Preventing bow cover from raising during high speed.

[JuneC]

A good customer of mine has an issue with a sunpad cover (not mine) raising about a foot off the deck during high speed.  It's very well fastened, with track and welt across the bow.  I believe the angle of the deck and speed of the boat is turning it into an airfoil (like an airplane wing) and the vacuum across the back edge is lifting the fabric and sucking air inside around the edges.  You pilots out there can tell me if I'm all wet here. 

Do you think putting a vent somewhere could cause it suck down, instead of billow up?  Where would I place it in relation to the bubble?

June

[Grebo]

Think you are spot on there June, I once had a boat with a bow pit ! big ring of seats set into the deck, it had a cover (Not mine) that spanned the whole 'hole' that would billow upwards with speed. It was zipped all the way around but still did it, The only thing I came up with was pockets running side to side across the whole width with webbing running through them & fastened under tension, didn't solve the problem but did reduce it.
Never though of putting a vent into.  ::)

Suzi

[Mike8560]

Ahh Suzie beet me to it June.
I was thinking you must have locking fastners as snaps would just blow off why not sew some webbing or somthing heavy under the cover and turnbutton the whole thing down with vents maybe if that would
help. Bow dast is this boat anyway? A friend here has a cat that will hit 100   

[stitchit]

Hope I'm not too late-- Have you ever used "Extreme Seal"? It's just a rubber type welt used for areas of a surface for mist/water where water might get in. Like a Windshield welt.

It is thick, and easy to use/sew. I bet it would eliminate the problem.

Good Luck!

Chris

[fragged8]

Xtream seal is good but air getting into a join
isn't always the problem. It could be like June
suspects an air pressure difference between the upper surface
and the lower surface causing lift just like a wing.

soft tops on cars do it, have you seen them going down the road
and the top is ballooning ?

Be interesting to try it though.

[DBR1957]

What make/model of boat. I've had some bow cushions that are joined at the middle front to back. Ran a strap down the center and it helped quite a bit. However, this is an inherent problem with bow cushions and I wouldn't be surprised if the owner's manual states the cushion should only be installed when the boat is anchored or moored.

[Mike8560]

I saw o. A new Larson. Boat before that said the top a d it wasn't a Bimini just a convertible top well it should not be o. When the boat is underway it could fall off a d cause bodily harm.

[Grebo]

What make/model of boat. I've had some bow cushions that are joined at the middle front to back. Ran a strap down the center and it helped quite a bit. However, this is an inherent problem with bow cushions and I wouldn't be surprised if the owner's manual states the cushion should only be installed when the boat is anchored or moored.

I think it's the cover over the cushions not the cushions that are the problem.  ;)
Thats it June, tell him to take it off, while moving  ;D   Simples....

[JuneC]

The boat is a monster Intrepid with triple Yamaha something-or-others.  Very fast.  I haven't actually seen the cover yet, but this is a long-standing customer who I've done lots of work for and will be building a pull-out sunbed on the transom of this boat, so I'll study it when I go over there to see what I might be able to do.  Maybe some non-stretch webbing straps sewn into the fabric and pulled tightly will hold it down.  But if it's too tight, that'll leave an impression in the foam and I don't want that either. 

June