A question about a form

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woodie
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A question about a form

#1 Post by woodie » Thu Feb 13, 2014 3:40 pm

H all, I would like to make a air hose longbow form, to use the hose that I got off bigbob a while back, but I have no idea where to start other than I need ply about 1.5"wide.
Also where can I get hose plugs other than Binghams or are they the only place. I could make them myself but if I can buy them that saves time.
Any ideas?
woodie
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bigbob
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Re: A question about a form

#2 Post by bigbob » Thu Feb 13, 2014 4:17 pm

hi woodie, I'm not sure where you might source them in Oz, but believe a few guys actually made their own. Re the ply depends what width glass and bow you plan but I'l assume 1.5'' glass . the ply these days is metric and 12mm whereas the glass is still imperial.Not much difference though. Usually the 3 strips of ply are glued and screwed together to get your width .Be careful not to whack screws where you'll be cutting the form. Top and bottom forms are made from the one piece.It is also a very good idea to screw a piece of angle iron to the base to help retain its true as the hotbox can cause warping.
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woodie
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Re: A question about a form

#3 Post by woodie » Thu Feb 13, 2014 4:47 pm

Thanks bigbob, but what is the distance that I have to leave between the top and bottom of the form when I put the holes for the bracket, the plats to hold them together when gluing.
How would a piece of chip board bench top go?
Yes it will be 1.5" that works out to be 38.1mm.
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bigbob
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Re: A question about a form

#4 Post by bigbob » Thu Feb 13, 2014 5:43 pm

IMO don't use chipboard for your form , it will almost assuredly warp, and will disintegrate from the heat with time. Using that hose for a straight laid longbow [?] make your gap or space between form at 1 1/4''. Its a good idea to drill the flatbar brackets [1 x 1/4'' is ok] or if you want to be pedantic :lol: :lol: 25 x 5mm or 6mm, and then position them on your form laying on its side and mark relevant holes.A piece of 12 mm ply goes under each bracket to leave it 'proud' of the form and is nailed to the form halves.The 1 1/4'' 'gap' is maintained around the riser cutout too. Hope this helps.
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Stickbow Hunter
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Re: A question about a form

#5 Post by Stickbow Hunter » Thu Feb 13, 2014 5:55 pm

woodie wrote:How would a piece of chip board bench top go?
Like Bob, I would suggest not using the chipboard either mate.

Jeff

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woodie
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Re: A question about a form

#6 Post by woodie » Thu Feb 13, 2014 6:11 pm

Thanks Bob, that give me a REAL good starting point.
I work with both metric and imperial so all good there.
Why I ask about the chip board ins there is an old bench top at work and I was going to use it as a trial form. At the moment I don't have a hot box, the couple of bows I have made I left in the form for a couple of days and left them for a week before it cut them out. I am one of those that like to make something with scrap and see if it works before I make a good one.
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Re: A question about a form

#7 Post by bigbob » Thu Feb 13, 2014 6:55 pm

might be able to use the chipboard for your hotbox as it should be lined with alfoil anyway and should deflect the heat back off the sides etc. It's also a good idea to run a small fan inside the box to circulate the heat, though I know you're not ready for a box just yet.
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Re: A question about a form

#8 Post by GrahameA » Fri Feb 14, 2014 7:42 am

Morning Woodie.
woodie wrote:H all, I would like to make a air hose longbow form, to use the hose that I got off bigbob a while back, but I have no idea where to start other than I need ply about 1.5"wide.
Also where can I get hose plugs other than Binghams or are they the only place. I could make them myself but if I can buy them that saves time.
Any ideas?
woodie
Plugs. I suggest you either make them or buy them from Binghams. They can be turned from alloy - or anything really that will not crush under the clamping pressure and any heat plus can be tapped to take the airline attachment. The easy solution is to find someone local who has a metal lathe and buy some bar/round stock from your local Alloy stockist. (If people want to be 'cheap'/low cost you could some blanks from alloy scrap).

I have used MDF to build forms - easy to work and easily available. If you are considering making a straight/flat laid longbow I would suggest/consider a piece of RHS for one half and a piece of shaped MDF for the other. Essentially it boils down to more what you prefer to work with, have experience/tools to work with and have available more than anything else.

Having the panels cut using a CNC cutter water/router/LASER would be bliss and depending on time and cost a viable alternative. Ask Longbow Steve about his experience.
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Re: A question about a form

#9 Post by bigbob » Fri Feb 14, 2014 8:08 am

Grahame, not wanting to get into an extended exchange with you re MDF and its relative merits /disadvantages I still humbly suggest that for anyone planning on making more than the odd bow it is a poor choice of material as it will warp and/ or crumble with extended exposure to confined heat. i think also that binghams would be the best bet for the plugs, as it woudbe quite expensive to have them turned here, but then again shipping costs from US etc might make it a viable option.
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Re: A question about a form

#10 Post by GrahameA » Fri Feb 14, 2014 9:52 am

Morning Bob.
bigbob wrote:Grahame, not wanting to get into an extended exchange with you re MDF and its relative merits /disadvantages I still humbly suggest that for anyone planning on making more than the odd bow it is a poor choice of material as it will warp and/ or crumble with extended exposure to confined heat.
How many bows does he intended to build off the form? If a person was intending a production run of several thousand then having forms made from steel/aluminium becomes an alternative if he is only going to build 1/2 dozen it is very hard to beat MDF.

Ply has it own issues and once again it depends on the intended use/life/storage conditions. Structural ply has it advantages and disadvantage, equally has marine ply or aircraft ply or even using glu-lam beams.
bigbob wrote:... i think also that binghams would be the best bet for the plugs, as it woudbe quite expensive to have them turned here, but then again shipping costs from US etc might make it a viable option.
Then again he may have someone that he knows who could turn them or he may decide to cut some plugs with a hole-saw and fabricate them.

As with all items you can buy it, make or get someone else to make it. It all depends on what options you have available.

I offered some options. There is no requirement for people to take any notice of them or take them up.
Last edited by GrahameA on Fri Feb 14, 2014 2:12 pm, edited 1 time in total.
Grahame.
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"Unfortunately, the equating of simplicity with truth doesn't often work in real life. It doesn't often work in science, either." Dr Len Fisher.

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Re: A question about a form

#11 Post by bigbob » Fri Feb 14, 2014 10:57 am

As with all items you can buy it, make or get someone else to make it. It all depends on what options you have available.

I offered some options. There is no requirement for people to take any notice of them or take them up.[/quote]
Exactly that my friend, give people some options and let them chose the path to take. :biggrin:
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Re: A question about a form

#12 Post by Goatchaser » Fri Feb 14, 2014 11:35 am

I use 2 pieces of 19mm ply glued together to make my longbow forms = 38mm. :wink:

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woodie
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Re: A question about a form

#13 Post by woodie » Fri Feb 14, 2014 4:45 pm

Thanks all.
Getting the plugs made is no issue as I am a fitter/machinist, I did not know if you can get them from here.
In the lines of the form, I am not sure how many I am going to make yet, but I have been asked to make 3 or 4 . The chip board idea was because there is a piece at work going to be scaped so I thought I would try it. I don't use a hot box at the moment so heat is no issue. I am in no hurry to get the bow made and I don't have the room for one yet either.
I was thinking of using RHS to make a form or two later though.
I appreciate all the info you are giving me.
woodie
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Re: A question about a form

#14 Post by longbow steve » Fri Feb 14, 2014 5:03 pm

Hi Woodie, I have a couple of chip board forms that Graeme K made that are fine. He has coated them with resin and glued on a steel spine.
For straight laid bows I use a 50x50mmx3mm steel post.

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Re: A question about a form

#15 Post by rodlonq » Fri Feb 14, 2014 5:48 pm

bigbob wrote:Grahame, not wanting to get into an extended exchange with you re MDF and its relative merits /disadvantages I still humbly suggest that for anyone planning on making more than the odd bow it is a poor choice of material as it will warp and/ or crumble with extended exposure to confined heat. i think also that binghams would be the best bet for the plugs, as it woudbe quite expensive to have them turned here, but then again shipping costs from US etc might make it a viable option.
Bob, I have made two air hose forms from MDF and I have absolute faith in them. They show no sign of being affected by heat. I certainly wouldn't want to see them get wet but that would probably warp a ply form as well. Each to their own I guess, but I will be building my next form from MDF too (probably the moisture resistant grade they use for kitchens nowadays). I have considered using concrete form ply as it has the thin phenolic coating that will provide some protection, but as Graham says, MDF is super easy to work. I have glued a section of Laminex on the lower form that shapes the back of the bow as per Bingham's manual. This is almost irrelevant as I use heat strips, so I have a heat strip and a protective galvanised sheet pressure strip laying on the form before the glad wrap and then the layup go on.

I have used also used MDF (the moisture resistant stuff made for kitchens) for pattern making and cooling jigs in a rotomoulding factory and I reckon it is more heat resistant and dimensionally stable than any wood I ever tried to use.

Just my 22 c worth.

Cheers..... Rod

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bigbob
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Re: A question about a form

#16 Post by bigbob » Fri Feb 14, 2014 6:01 pm

Ok gents I will bow to weight of opinion and gallantly admit defeat! I'm only basing my assumptions on some experience with the stuff I've had. Never as a form material but in other endeavors. I think 'form ply' would be the best all rounder but is a bit more expensive too . I am going to make a recurve form at some stage and hope to us LVL beams
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Re: A question about a form

#17 Post by rodlonq » Fri Feb 14, 2014 6:15 pm

Hey Bob, are you mistaking the old school chipboard (weetbix :biggrin: ) with the more modern MDF. I can understand reservations about chipboard under very high pressure, however I believe they have made a lot of advances in the quality of that recently too (due to glue quality).

Cheers...... Rod

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