Thats a great looking board, although Im not a fan of the construction method You used.
The foam core makes for a bone like, and bone hard board, if you reduce the glass to get some flex, these boards tend to break easily, saying that, if you want a board with very little flex, this is the way to go.

Great finish and smooth shape!

If you don't mind me asking, what resin did you use, what footstrap inserts how did you do the rails?

Hey Matt, thanks for sharing. It's about 15 years since I made anything from fibreglass and back then epoxies all had pretty poor UV tolerance. Has anything changed or are you just going to try to minimise exposure?

ABS is durable for sure but heavy and hard to get stuff to stick to as you mentioned. There have to be better rail alternatives. Slingshot are now doing single shot urethane rails. That's out of my area so I've no idea how that would translate to DIY situations. Any other brainstorm ideas on DIY rail materials and techniques?

suimike said...

Adding to the material discussion. Some experience gained working with fibre reinforced plastics in the aerospace and oil/gas industry over the last few years:

Alternative rail materials:
I don't understand why everybody uses ABS (as said it is difficult to bond). Some thermoplastics which bond well to epoxys and which are tough enough for rails are: HTPE, TPU, PA11/PA12, PSU, PES, PEI, PEEK. (in order of price left->low, right->high). HTPE and TPU shuld do the job and are easy to bend using a BBQ . For a high-end board maybe PA11. The others are hard to bend as Tm/Tg to high - for BBQ.

UV resistance:
UV resistance of epoxies are poor however the effect over the lifetime of a board is small (maybe some yellowing) - more of a problem for boats which are outside 24/7.
The industry standard seems to be to use PBT film to protect the board from UV. On top of that PBT is easy to print. I think for "home made" PU top coat would do the job too.

Inserts:
Would be interesting to try non-metal inserts made from some of the plastics mentioned above using "plastic screws".

Thanks for the info. I have a feeling that the use of ABS is a hang-over from snowboard technologies that have been adopted into kiteboards. I have to say though that I haven't had any delamination problems so far and have subject it to some serious impacts so I wonder if the bond issue manifests more over time?

I'm not familiar with HTPE. What's the 'HT' part?

I understand that Liquid Force are also using urethane to pour the rails on some of their boards as well. I've read on kiteforum.com ( the board builders forum is an awesome resource)
kiteforum.com/viewtopic.php?f=107&t=2360170

about DIY'ers using liquid urethane called poly75-90 instead of the epoxy. Not sure about its merits over using epoxy? suimike, any thoughts??

Lots of people advocate using epoxy cause its on hand ( using for laminating anyhow), you'll have zero dramas bonding to it and you can easily strengthen it by mixing in milled fibres.

I've also heard from the guys at FGI that the UV-resistant epoxy is something they are still trying to develop so a PU coating sounds like a good idea. It also allows you to put vinyl stickers on the board and paint the PU over them to protect them.

There's a place in the US
snowboardmaterials.com/pages/print_your_graphics.htm
that will print the graphics on the back of PBT plastic that you could use as a top or bottom sheet. Drawback is cost which from memory is about $50 per sheet+$30 delivery! These guys also sell metal inserts for the footstraps if you want top quality stuff.

Cheers
Matt

suimike said...

Should have written HD not HT (HD=High density) -sorry

PU vs. Epoxy: The only advantages of PU is the lower price, slightly higher toughness, better UV resistance and mixing ratios can be varied. However, I think epoxies are still the way to go. Mechanical properties are a lot better, bonding is easyer and modern epoxy formulations have significantly increased toughness. In addition and maybe the most important point when doing it at home (if you have girlfriend, wife, etc.) is that epoxy are odour less- most PUs smell horrendous…

Brilliant. Thanks for sharing the info.

Can you see any downside to using milled fibres in the mix for pouring rails. I read a post of kiteforum.com where the guy suggested that adding short fibres for strength can 'dry it out' and make it brittle. I would have thought it would have taken a lot of fibres to make it less flexible than the laminate ? Maybe the impact resistance is affected? What do you think?

Cheers
Matt

djdojo said...



he had a major reaction to things like shampoo and beer.

Damn, Allergic to beer !!!!......top incentive to wear safety gear

Excellent advice from Djdojo.

I spoke to the rep from;
http://www.kbs-coatings.com.au/Diamond-Finish-Clear_ep_93-1.html

regarding coatings for a different project. the Diamond finish that they sell is used to reduce UV effects on coatings, as well as add a seriously tough clear coat.

This has good flow properties and can be applied with a brush and still result in a smooth finish.

If this works OK then achieving a smooth, tough finish may be made a little easier to achieve.

I asked about the compatibility with epoxy surfaces and was told that it will bond exceptionally well to epoxy finishes as apparently they have a mildly acidic finish.

TAKE HEED of the safety procedures with this product.

It belongs to the same cyanoacrinate family as SUPER GLUE !!!

I have purchased some of this and will keep the board builders posted as to its result

Fossil.

StickFlick said...



What sort of cost are we looking at?

500ml - $51.00 + Postage,
1 ltr - $79.00 + Postage

* freight costs per order, cut from their web page *

http://www.kbs-coatings.com.au/Shipping-Info_ep_55-1.html

(to cut out the postage, you can buy from a distributor, listed on their website)

www.kbs-coatings.com.au/NSW-Resellers_ep_79-1.html

I don't have any affiliation with this company, I am just looking for a faster, easier to apply, method which can be re-coated for repairs.

(plenty of rocks etc. where I kite )

Fossil

suimike said...


Inserts:
Would be interesting to try non-metal inserts made from some of the plastics mentioned above using "plastic screws"…

Hey Suimike,

I am curious as to why you would look at plastics for this application?

To get the same shear strengths, (vs metal), you would have to increase the thread sizes, which would then bring complications to the design regarding the depth of the threads, (i.e. thickness of board).

I am not trying to snuff out inquisitive, inventive discussion, I'm just trying to understand where or why the idea originated.

Fossil

@ StickFlick: Nice to see a well laid out spreadsheet, great work .

Lang said...



Where would you recomend getting foot pads/straps, and fins?

Hi Thomas,

Nice to see another local Gawler kiter interested in Board Building.

Straps: I hunt Seabreeze buy & sell and also Ebay.
Also talk to the local kiters, go to kite events & ask for any 2nd hand items for sale.

Also try these guys (SA company) oceanculture.com.au/
Straps are OK but I have not tried their pads.

Pads: Seabreeze/Ebay or;
You can cut your own pads from EVA foam, bought from places like Clark Rubber www.clarkrubber.com.au
Get the higher density foam as it does not compress as much.
Keep mindful that you may pick up 2nd hand proprietary pads for near the cost of a foam block.

You could learn to cast your own pads from EVA foam.
Talk to the guys from www.amcsupplies.com.au

It may cost more but you would end up with pads that are fully customised to your feet.
I also thought it would be good to insert some gel in a cavity under the heel section of the pad to shock absorb like the sports shoes.

I have found the strap/pad/pad base combos to be the easiest to work with. Most board manufacturers use this rather than gluing direct to the board. Easy to change out.

Fins: 2nd hand as above or;

You can carve your own from Perspex, wife's cutting boards etc.

Or try online: www.omnitech-engineering.com/fins/default.asp

Or mold your own as I have done.
Again www.amcsupplies.com.au are your friend and even run classes as to how to set up.
For the price of a couple of beers it may be worthwhile to make a trip to Lyndoch & see some of my molds.

For riding at Parham I am considering trying finless in the next season.

Fossil

Great looking board . The spred sheet program looks good too all i need is to be a expert in spread sheets to drive it any tips like wear and how to look at the designs that are there or build own on it like wear do ya start to put in legth and width . i am doing one very soon for first time . Also what is the resign part number ( there is like a billon differt type of epoxy resin) for building boards with foam core .

Hey Fossil

Very interested in the ones you've molded. Would be keen to see some pictures if you got them.

How much glass/resin did you use? Any tips no what to-do and not to-do?

The price of fins is stupid so I'm keen to try make your own.

Cheers
Matt

StickFlick said...

Hey Fossil

Very interested in the ones you've molded. Would be keen to see some pictures if you got them.

How much glass/resin did you use? Any tips no what to-do and not to-do?

The price of fins is stupid so I'm keen to try make your own.

Cheers
Matt

Hi Matt,

I began this odessy into casting etc. when I first broke a fin on my old monster Gasstra board. I could not source Gaastra fins easily so went to DIY.

I don't want to add up the cost in time & materials to produce my fins. I probably could have bought many, many fins.
My casting & epoxy learning curve was priceless
I enjoy the DIY chase and creating things

I was lucky as I was given some surplus industrial epoxy paste, so this reduced my costs.

At this point in time, if I were starting again, I would seriously consider this company in the states. omnitech-engineering.com/

The dollar is at a good exchange rate.

I costed 4 x "2 hole" fins plus freight, landed in Oz at AU$ 53.25 total!!
Also if you want 4 x "1 hole " fins the cost landed is AU$34.95.

If you wanted to try different styles of fins or do a bulk buy with some mates, the freight costs remain the same up to 20 fins.

I don't know what these fins are like but they are cost effective.

I will get some pics of my molds etc. this weekend and post some info next week.

Fossil

Hi Board builders,

I finally got around to photographing my fins& mould.

You can find a similar moulding technique on the Freeshaper website (might need to brush up on your French)
www.freeshaper.com/kite/index.php?rub=MAKING&ssrub=Fins

My wife & I attended a moulding class @ Adelaide moulding & Casting, her for resin jewellery & me for the fins.

As I have stated before you may need to weigh up the cost of making your own vs. buying outright.
A quick add up for my type of mould would be approx $70.00 +

Kleen Klay $5.25
Pinkysil $33.60
“Stoner E302 Rocket Release” Spray release agent $ 23.10
Enough Epoxy for fins $??
Freight for online purchases $??

These are just some of the fins that I have moulded



The fins I have created so far have been without reinforcing i.e. no matt in the fin.
They tend to break easier than the original fins. Difficulties easily overcome by the addition of scrap matt.

I use a grey epoxy paste which is similar density to normal fluid epoxy which has been thickened with micro balloons etc.
I have not experimented with fluid epoxy but that may come soon.

The Mould

Mine is a 2 piece mould, sometimes referred to as a Splat mould.

Find a reservoir (mine is a rectangular plastic box)
Embed half of your original fin in the clay to half the depth of the reservoir.
Smooth the clay flat. Poke some indents in the surrounding clay with a pen/pencil to create locating pins for the mould. (see pic )
Spray with release agent (important step)
Pour the top full of silicone & let fully cure
Clear out your reservoir of clay etc.
Place your cured first half of the mould into the reservoir.
Place your original fin on this cured half .
Spray with release agent (important step)
Pour the top full of silicone & let fully cure.

This should result in a two piece mould (with locating pins).




You can use the 2 piece mould clamped together & pour in epoxy or you can use the same method as me & thicken the mix and lay into 2 pieces then “splat” together, hence the name.
If you are pouring in your epoxy you should pour from a high position to get a thin, slow stream of epoxy into the mould. This reduces/breaks bubbles entering into the mould.
My original fins were 65 mm high, so I made an extra silicone mould piece to fit into the top of my mould hence reducing the height to 50mm.

A stumbling point for most will be the threaded holes in the fin. Get them wrong & the fin will break out on the sides. (Unless you mould really fat fins).

I have had two differing fin mounts. The first was to shave the heads of 6mm stainless bolts then embed the heads into the fin. I attached the fins using nylock nuts (ugly but strong).

**note If my un-reinforced fins break, it is usually below the level of the threads, (see red broken fin in the pics).

The preferred method I use is to drill & tap the holes (10-24 UNC), as per the usual method on most boards.

Cheers
Fossil

RayQ said...

For threads, I wraped a wetted out strand of fibre glass around the thread of two stainless screws and pushed them into the soft resin, works great.
My bigest problem was bubbles in the finished fin.

RayQ,

My next experiment to try is with s/s heli-coil thread inserts.

Don't know what a helicoil is?........
http://www.helicoil.com.sg/HeliCoil-Screw-Thread-Inserts.htm

My idea would be to get a s/s bolt of the required thread size, spray it with release agent, then carefully wind the heli-coil onto the bolt, much like they do on the mandrill, here,(step 3)

www.helicoil.com.sg/HeliCoil-Installation-Instructions.htm

Being carefull to not transfer any release agent to the outside of the coil and therefore get a good bond with the epoxy. Leave the tang on the helicoil to add extra anchorage.
Once set you should be able to remove the bolt leaving a strong s/s thread in the cured epoxy.

The problem with bubbles can be alleviated by pouring the epoxy from a higher position from the mould.
This is to get the thinnest stream of epoxy as it enters the mould. This helps break any bubbles.
Also take great care to not introduce bubbles with too vigourous mixing

regards
Fossil