Post by: kenboonejr on July 14, 2021, 06:23:55 AM
Got my form finished this weekend for the Bingham take down bow I am working on. I know I questioned the need for the heat box on another post and several of you guys said I don't need it and I can use my truck to help it to cure or I could just let the smooth on cure in 24 hours at 72 degrees. But I also understand, that if I go ahead and cure it at a higher temp, it may give it more durability to stand up in higher temperatures down the road without delaminating. I think the truck thing is a good idea, but I am beholden by time of when I can do it versus the heat box I can do it when I have time. Basically I think I want to go ahead and build the heat box but I don't want to spend the $180 on the 2 sheets of plywood for Bingham's plans. I have some old lumber that I pulled out of a house that was built in 1840 that I have had sitting around for years. I would have to plane that wood and get it shaped, but the net effect would be that the heat box would not be built with 1 piece of wood per each side. I would have to build it up say with boards that are 6" to 8" wide and on each side. So in effect all the sides bottom/top etc.. will be boards that have to be joined. My thinking was even if I didn't glue the boards up to make that perfect joinery piece in the wood, I could come back and caulk all the seems once the box is finished. If I did it this way, I don't have to outlay any $$$ just a little more time in the build.
So my question to you is - there is nothing magical about the plywood box right? I would think I would have the same effect as long as I caulked all the seems thereby closing any gaps where heat could escape right? Just thought I would double check with you guys before I put the time into planing and ripping these old boards up.
Second question I have is when I watched the Bingham video, they used contact cement and sprayed the top of the bottom mold and the bottom surface of a strip of formica and then glued that formica strip to the bottom mold where the lams will glue up. Well in the video, it was more of a 30 second deal. Spray form, spray formica, then lay the strip in carefully aligning it on the mold. Well when I did it, it didn't work that way at all. The contact cement I used said let it sit for 5 mins until it got sticky and then attach it so I did. However, the bend in the recurve form was just too much for the formica and I sat there trying to work the formica into the curve section and it did not want to stay. The glue held in the straighter section of the mold, but not in the curve at all. I simply could not hold it anywhere without gaps forming between the formica strip and the mold. I fought it for about 5 mins or so and then decided to use the filament tape. I would hold tight a section of it and my wife would wrap it. Then I would move a little further into the curve and we would wrap that too. I went all the way around the curve and let it set for 24 hours. Of course now I had glue chunks all over this smooth piece of formica. In the end I cleaned up all the glue with acetone and it is glued in place with no gaps.
Now that I am thinking about it, do you think since this formica sat in the box in my office for 4 years it stiffened up with time and that is why it was so much harder than what they showed in the video? or is this just normal? or did I do something wrong?
Thanks again for all the help.
Post by: Pat B on July 14, 2021, 08:19:50 AM
Post by: Flem on July 14, 2021, 08:42:24 AM
Post by: OldRawhide42 on July 14, 2021, 09:03:01 AM
I use the air hose to hold the formica on. And smooth on to glue it on.
Post by: OldRawhide42 on July 14, 2021, 09:18:15 AM
Post by: Longcruise on July 14, 2021, 10:27:37 AM
Go with Flems suggestion and use the thinner plywood. Even luan would be fine. Mine is built with 3/8" ply and it still needed foam board to keep temperature up. The only thing it gained was weight?
Post by: kenboonejr on July 14, 2021, 11:00:24 PM
@Longcruise - no none of it is bow wood. A lot of it I think would be too brittle.
@OldRawhide42 - that is a good idea about using the air hose!
Thanks again guys!
Post by: Shredd on July 14, 2021, 11:54:13 PM
Fold it up and put it anywhere you like... :)
Post by: Crooked Stic on July 15, 2021, 07:31:05 AM
Post by: Longcruise on July 15, 2021, 09:20:13 AM
The last forms I made have no Formica at all. Using a router leaves a good surface and touch up with 120 grit. Any voids .ca be filled with bondo and sanded smooth
I've been wondering about that and may try it. :thumbsup:
Post by: Longcruise on July 15, 2021, 09:58:43 AM
And the airhose suggestion is excellent insurance especially on a recurve form.
Post by: kenboonejr on July 15, 2021, 10:31:05 AM
Post by: Longcruise on July 15, 2021, 11:16:25 AM
Post by: kennym on July 15, 2021, 11:34:10 AM
I've been using black electrical tape to tape lams down on form when gluing up. I can just break it after a couple wraps, unlike filament tape I have to cut and keep the end from sticking back on the roll. LOL
Post by: Flem on July 15, 2021, 11:46:00 AM
Formica is some hard and brittle material and like virtually every other material if you excite the molecules with a little heat, it becomes more pliable. Next time throw it in your new heat box before bending.
Which is another good reason to have a heat box. I use mine for all kinds of projects in addition to baking Bows.
Put a muffin fan in and it becomes a wood dryer. Heat up a stave or shafts for straightening, etc....
Post by: kenboonejr on July 15, 2021, 12:07:45 PM
@Flem - That is a real good idea to heat the formica as well. I know as soon as this one is done, there is going to be another coming real quick. My youngest daughter already wants to build one now so I am sure that will happen as soon as I am done with this one!
Post by: Robertfishes on July 15, 2021, 05:32:36 PM
Post by: Longcruise on July 15, 2021, 07:11:20 PM
Post by: beachbowhunter on July 15, 2021, 07:47:52 PM
I have only used a strip of 0.040 black fiberglass on my forms. I have at least 12 pieces of the Streaky clear glass from 6 years ago I will use if I ever build another form. I use 3M High Strength 90 spray adhesive to glue the glass to form, I have forms that are 12 years old and the glass is still stuck to them. https://www.3m.com/3M/en_US/p/d/b40069424/
I use this stuff too.
Post by: kennym on July 15, 2021, 07:49:00 PM
Kenny, do you cook em with the tape on?
Yep , it is over the pressure strip tho, so no marks in limb...
Post by: Longcruise on July 15, 2021, 08:03:37 PM
Post by: Crooked Stic on July 15, 2021, 10:16:48 PM
Post by: kenboonejr on July 21, 2021, 05:29:35 PM
Here are some pics of what I did. Thanks everyone for all the help!
Post by: Longcruise on July 21, 2021, 07:11:59 PM
Post by: Crooked Stic on July 21, 2021, 07:53:35 PM
Post by: Robertfishes on July 21, 2021, 08:53:28 PM
Post by: Flem on July 21, 2021, 09:16:36 PM
Post by: Pat B on July 21, 2021, 11:08:05 PM
Post by: Mad Max on July 22, 2021, 09:12:52 AM
be careful :thumbsup:
https://www.joom.com/en/products/5f8b1f2b5aa4af010666438c
Post by: kenboonejr on July 22, 2021, 10:17:41 AM
@Mad Max - Yea the handle on the form is a great idea!
There is absolutely no insulation or foil under the top board. It is only 3/16" or maybe 1/4" plywood that I had laying around so it is very flimsy and you can see light around the top edge when it was running. I was just testing it and was planning to cut a sheet of foam board to adhere to the top board but when I ran the test it hit 150 degrees in about 20 mins so I don't guess I need to worry about it.
Thanks again for all the help! Going to start gluing up a set of limbs next!
Post by: Mad Max on July 22, 2021, 12:11:08 PM
Post by: kenboonejr on July 22, 2021, 11:14:21 PM
When you get the mass of the form in there it may take a hour to come up to 150
So I figured I would get things heated up to temp before I glued the limbs together and then put the form in and start the timer for 4 hours. So will that be good enough or do you think I really should add more insulation to the top? It would not be hard to do. Also, this is a small form because I'm just doing 1 limb of the recurve at a time - I just wanted to build the full size box, cause I'm already thinking of the next bow ;)
Post by: Mad Max on July 22, 2021, 11:52:23 PM
Then leave it turned off until the next morning more than likely.
Post by: Longcruise on July 23, 2021, 12:44:22 PM
Like Max says, I leave it in the box overnight and pull it in the morning.
Post by: Crooked Stic on July 23, 2021, 03:41:26 PM
And I have few that never seen an oven and doing fine.
.
Post by: Flem on July 24, 2021, 11:35:38 AM
Post by: Shredd on July 24, 2021, 12:45:01 PM
Although I don't agree with your 200* cure... You are just thinking about the epoxy... You are not thinking about the wood... There are things that can go wrong at such high temps... I think a happy medium is best... But that is just my 2 cents...
Post by: Mad Max on July 24, 2021, 01:22:42 PM
So A hot box let's you work on the bow the next Morning :bigsmyl:
And if you do over and underlays, striped riser and so on, you can cut day's off you curing.
That's the best thing about it.
Post by: Crooked Stic on July 24, 2021, 03:12:29 PM
And I have done two limbs in the same day on the same form
.
Post by: Flem on July 24, 2021, 03:40:09 PM
"Bamboo in the Laboratory"
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I'm thinking since Bamboo has a much lower specific gravity than most woods and certainly less than any bow woods, that this info can apply to wood bow laminations with a generous margin of error built in.
Post by: kenboonejr on July 24, 2021, 04:07:33 PM
It may take you until noon to get one in the hot box.
So A hot box let's you work on the bow the next Morning :bigsmyl:
And if you do over and underlays, striped riser and so on, you can cut day's off you curing.
That's the best thing about it.
Yea I didn't think about that aspect. I plan on doing a few accent stripes in the riser so I guess that needs to be tossed in the hot box too to cure.
Getting a lot of good info on this thread.
I am "hoping" to attempt gluing up my first limb tomorrow after church. We will see how it goes.
Post by: Shredd on July 24, 2021, 04:35:08 PM
Post by: Shredd on July 24, 2021, 04:46:15 PM
Post by: Flem on July 24, 2021, 06:53:27 PM
Post by: Crooked Stic on July 24, 2021, 10:06:41 PM
Post by: Shredd on July 25, 2021, 01:59:42 PM
:dunno: maybe over thinking :biglaugh:
And they say, "Ignorance is Bliss'.... That is until you get bubbles under your glass... :laughing:
A little common sense goes a long ways... Put any 6 foot length of wood you have in the sun on a hot day and see what happens... 6 feet will multiply the effect... Just because you use a 16" to 20" hunk of wood for your riser does not mean it's not moving... The more heat you add the more the stresses are between the surface of the wood and the core of the wood... Plus I have heard from multiple experienced bowyers say that heat can be hell on risers and the whole bow in general... That's why they say don't leave your bow in a hot vehicle...
Like I said, There is more than one way of skinning a cat and you can get by with your methods whether they are accepted to be right or wrong but I just choose to err on the side of caution...
Stic... Under-Thinkers are awesome... :biglaugh:
Post by: Crooked Stic on July 25, 2021, 09:44:18 PM
Still learning about design tho.
Post by: kenboonejr on July 25, 2021, 09:55:22 PM
So a question - Would the one piece recurve be easier or harder to get setup in the form than the take down recurve limb? Just wondering.
Post by: Mad Max on July 25, 2021, 10:07:16 PM
Make the butt end longer and use a 1/4" dowel threw all the glass and lams and butt wedge into the form.
Make sure and use some car wax in the dowel hole in the form and around the hole.
Post by: Shredd on July 26, 2021, 01:10:30 AM
Perfectly al I am saying is I been doing this for several years. I know what works for me.
Still learning about design tho.
:thumbsup: :thumbsup:
Post by: Flem on July 26, 2021, 08:51:36 AM
[ You are not allowed to view attachments ]
Here is a piece of Teak I am using for a riser. It has been outside, under a shed roof in a bin for a few years. It's hard to see, but after a fresh cut the moisture meter reads <7%. Mine is not the best meter, but it's accurate to .5deg, so the wood is bone dry. Kiln dried wood or in this case Desert air dried wood is not going to check, crack, warp or twist at that MC. If you don't believe that, check out the USDA Wood Handbook or Dry Kiln Operators Manual. No hearsay or second hand anecdotes, just facts.
Something else to consider beyond the temperature, is the duration of heat exposure.
If you are cooking at 150deg for 5hrs, plus ramp up and cool down time, your degree hours of exposure is going to be in the range of 800-1000deg hrs. I might have 250-300deg hrs total with my program.
Conclusion? Both work fine. One is more optimized for efficiency.
Post by: Mad Max on July 26, 2021, 09:21:33 AM
Post by: Longcruise on July 26, 2021, 09:33:45 AM
Post by: Flem on July 26, 2021, 09:44:13 AM
Post by: kenboonejr on July 26, 2021, 10:15:43 AM
NO
Make the butt end longer and use a 1/4" dowel threw all the glass and lams and butt wedge into the form.
Make sure and use some car wax in the dowel hole in the form and around the hole.
Yea I see how that would force the limbs to line up. That is a good idea. This is my first build and and am using the kit from Bingham's so the lams were already pre-cut. I did have to shorten there for my bow length, but not the wedge so I didn't have the option. - Nor did I know about it until now ;)
And by the way the humidity in SC here is pretty bad too this time of year. Most of us do NOT love it! I left Florida to go to SC. Basically moved from 10 hot humid months in the year to 3 hot humid months.
Post by: Shredd on July 26, 2021, 01:18:09 PM
I cure at 110 to 120* for 5 hours... Considering about an hour to get up to temp. I am doing about 500 deg. hours... I guess that is about in the middle of both methods...
I am on Island time... Have been for a long time... Have never seen the need to rush anything... Slow and steady as she goes...(even slower now that I am older) But things get done and fewer mistakes are made... Sorta my Zen or philosophy That I go by...