Blackfoot body repair advice sought

[wilysloth 22]

I am currently returning my vintage Blackfoot to running order and would like to keep as much original as I can, mostly for sentimental reasons. I need some advice on how best to repair the hard body shell making as few non-reversible changes as possible.

In my youth the front body post clip broke off and was fixed by putting a screw down through the body post. Over time the hole in the body shell widened and is now larger than the new post I ordered. Furthermore there is a crack running front to back in the middle of the bonnet/hood.

My plan was to use plastic weld to fix the crack but don't know how to make the hole for the body post smaller. Plastic weld a plastic washer in there or something? Basically I don't have any experience in this regard so any ideas would be very welcome.

 

 

[KEV THE REV 2307]

I had a similar repair to do on my vintage BF shell along with countless other repairs on it . I first cleaned the surfaces of the crack with a medium paper to remove any contamination and excess plastic ( not too much ) to make sure the crack closed up tight . I used liquid glue to bond the crack back together and left it to set . I then cut out some thin plastic card and bonded that under the bonnet to reinforce the repair . The card can't be too thick as the body post won't protrude through enough once the bonnet is drilled out again . I then made some plastic infills to reinstate the bonnet area the replicate the original post hole with its raised part , this takes patience to get a nice circle . I drilled out some plastic card to fit the body post through then I used a hole punch the cut out the circle , then cleaned it up with paper . If you want to run the BF hard to would be best to epoxy bond some thin aluminium under the bonner instead of plastic card to stop the post pushing through again . I have also made some front body supports to balance the front end to prevent the front body mount stress from the shell having a centre only body post .

Have a look here on my Brat restoration ( my BF project is not in my showroom yet ) and you will see the supports ( same chassis as BF same post design)

https://www.tamiyaclub.com/showroom_model.asp?cid=127067&id=5280

[Juggular 4961]

Very well explained, Kev.  

[WillyChang 1814]

are you using Bondene PlastiWeld?

This stuff is best when you've got 2 tight fitting styrene surfaces and the thin liquid wicks in by itself. 

Its not as good for when there's cracks with daylight showing thru it. Any space gap between styrene needs to be filled either by cutting slivers and packing the gap before solvent welding. Or grind some shavings into a tiny glass jar, dissolve it with the solvent and it'll make a decent gapfiller.

Weld a thin styrene sheet underneath to support your repairs perhaps. Afterwards you can grind it away or just leave it if it doesn't get in the way.

[Juggular 4961]

Another vote for Bondene PlastiWeld.  

It smells strong so vent well.  Once you use it, you can't take it off. Plasti-weld is a fitting name.  

 

[wilysloth 22]

Thank you for the detailed responses.

WillyChang, I have some EMA Plastic Weld Cement which I guess is similar to Bondene PlastiWeld.

So my current plan is to:

• Clamp the shell shut such that the crack closes up.
• Apply some plastic weld to repair the crack.
• Cut and plastic weld some plastic card (0.25mm styrenne sheet sound okay?) under the crack and the enlarged body post hole.
• Where there were missing material gaps in the crack above the new plastic sheet, melt some plastic card shavings using plastic weld in the hole(s).
• Cut a circular piece of plastic card to fit the enlarged body post hole, hole punch an internal hole into it to fit the body post, and plastic weld that to the new plastic card welded to the underside of the bonnet/hood (filling any gaps as above).
• Sand down the new plastic when dry.

I intend to run it hard so additional aluminium strengthening under the new plastic work is probably a good idea too.

 

[zomboided 374]

I've recently fixed a cracked freezer drawer and a cracked washing machine door with JB Plasticweld https://www.amazon.co.uk/JB-Weld-Plastic-Syringe/dp/B009EU5ZMK and some fine glass fibre matting.  I score the surface up, spread the epoxy on the surface being fixed, then push the glass fibre matting onto it.  I then cover another piece of matting with epoxy and push that over the top.  I've found it better than using plasticard where there surface is uneven as you can push it into place and it doesn't resist/spring back.

The freezer drawer incorporated a piece of aluminium around the handle to fully strengthen it and everything seemed to stick together well.

I've repaired cracked bodies using a similar approach, only with proper fibre glass resin rather than plasticweld, but I'm thinking that plasticweld adheres to the plastic surface better rather than just hardening up the glass fibre.

I've found plastic cement https://www.amazon.co.uk/Tamiya-87003-Cement-40ml-Toy-transparent/dp/B000RLWAN2/ref=pd_sim_107_1?_encoding=UTF8&psc=1&refRID=SBKGZQQ9W7VW2WF2XS7W to be lacking strength wise and avoid using it for any kind of stressed pieces.