The question came to mind after I make 2 speargun 15cm difference in total length (115/130) cm ,I used same spear 150 cm 7mm but overhange is 20 to 35 cm
Rubber 3:1 16 mm so in both cases even the hole to shark fin is difference the power is same ,am I right?
1- I just want to share a simple way of making your band slope ,I found out best angle for band sis 15 to 20 degree and flat /curved / round file is enough to make that slope ,even with small saw its possible but keep always the angle less than 20 ,single 16 mm band may need a 8 mm space during stretch .
2- cleaning the C clamp from epoxy /polyurethane glue is very simple just use the heat gun at the higher temp. to burn that glue residues and its look new again be careful from the toxic fumes .
3- round shaping is very easy if y use a big flat file then follow by small planer or spoke ,use template to check for out of profile and its done
mixing copper powder for track with epoxy ,the powder used for lubricating the bearing so its same like graphite but good point u said it react with salty water .
https://www.ebay.com/itm/Coppe…m:mxTTJRaH1zdq2cwYrlIybZw
what u think using this powder ?service/strength /performance
u can put a specimen of ABS in salt water in direct sun exposure ,use an old big pot in your yard or in roof top ,check after a month of direct exposure ,this 30 days equal to 720 hrs of service .
what about exposure to sun ,UV and salty water ?
when you drill a screw pilot holes in a laminated teak speargun to mount your AR 15 frame , in my case the 2 screws is located in middle of the laminated pieces and 2 in the line of epoxy between the lamination , I am going to use teak oil for finishing , any risk of delamination from the 2 screws in the epoxy line ? any holes for screw should be seal by epoxy then re drill the pilots even in oil finished or teak oil is a good seal ?
what is the rubber diameter?
14 or 16 mm ,but we talk about length
if I have a 2 rubbers set same diameter with different length ,50 cm /80 cm ,and each stretch to 300 % (150 cm / 240 cm) ,each will have same stored energy ,if we check separately that energy for example by pulling scale ?the formula in spearit show energy for different cross section but what about the length ?it seem like length factor won't be considered ,is it true ?
got it finally
if we know the required weight to ballast a gun through calculation and want to distribute it along the gun without visiting the pool or the sea , if i want it when its full rig to be in horizontal level , can I divide the required lead to two mass and located at equal distance from the center of mass of the rigged gun ? is their any disadvantage in this theoretical idea ?I think it was discuss some where but I forget where it was discussed.
i m waiting for the results of spring steel (rob allen,spearmaster etc ...)its critical when u have to buy thick stainless like 8mm but u can use 7.5 spring instead and save a lot in my place ,is it true 7mm spring have similar stiff to 7.5 stainless ?getting stiff low weight spear help to reduce recoil and cost.
Sometimes it is difficult to achieve the proper Shaft / Band configuration
If shaft not damaged then this may give you idea.
http://youtu.be/FSK4HkkimXk
I have used that video ,either the band i bought is bad quality or the video made in pool is ideal (not considered sea currents and environment ) ,but whats the reference points for 130*7.5 mm? classic 16 mm rubber .
here below different supplier for specific handle shape ,I want to give a try as handle shape is look nice and ergonomic ,all of them copy it from each other but what a bout material ?is it strong enough and can take the load of 3 and 4 bands without breaking your jaw ? anyone try that ? I can shape my wood handle similar to that but long time it take .
https://www.subprof.com/en/muz…-wooden-speargun-53167231
https://www.mvd-retail.gr/inde…vd-handle-for-wood-detail
Display More380% may be a little too much. with multi band guns i try to stay around 315%-330% stretch...using 16mm rubber as well as small ID 14mm rubber.
Low shots and loss of energy could be caused by muzzle flip and shaft whip.
Try to find that sweet spot where the shaft can handle the force of the rubber without bending (that's what she said):D
I find railguns and wood guns will perform well with this band stretch, where i believe enclosed tracks can handle a bit more force and not whip....it is not needed. If youre using a wood gun or enclosed track, dont overpower it, utilize the mass of the gun to your advantage: reducing recoil.
also 33cm seems a bit long for over hang especially using a 7.5mm shaft. this may be causing the shaft drop
Im assuming 380% is counting the relaxed rubber as 100%.
what s your recommendation for spear OH ? for both 7.5mm and 8mm
1-95 cm with 7.5 mm spear 130 cm with 33 cm overhang , rubber : 2*14.5 small ID 380%
2-120 cm 7 mm spear 150 cm with 33 cm overhang ,rubber : 14.5 small ID 360% ,14 small ID 380%
test them this morning and results was really bad,in the beginning I was thinking about my design why the spear won't penetrate the target at 4 m ! it just hit then bouncing ,I found out he problem when I add a third rubber to the gun ,it shoot very strong and accurate @5 m ,I can't understand why these small ID rubbers cut at 380% not work as everyone showing in the youtube ! I have to go back to the classic way and use 16mm cut at 315% -330% ,also I will use the rubber I purchase from you DAN year ago 16 small ID I ll cut 290% for the 120 and try 2 rubbers for performance .
Resin can be lightened up with cabosil or microballons added to the resin but that's more of a surfboard repair technique. Your wood might be outgassing due to heat or the resin was over agitated while mixing?
yes I break the wood and cross section show very small voids ,never had delamination but just worried ,its good to make padouk less heavy I can use heavy setup
I d like to update one thing ,after experiment I found out after using epoxy to glue the padouk the floating ratio I calculated increase ! I mean the required weight to sink the specimen is different when u laminate the piece padouk ratio increased to 0.41 ,the epoxy glue have air bubbles which impossible to eliminate it 100% so is that the main reason? uncountable air bubbles trap air inside increase the flotation ?
yesterday I tried my heavy wood short gun 95 cm with 7.5 mm spear 130 cm with 33 cm overhang , rubber : 14.5 small ID 360% ,14 small ID 380% , shooting in short range perfect little high but at end of 2 wrap mono it seem it shoot low ,I am confused what I should do ?I shoot a board from 4 m and its low .also the rubber inside the wide slot will be changing position after each shoot ,first move to second and second come in front I pull rubbers according to each position (hope this explanation clear for someone using wider slot) . likely I shoot the mackerel when it was near but missed many far fish ,I am planning to return to classic age 16 mm rubber cut at 3.3 
ARAB/Persian Gulf , this fish is allow to hunt in that size and its tasty .large population in that place
