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Old 11-05-2021, 04:01 AM   #1
Mikel_24
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BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Hello all,

I started making timber guns a few years ago and by my second gun I was already messing with CF and vacum systems. Nowdays I spend more time CF skinning and finishing other peoples timber guns than making my own

Recently I have been tempted to make a very thin gun because here we fish basically in the surf with heavy seas quite a few times. Seabass and breams are the main catch, as they feed in the white water.

Something along the lines of the FFSUB MINIKRAKEN 90. You can find them here:
https://www.ckv-ffsub.com/ffsub-mini...0-100-110-120/

First thought was to make a balsa wood (or equivalent low density timer) and CF skin the heck out of it (1 layer of unidirectional fiber + two of bidirectional cloth all the way arround).

However balsa wood is difficult to find in suitable amounts in the required sizes (I guess I would need 1200x40x15mm strips), and also being very expensive.

I have been offered AYOUS or SAMBA WOOD (Triplochiton scleroxylon 380kg/m3 ) but it is about twice as heavy as balsa wood (150kg/m3), so I am not sure it would be suitable to float a 6mm or 6,25mm spear in the thickness I want the stock to be.

Also, searching in Spearboard, I have come across this particular post (http://www.spearboard.com/showthread.php?t=178120) where Daniel, while not disclosing the construction details, explains that he uses Divinycell H80, wich is 80kg/m3. So about half the weight of balsa wood and 1/4th of the weight of Ayous. He also states that he had to balast his gun as it came out too light, but not knowing how much, I don't know if I could get by with a denser core to avoid.

With wood it shouldn't be a problem but seems like foams are not rigid enough to be shaped, so I understand the stock must be laminated with reinforcements within each strip. I also see the need for a harder core in those areas where screws or pins are to be used such as the reel area, mech and maybe the muzzle. I use almost exclusively screw on mechs, such as the Meandros LS. If I were to use a pinned mech, I would thick wall CF tube of the appropiate ID.

Would it make sense to make a Irocco or Sapelli (which I can buy locally no problem) main beam (15mm thick, for example) and build up the rest of the volume arround it with foam and then shape it? Would Ayous wood be strong enough?

If I were to do so, which product should I use to glue foam-to-foam and foam-to-wood? Straight laminating epoxy resin? Epoxy adhesive? Others? I don't know how glue-able is the PVC foam.

I am not in the quest of making a FUL SINTHETIC gun... so foam for the core is not an absolute neccesity. Light timber is also welcome if it suffices.

Let's discuss.... (if you feel like doing so)

Mikel
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Old 11-05-2021, 08:29 AM   #2
popgun pete
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

I remember a gun built around a foam core with a carbon fiber outer skin being described here some years back. I think Tin Man may have done it and just searched the threads, can only find this one, but I am sure that there are others.

http://www.spearboard.com/showthread...rbon+fiber+gun

I remember a photo of the cross section with a white core surrounded by a black skin where a sample stock was sectioned.
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Old 11-05-2021, 08:30 PM   #3
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Daniel Mann (AKA Nanna Arms) has made a few of these. I don't know how to search on here sorry. I have not gone down the path of foam core yet because my expertise is with timber. If I were, I would use a timber stringer. Something to anchor some of the hardware too. It is pretty easy to calculate the mass of the shaft and design a gun that will allow it to sink muzzle down. Being carbon wrapped and the timber very well protected, don't be concerned about blending timbers to obtain the properties you desire. A really straight and stable stringer that is 850kg/m3 occupying no more then 1/5 the width and laminate lighter timbers at 450 - 500kg/m3 (for example) so it floats like you want.

I have blended timbers together that have very different properties and epoxy coated them. 14 years on they have not split, delaminated nor failed.
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Old 11-05-2021, 10:25 PM   #4
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Here is one of them.
http://www.spearboard.com/showthread.php?t=178120
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Old 11-06-2021, 08:08 AM   #5
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

I have all the threads in Spearboard regarding CF skinning well studied, and actually the one that Pete has linked in his last post is the one which inpsired me to go this route.

Regarding the woods, thanks for the tips, I was actually considering Iroco+Samba (now that I cannot find balsa wood anywhere) or full Samba with some Iroco inserts where I plan on screwing stuff.

I am kinda worried right now as I am having issues in the finishing coats of my latest CF skinned guns...

The problem is that, somehow, I am getting foggy finishes. There seems to be some kind of residue on top of the epoxy coat. I use a rottisiere design and follow all rules regarding epoxy ussage. That is, mixing in two consecutive cups to insure a nice mixture of both components, new disposable brush each time, rottisiere system to avoid drips, gentle cleaning of surfaces with acetone and disposable paper towels before applying, etc...

I think the culprit of this is the 3M Super 77 spray adhesive I am using to fix the CF to the stock before wetting it with epoxy. I got this recommendation here in SB and I decided to try it out. Sure it helps to keep the cloth in place and allows to install reinforcements on top of each other withouth shifting.

It appears to me that, even though it does not affect the curing of the epoxy, it does mix into the resin somehow. After skinning it with the vacum setup, I sand any imperfections and give it a coat of epoxy top coat, then sand, apply stickers and give a second coat.

If after the first coat I clean it again with acetone... I get a sticky feeling that lasts a while. Epoxy is well cured, so it shouldn't affect it. Might be the 3M Super77 in the epoxy softening? No matter how many times I clean it, I cannot get rid of that feeling.

I have three guns to finish that I have coated using this process and I guess I will end up doing what I did to a previous one... finish them off as they are right now and then wet sand from 800 all the way to 2000 and then automotive polish in a pad in the sander.

I know there is another 3M spray adhesive formulated precisely to not interfere with resins... it is the 3M 71.
https://www.windsourcing.com/en/3m-h...1-green-534-ml

If I can find a way to buy one or two cans, I may grab it. I don't feel like buying a whole case of 12 cans at 24€/ud just to try it out...

The option is to go back to the wet lay technique... apply resin, wait until it cures some, lay cloth, wet again with new batch of resin, roll with a metal roller to knead it throuh and bag it... Messy and not as precise in the layout of the CF cloth.

Throw me a bone here!!!!!
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Old 11-07-2021, 02:06 AM   #6
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

By far the easiest way to CF a speargun is to use CF sleeves. These constrict and expand to perfectly contour around the shape of your gun. They are also provide a seamless CF wrap which is probably much stronger. For the track you can use a taped up rod made out of an old shaft which you place on your track and vacuum along with the gun.

Today probably the best way to do make these smaller guns is to use a pipe gun and then add a cuttle shape ballast to it and then CF the entire thing. A CF pipe makes a gun extremely light and strong (although much more expensive). You can also get away with an aluminium pipe but ballast might have to be a little bigger (especially if using 7mm shafts for longer range). I have made a few of these guns at 80cm to 90cm and to be honest I can't imagine a gun performing any better. Of course you have to shape the handle and use a good reliable and predictable trigger. But the performance of these little guns once optimized can easily outperform most out of the box 120 guns in both power and accuracy. Also it takes very little time to make one.
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Old 11-08-2021, 01:59 AM   #7
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

dang, interesting design and manufacturing topics being discussed on Spearboard? To the original question, there are different densities of foams and many foams are suitable for shaping. It can be an advantage to use a more dense and rigid Stringer or form to keep a foam core straight. Just thinking about this topic makes me miss our old friend SEAL. Wish he was here.

Regards the tackiness and cloudy finish of the Epoxy Resin. Maybe it's the spray? I've had similar issues in the past when it was very cold or using Wax lined cups for mixing where the Epoxy cured funny like that.
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Old 11-08-2021, 09:25 AM   #8
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Quote:
Originally Posted by Behslayer View Post
dang, interesting design and manufacturing topics being discussed on Spearboard?
Feels like Spearboard has been a bit down lately... so time to bring up the discussions!

Quote:
Originally Posted by Behslayer View Post
It can be an advantage to use a more dense and rigid Stringer or form to keep a foam core straight.
I am certain about this. Not only to keep it straight, but to have something to screw into whatever needs to be fixe (such as the reel). But given the dimensions of the gun I want to make, it would need to be a single wood strip. No room for laminating anything (to help keep things straight) unless I use 5mm thick wood... My main problem is that I don't rip my own wood pieces, that I need to get done or buy off the shelf pieces. I am not much of a woodworker so I don't have a table saw. I get by with a handheld circular saw and lots of ingenuity with guides and suports to do my tapers and such. But ripping wood pieces to laminate them later on is out of the question.

Using SAMBA wood with some leftover pieces of IROCCO that I have lying arround is becoming the most economic and easy approach... As I have found SAMBA wood strips for cheap locally.

Quote:
Originally Posted by Behslayer View Post
..Just thinking about this topic makes me miss our old friend SEAL. Wish he was here.
Exactly my thoughts, what a bummer...


Quote:
Originally Posted by Behslayer View Post
Regards the tackiness and cloudy finish of the Epoxy Resin. Maybe it's the spray? I've had similar issues in the past when it was very cold or using Wax lined cups for mixing where the Epoxy cured funny like that.
It HAS to be the spray... I cannot think of anything else that has changed from the previous CF skinning jobs I have done. I have another two to start so I guess this time I will avoid it and see what happens.

Also I have a brand new epoxy resin kit, so I will try that too and see if the one I am using right now is somehow contaminated (I doubt it, but will try anyway).

I will also try and use laminating epoxy instead of the usual top coat, as it cures much faster and if the cloudy finish is something related to the uncured epoxy floating up contaminants... maybe, JUST MAYBE, the fastest curing (20 minutes gel time VS 3h)... helps to avoid the crap raising up.

I always use disposable plastic cups so wax from a paper cup is not an issue here.

I am going to give the second and final epoxy coat to another gun I have in the works right now so will see what happens. I will avoid cleaning again with acetone, as it might soften the glue residue too much (it was cleaned like three days ago) and go straight to the epoxy.

Mikel
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Old 11-08-2021, 09:29 AM   #9
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Quote:
Originally Posted by spearq8 View Post
By far the easiest way to CF a speargun is to use CF sleeves. These constrict and expand to perfectly contour around the shape of your gun. They are also provide a seamless CF wrap which is probably much stronger. For the track you can use a taped up rod made out of an old shaft which you place on your track and vacuum along with the gun.

Today probably the best way to do make these smaller guns is to use a pipe gun and then add a cuttle shape ballast to it and then CF the entire thing. A CF pipe makes a gun extremely light and strong (although much more expensive). You can also get away with an aluminium pipe but ballast might have to be a little bigger (especially if using 7mm shafts for longer range). I have made a few of these guns at 80cm to 90cm and to be honest I can't imagine a gun performing any better. Of course you have to shape the handle and use a good reliable and predictable trigger. But the performance of these little guns once optimized can easily outperform most out of the box 120 guns in both power and accuracy. Also it takes very little time to make one.
True, using a working CF pipe gun as a base to build from would be a good idea but I am more after making a whole gun from the ground up.

I am also not looking to power up an existing gun (cuttlefish shape floats more and allows to use thicker spears and more bands) but pretty much the other way arround. I will probably use 6 or 6,25mm in 115cm length shafts.

I looked into the CF sleeves and they look good. However, they only work if you use screw on handles, ala Abellan, for example. You can sleeve the whole thing and then trim the leftovers. BUT if you have the handle (and maybe even the trigger guard if integral) attached to the gun... you will have to make some trimming and overlaping in the handle area with CF cloth anyway.

Mikel
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Old 11-08-2021, 07:00 PM   #10
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Interesting thread!
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Old 11-09-2021, 04:14 AM   #11
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

Aimrite and a number of other Chinese manufactured "cuttlefish" spearguns start life as a tube speargun (Fibreglass finished with carbon)with a simple 2 part mould for a 2 pac filler (Like aerated body filler) then skinned with more carbon.

Very simple and very cheap to produce once the initial tooling is fabricated. Hand craft timber or foam gun and then carbon wrap it is way more labour intensive and expensive. That is why those Chinese barrels can be bought for $36 ea if you are willing to risk the money for bulk orders or your design stolen and used to make your product they sell on your behalf without compensation. (Happened to an Australian manufacturer whom I know).
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Old 11-09-2021, 04:40 AM   #12
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

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Originally Posted by Mikel_24 View Post
True, using a working CF pipe gun as a base to build from would be a good idea but I am more after making a whole gun from the ground up.

I am also not looking to power up an existing gun (cuttlefish shape floats more and allows to use thicker spears and more bands) but pretty much the other way arround. I will probably use 6 or 6,25mm in 115cm length shafts.

I looked into the CF sleeves and they look good. However, they only work if you use screw on handles, ala Abellan, for example. You can sleeve the whole thing and then trim the leftovers. BUT if you have the handle (and maybe even the trigger guard if integral) attached to the gun... you will have to make some trimming and overlaping in the handle area with CF cloth anyway.

Mikel
Mikel have you you considered making a hybrid (Like a Daryl Wong) with a timber handle and then carbon wrapping the whole thing?

I refurbished and wrapped a Abellan (PITA) that turned out pretty good. I am confident a hydrid would be far easier.









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Old 11-09-2021, 01:30 PM   #13
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

I think I am understanding more of the situation. You are trying to make a low volume monocoque and still have it buoyant enough to float your hardware. In this case. The best way to make such a gun would be to use a mould and air bladders and use mostly Carbon to take advantage of the strength to weight. The form would be hollow, but strong and stiff. Then you could fill with a lighter compression resistant expanding foam. I use the word Monocoque, meaning single structure, but that could also be a full composite gun which is chemically fastened in parts ie Handle/Barrel/Muzzle or filled in different areas to become solid, for example a muzzle area could be filled with epoxy and filler and then machined out to form a band recess.
Have a look at these. http://www.huntechnology.it/en/randall.aspx
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Old 11-11-2021, 03:01 AM   #14
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

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Originally Posted by Pankrationist View Post
Aimrite and a number of other Chinese manufactured "cuttlefish" spearguns start life as a tube speargun (Fibreglass finished with carbon)with a simple 2 part mould for a 2 pac filler (Like aerated body filler) then skinned with more carbon.

Very simple and very cheap to produce once the initial tooling is fabricated. Hand craft timber or foam gun and then carbon wrap it is way more labour intensive and expensive. That is why those Chinese barrels can be bought for $36 ea if you are willing to risk the money for bulk orders or your design stolen and used to make your product they sell on your behalf without compensation. (Happened to an Australian manufacturer whom I know).
I heard horror stories about chineese manufacturers and carbon tubes... ID not fitting specifications (son handles and muzzles wouldn't fit), crappy finish... etc.

Besides, I am looking for a DIY thing more than production, so I will not be outsorcing anything.

For a one off, I don't mind spending extra time making the core, be it timber or foam or hibrid!
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Old 11-11-2021, 03:09 AM   #15
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Re: BRAINSTORMING AND TIPS: Foam/light timber cored CF skinned gun

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Mikel have you you considered making a hybrid (Like a Daryl Wong) with a timber handle and then carbon wrapping the whole thing?
What do you mean by HYBRID? I have seen wood/carbon guns that I didn't really like much, besides, a lathe seems mandatory to be able to turn ID's to mix and match between timber and the CF tube.

What I have been doing lately is making my own handles by casting them in a silicone mold. I made a clay pattern for an anatomic right handle long ago, clear coated, used it to make the mold and from then on I make all my handles identical in matter of seconds.

Actually I am finishing right now the left hand equivalent since I have a leftover silicone mold kit (which I don't want to let it go bad) and I have found a shortage of anatomic handles for lefties... so I might be able to sell a few.

Does a PU handle attached to a timber gun and CF skinned constitute a hybrid??

Quote:
Originally Posted by Pankrationist View Post
I refurbished and wrapped a Abellan (PITA) that turned out pretty good. I am confident a hydrid would be far easier.
I feel quite comfortable doing full wraps in guns using my vacum setup (besides the aforementioned foggy finish that forces me to polish them once the last epoxy coat is applied).

A trick I have found makes the CF skinning easier is to leave the track exposed. overlap the seam at the track and then sand with a rod wrapped in sandpaper all the way down to the wood, so you don't really change the height of the track in relation to themech. If you also Dremel out the mech ears (if you go Meandros LS or Ermes Evo Back style mech) you maintain the height relation. This is a must if you are using a pinned mech, not so much if you use one that screws on from the top.

BTW, that roller looks great, you have the process nailed down!
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