Z-Foam Repair - RC Groups
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Oct 13, 2006, 09:29 AM
Registered User
Discussion

Z-Foam Repair


Newbie here looking for help.

After watching my father-in-law enjoying his electro-foamie, I decided to purchase a Hobbyzone Super Cub. I love it and it is so easy to fly, people think I actually know what I'm doing....right up 'til the unsuccessful neg G-loop....into the neighbor's house...they've been very gracious about the entire matter. (Tip: the plane wasn't built for that type of activity).

Anyway, so the Super Cub is banged up pretty well. The good news is that the radios and motor still work. And, the replacement parts only total $8.59. However, the fuselage took a real beating but I think it's still usable.

The front of the radio compartment has noticeable vertical stress seams along the front wall. Also, the engine mount was ripped off the firewall which gives the foam a real rough edge, but I think I will still be able to glue a new firewall back on. Which brings me to the questions:

1) How to build up/support those stress seams
2) What adhesive to use to mount the firewall to the fuselage.

Thanks for any advice you might have.
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Oct 13, 2006, 11:33 AM
Registered User
Peteohms's Avatar
I like Sumo glue from Lowes. It is Polyurethane glue and it foams up filling in gaps. As far as reinforcing the fuselage try foam from takeout containers or a foam egg container. Just cut out a piece the size you need. You can do a search on Sumo on rc groups and read more about it. Good luck.
Oct 15, 2006, 01:32 AM
Registered User
Culpable
Glad you like the Cub, you are correct, the plane wasnt designed to do any negative G work, but it is an awsome machine the right way up!

To repair torn "Z" foam, you can just use any grade of CA, it doesnt have to be the foam friendly type. The "Z" foam is not effected by CA like polystyrene based foams.
To repair a broken piece, just apply a light film of medium CA onto one side of the join and a light spray of accelerator onto the other side to help the CA go off in reasonable time, carefully align the parts and push them together, they will be stuck back together in short order
To repair the torn areas that havn't broken apart, just wick in a little thin CA.
The most effective way of reinforcing the weak areas is to use a little of the fibre reinforced packing tape that is pretty common these days. You dont need much of it, as it sticks very well to the unpainted "Z" foam, and is very well suited to the task.

The glue originaly used by the factory to apply the firewall is simply a white silicon sealant/adhesive that is commonly available in China(I think the generic name for the sealant in China is "703"). When used properly, it gives a very good joint, that will normally tear the "Z" foam near the glue joint rather than fail the joint itself, and remains flexible like the foam. I would try to use the same material, as there are not so many things that will adhere to the silicon already on the model.

Mike
Oct 15, 2006, 10:22 AM
Registered User
Thank you both for the responses. The parts should be here on Monday and I'm eager to get started. I will be heading out today to try and find the CA & Sealant/adhesive. Mike, you were right about the stuff the Chinese used on the firewall. The crash broken the firewall roughly in half. One half was almost ripped off and you could easily see that the bond of the sealant/adhesive wasn't the issue as little pieces of foam had come off with the plastic part. I used a knife to cut the other half off so I wouldn't rip any more foam chunks off the front of the plane.

I must effect these repairs ASAP if I want to fly again this year. In Northwest Ohio, the "winter winds" start up around November 1 and don't stop 'til Easter. A light weight foamie wouldn't stay up long in this wind. Even our trees are oblong shaped easterly.

Thanks for the tips.
Nov 10, 2009, 06:13 PM
Registered User
Quote:
Originally Posted by Mike_r9909
Culpable
Glad you like the Cub, you are correct, the plane wasnt designed to do any negative G work, but it is an awsome machine the right way up!
Mike
If you move the elevator control horn all the way in and get enought altitude(and have steady hands and quick reactions), the Cub will preform a negitave G loop very nicely. I have done it multiple times without ever crashing, and I just started flying rc planes two months ago
Sep 02, 2010, 11:12 PM
Registered User
Hi guys.....i crashed my Parkone Messerschmitt today and while no serious damage resulted, the horizontal and vertical tail fin have been weakened. The foam is now 'soft' near the top of the vertical fin and i'm just wondering what would be the best way to strengthen it up? I read above about the tape.....but will that same method work well?
Could it be painted over??

I was thinking of poking a hole down vertically into the vertical tail fin and inserting a kebab stick or carbon rod or something.....but the fin is quite thin and i risk poking the stick/rod out through the side of the fin.

Any thoughts or experiences??

All advice appreciated. Thanks heaps in advance.

Michael
Sep 03, 2010, 10:19 PM
RC Adddict
Wilfor's Avatar
your on the right track here . A small carbon rod would be best ,just glue in place but if your careful a bamboo skewer would work as well . I like making a guide hole in the foam first ,the easiest way i find to do this is to use a lighter or propane torch to heat up the end of a really small screwdriver or small wire and then push it in . Dont get it to hot or it will really melt the foam but if you get the temp right it works great . Then just glue the rod in place , cover the hole with light weight spackle and then add paint ..

Quote:
Originally Posted by Maccanaut
Hi guys.....i crashed my Parkone Messerschmitt today and while no serious damage resulted, the horizontal and vertical tail fin have been weakened. The foam is now 'soft' near the top of the vertical fin and i'm just wondering what would be the best way to strengthen it up? I read above about the tape.....but will that same method work well?
Could it be painted over??

I was thinking of poking a hole down vertically into the vertical tail fin and inserting a kebab stick or carbon rod or something.....but the fin is quite thin and i risk poking the stick/rod out through the side of the fin.

Any thoughts or experiences??

All advice appreciated. Thanks heaps in advance.

Michael
Jan 24, 2011, 01:11 AM
Registered User

Fill in holes ?


I have an e-flight apprentice made of Z-Foam and I have a few puncture holes in the foam where the foam is missing. What can I fill in the gaps with? Can I use expanding foam in a can? Help much appreciated.
Mar 29, 2011, 12:02 AM
Registered User
RootCanalGuy's Avatar

FOAM PUTTY, and GLUING Z-foam


you can fill in foam gaps with "Foam Putty by Woodland Scenics"; fill cracks, sculpt, carve, sand smooth. Very hard to find this type of product, almost had to order similar product from UK, but there it was in Linn Creek, MO; works well.

Also, regarding CA and insta-set it works great most of the time when it does NOT involve HEAVY SHEARING forces on Z-Foam, such as several areas of the Habu fuse; in cases like that if you want to force the CA to work you need WIDE carbon fiber as inserts ( https://www.rcgroups.com/forums/show...2#post17184489 ) to redirect the shearing forces away from popping the CA glue joint right open. In these cases save yourself a lot of time and worry...plug in your GLUE GUN and in less time wondering whether all that CA has really set or not deep in the cracks and whether it is going to give out.... YOU KNOW THE GLUE of GLUE GUN has set and it is dependable, like Epoxy is to wood.

I use CA and accelerator 99% of the time especially on my T-28, but for those times that I get a BAD feeling about using CA, I use Glue Gun and uncross my fingers. (ZAP KICKER has worked poorly for me leaving white residue on Zfoam....I use "Insta-Set by www.bsi-inc.com " )
Last edited by RootCanalGuy; Mar 29, 2011 at 12:09 AM.
Nov 10, 2017, 09:02 AM
Registered User
What is the best way to remove dents in the foam, will heat applied lightly allow it to smooth out, or is filling and painting the only way?
Nov 10, 2017, 03:24 PM
AndyKunz's Avatar
Wet heat.


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