Below is a reply I sent to Dan Heath on a question of his. In thinking this over I have determined that this is the best way that I have of giving of my experience to the group that has and will help me over the next few years with things I have no clue about. I will make up a prototype in miniature of a female mold and framework and do this, taking pictures for a web site. Now true I have not gotten to this stage myself and have not made my own canopy yet. ( Yes I am sticking my neck on the block here but wait) This is the type of work I have been in for 17 years. If I can not figure out a reasonable way to do it easily - I would like to say we are all doomed to buy them. If all goes well, besides the web page I will bring the equipment to the next gathering in Mt. Vernon and do a demonstration if there is enough interest.
Steve McGee Endeavor Wi. USA Building a KR2S widened. lmc...@maqs.net ----- Original Message ----- From: Steve and Lori McGee To: KRBuilder Sent: Tuesday, December 02, 2003 10:13 AM Subject: Re: windshield Okay wait - I am a little confused in the writing. So when you had the plastic on the mold and let it drape, there was no visual deformations. ( but if I remember right you had problems with cracking later? I believe this is from the plastic being stressed at its earliest possible bending point and not truly bagging.) But now you are heating the plastic on flat sheet of steel and picking it up hot? This might be where the problem is or part of it. You may be stretching the plastic in ununiformed ways when handling. ( I can not believe this is what Todd is doing, this is his bread and butter, you think he is going to tell you exactly?) Now what I intend to do is vacume form the plastic. This can be done with a male or female mold but is easier at home with a female, as you would not have to suspend the mold in the air some how, but can build it to sit on the ground. For a look at the type of work I am in, go to this website and watch the steps to the forming at the lower right. Very sophisticated and not exactly what I am going to try as it is using a plug and forming a female upwards. http://thermoforms.com/forming.html Notice what these are made out of. http://thermoforms.com/gallery/mannequins.html Okay - visualize a rectangle picture frame large enough to hold the plastic and fit around your mold. Heat the plastic so it bags naturally from its own weight. If you want to use a MALE mold, you will bring the mold into the plastic from the top, trying not to stretch it much. ( but you do not want the bag so big, that it is hard to conform to the mold) The mold will have to have a frame built around it to match the picture frame, but about a 1/4 inch smaller all around. ( It should just touch the plastic and make a seal) Also a vacume box is built at the base of the mold to hook up a simple shop vac. ( not too powerful now) ( I know this sounds like a lot but is not!) You will need a small drill bit, 1/16 might work but 3/64 or even 1/32 would be better. Now you drill lots of holes in your mold into the vacume box and that is how the plastic is formed into or against the tool with the shop vac. Now hold on, what about the holes? will they suck plastic in and be visible? What if they are under the felt? Now we do not form clear parts where I work but I know that we heat up plastic and form to an aluminum mold and wood molds with no problems of the plastic going into the holes or even being visible in the part UNLESS the plastic is too hot and the vacume is too high! So I may try this without even using felt, or by putting the vacume holes where it will not matter if it does leave marks. Realistically this type of part should be done with a female mold. It would be SO much easier. In fact I should try and make one of these up in miniature, take pictures and let someone throw a web page together. I plan on being down your way in May. Maybe I can stop in. Steve McGee Endeavor Wi. USA Building a KR2S widened. lmc...@maqs.net
