epoxy but I've never done any vacuum bagging (except helping others with their layups). I thought I'd take on the challenge of learning a few new tricks and try to make a few pieces. The first thing I was thinking of was new hatch boards for the columbia. I measured the thickness yesterday at 10mm, and I have some questions.

1. can I lay carbon that thick, or should I make them with a foam core? 

2. if its a foam core, any tips or tricks for wrapping the edges and making them look nice? 

I know I could probably buy dragonplate for a lot less than I'll spend setting up for this, but again this is more to learn the technique. I'd like to feel more confident in working with modern materials than when I started with this stuff back with Gale Yount in Noank in the 80's.

thanks in advance

Share this post


Link to post
Share on other sites

If you make solid CF boards 10mm thick the boards will be the strongest, and possibly the most expensive, things on the boat. I'd definitely core them.

Share this post


Link to post
Share on other sites
3 minutes ago, IStream said:

If you make solid CF boards 10mm thick the boards will be the strongest, and possibly the most expensive, things on the boat. I'd definitely core them.

thanks IStream, that's kind of what I thought. I also thought of using some fiberglass layers between carbon outer skins, but foam is probably the better way to go. I just wasn't sure how much compression you get, and how much thickness per layer of cf I should account for.

Share this post


Link to post
Share on other sites

About a 1000 grams or slightly less each side of an 8mm core, depending on supports below and span etc.  

Edit, also depends on core material, don’t use Home Depot shit, use PVC etc. 

  • Like 1

Share this post


Link to post
Share on other sites

For hatch boards, why bother with the expense of carbon?   These aren't structural elements.  

Skins of regular 1708  or 2 x 6 oz cloth should be more than sufficient.  Will flex a bit more than carbon skins if they are the cabin top sliding boards (when someone stands on them)

A simple method is to rout the sides of one face of the foam with 1/4" or 3/8" roundover bit.  Sand the corners to match.

Dart the corners, lay up on routered face.  Trim edges while layup is not fully cured (8 hrs or so). then layup other side and again trim before fully cured.  Sand when cured then apply fairing compound and sand again to smooth out when cured

Share this post


Link to post
Share on other sites

Assuming your boards are flat lay up on something flat starting with a layer of drafting mylar'. Gelcoat then glasscloth then core material  [ honeycomb is best  ]

https://youtu.be/DsQ8JGBhR-8

glasscloth more mylar flat board and sand bags.

You could bag it but you don't gain much on flat laminates over simple sandbags.

If doing a vacumbag with a diy set up you need a regulator and some idea on a setting that does not cause core collapse

Share this post


Link to post
Share on other sites
3 hours ago, 12 metre said:

For hatch boards, why bother with the expense of carbon?   These aren't structural elements.  

agreed, but again I figured something that's not critical and that can easily be replaced with the originals might be a good way to practice the techniques. I could make it cheaper by doing it with glass only, but eventually there are some projects that will be structural and I don't want that to be a 'first.'

Share this post


Link to post
Share on other sites

I totally get it...sounds like fun.  Easy enough to use massonite for the vacuum base, wax paper or Mylar for release.  The edges are the tricky part.  For simple, make a frame out of teak or mahogany, fill the center with foam, balsa, or honeycomb and laminate a single layer of carbon on each side.  More than strong enough and light.  Substitute G10 for the wood if you want.  I see the frame as 8mm square stock....just enough to give a good edge for wear and rounding on the corners.  Or, you can just lay up sheets,  cut the correct size out and fill the edges with resin after cutting out a shallow relief.....maybe 3mm?  A basic Harbor Freight vacuum pump will do.  Enjoy!

Share this post


Link to post
Share on other sites
7 hours ago, TQA said:

Assuming your boards are flat lay up on something flat starting with a layer of drafting mylar'. Gelcoat then glasscloth then core material  [ honeycomb is best  ]

https://youtu.be/DsQ8JGBhR-8

glasscloth more mylar flat board and sand bags.

You could bag it but you don't gain much on flat laminates over simple sandbags.

If doing a vacumbag with a diy set up you need a regulator and some idea on a setting that does not cause core collapse

To the OP, do not use honeycomb core! Especially not without a good vacuum setup. 

Use a foam core, it’s cheaper and more damage tolerant. 

As for core collapse under vacuum?!!!! :P bullshit. 

Share this post


Link to post
Share on other sites
6 hours ago, mad said:

As for core collapse under vacuum?!!!! :P bullshit.

I mean ideally you're pulling 1 atmosphere max right? that's 15psi (roughly).

Share this post


Link to post
Share on other sites
32 minutes ago, ryley said:

I mean ideally you're pulling 1 atmosphere max right? that's 15psi (roughly).

Correct, you won't crush the core with that.  Personally i would only ever bond to core material with a vacuum, placing weights on top is a waste of time.

Share this post


Link to post
Share on other sites

I used to build lightweight composites for competition use. I can assure you that both foam and stretched honeycomb will deform and or collapse well before you get to 1 bar. End grain balsa would be OK though. 

The OP is starting from scratch. A vacuum pump regulator and hose with a pro bag would be nice but sandbags on the top board will work. Just the cheapest new pump will be 400$

You can build a DIY rig but it is a fair bit of faffing around to get it to work and as you need an old fridge or freezer pump there are environmental considerations to get in the way. 

 

Share this post


Link to post
Share on other sites
56 minutes ago, TQA said:

I used to build lightweight composites for competition use. I can assure you that both foam and stretched honeycomb will deform and or collapse well before you get to 1 bar. End grain balsa would be OK though. 

The OP is starting from scratch. A vacuum pump regulator and hose with a pro bag would be nice but sandbags on the top board will work. Just the cheapest new pump will be 400$

You can build a DIY rig but it is a fair bit of faffing around to get it to work and as you need an old fridge or freezer pump there are environmental considerations to get in the way. 

 

I’m still building and have never seen or heard this urban myth confirmed by vacuum alone. Throw heat in the mix, maybe. 

What density core materials are you referring to? 

Sandbags will never provide the level or even pressure required for foam core bonds, let alone remove the voids, especially if you want a high quality lightweight product that will last.   Out of curiosity, what weight of sand do you recommend for an 8 x 4 sheet? Or similar area  

 

Share this post


Link to post
Share on other sites

Foam collapse? Really, what kind of foam are you using? Styrofoam?

Random foam data sheet: Airex C70. 40 kg/m3 (about the lightest you can get)  Compressive strength = 0.6 N/mm2 (MPa)

(1 atm = 1 bar = 0.1 MPa)

If he's laying up hatchboards and just learning about wetting out carbon I don't see any problem using weights to bed the core. Not ideal, not perfect but unlikely to cause massive delamination and failure. 

 

Share this post


Link to post
Share on other sites

If this is a pedagogical exercise it's worth thinking about the specific skills you want to learn and the best way to go about that. Starting with a project and hoping that it'll teach the skills you want may be inefficient. NTTAWWT, but if you want to maximize the educational content then you have a different problem to solve than filling the companionway void.

In FRP work often the great majority of the time and effort goes into tooling. I think improving design, construction, and use / reuse tooling skills will pay the big dividends for the student of FRP production. I'd consider going to the trouble of making up some tooling for the boards. It's an exercise worth doing.

I would consider vacuum clamping (low vac bagging with glass/resin similar to open layup). It's useful for some stuff in it's own right. You can get away with less expensive equipment and expendables. All the skills learned should apply to fancier systems. 

I'd go with a foam core. I like stitched cloth (eg. 1708) for this kind of thing but maybe for learning a layup of different types of cloth would be worth it just to get a feel for them. Working towards carbon layups epoxy makes sense as the glue to learn about.

Or whatever... Just wanted to suggest looking at the project from the teaching perspective.

Share this post


Link to post
Share on other sites
5 hours ago, mad said:

I’m still building and have never seen or heard this urban myth confirmed by vacuum alone. Throw heat in the mix, maybe. 

Polystyrene foam will crush around 0.25 bar Lightweight urethane foam at around 0.5 bar

What density core materials are you referring to? 

Low very low if we had a choice w asked for the lightest

Sandbags will never provide the level or even pressure required for foam core bonds, let alone remove the voids, especially if you want a high quality lightweight product that will last.   Out of curiosity, what weight of sand do you recommend for an 8 x 4 sheet? Or similar area  

We only used 'sandbags' a couple of times panels were about 35 in by 25 in again it is a long time ago but I know we used 1/2 bags of Portland cement maybe 3.so not that much pressure on the boards end result was OK.

 

Share this post


Link to post
Share on other sites

If you subscribe to the Off Center Harbor website they have a couple of excellent vids on an introduction to vacuum bagging (plus lots on epoxy techniques, etc) - worth the subscription !

(You can often get a used vacuum pump quite cheaply on eBay, etc, fine for vac bagging.)

Share this post


Link to post
Share on other sites
17 hours ago, mad said:

Correct, you won't crush the core with that.  Personally i would only ever bond to core material with a vacuum, placing weights on top is a waste of time.

One atmosphere is 29.9 in lbs of mercury or vacume as most call it 15 or roughly a half an atmosphere is ideal.

Share this post


Link to post
Share on other sites
21 minutes ago, Elusive36051 said:

One atmosphere is 29.9 in lbs of mercury or vacume as most call it 15 or roughly a half an atmosphere is ideal.

Huh? Better skip the science. The well known Rule-of-thumb is a complete vacuum creates a force of 15 pounds per square inch. (lbf/sqin). Only way to get more layup force would be to apply a pressure greater than one atmosphere.

Share this post


Link to post
Share on other sites
11 hours ago, TQA said:

 

Must have been some very lightly loaded panels, the shear properties of that stuff is awful. As is it’s propensity to suck up excess resin and water. 

Share this post


Link to post
Share on other sites
5 hours ago, mad said:

Must have been some very lightly loaded panels, the shear properties of that stuff is awful. As is it’s propensity to suck up excess resin and water. 

They were generally components for model aircraft. Mostly control line combat and F3J gliders.The highest loads were experienced by the F3J sailplane wings. We used a winch launch. The last part involved a large flywheel which was spun up prior to launch and connected to the drum to rapidly accelerate the glider to 200 mph + which then was pinged off by applying up elevator. All sorts of figures were bandied around on the G force involved but 20 G would be conservative. We could achieve launch heights of 350 400m + with a 200 m cable. We broke a lot of stuff learning how to do this. Our 'gorilla' winch with a v8 race car flywheel was eventually banned. We were circumventing the rules which limited the voltage and amperage of the winch motor by using the motor to spin up the fly wheel prior to launch storing a LOT of energy. 

We settled on an I section mainspar with carbon fiber top and bottom. We tried kevlar and boron but CF was easiest to obtain at the time. Blue urethane foam for the core unidirectional glass cloth with additional CF tows on the bottom reducing toward the tips. West System epoxy. Vacuum bagged at 0.4 - 0.6 bar. We used a mould to maintain the airfoil shape. 

The technology lives on in the models used to achieve speeds in excess of 500 mph [ current record is 545 mph I think ] using a technique called dynamic soaring. Yup toy gliders doing 500 mph!

Share this post


Link to post
Share on other sites

I've used this- fine for small home projects- copy and paste:   harborfreight.com/25-cfm-vacuum-pump-98076.html

Share this post


Link to post
Share on other sites
5 hours ago, TQA said:

They were generally components for model aircraft. Mostly control line combat and F3J gliders.The highest loads were experienced by the F3J sailplane wings. We used a winch launch. The last part involved a large flywheel which was spun up prior to launch and connected to the drum to rapidly accelerate the glider to 200 mph + which then was pinged off by applying up elevator. All sorts of figures were bandied around on the G force involved but 20 G would be conservative. We could achieve launch heights of 350 400m + with a 200 m cable. We broke a lot of stuff learning how to do this. Our 'gorilla' winch with a v8 race car flywheel was eventually banned. We were circumventing the rules which limited the voltage and amperage of the winch motor by using the motor to spin up the fly wheel prior to launch storing a LOT of energy. 

We settled on an I section mainspar with carbon fiber top and bottom. We tried kevlar and boron but CF was easiest to obtain at the time. Blue urethane foam for the core unidirectional glass cloth with additional CF tows on the bottom reducing toward the tips. West System epoxy. Vacuum bagged at 0.4 - 0.6 bar. We used a mould to maintain the airfoil shape. 

The technology lives on in the models used to achieve speeds in excess of 500 mph [ current record is 545 mph I think ] using a technique called dynamic soaring. Yup toy gliders doing 500 mph!

This little splinter of a RC glider flies at the cruising speed of a 747 airliner. Pushing the transonic envelope! 

  • Like 1

Share this post


Link to post
Share on other sites
8 hours ago, TQA said:

We used a winch launch. The last part involved a large flywheel which was spun up prior to launch and connected to the drum

Yeah we did that in Germany with full size sailplanes. Then we'd thermal off the autobahn cloverleafs. it's quite a rush when those big trucks start the reels.

Share this post


Link to post
Share on other sites

Winch launch in a sailplane is the closest thing you can get to a aircraft carrier catapult launch. 

 

 

Share this post


Link to post
Share on other sites
On 12/4/2018 at 3:53 PM, TQA said:

They were generally components for model aircraft. Mostly control line combat and F3J gliders.The highest loads were experienced by the F3J sailplane wings. We used a winch launch. The last part involved a large flywheel which was spun up prior to launch and connected to the drum to rapidly accelerate the glider to 200 mph + which then was pinged off by applying up elevator. All sorts of figures were bandied around on the G force involved but 20 G would be conservative. We could achieve launch heights of 350 400m + with a 200 m cable. We broke a lot of stuff learning how to do this. Our 'gorilla' winch with a v8 race car flywheel was eventually banned. We were circumventing the rules which limited the voltage and amperage of the winch motor by using the motor to spin up the fly wheel prior to launch storing a LOT of energy. 

We settled on an I section mainspar with carbon fiber top and bottom. We tried kevlar and boron but CF was easiest to obtain at the time. Blue urethane foam for the core unidirectional glass cloth with additional CF tows on the bottom reducing toward the tips. West System epoxy. Vacuum bagged at 0.4 - 0.6 bar. We used a mould to maintain the airfoil shape. 

The technology lives on in the models used to achieve speeds in excess of 500 mph [ current record is 545 mph I think ] using a technique called dynamic soaring. Yup toy gliders doing 500 mph!

Got it, a slightly different use and set of loading parameters than I’m used to with race boats and commercial structures etc.  

Impressive speeds!! 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now