Jump to content

Making a buck to mould a cockpit canopy.


Recommended Posts

Foam would definitely melt at the required temperature.

When I've made canopies (+ other odds & ends) from pop bottles I've used off cuts of pine - cheaper (it doesn't come cheaper than free), easily obtainable & more robust to knocks especially if a second one is required later. 

Mine are rough cut using a band saw then a small plane, a disc sander & finished with wet & dry (used dry).   

 

PS - I've got some pics of my method somewhere on my PC, if I can find them I'll post some on here. 

Edited by PatMc
  • Like 1
Link to comment
Share on other sites

About 16 years ago I picked up a Protech Unlimited e-glider from a deceased clubmate's estate. It came with two battered blown plastic fuselages but no canopies.

The main section in the photo is the actual canopy shape the base & ply end pieces were added to allow an oversize finished article that would be trimmed to fit.

It's fixed to a batten from underneath by a couple of long screws.  The whole lot is from scrap wood left over from DIY projects.

 

1_Plug_profile.jpg.9a922254afefebc03a04e4c45352bcc6.jpg

 

2_Plug.jpg.719a8e21c761b45628bc107e8c03d7c9.jpg

 

863298042_3_Popbottleprepared.thumb.jpg.582515b6841b0598f93686625ff896af.jpg

 

Prep - add a pair of oven gloves & a pair of pliers.

 

4_.thumb.jpg.1827d3c83ff1f5a3b7aeaa25bbeb9e5d.jpg

 

5_.thumb.jpg.6cf4195121bfdf320379baafb33c53d8.jpg

 

6_.thumb.jpg.bb21d77062d7c3f110d4e392d2b461a9.jpg

 

7_.thumb.jpg.3e25127fab30f96a1fc0c24e862a00cb.jpg

 

The mounting batten also proved the bulk underneath to get the size within the shrinkage limit.

  • Like 2
Link to comment
Share on other sites

I think the canopy in the previous post was a first try that was scrapped but I made a number of useable canopies from green, brown & plain bottles for myself & someone on a forum. 

 

6_In_use.jpg.61130cb86cda89392cff7febec901b76.jpg

 

One of the fuselages was used for a slope soarer.

 

8_GF_in_use.jpg.9e965d8e117d32f88a8b05ca62b7bb6f.jpg

 

 The other as designed but with lipo & brushless motor.

 

7_GF_canopy.jpg.f24662813abec7a8cbf4bb00e5199615.jpg

 

This fibre glass moulding was made by leaving a shrunk down bottle on the former, trimming the bottle neck away, laying up FG & resin on top then while the resin was still wet shrinking down another bottle over it.

 

DSCN3068.thumb.JPG.9babb5ddd847ef5008a19531b244f8f7.JPG

 

When painted the finished is "stand off" acceptable. 

  • Like 5
Link to comment
Share on other sites

I tried using a  blue foam inner with a plaster of paris skin and found that the outer shell cracked when used as a plug in my vacume mold set up.

A solid plaster plug did work OK for another larger canopy but it did have surface damage after its first use.

Link to comment
Share on other sites

I've had success with wooden plugs, like those featured in Pat's pictures, with plaster of paris -multiple pulls possible with care - and latterly, most surprisingly, with 3D printed PLA plugs in my vac-former. I don't think either pink or blue foam would stand the heat required to make PETG or similar workable enough to make a good canopy.

Link to comment
Share on other sites

I thought i would persevere with the foam plug idea as it so much quicker to shape and sand, i used some of that insulation board that has the silver foil on both sides. The heat gun didn't seem to melt it so i made the plug, gave it several applications of Easy-kote then primed and top coated it yesterday. Today i shoved it in a pop bottle and formed it with my heat gun. Some of the paint came off on the canopy but i removed that with thinners and trimmed it down. Here are the results, very pleased with it, canopy glue has just gone on in the picture, i will paint the frame tomorrow. So result is you can use foam but obviously only certain types. 

IMG_20220806_130014.jpg

Edited by martin collins 1
  • Like 4
Link to comment
Share on other sites

Hi


foam works just fine depending how much heat you are using.  Ive recently gone from ‘zero to hero’ in my own estimation 😀 using vac forming.   Like a lot of things, its a lot easier than it looks.

 

Ive used foam, liteply and 1/16 ply, glassed, to ‘build’ the plug.  Glassed with 3/4 oz and wet sanded smooth.  Takes a couple of hours end to end but us very rewarding.

 

 

BC19DDAD-24AD-4DDC-A419-B8ABA38A683E.jpeg

06D49E61-FABF-4D94-91F5-63DF600CD45F.jpeg

E22EE850-0EA6-4404-807F-B7A8A1B5AB55.jpeg

230360D1-2BA0-415E-AEB6-45155F18A74A.jpeg

33CC68D3-AD0B-43CB-9A09-DBE09AC0D12F.jpeg

15DB8CBE-494B-4669-8075-90951DE54002.jpeg

E7AC907B-35B6-49B6-AB76-3F85179086B5.jpeg

D2F8508F-9173-41FD-8B64-2FA7AFE906C0.jpeg

DAC80DF8-6CFC-4D96-A469-CE11F46D4BFD.jpeg

D3DF3273-5987-4355-9590-67846E391872.jpeg

DE4C698A-FBFB-40CF-8B50-C8C1C430DD2F.jpeg

A71D67EC-0421-4596-96C9-9FA16C27D363.jpeg

  • Like 3
Link to comment
Share on other sites

This stuff worked great and its A3 sized.  A4 is also available ... https://www.amazon.co.uk/gp/product/B07NGM3CCR/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1


This is useful for a the plastic pipe that fits Henry styke vacuums ... https://www.ebay.co.uk/itm/182227316539?var=484422434514

 

the oher essential is a wife who is happy for you to use her oven.

 

mike

 

PS the vac boxes are actually 3/4 full of foam to reduce the volume of air that needs sucking.  Big one has a socket  each side as she has a house Henry and I have a workshop one.  In the end i only needed one vacuum cleaner, the other socket being ‘blanked off’.

 

 

 

74B88F85-2F00-4EDE-941C-71882917544C.jpeg

537A2DA1-F9BE-4140-A9C5-51BA7083833D.jpeg

A6420A9F-1A57-4C85-9FD4-6322400D64CA.jpeg

3946700A-390B-4BEE-B175-D9D38C2EAC43.jpeg

A765EAB1-5E0A-4187-9B3E-6AB05459D5D6.jpeg

5CECB840-C267-4E02-93E5-6831CE3CD808.jpeg

B03888AB-30AF-40D5-B74D-530783B62975.jpeg

543DF59B-3A64-4D15-8FA1-DD8448E9D595.jpeg

B36C83FA-85F1-4710-851E-F10E4B628F73.jpeg

5CE96B26-D254-45C3-B4CA-53A0CC23312C.jpeg

ACB52899-4A00-48A1-BD16-12A27313D1E8.jpeg

Edited by MikeQ
  • Like 2
  • Thanks 1
Link to comment
Share on other sites

  • 10 months later...

Help!

I have just managed to get fusion 360 to generate a rough spitfire mk24 canopy shape (took ages as first attempt at lofting 🙄). Had not really got as far as to thinking about how to use it  to form the canopy!! as I was using it to come up the (for me, very steep) learning curve on the 3D modeller. Had vague thoughts of using Easycomposites XCR epoxy coating resin to produce a mould and then tool but this seems overly complex. Am tempted to try sanding and then covering in polymeric vinyl or easycoat x 3 as suggested above. I'm a bit worried about covering it without wrinkles as it is quite curvy.:

 

 

image.thumb.png.a7621a8a2a7c6310331db50916ed2832.png

 

Printed with in PLA with .4mm nozzle and .3mm layers.

 

Likely to try plastic bottle and heat gun to start as I think I deconstructed the vacuum box 😞

 

Any suggestions as to covering material, approach or other useful threads very much appreciated!

  • Like 1
Link to comment
Share on other sites

Hi, 25g glass cloth, in or ot two layer and finishing resin (not regular epoxy for gluing stuff together) can be sanded , body filled, primed super smooth.  Bit pricey though unless you already have some on hand though.  Regular epoxy might well be just as good but the one time i tried using it, it didnt come out as hard and wasn’t as easy to spread unless thinned (which is why it probably didnt end up as hard in the first place)
 

That would be my recommendation.

 

cheers

 

Mike

Edited by MikeQ
  • Like 1
Link to comment
Share on other sites

Is it just the fine lines on the 3D print that you are looking to eliminate or is it concerns that the 3D printed plug will melt on application of heat?

 

If it's the former, that could be alleviated by a little wet sanding with very fine wet and dry paper. An alternative is the polymer coating for 3D prints, which is a bit messy, mucks up the dimensions a bit, but does produce a very smooth flow coat finish - probably better for figures than engineering objects though and I'm not sure how that would stand the rigours of heating.

 

If it's the latter I was pleasantly surprised to find that the PLA plugs that I had printed for my Dornier DO17 canopies were able to be used for at least four vac-forming attempts to produce an acceptable canopy, without any noticeable degradation. I'd be happy with that for a plaster of Paris plug- can't vouch for the integrity in producing a large number of canopies but might be worth having a try to simplify the process. My original intention had been to use the PLA male plug to create a glassfibre female mould and then a Plaster of Paris replica of the original 3D printed male plug. However I decided to just experiment and give it a try on the PLA master plug and it worked.

 

 

Edited by leccyflyer
  • Like 1
Link to comment
Share on other sites

So I was lazy and tried the prototype directly in a bottle with heat gun 🙂

 

image.thumb.png.c958570cb13a44990467da8397b46eb0.png

 

Trouble is, it's actually quite a small canopy and needs quite a bit of heat to shrink onto the plug which has distorted the plug but not as much as you would think given the level of heat used. Interestingly you could see the pattern of the 3D print support structure beginning to emerge 🙂

 

The bit that killed it was a wrinkle I could bot get out (green).

 

image.thumb.png.1a82c4136c7c4c4b670e1e9dfbe6ffa3.png

 

So before I attempt to smuggle plastic into the oven I'm going to try dividing the plug up into bits to reduce the shrinking requirements:

 

So am now printing:

 

image.thumb.png.8ca013cf1e9e7776e45676c811601801.png

Green bit is front canopy, purple is support so I don't melt the corners of the plug as much as I did last time 😊

 

 

 

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.
Note: Your post will require moderator approval before it will be visible.

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...