Jump to content

Seatback - cutting cloth


rnbraud
 Share

Recommended Posts

Ok, I was all ready to do my very first layup on the seatback when I went into mini panic mode. I went to cut my UNI cloth when I realized the with of the cloth would not completly cover the seatback since it would be laid diagonally. The diagonal length is 50+ inches while the cloth width is only about 36 inches.

 

Now I am pretty sure I need to use two pieces of cloth per ply and simply but up the ends, since this is UNI.

 

BUT, I just wanted to be extra sure since this is the very first layup.

 

So, please confirm that I will need two pieces of UNI, butted together, to get complete coverage of the seatback bulkhead?

 

Thanks.

Link to comment
Share on other sites

 

So, please confirm that I will need two pieces of UNI, butted together, to get complete coverage of the seatback bulkhead?

 

Thanks.

Two pieces and butted together (Check Chp. 3, page 4, Note para.)It is not necessary to overlap uni along the major fibers because the strength direction is along the major fibers, not across them.

 

Overlapping at least 1" would occur if you were crossing the major fibers with a second ply.

 

(I'm on Chp. 5, not an expert...yet.:confused: ... :) )

Carlos Fernandez

AeroCanard FG

Plans #206

Chp. 13

aerocanard.kal-soft.com

Sales & Support

GRT Avionics

Link to comment
Share on other sites

The great thing about the seatback is that you can practically get the entire layup wrong and still end up with a more-than-sufficient part. I accidentally overlapped the UNI where it was supposed to be butted, and my fiber orientation was completely incorrect. I forget how I fixed the latter, or if I did at all, but either way I'm NOT worried about it. If it was another part, that would be a different story.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

Link to comment
Share on other sites

Yes, you are right Jon, but as a newbie any mistakes are cause for panick.

 

I did my first layup last night. All seemed to go well. I really didn't like the butting of the small triangular piece to get complete coverage, but it was unavoidable.

 

I did have one problem, well really two. I made my slurry really thick and it went on well. I did as advised,and poured on the epoxy for the first layup, spread it around, then laid down the first layup. Man, it takes a lot of epoxy for coverage. After getting the first layp wetted out, I made a new batch of epoxy and poured it on top of the first ply. When I placed the second ply on and started to wet it out, I discovered the poured on epoxy "pooled" underneath the first and second ply causing epoxy bubbles, not air, but epoxy. When I tried to spreat out the epoxy, it mixed in with the micro slurry and caused some cloudy spots.

 

The second problem was with the 4-mil plastic. I was only able to obtain some folded stuff from the depot, so it had creases. Even thought it is on top of the peel ply, I am sure it will cause ridges. I haven't checked the layup since last night since I have a piece of plywood on top to keep it flat.

 

Oh, yeah, I seem to be having trouble getting the MGS 335 to cure fast enough. I am using the slow hardner with Larry Wimbles spreadsheet; i.e. 100:38, but it is taking 10 to 12 hours to fully cure. My garage dips down into the upper 60's at night, but in the upper 80's during the day. Could this temp be causing the slow cure. I am hesitant to add the fast hardner, but I may need to in order to make better progress.

 

Later.

Link to comment
Share on other sites

I really didn't like the butting of the small triangular piece to get complete coverage, but it was unavoidable.

I recall the same. Just know that it's perfectly fine structurally.

 

After getting the first layp wetted out, I made a new batch of epoxy and poured it on top of the first ply. When I placed the second ply on and started to wet it out, I discovered the poured on epoxy "pooled" underneath the first and second ply causing epoxy bubbles, not air, but epoxy.

Next time try putting the 2nd layer of glass on after you wetted out the first. You don't want the layers to 'float' as it seems you had happening. I lean towards making dry glass wet versus trying to remove excess epoxy.

 

When I tried to spreat out the epoxy, it mixed in with the micro slurry and caused some cloudy spots.

That's actually quite normal -- happens all the time and does not represent a structural issue.

 

The second problem was with the 4-mil plastic. I was only able to obtain some folded stuff from the depot, so it had creases. Even thought it is on top of the peel ply, I am sure it will cause ridges.

Peel ply will cause ridges where it has folds. I would only use the plastic to assist with squeegying. Once you're satisfied with how wet you want your layup to be, you can carefully roll the plastic off (so not to disrupt the fibers) and throw it away -- especially if you're NOT using peel ply. The only other thing I've done here is to put an old blanket on top of the whole thing (leaving the plastic on top of the peel ply), a board on top of that, and some light weights to minimize bubbles and ridges and let it cure. This provides a similar effect as vacuum bagging, and is easy to do for flat parts.

 

Oh, yeah, I seem to be having trouble getting the MGS 335 to cure fast enough. I am using the slow hardner with Larry Wimbles spreadsheet; i.e. 100:38, but it is taking 10 to 12 hours to fully cure. My garage dips down into the upper 60's at night, but in the upper 80's during the day. Could this temp be causing the slow cure. I am hesitant to add the fast hardner, but I may need to in order to make better progress.

Yes, the temp could be causing the slow cure, as well as improperly mixed epoxy. Is that ratio good for weight or volume? Is Larry Wimble's spreadsheet correct? If the temp is too cold for cure (and 60 degs is not entirely 'too cold'), the cure will just take longer, but will eventually cure (can take days). There's a minimum recommend temp, but you want to verify your data with www.mgs-online.com

 

Also, be sure to keep small cups of all your batches so you can perform scratch tests on them instead of your actual parts.

 

You're well on your way, and going through the exact same problems as everyone else. Good job, and good luck!

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

Link to comment
Share on other sites

When I placed the second ply on and started to wet it out, I discovered the poured on epoxy "pooled" underneath the first and second ply causing epoxy bubbles, not air, but epoxy.

Have you tried using a roller? Rolling the glass and then the peel ply pushes the glass down into the epoxy as well as the peel ply when you roll them. By doing that you bring up (over and out, whatever the case may be) into the ply and eliminate epoxy and air bubbles.

 

My buddy Andy found Bodi rollers www.bodico.com to be the best value. 1" x 3" plastic roller and 1/4" x 2" corner roller are a must in Andy's and my book.

 

My $.02

Carlos Fernandez

AeroCanard FG

Plans #206

Chp. 13

aerocanard.kal-soft.com

Sales & Support

GRT Avionics

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information