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Mast Building Method

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downunder
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Re: Mast Building Method

Postby downunder » Thu Dec 01, 2016 2:50 am

^
Yes, I've seen this on Tom's (memberlist.php?mode=viewprofile&u=11000) F.book page.

Great idea and would definitely explore that. Could you fix the Amazon link please?

Cheers

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Re: Mast Building Method

Postby kitexpert » Thu Dec 01, 2016 8:09 pm

Bille wrote:
kitexpert wrote:I close vac bags using iron, tapes cost and are too difficult. I fold the ends two times and then iron through a narrow sheet of paper. No leaks, no costs and easy to do.
What kind of plastic ?
What surface Ya sticking it to on your mold ; epoxy surfacing agent , or .. ?
How much Heat with the iron ?

Last night it was Cold, and i spent Hours getting my vacuum-tape to seal
on a project for a HG.

Thanks : Bille
Lately I've been using PE tube, it is so cheap and seems to work well enough. It is thin and very probably wouldn't stand owen curing, but because I use just some lamps and a box for cover to get heat up and work carefully it is ok. For bigger work I have "official" vacuum plastic, but I've not tried iron seal it and I don't know what plastic it is. But I am quite sure it will seal with heat.

The temperature for iron is some middle setting, when paper sticks a bit to plastic seal becomes air tight. If seal is not melted enough some more heat and pressure will do it.

I haven't tried (yet) to get perfect surface out of the bag. So I use normal perforated plastic and breather on my carbon parts.

Other good methods for vac bags there :thumb: These heat sealing methods are not very far from DIY bladder work, if some day I get PU material I'll have a try. I would think some aluminium roller fixed to soldering iron would be the tool for that.

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Re: Mast Building Method

Postby faklord » Fri Dec 02, 2016 12:52 am

downunder wrote:^
Yes, I've seen this on Tom's (memberlist.php?mode=viewprofile&u=11000) F.book page.

Great idea and would definitely explore that. Could you fix the Amazon link please?

Cheers
Think the link is now fixed ? For info the make I have used are "dibag"

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Re: Mast Building Method

Postby TomW » Thu Dec 29, 2016 5:28 pm

Hi,

Using the vacuum bags is really easy. For smaller stuff you can pick them up in household stores.

On topic, I have Moses Fluente with 93cm mast, have not learned yet, only got in 3 sessions before winter came. Moses is offering 71CM mast, but it costs 699€....
Several reasons I want a 60 -70cm mast. Local here I trust said it will be easier to learn and several shallower spots open up with shorter mast. But, I'll probably use it 10 times, then go to 93cm, might revert back to it when at point of learning transitions.
At this point I am getting up on board, but not even surface riding with confidence.

I can build stuff, so was thinking making quick and dirty 65 cm mast.
I would laminate up a mast Core using 1,5 mm Abachi veneer scraps I have lying around. That would be grain in longitudinal direction.
Then vbag 200g twill glass over it. I can add CF tow ribbon, 15mm wide too.
Then add plywood and glass plate to replicate Moses mount.
Hardest part seems to make mast to fuselage connection.
My idea is to sand down the tip before glassing so it fits into fuselage hole with margin.
then after glassing mast use existing fuselage ( protected with thin tape) as a mold and mold pour epoxy into fuselage, with mast positioned in the fuselage hole to make sure it's all straight.
Let it set and then remove fuselage and clean it up, add some glass to joint.

Add screw inserts. I have some TT/ snowboard type m6 inserts. But those are not right kind.

The other difficulty is the Moses mast is not straight, but figured I could:
1. angle the mast
2. Make it straight and compensate by attaching mast to plate further back.

I'd appreciate any advice on:
1. Making fuselage to mast connection
2. Screw inserts in the mast for fuselage.
3. How to compensate for mast curve/ offset.

Have all the materials to make this, so I'd save a bunch of money.

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Re: Mast Building Method

Postby TomW » Thu Dec 29, 2016 5:38 pm

How about this way:
Mold fuse rabbet in fuselage Dado, Glass + epoxy mix.
Remove rabbet.
Attach with epoxy and carbon rods.
Glass fillet.
_20161229_173444.JPG

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Re: Mast Building Method

Postby faklord » Thu Dec 29, 2016 7:34 pm

Tom. A few suggestions/comments:
1) From what I've read mast construction really does need to use a carbon skin and even then UD rather than twill. That said the stresses should be significantly reduced for a shorter mast...but I wouldn't risk using glass.

2) I think it would be much better if the finished mast could be dropped into and potted in the fuselage aperture..guess this depends on the size of the aperture?

3) some of the Alu foils seem to get away with a butt joint and 2 x 8mm screws for the mast to fuse connection. Not sure what the configuration is for your Moses? But if it is 2 x 8mm (or better), your idea of making a separate plug to go into the fuse with a flat top surface to butt against the mast might work, replacing the carbon rods with attachment screws??

4) if you are making a composite mast, i would use barrel nuts in the mast to give something solid to screw into.

5) This may be an option for you: http://www.thekitefoil.com/e-shop/!/Man ... 3D12622627
The sad bit is that even though they are only $55 the postage is likely to be the same :-(
Depending on your moses screw sizes and spacing, you may be able to use 3) in conjunction with one of these?
For mast to plate connection you could use http://www.ketos-foil.com/en/kf-box/25- ... isser.html and pot the mast into it..or possibly just butt the mast onto an aluminum plate and use the two 8mm screws..Zeeko seem to do this but they have 3 screws..Revhed has claimed success with two screws and a fillet of some exotic 'putty' - In this case I cant believe the fillet added much strength. In your case, with a reduced mast length, I would guess there is a good chance of success?
one of the advantages of the Al mast approach is you can cut it down to whatever length you like. I you want to know dimensions and screw spacing for the Manta mast, I can get these for you.

Food for thought..

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Re: Mast Building Method

Postby TomW » Fri Dec 30, 2016 1:46 pm

Thanks faklord,

Mast construction - how about if I put 4x 15mm wide strips of Cf spread tow 80g along each side and cover with 4 layers 200 g glass each side. Along with Uni directional 1,5 mm Abachi veneer v-Bagged in epoxy in 6-8 layers for Core. Have not researched the lamination schedules for masts, but this seems reasonable.

I think you are right about potting. I think I will make a simple silicone mold of the rabbet, Mount the mold on a plywood jig and use that for potting. Don't want to mess up my fuselage.
Attachment is 2 x M6 screws. Didn't think of barrel nuts. could I use the solid Cf rod I have as barrels and drill tap them. Or find some SS rod and drill tap them (don't have any metal working tools really). Screws for Moses rabbet are only 25-30 mm long though, so barrels will be placed close to end of rabbet.
_20161230_134339.JPG
The mast needs to be at an angle because Moses mast is curved. So I can't use that KF box or standard ALU mast. I could use a straight mast, but then have to move attachment to the board or convert one of my surfboards, but want the short mast to be compatible to Moses board.
My thinking now is to take a piece of plywood, cut a hole so mast fits into the hole, glue and fillet, then add many layers glass. and glass flat attachment side too. The Moses base has huge fillet. I have some small scraps of carbon I could use in this area.
_20161230_133226.JPG

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Re: Mast Building Method

Postby faklord » Fri Dec 30, 2016 7:10 pm

Tom,
Mast Layup: I'm not sure your proposed mast layup would be stiff/strong enough. I think you typically want a carbon skin thickness of 2-3mm comprised of a mixture of UD running lengthwise (for bending) and +/-45deg (for torsion). ie typically 5-600gms of carbon in total. Maybe add a layer of cosmetic twill. OK-this is for a full length mast so you may get away with some reduction..but it gives you a feel for what is required.

Barrel nuts: I would be dubious about using carbon rod (likely to split or threads pull out). My preference would be Brass (maybe 10 or 12mm diameter?). Stainless on stainless tends to bind/jam (not quite so bad if two different grades of stainless are used). " Screws for Moses rabbet are only 25-30 mm long though, so barrels will be placed close to end of rabbet." - nothing to stop you from using longer screws (if it helps)

Mast to Board location: "have to move attachment to the board"...not necessarily - you may be able to just move your foot positioning.
Alternatively, if you go the Al mast route & just bolt a mast to a flat Al plate (say 8-10mm thick), you could just extend the plate so the mast position is offset in relation to the plate to board mounting holes? However.i think the reel problem with Al mast is the fuselage connection?

Mast to plate connection: "My thinking now is to take a piece of plywood, cut a hole so mast fits into the hole, glue and fillet, then add many layers glass. and glass flat attachment side too" This is the most highly stressed joint. If it fails you will likely loose your foil !!!!!. If you go this route i would at the the very least:
a) Fully wrap your plywood plate in carbon and vac bag.
b) Maybe add bolts and barrel nuts for extra strength and a backup.
c) Ensure all your fillets are applied before the epoxy on the mast & plate is fully cured, so you get chemical + mechanical bonding.

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Re: Mast Building Method

Postby downunder » Sat Dec 31, 2016 2:51 am

^
Might not loose it since a wood core. It will float, but add some color for visibility :)

I would add a SS washers:
Tom.jpg
Tom.jpg (41.06 KiB) Viewed 514 times
Hmm, must get onto it but it's hard when blowing 20-30kn every day :)

D.

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Re: Mast Building Method

Postby TomW » Sat Dec 31, 2016 12:36 pm

Hi Faklord,
Thanks again fir advice.
I bagged the wood Core last night and ordered 1m each of 300g biax and 450 g twill carbon, enough to have 1800g or more on each side. I can add CF uni tows if needed.
Also trying to get some SS inserts from UK recommended in another thread.

I have to measure the offset of the curved strut ( I've learned it's not called a mast). I think it is 50mm or less. ( strut is not with me now) But if I use the Moses board, and a straight strut, I'll have to move forward on the board, and that messes up footstrap position. I'm a total noob, but my feeling was footstraps already are not far enough forward.
Making strut plate to board longer moves bolt position relative to strut, perhaps putting more stress on the plate.
What do you think of just angling the strut back? Meaning strut is not vertical, but slightly angled backwards, seen from side.

Taking your advice on strut plate to board:
Make plywood with recess for screws and plate, cover with cf.
Screw strut to plate with steel plate
Cover in more cf
Fillet
Cover in more cf.
Starting to realize why a strut costs 699:- € and a wing 199 €
_20161231_113829.JPG


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